A Text-Book of Mineralogy 1000718555

TEXT-BOOK

A

OF

MINERALOGY AN

WITH

EXTENDED

TREATISE

AND

CRYSTALLOGRAPHY

ON

PHYSICAL

MINERALOGY

BY

EDWARD

SALISBURY

DANA ft

ProfessorEmeritus

THIRD

of Physics and Curator of Mineralogy Yale University

REVISED

EDITION,

AND

ENLARGED

BY

WILLIAM

E.

FORD

School of Professorof Mineralogy,Sheffield Scientific Yale University

TOTAL

ISSUE,

NEW

JOHN LONDON:

THOUSAND

TWENTY-SEVEN

WILEY

YORK

"

CHAPMAN

"

1922

SONS,

INC.

HALL,

LIMITED

EARTH

SCIENCES LIBRARY

COPYRIGHT,

1898

BY

EDWARD

S. DANA.

COPYRIGHT,

1922

BY

EDWARD

S. DANA AND

WILLIAM

TECHNICAL

CAMBRIDGE,

E.

FORD.

COMPOSITION

MASS.,

CO. U.

S.

A.

PREFACE

of this book

first edition

The years

later

again

after

(1898) the the

and

character section

of the

Minerals

employed

has

simpler and

readily

more

all

Descriptive Mineralogy corrections

been that

in the

is

unwise

to

attempt

edition

of

that

table has

been

into lists

added

has

to.Appendix to their

been

to

editor

and

many

The

support

has

a

is indebted Professor

have

Optical Character constant

been

Only

section

the

of

results

It

it

was

a

new

until

methods

the

A

largely rewritten. have

of

been

grouped the

Throughout

new

book

all the information science.

especially to the published and L.

Penfield

for

in the

sections

of

Samuel used

given him

He

also

much

by Professor WILLIAM

HAVEN,

CONN., Dec.

1, 1921.

469105 m

published unterial ma-

raphy Crystallog-

acknowledges Edward

Dana.

NEW

of

felt

was

Mineralogy

classification

of the

on

have

changes have

species.

concise way

student

of

changes and

minor

the minerals

of Minerals.

assistance

other

description of been

the

embody

to

System

chemical

jections. pro-

portion of the book In

mineral

the

clear and

advanced

late

figures that and

decades.

The A

order

gnomonic

the previous edition

important basic elements.

of this edition

writings

the

this

Numerous

of the

in which

B

present in

of the

in

to

appear.

by the elementary and

and

cordial

should

given in Appendix

according

the endeavor

of

revision

any

work

Crystal Drawing

closelyrelated

the

In

Optical Characters

student.

since

places.

of classification

so

to make

by

last two

the

general

unchanged.

the

on

the

described

made

been

course,

order

this book

as

The

species

investigation during

made

needed

of

have,

retained

Now,

changes

addition, the

stereographic and

endeavor

understood

in their proper

brieflymentioned

mineral

of the

use

edition.

of

The

change consists in the introduction

important

in the

rewritten

been

been

published.

was

third

chiefly those

having

approximately twenty

edition

portion of the section

considerable

A

been

the

and

the

comes

are

in the

EDITION

in 1877

revised

years,

book

Crystallography

on

and

edition

present

form

methods

of the

twenty

THIRD

appeared

second

than

more

in

involved

THE

TO

E.

FORD

the

S.

PREFACE

in the

necessary,

add

to

new

work

being designed

chapter

In the

The

symmetry.

The

elementary isometric

group"

of

The

symmetry. different

forms

the

In former

common

chapters

edition of the true

student

methods

is retained

science in the the

of

upon

of

investigation

therefore,given

of

to the

different

the

original literature.

The Sixth

which

the mineral of

To

this work

fuller

practically

to

System

future

of

as

is

is,to the

shows

the

of the

given

of

the

to

the

which

group

is

the

highest degree regards the indices of the

of

the

are

is

effort has

been

with

Especial

student's

essentiallyan student

crystallographicand analyses,lists of localities, etc.; also for the the work

has

to

for data

expanded

when

is,

papers

on

attention

to

of

the

abridgment

opticalproperties

give

scope. by the micro-

(1892).

is,therefore, referred

authorities been

the

modern

attention

important

to

the

made

all the

Mineralogy, prepared by the author the

of

this is particularly

depend;

familiar

direct

to

plan

fully the elementary principles

introduced

order

Appendices)

directions,however,

suggest

groups

optical properties of crystalsas revealed

of Dana's

their

possible,

as

demands

simple

applied.

descriptionsof the

In certain

also

Mineralogy,

The

commonly

subjects discussed,in

(and

so

far

the

to

characters

Optics.

becoming now

according to

are

calculations. Chemical

and

Descriptive part of the volume Edition

that

which

followed

are

Further, frequent references the

presentation.

Especial prominence

and

private

or

principles of hemihedrism.

presenting somewhat

department

means

topics discussed,

suited

systems,

mathematical

Physical

on

the

seems

first.

of Miller

the

of

of

mathematically

occurrence

methods and

choice

intended

are

with

the successive

as

class

types of crystal forms

are

groups

alone

special and

well

as

of

method

different

each, and

which

it

wants

based,

these

being described

relativelyof most

the whole

given form

under

the

the

and

to

years

1877, has made

classed

student, the

system

normal

the

once

in

accepted thirty-two groups

is that

adopted

order

the

meet

to

determined

formerly applied in accordance

terms

"

names

characteristic

the

many

of treatment

now

first issued

illustrations.

new

chiefly

at

Mineralogy, during the

edition,to rewrite

new

a

EDITION

of

was

Crystallography, the

on

the

under

described

upon

object has

fullness

and

order

and

matter

instruction, this the

of

preparation

much

The

Science

elapsed since this Text-Book

have

that

SECOND

in the

advance

remarkable

THE

THE

TO

of

for

species,for

here

quoted.

the interests

the

of

have

student

characters

of

the

paragraph

headed

which to

it

separate list

The in

the

earlier

requires

more

here

System been

is of

require

particularly special

his

part under Haven

colleague, of

the the and

work

the to

accessible

in

separate

Index

those

of

Groth

of

given

to

to

all

L.

dealing

V.

to

the

with He

H.

A.

is

also

Miers

well-known

works

however, has

who

optical

given

properties

indebted of

form

tion reproduconly

has

Oxford,

to

Prof.

England,

of

his

express

material

him of

minerals

S.

L. for

Penfield

to

gratitude

EDWARD

HAVEN,

CONN.,

Aug.

1, 1898.

SALISBURY

the

in

aid

as

various

thors au-

obvious

too

are

other

examined of

New

valuable

suggestions.

NEW

the

in

Index

topical

Rosenbusch

must,

Pirsson,

its not

full

Appendix

Species.

and

author

The

Prof.

an

further,

A

serve

expanded

present

it;

which

as

interested

form.

volume

present

mention.

Prof.

is

its

in

confounded.

easily

appeared

in

to

species,

those

"

microscope. to

usual

the of

it

be

called

also

common

be

which

since

well

each

might

it

minerals,

omitted,

also

but

besides

of

could

since

Mineralogy

obligations "

to

space

of

of

statement

is

particularly

which

the

in

Attention

characters,

been

than

unnecessary

added,

The

has

example,

description

with

species localities

edition,

for

groups.

the

in

EDITION

it;

isomorphous

distinguishing

American

of

demand

"Diff.,"

other

from

SECOND

THE

to

various

the

given

are

seemed

the

the

it

TO

PREFACE

VI

DANA

TABLE

CONTENTS

OF

PAGE

INTRODUCTION

1

PART GENERAL

MORPHOLOGICAL

GENERAL

MATHEMATICAL

I.

ISOMETRIC

RELATIONS

Pyritohedral

3.

Tetrahedral

4.

Plagiohedral Class

5.

Tetartohedral

Class

Type

52 ,

(2). Pyrite Type Tetrahedrite

(3).

Class

(4).

63

Type

66

Cuprite Type Ullmannite

(5).

Class

of the

Relations

Isometric

71

Type

72

System

72

SYSTEM Class

Normal

77

(6).

Zircon

Class

(7).

3.

Hemimorphic Pyramidal Class

4.

Pyramidal-Hemimorphic

5.

Sphenoidal

6.

Trapezohedral

7.

Tetartohedral

Class

(10).

Class

Relations

77

Type lodosuccinimide

Type Type Class (9). Wulfenite Type Chalcopyrite Type

Hexagonal

(11).

Nickel

2.

Hemimorphic

3.

Pyramidal

of the

89

Tetragonal System

Class

90

95

(13). Beryl Type Class (14). Zincite

Class

95 98

Type

5.

Trapezohedral or

Class

Class

Trigonal

2.

Rhombohedral

(18). Class

Division

103

Benitoite

103

(19).

Class

Type

Calcite Class

Rhombohedral-Hemimorphic Trirhombohedral

(21).

Type. (20).

Phenacite

104

Tourmaline

Type

ORTHORHOMBIC

Relations

of the

SYSTEM

2.

Type Hemimorphic Class (26). Calamine Sphenoidal Class (27). Epsomite Type

Mathematical

Class

(25).

Relations

Barite

vii

115

121

Type

of the Orthorhombic

110

121

"

Normal

109

114

Hexagonal System

1.

Type

112

Trapezohedral Class (22). Quartz Type Other Classes (23) (24)

Mathematical

101 102

(17)

Rhombohedral

1.

100

(15).

4.

3.

89

(12)

6. 7. IV.

87

Sulphate Type

Apatite Type Class (16). Nephelite Type Pyramidal-Hemimorphic

5.

86

Division

Normal

4.

85

94

1.

3.

.

SYSTEM

HEXAGONAL

Trigonal

84

Scheelite

(8).

Class

Mathematical

B.

Galena

(1).

2.

II. TETRAGONAL

A.

26 52

Class

Mathematical

III.

7

CRYSTALS

OF

SYSTEM

Normal

2.

CRYSTALS

OF

RELATIONS

1.

1.

CRYSTALLOGRAPHY

I.

126

128

System

128

yiii

CONTENTS

OF

TABLE

PAGE

V.

1.

Normal

2.

Hemimorphic

3.

Clinohedral

138

Class (29). Tartaric Acid

Type Class (30). Clinohedrite Type

System

of the Monoclinic

Relations

'138 139 143

SYSTEM

TRICLINIC

Normal

2.

Asymmetric

Examples

OF

152

CRYSTALS

160

CRYSTALS

TWIN

OR

ANGLES

148

of the Triclinic System

Relations

THE

OP

147

Thiosulphate Type

Class (32). Calcium

Mathematical MEASUREMENT

144

Class (31). Axinite Type

1.

COMPOUND

133

Gypsum Type

Class (28).

Mathematical VI.

133

SYSTEM

MONOCLINIC

165

of Twinning

of Important Methods

172

Regular Grouping of Crystals IRREGULARITIES

OF

174

CRYSTALS in the Forms

1.

Variations

2.

of Imperfections

3.

Variations

CRYSTALLINE

in the

178

178 182

AGGREGATES

PART

I.

176

Crystals Crystals

the Surfaces of

Angles of Internal Imperfection and Inclusions

4.

CHARACTERS

PHYSICAL

174

of Crystals

Dimensions

and

Characters

MINERALOGY

PHYSICAL

II. MINERALS

OF

"

and Elasticity

Cohesion

dependingupon

185 186

'

II.

195

Relative

Density Light Principlesof Optics

Gravity, or Specific depending upon

200

General

200

III. Characters

and Methods OpticalInstruments General OpticalCharacters of Minerals 1. Diaphaneity

241 .

.

246

/ ,

247

-

IV. V. VI.

2.

Color

3.

Luster

247 249

SpecialOptical Characters of Minerals belonging to the A. Isometric Crystals B. Uniaxial Crystals General OpticalRelations of Uniaxial Crystals OpticalExamination C. Biaxial Crystals General OpticalRelations of Biaxial Crystals OpticalExamination Heat Characters depending upon Electricityand Magnetism Characters depending upon Taste

and

GENERAL

PRINCIPLES

251 252 253 253

259 270 270

278 303 306

310

Odor

PART

CHEMICAL

different Systems

OF

EXAMINATION

CHEMICAL

III. CHEMISTRY OF

AS

APPLIED

in the Wet

Examination

by

Means

MINERALS

311

328

Way of the

TO

327

MINERALS

Examination

MINERALOGY

Blowpipe

329

TABLE

PART

IV.

OF

CONTENTS

IX

DESCRIPTIVE

MINERALOGY

PAGE

ELEMENTS

NATIVE

344

SELENIDES,

SULPHIDES,

TELLURIDES,

357

ETC

SULPHO-SALTS

383

CHLORIDES,

BROMIDES,

FLUORIDES

IODIDES,

394

OXIDES

402

CARBONATES

436

SILICATES

454

TlTANATES

TlTANO-SlLICATES,

583

TANTALATES

NIOBATES,

587

ARSENATES,

PHOSPHATES,

VANADATES,

592

ETC

NITRATES

619

BORATES

619

URANATES

'

SULPHATES,

CHROMATES,

623 624

ETC

MoLYBDATES

TUNGSTATES, OXALATES,

641

MELLATES

HYDROCARBON

644

COMPOUNDS

645

APPENDIX

ON

DRAWING

THE

CRYSTAL

OF

A.

FIGURES

649

B.

APPENDIX

TABLES

TO

GENERAL INDEX

BE

USED

IN

INDEX TO

THE

DETERMINATION

OF

MINERALS

663

695

SPECIES.

703 .

INTRODUCTION

1.

THE

SCIENCE

minerals, which material as

it is

of the

MINERALOGY

OF

together crust

in

of the

rock

earth,

treats

in

masses

or

and

of other

in the

possible to study them

of those

form

inorganic species called

isolated bodies

form

in the

make universe

up so

the far

of meteorites.

is a body produced by the procA Mineral of a Mineral. Definition esses of inorganic nature, having a definitechemical composition and, if formed which structure under favorable conditions, a certain characteristic molecular is exhibited in its crystalline form and other physical properties. further explanation. This definition calls for some be a homogeneous when First of all, a mineral must substance, even it the have examined must by microscope; further, definite a minutely formula. chemical composition, capable of being expressed by a chemical examined basalt appears to the eye, but when to be homogeneous Thus, much of different to be made under the microscope in thin sections it is seen up volcanic of its own. Again, obsicftan, substances, each having characters or glass,though it may be essentiallyhomogeneous, has not a definite composition formula, and is hence classed as a rock, corresponding to a specificchemical several not as a mineral species. Further, substances, as tachylyte, hyalomewhich time been at relegated to passed as minerals, have one lane, etc., of basalt, it has shown local forms because been that they are only petrology, form due to rapid cooling. retaining an apparently homogeneous has in all cases Again, a mineral a definitemolecular structure,unless the is rarely true. conditions of formation have been such as to prevent this,which This molecular later,manifests itself in the physical structure, as will be shown characters and especially in the external crystallineform. mineral It is customary, of convenience, to limit the name to matter as a those compounds which have of been formed the nature alone, by processes while compounds made in the laboratory or the smelting-furnace are at most been procalled artificial minerals. have which Further, mineral substances duced included of organic life are not minerals, through the agency among the pearl of an as oyster, the opal-silica(tabasheer) secreted by the bamboo, etc. Finally, mineral species are, as a rule, limited to solid substances; the and water. Petroleum, or only liquids included being metallic mercury mineral oil,is not properly a homogeneous substance, consisting rather of several hydrocarbon mineral it is hence not species. a compounds; restricted It is obvious from the above that minerals, in the somewhat called the often is what constitute of sense usually adopted, only a part Mineral Kingdom. 3. Scope of Mineralogy. the general subject In the following pages, of mineralogy is treated under the following heads : (1) Crystallography. This comprises a discussion of crystals in general and especially of the crystallineforms of mineral species. 2.

"

"

"

1

INTRODUCTION

This

(2) Physical Mineralogy. "

includes

characters of minerals,that is,those

a

discussion of the physical cohesion and elasticity,

depending upon

and so on. density,light,heat, electricity, Chemical this head (3) are Mineralogy. Under presented brieflythe o f to mineral ters generalprinciples chemistry as applied species;their characchemical also the of investigating methods as compounds are described, them from the chemical side by the blowpipe and other means. (4) DescriptiveMineralogy. This includes the classification of minerals of each specieswith its varieties, and the description in its relations especially to closelyallied species, as regards crystalline form, physicaland chemical in nature, and other points. occurrence characters, "

"

4.

Literature.

Edition

of Dana's

is made

to

the

Introduction

System of Mineralogy, pp. xlv-lxi,for

an

to

the

extended

Sixth list of

Mineralogy up to 1892 and to its Appendices I, II also given of the are published up to 1915; the names scientific contain memoirs w hich on periodicals original mineralogical many of the student the titles of a few works, subjects. For the convenience mostly of a general character,are given here. Further references to the literature of Mineralogy are introduced through the first half of this work, at the end of the sections dealingwith specialsubjects. particularly independent

works

Reference

"

on

III for works

and

Crystallographyand

Physical Mineralogy

* de Flsle,1772; Haiiy, 1822; Neumann, WORKS include those of Rome EARLY Krystallonomie,1823, and Krystallographie,1825; Kupffer, 1825; Grassmann, Krystallonomie, 1829 and later; Quenstedt, 1846 (also 1873); Miller, 1839 and 1863; 1829; Naumann, Grailich,1856; Kopp, 1862; von Lang, 1866; Bravais, Etudes Crist.,Paris,1866 (1849); Schrauf,1866-68; Rose-Sadebeck, 1873. include the following: RECENT WORKS 1910. Bayley. Elementary Crystallography,

Introduction to Crystallography, 1915. Statische und kinetische Kristalltheorien, 1913-. der Krystallographie, 1902. Elemente Bruhns. der Krystallformen der Mineralien; 3 vols., 1886-91. Goldschmidt. Index Also Berechnen der Krystalle,1887. Atlas der KrystallAnwendung der Linearprojectionzum formen, Beale.

Beckenkamp.

1913-.

KristallberechnungUnd Kristallzeichnung,1914. Einleitung in die krystallographische Physikalische Krystallographie und der wichtigerenSubstanzen, 1905. Kenntniss Klein. Einleitungin die Krystallberechnung, 1876 Lewis. Crystallography,1899. Geometrische Liebisch. Physikalische Krystallographie, Krystallographie,1881. Gossner. Groth.

1891.

Mallard.

Traite

de Cristallographie geometrique et physique; vol. 1, 1879; vol. 2,

1884. 1899. Characters of Crystals, Hints for Crystal Drawing, 1908.

Moses. Reeks.

Sadebeck. Angewandte Krystallographie(Rose'sKrystallographie,II. Band), 1876. Sohncke. Entwickelung einer Theorie der Krystallstruktur,1879. Sommerfeldt. PhysikalischeKristallographie, 1907; Die Kristallgruppe,1911. Story-Maskelyne. Crystallography: the Morphology of Crystals,1895. Tutton. CrystallineStructure and Chemical Constitution,1910; Crystallography and Practical Crystal Measurement, 1911. 1904. Grundziige der Kristallographie, Crystallography,1914.

Viola. Walker.

*

The

full titlesof many

1892.

of these

are

given in

pp. li-lxiof

Dana's

alogy, System of Miner-

3

INTRODUCTION

1909. Cristallographie,

Wallerant.

Berechnen

der Linearprojection zum Anwendung III. Band), 1887. Krystallographie

Websky.

1890. of Crystallography, Elements Die 32 krystallographischen Symmetrieklassen und

Williams.

Wulfing.

der

Krystalle (Rose's

ihre einfachen

Formen,

1914. In

PHYSICAL

the

MINERALOGY

most

important general works

(1868),Mallard (1884), Liebisch (1891), mentioned etc. (1892). Important later Mikr. Physiographic,

those of Schrauf are above list;also Rosenbusch, include the following.

-in the

works

of the Ore Minerals, 1920. Microscopic Examination Davy-Farnham. Traite de Technique Mineralogique et Petrographique, 1907. Duparc and Pearce. 1905. Krystallographie, Physikalische

Groth.

Jackson. OpticalPropertiesof Crystals,1910. of Rock-Forming Minerals,1908. Manual of Petrographic Johannsen. Determination Methods, 1914. of the Opaque Minerals,1916. Murdoch. MicroscopicalDetermination La Methode Universelle Nikitin,translated into French by Duparc and de Dervies. de Fedoroff,1914. of Optical Mineralogy, 1909. Elements Winchell. of Petrographic-MicroscopicResearch, 1911. Wright. The Methods Groth-

General

Mineralogy

Of the many works, a knowledge of which is needed by one who wishes a full acquaintance portant. with the historical development of Mineralogy, the following are particularlyiminclude those of Theophrastus, Pliny, Linnaeus, Wallerius, Very early works

Cronstedt, Werner, Bergmann,

Klaproth.

Within the nineteenth century: Hauy's Treatise,1801, 1822; Jameson, 1816, 1820; Werner's Letztes Mineral-System, 1817; Cleaveland's Mineralogy, 1816, 1822; Leonhard's Handbuch, 1821, 1826; Mohs's Min., 1822; Haidinger'stranslation of Mohs, 1824; BreitMin., haupt's Charakteristik,1820, 1823, 1832; Beudant's Treatise,1824, 1832; Phillips's 1823, 1837; Shepard's Min., 1832-35, and later editions;yon Kobell's Grundzuge, 1838; Mohs's Min., 1839; Breithaupt's Min., 1836-1847; Haidinger's Handbuch, 1845; Naumann's Min., 1846 and later; Hausmann's Handbuch, 1847; Dufrenoy'sMin., 1844-1847 (also1856-1859); Brooke " Miller,1852; J. D. Dana's System of 1837, 1844, 1850, 1854,. 1868.

More

RECENT

Bauer. Bauerman. Baumhauer.

Brauns. Clarke.

Dana,

are

the following:

der Mineralogie,1904. Lehrbuch Text-Book of DescriptiveMineralogy, 1884. Das Reich der Krystalle,1889.

Bayley. Blum.

WORKS

DescriptiveMineralogy,

1917.

der Mineralogie,4th ed.,1873-1874. Lehrbuch Das Mineralreich,1903. English,translation by Spencer, 1912. The Data of Geochemistry,1916. E. S. Dana's System of Mineralogy, 6th ed., New York, 1892. Appendix I, to study them, New 1909; III, 1915. Also (elementary) Minerals and How

1899; II, York, 1895.

Dana-Ford. Des

Cloizeaux.

Manual of Manuel

Mineralogy,1912. de Mineralogie; vol. 1, 1862; vol. 2, ler Fasc., 1874; 2me.

1893.

Tabellarische Uebersicht der Mineralien,1898. Handbuch der Mineralogie,1889-1915. Iddings. Rock Minerals, 1906. Groth.

Hintze.

Kraus.

DescriptiveMineralogy,1911. Mineralogie de la France et de ses Colonies,5 vols.,1893-1913. Miers. Mineralogy, 1902. Moses and Parsons. Mineralogy, Crystallography and Blowpipe Analysis,1916. Merrill. The Non-metallic Minerals, 1904. Phillios. Mineralogv, 1912. Rogers. Study of Minerals, 1912. Schrauf. Atlas der Krystall-Formen des Mineralreiches, 4to, vol. 1, A-C, 1865-1877.

Lacroix.

Tschermak.

Lehrbuch

der

Mineralogie, 1884; 5th cd., 1897.

4

INTRODUCTION

1875. Synopsis Mineralogica,systematischeUebersicht des Mineralfeiches, 13th edition of Naumann's Mineralogy, Leipzig,1897. works on related subjects, Wiilfing. Die Meteoriten in Sammlungen, etc.,1897 (earlier Dana's System, p. 32). Weisbach. Zirkel.

see

For a catalogueof localitiesof minerals in the United States and Canada the volume see sources (51 pp.) reprinted from Dana's System, 6th ed. See also the volumes on the Mineral Reof the United States published (since1882) under the auspices of the U. S. Geological Survey.

Chemical

and

Determinative

Mineralogy

der chemischen und physikalischen Geologic,1847-54; 2d ed., Lehrbuch (Alsoan Englishedition.) Die Pseudomorphosen des Mineralreichs,1843. With 4 Nachtrage, 1847-1879. Manual of Determinative Brush-Penfield. pipe Mineralogy, with an Introduction on BlowAnalysis,1896. Doelter. Handbuch der MineralAllgemeine chemische Mineralogie,Leipzig,1890. chemie, 1912-. Traite de Technique Mineralogique et Petrographique, 1913. Duparc and Monnier. of Minerals by their PhysicalProperties, Eakle. Mineral Tables for the Determination Bischoff.

1863-66. Blum.

1904. Endlich.

of QualitativeBlowpipe Analysis,New York, 1892. Tafeln zur Bestimmung der Mineralien mitteist einfacher chemischer und nassem Versuche auf trockenem Wege, lite Auflage, 1878. of Minerals, 1911. Tables for the Determination Kraus and Hunt. Lewis. Determinative Mineralogy, 1915. Handbuch der krystallographisch-physikalischen Chemie, Leipzig, Rammelsberg. Handbuch der Mineralchemie, 2d ed.,1875. 1881-82. Erganzungsheft, 1, 1886; 2, 1895. lien, Roth. Allgemeine und chemische Geologic; vol. 1, Bildung u. Umbildung der MineraManual

Kobell, F.

von.

etc.,1879; 2, Petrographie,1887-1890. Die Mineral derselben angeGewicht Species nach den fiir das specifische Websky. und gefundenen Werthen, Breslau, 1868. nommenen nach Tabellen der Mineralien Weisbach. zur ausseren Kennzeichen, Bestimmung tion Also founded Weisbach's 3te Auflage, 1886. on work, Frazer's Tables for the determinaof minerals,4th ed.,1897. Formation Artificial

Minerals

MineralsynthetischesPraktikum, 1915.

Dittler.

'Gurlt.

of

der pyrogeneten ktinstlichen Mineralien, namentlich lisirten Hiittenerzeugnisse, 1857. Fuchs. Die.kiinstlich dargestellten Mineralien, 1872. Daubree. Etudes synthetique de Geologic experimentale,Paris,1879. et des Roches, 1882. Fouque and M. Levy. Synthese des Mineraux Bourgeois. Reproduction artificielledes Mineraux, 1884. Meunier. Les methodes de synthese en Mineralogie. 1903-1904. Vogt. Die Silikatschmelzlozungen, Uebersicht

der krystal-

MineralogicalJournals followingJournals

The

are

largelydevoted

to

originalpapers

on

Mineralogy:

Min. Amer. The American Mineralogist,1916. 1878-. Bull. Soc. Min. Bulletin de la Societe Francaise de Mineralogie, 1900-. Centralblatt fiirMineralogie,Geologie und Palseontologie, Centralbl. Min.

Fortschr. 1911-

Min.

Fortschritte

der

und Mineralogie, Kristallographie

Petrographie,

.

Neues Jahrbuch fiirMineralogie,Geologie und Palaeontologie, etc.,from 1833. Jb. Min. The MineralogicalMagazine and Journal of the MineralogicalSociety of Mag. Gt. Britain,1876-. Min. Mitth. Mineralogische und petrographische Mittheilungen, 1878- ; Earlier, G. Tschermak. from 1871, MineralogischeMittheilungen gesammelt von Riv. Min. Ri vista di Mineralogia e Crystallografia, 1887-. Zeitschrift fiirKrystallographieund Mineralogie. 1877-. Zs. Kr. Min.

5

INTRODUCTION

ABBREVIATIONS

Ax.

pi.

Plane

Bx,

Bxa.

Acute

of

the

B.B.

Before

Comp.

Composition.

Diff.

Differences,

H.

axes.

(p.

bisectrix

Obtuse

Bxo.

optic

the

bisectrix

(p.

Blowpipe

277). 277). (p.

330).

Specific The

=

44"

sign 30'.

A

Observations

O.F.

Oxidizing

Pyr.

Pyrognostics allied

distinctive

or

char-

acters. G.

Hardness.

Obs.

R.F.

Reducing

Var.

Varieties.

on

etc.

occurrence,

Flame

(p.

331). and

blowpipe

or

characters. Flame

(p.

331).

Gravity.

is used

to

indicate

the

angle

between

two

faces

of

a

crystal,

as

am

(100

A

110)

8

CRYSTALLOGRAPHY

cohesion,action on light,etc. This is clearlyshown by the elasticity, cleavage,or natural tendency to fracture in certain directions, yieldingmore less smooth or surfaces;as the cubic cleavageof galena,or the rhombohedral cleavageof calcite. It is evident,therefore,that a small crystaldiffers from a largeone a only in size,and that a fragment of a crystalis itselfessentially faces. though showing no crystalline crystalin all its physicalrelations, Further, the external form without the correspondingmolecular structure does not make a crystalof a solid. A model of glass or wood is obviously not a crystal, though having its external form, because there is no relation between form and structure. Also, an octahedron of malachite,having the form of the crystalof cupritefrom which it has been derived by chemical is not a crystal of malachite, but what is known as a pseudomorph alteration, of malachite after cuprite. (seeArt. 478) On the other hand, if the natural external faces are wanting, the solid is of fluorite and a cleavagerhomnot called a crystal. A cleavageoctahedron because the surfaces have been of calcite are not properlycrystals, bohedron yieldedby fracture and not by the natural molecular growth of the crystal. When 8. Crystalline and Amorphous. mineral shows external a no be it It to massive. is said definite have a form, crystalline however, may, as

of

"

molecular shown

structure, and then it is said

by the

cleavage,

or

to be

by opticalmeans,

crystalline.If this structure, as is the

same

in all

directions parallel

through the mass, it is described as a singleindividual. If it varies from it is said to be a crystalline grainto grain,or fiber to fiber, aggregate*since it of individuals. Thus in a granularmass it may be possible to separate galenaor calcite, the fragments from one bohedral, another,each with its characteristic cubic,or rhomcleavage. Even if the individuals are so small that they cannot be dent structure, may be eviseparated,yet the cleavage,and hence the crystalline from the spanglingof a freshly broken surface, ary statuas with fine-grained be so fine that the marble. Or, again,this aggregate structure may be resolved structure methods with the aid of can only by optical crystalline is said to be crystalline. the microscope. In all these cases, the structure If opticalmeans less distinct crystalline show a more or structure, which, be is said to be cryptoresolved into the mass individuals, however, cannot this is true of some massive varieties of quartz. crystalline; If the definite molecular structure is entirely wanting,and all directions in the mass are sensiblythe same, the substance is said to be amorphous. This and nearlyso of opal. The amorphous state is rare is true of a pieceof glass, minerals. among is in fact made

up

of

a

multitude of

be in the glass-like A piece of feldsparwhich has been fused and cooled suddenly may in such But even amorphous condition as regards absence of definite molecular structure. into the crystalline there is a tendency to go over condition by molecular rearrangecases ment. A transparent amorphous of arsenic trioxide (AsaOa),formed mass by fusion, after a time. and crystalline the steel beams of a railroad bridge becomes Similarly opaque and thus lose some of their originalstrength because of graduallybecome crystalline may the molecular rearrangement made possibleby the vibrations caused by the frequentjar of passingtrains. The microscopicstudy of rocks reveals many cases in which an analogous change in molecular structure has taken place in a solid mass, as caused, for example, by great pressure.

* The consideration of the various forms end of the present chapter.

of crystalline aggregates is postponed to the

MORPHOLOGICAL

GENERAL

RELATIONS

OF

9

CRYSTALS

crystal-is bounded by smooth plane surfaces, in their or arrangement a certain characteristic planes,*showing laws. symmetry, and related to each other by definite mathematical at the moment, into the exact meaning of the Thus, without inquiring, and the kinds of symmetry term symmetry as appliedto crystals, possible, detail i which will be explainedin later,t is apparent that the accompanying 1-3, show the external form spoken of. They represent,therefore, figures, 9.

External

Form.

"

A

called faces

certain definite types.

Galena

10.

certain

Variation

Vesuvianite

of Form

from limits,

First,there

and

Surface.

"

Chrysolite Actual

crystalsdeviate,within

the ideal forms. be variation in the size of like

faces,thus producingwhat are as place,the faces are rarely forms. smooth and lack and they absolutely brilliant; commonly they perfectpolish, be rough or more less covered with fine parallel lines (called even or may show minute or striations), elevations,depressionsor other peculiarities. Both the above subjectsare discussed in detail in another place. It may be noted in passing that the characters of natural faces,just alluded to, in generalmake it easy to distinguish between them and a face facet cut the like the of on a one artificially ground, hand, gem; surface commonly uneven or, on the other hand, the splintery yieldedby cleavage. 11. Constancy of the Interfacial Angles in the Same Species. The angles of inclination between like faces on the crystals of any speciesare essentially constant, wherever they are found, and whether products of nature or of the portant of the imlaboratory. These angles,therefore,form one characters of a species. distinguishing Thus, in Fig.4, of apatite,the angle between the adjacent faces x and m like faces, for any two (130" 18')is the same this with s ituated each other. to reference Further, similarly Apatite is of the size constant matter what for the angle speciesno the crystal be or from what locality it may Moreover, the angles come. may between all the faces on crystals of the same species(cf Figs.5-8 of zircon less closelyconnected more or below) are together by certain definite defined

may

later

distorted

In the second

"

.

mathematical

laws.

* This latter word is usually limited to definite surface itself, is designated.

cases

where

the direction,rather

than

the

10

CRYSTALLOGRAPHY

12. Diversity of Form, or Habit. While in the crystalsof a given speciesthere is constancy of angle between like faces,the forms of the crystals be exceedinglydiverse. The accompanying figures(5-8) are examples may of a few of the forms of the specieszircon. There is hardly any limit to the "

of faces which may and as their relative size changes, the occur, it is called, may vary indefinitely.

number

habit,

as

Zircon

of all sizes,from the merest Diversity of Size. Crystals occur in stand, to It is important to underdiameter. more a or microscopicpoint yard in is that the minute as a however, development complete as crystal of with a largeone. form and Indeed the highestperfection transparency is in found only crystalsof small size. 13.

"

A singlecrystalof quartz, now at Milan, is three and a quarter feet long and five and a and seventy pounds. half in circumference,and its weight is estimated at eight hundred A singlecavity in a vein of quartz near the Tiefen Glacier,in Switzerland,discovered in number of which had a weight of 200 a considerable 1867, afforded smoky quartz crystals, four feet in A giganticberyl from to 250 pounds. Hampshire, measured Acworth, New length and two and a half in circumference; another, from Graf ton, was over four feet long, of its diameters,and weighed about two and a half tons. and thirty-twoinches in one

14. Symmetry in General. The faces of a crystal are arranged according to certain laws of symmetry, and this symmetry is the natural basis of the division of crystalsinto systems and classes. The symmetry be in axis relation defined to an a of symmetry, (2) (1) planeof symmetry, may and (3) a center of symmetry. "

in the different kinds of symmetry may, or may not, be combined It will be the is shown later that there one same class, crystalsof crystal. where which have neither center, axis,nor there plane of symmetry; another have all is only a center of symmetry. these classes On the other hand, some

These

elements

of^symmetry represented. of Symmetry. A solid is said to be geometrically* symmetrical with reference to a plane of symmetry when for each face,edge, or solid angle there is another similar face,edge, or angle which has a like position with reference to this plane. Thus it is obvious that the crystalof amphibole,shown in Fig. 9, is symmetrical with reference to the central plane of symmetry indicated by the shading. 15.

*

The

symmetry

Planes

"

relation between the ideal geometricalsymmetry is discussed in Art. 18.

and

the actual

crystallographic

MORPHOLOGICAL

GENERAL

In

the

OF

11

CRYSTALS

is rightsymmetry in the geometrical crystalthis symmetry of the plane of symmetry the side one has a corpoint on responding every distances the other side, on point at equal to it. In other words, in line normal on a geometricalsymmetry, one half of the crystal ideal

where

sense,

measured

the ideal is the exact A

RELATIONS

mirror-image of have

the other

half.

as

nine

a

solid

planes of symmetry, another,as is illustrated by the cube * (Fig.16). Here the planesof the firstset to the cubic faces;they pass through the crystalparallel The planesof the second set join shown in Fig. 10. are the oppositecubic edges; they are shown in Fig. 11. crystalmay three of

16.

one

of

Axes

as

set and

many

six of

Symmetry.

certain number

If

"

be revolved line as some

can

degreesabout

through a an axis,with the result that it again occupiesprecisely the same that axis is said positionin space as at first, be

to

of

four different There axis of symmetry. are Amphibole of symmetry fined crystals;they are deamong of times which the crystalrepeats itselfin accordingto the number pearance apduring a complete revolution of 360". an

kinds of

axes

Symmetry

(a) A crystalis said a

of 180"

revolution

to have

produces

an

Planes

in the

axis of

Cube

binary,or twofold,symmetry when above; in other words, when it

the result named

This is true of the crystalshown repeats itself twice in a complete revolution. Fig. 12 with respect to the vertical axis (and indeed each of the horizontal

in

axes

also). (6) A crystalhas

axis of trigonal, or threefold, symmetry when a when itself that it three times in a is, needed; repeats revolution. The vertical axis of the crystalshown in Fig. 13 is an an

of 120" is

of

lution revoplete com-

axis

trigonalsymmetry. (c) A crystal has

axis of tetragonal, an when or a fourfold,symmetry revolution of 90" is called for; in other words, when it repeats itself four times in a complete revolution. The in vertical axis in the crystalshown

Fig. 14 is such an axis. (d) Finally,a crystalhas

axis of hexagonal, an or sixfold, symmetry when revolution of 60" is called for; in other words, when it repeats itself six times in a complete revolution. This is illustrated by Fig. 15. a

*

This is the cube of the normal

class of the isometric system.

12

CRYSTALLOGRAPHY

The different kinds of symmetry hexad axes.

axes

known

13

12

Chrysolite

sometimes

are

as

diad, triad,tetrad and

14

16

Rutile

Calcite

Beryl

with respect to axes illustratesthree of the four possiblekinds of symmetry of binary symmetry joiningthe middle points of opposite It has six axes edges (Fig.16). It has four axes of trigonalsymmetry, joiningthe opposite solid angles of tetragonal three axes symmetry joiningthe middle points of (Fig.17). It has, finally, 18). faces opposite (Fig. The cube of symmetry.

*

17

16

18

-v

Symmetry 17.

Axes

in the Cube

Most Center of Symmetry. of crystals,besides planes and axes On the other hand, a crystal, symmetry, have also a center of symmetry. though possessingneither plane nor axis of symmetry, may yet be sym"

Rhodonite

Heulandite

metrical with reference to a point,its center. This last is true of the triclinic crystalshown in Fig. 19, in which it follows that every face,edge, and solid anglehas a face,edge,and anglesimilar to it in the oppositehalf of the crystal. This is again the cube of the normal

class of the isometric system.

MORPHOLOGICAL

GENERAL

18.

Relation

of Geometrical

RELATIONS

to

OF

13

CRYSTALS

CrystallographicSymmetry.

"

Since

the symmetry arrangement of the faces of a crystalis an expressionof molecular the internal structure, which in general is alike in all paralleldirections, size of the faces and their distance from the plane or axis of the relative in the

their angular positionalone is essential. The of no moment, are crystalrepresentedin Fig. 20, although its faces show an unequal development, has in the crystallographic sense as trulya vertical plane of symmetry in Fig. 21. to the face 6) as the ideallydeveloped crystal shown (parallel The strict geometricaldefinition of symmetry would, however, apply only to the second crystal.*

symmetry

22

23

24

Distorted

Cube

Cubes

to each Also in a normal cube (Fig.22) the three central planesparallel pair of cubic faces are like planesof symmetry, as stated in Art. 15. But a a cube,though deviatingwidely from the crystalis still crystallographically in Figs.23, 24, if shown as requirementsof the strict geometricaldefinition, only it can be proved, e.g., by cleavage,by the physicalnature of the faces, or by opticalmeans, that the three pairsof faces are like faces,independently is the same in of their size,or, in other words, that the molecular structure the three directions normal to them. 25

26

Cube

and Octahedron

Further,in the case of a normal cube,a face of an octahedron on any solid as explainedbeyond, similar faces on the other angles. It is anglerequires, not necessary, however, that these eightfaces should be of equal size,for in the crystallographic sense Fig. 25 is as trulysymmetrical with reference to the planesnamed 26. as Fig. * It is to be noted that the perspectivefiguresof crystalsusuallyshow the geometrically ideal form, in which like faces,edges, and angles have the same shape, size,and position. In other words, the ideal crystalis uniformly represented as having the symmetry called for by the strict geometricaldefinition.

14

CRYSTALLOGRAPHY

19.

the other hand, the molecular and hence the crystallographic would is not always that which the geometricalform suggest. the consideration of pseudo-symmetry, an Thus, deferringfor the moment It has already been illustration of the fact stated is afforded by the cube. while cube of the normal later the be that and will fullyexplained implied in Arts. 15, 16, a class of the isometric system has the symmetry described On

symmetry

geometricalform but belongingmolecularly,for example, has no planes of symmetry to the faces but parallel class, the four shown in Fig. 17 axes only the six diagonalplanes;further,though stillaxes of trigonal are symmetry, the cubic axes (Fig.18) are axes of binary of symmetry correspondingto those symmetry only, and there are no axes represented in Fig. 16. Other more complex cases will be described later. a cube : Further,a crystalhaving interfacial angles of 90" is not necessarily in other words, the angular relations of the faces do not show in this case whether the figureis bounded by six like faces; or whether only four are whether there are three pairsof alike and the other pairunlike; or, finally, be decided,in such cases, by the molecular unlike faces. The questionmust indicated by the physicalnature of the surfaces,by the cleavage, structure as with those connected or by other physical characters,as pyro-electricity, lightphenomena, etc. Still, again,the student will learn later that the decision reached in regard to the symmetry to which a crystal belongs,based upon the distribution of the and before being finally is and accepted approximate, faces, only preliminary be confirmed,first, by a accurate it must second, and, measurements, by minute study of the other physicalcharacters. cube

of the

same

to the tetrahedral

conclusive results based upon the physicalcharacters,which gives most The method is the skillful etching of the surface of the crystal by admits of the widest application, it minute there are, in general,produced upon some appropriate solvent. By this means cules. depressionsthe shape of which conforms to the symmetry in the arrangement of the molelar This process, which is in part essentially one involvingthe dissection of the molecuparticularlydiscussed in the chapter on Physical Mineralogy. structure, is more and

The crystalsof certain speciesapproximate Pseudo-symmetry. and in apparent symmetry, to the requirements therefore angle, of a system higher in symmetry than that to which they actuallybelong: then exhibit to said examples are pseudo-symmetry. Numerous they are to be shown been have the different micas Thus the systems. given under in be in some to angle they seem though trulymonoclinic in crystallization, 20.

"

closelyin

rhombohedral, in others orthorhombic. also simulate It will be shown later that compound, or twin,crystals may by their regulargrouping a highergrade of symmetry than that which belongs to the singlecrystal. Such crystalsalso exhibit pseudo-symmetry and are mimetic. Thus called aragoniteis an example of an orthorhombic specifically imitate often whose by twinning those of the hexagonal crystals species, twinned crystalof the monoclinic species, system.* Again, a highlycomplex metric of the isododecahedron rhombic have form of the a nearly phillipsite, may the among system. This kind of pseudo-symmetry also occurs cases

classes of

a

may

*

The

terms

singlesystem, since a crystalbelongingto by twinning gain the geometricalsymmetry etc.,used pseudo-hexagonal,

in this and similar

cases

a

class of low

of the

metry sym-

corresponding

explainthemselves.

16

CRYSTALLOGRAPH

24.

Each of the six systems, as will be understood from Art. 21, one in their symmetry. several classes differingamong themselves One of these classes is convenientlycalled the normal class,since it is in it since further exhibits and the generalthe common highestdegree of one, the while others for the lower in grade are system, given symmetry possible of symmetry. It is important to note that the classes comprised within a given system at once connected togetherby their common are opticalcharacters, essentially and in generalseparated* from those of the other systems in the same way. Below is given a list of the six systems togetherwith their subordinate classes, given firstare those that thirty-twoin all. The order and the names used in this book while in the followingparenthesesare are given other Under that are also in common use. equivalentnames nearly all of the classes it is possible of a mineral or an artificialcompound to give the name whose to illustrate the characters of that particularclass. crystals serve There is some slightvariation between different authors in the order in which the crystalsystems and classes are considered but in the main essentials all uniform. modern discussions of crystallography are embraces

ISOMETRIC

SYSTEM

(Regular,Cubic System) CLASS. (Hexoctahedral. Holohedral.) Galena Type. CLASS. PYRITOHEDRAL (Dyakisdodecahedral. Pentagonal Hemihe-

1. NORMAL 2.

dral.) Pyrite Type. CLASS.

3. TETRAHEDRAL Tetrahedrite Type. 4. PLAGIOHEDRAL

CLASS.

(Hextetrahedral.Tetrahedral (Pentagonal Icositetrahedral.

Hemihedral.) Plagiohedral

Hemihedral.) Cuprite Type. CLASS. TETARTOHEDRAL Sodium Chlorate Type. 5.

TETRAGONAL 6.

NORMAL

CLASS.

(Tetrahedral Pentagonal Dodecahedral.)

SYSTEM

(DitetragonalBipyramidal. Holohedral.) Zircon

Type. Hemi(DitetragonalPyramidal. Holohedral Type. hedral.) CLASS. 8. TRIPYRAMIDAL (TetragonalBipyramidal. Pyramidal HemiScheelite Type. dral CLASS. 9. PYRAMIDAL-HEMIMORPHIC (TetragonalPyramidal. HemiheWulfenite Hemimorphic.) Type. dral. CLASS. 10. SPHENOIDAL (TetragonalSphenoidal. Sphenoidal HemiheScalenohedral.) ChalcopyriteType. 11. TRAPEZOHEDRAL CLASS. (Tetragonal Trapezohedral. Trapezohedral Hemihedral.) Nickel Sulphate Type. 12. TETARTOHEDRAL CLASS. Bisphenoidal.) Artif. (Tetragonal 2 CaO.Al203.SiO2 Type. 7.

HEMIMORPHIC

CLASS.

morphic.) lodosuccinimide

* Crystals of the tetragonaland hexagonal systems are alike in being opticallyunaxial; but the crystalsof all the other systems have distinguishing opticalcharacters,

MORPHOLOGICAL

GENERAL

RELATIONS

HEXAGONAL

CLASS.

NORMAL

13.

17

CRYSTALS

SYSTEM

HEXAGONAL

A.

OF

DIVISION

(Dihexagonal Bipyramidal. Holohedral.) Beryl

Type. CLASS.

HEMIMORPHIC

14.

morphic.)

Zincite

Hemi-

Type. CLASS.

TRIPYRAMIDAL

15.

(DihexagonalPyramidal. Holohedral

(Hexagonal Bipyramidal. Pyramidal Hemi-

hedral.) ApatiteType. PYRAMIDAL-HEMIMORPHIC Hemihedral Hemimorphic.) CLASS. 17. TRAPEZOHEDRAL 16.

CLASS. (Hexagonal Pyramidal. Pyramidal NepheliteType. (HexagonalTrapezohedral. Trapezohedral

Hemihedral.) /3-QuartzType. TRIGONAL

B.

DIVISION

RHOMBOHEDRAL

OR

(TrigonalSystem) CLASS.

18. TRIGONAL Benitoite Type.

Scalenohedral. (Ditrigonal

CLASS.

RHOMBOHEDRAL

19.

Bipyramidal. TrigonalHemihedral.) (Ditrigonal Rhombohedral

Hemihedral.) Calcite Type^ HEMIMORPHIC

RHOMBOHEDRAL

20.

gonal (Ditrigonal Pyramidal. Tri-

CLASS.

Hemihedral Hemimorphic.) Tourmaline Type. CLASS. 21. TRI-RHOMBOHEDRAL (Rhombohedral. Phenacite tartohedral.) Type. CLASS.

TRAPEZOHEDRAL

22.

Rhombohedral

Te-

(TrigonalTrapezohedral. Trapezohedral

Tetartohedral.)Quartz Type. 23.'

tohedral. (TrigonalBipyramidal. Trigonal Tetarhedral (TrigonalPyramidal. Trigonal TetartoType.

24.

Hemimorphic.)

Periodate

Sodium

ORTHORHOMBIC

(Rhombic 25.

NORMAL

CLASS.

or

SYSTEM Prismatic

System)

(OrthorhombicBipyramidal. Holohedral.) Barite

Type. 26.

HEMIMORPHIC

27.

SPHENOIDAL

CLASS. CLASS.

(OrthorhombicPyramidal.) Calamine Type. (OrthorhombicBisphenoidal.) Epsomite Type.

MONOCLINIC

SYSTEM

(ObliqueSystem) 28. 29. 30.

NORMAL CLASS. (Prismatic. Holohedral.) Gypsum Type. HEMIMORPHIC CLASS. (Sphenoidal.) Tartaric Acid Type. CLINOHEDRAL CLASS. (Domatic. Hemihedral.) Clinohedrite TRICLINIC

Type.

SYSTEM

(AnorthicSystem) 31. 32.

NORMAL CLASS. (Holohedral. Pinacoidal.) Axinite Type. ASYMMETRIC CLASS. (Hemihedral.) Clacium ThiosulphateType.

18

CRYSTALLOGRAPHY

25.

In the paragraphs immediately following, Symmetry of the Systems. of the normal a synopsisis given of the symmetry class of each of the different systems, and also that of one subordinate class of the hexagonal is of so great importance that it is also often conveniently system, which treated as a sub-system even when, as in this work, the forms are referred to those of the strictly the same axes as not adopted hexagonal type a usage by all authors. I. ISOMETRIC Three SYSTEM. like axial planes of symmetry (principal planes)parallelto the cubic faces,and fixingby their intersection the crystallographic six like of planes diagonal symmetry, passingthrough each axes; oppositepair of cubic edges,and hence parallelto the faces of the rhombic "

"

*

dodecahedron.

Further, three normal

axes

like

axes

of

tetragonalsymmetry, the crystallographic cube; four like diagonalaxes of trigonalsymmetry, of the octahedron; and six like diagonalaxes of

to the faces of the

normal

to the faces

There is also binary symmetry, normal to the faces of the dodecahedron. These center of relations illustrated a obviously symmetry.! are by Fig. 27 also by Fig.35; further by Figs.92 to 125. 27

28

29

Rutile

Rutile

\m

a

Galena

II. TETRAGONAL SYSTEM. Three axial planesof symmetry : of these,two like planes intersecting at 90" in a line which is the vertical crystallographieaxis,and the third plane (a principalplane) is normal to them and hence contains the horizontal axes. There are also two diagonalplanes of are

in intersecting anglesof 45".

symmetry, at

the vertical axis and

meeting the

two

axial

planes

axis ; this is Further, there is one axis of tetragonalsymmetry, a principal the vertical crystallographic axis. There are also in a plane normal to this four axes of binary symmetry like two and two those of each pairat right "

"

anglesto each other. Fig.28 shows a typicaltetragonalcrystal,and Fig.29 of it,that is,a projectionon the principal a basal projection plane of symmetry normal to the vertical axis. See also Fig. 36 and Figs.170-192. *

Two

planes of symmetry

said to be like when are they divide the ideal crystalinto identical to each other; otherwise,they are said to be unlike. Axes of also like or unlike. If a plane of symmetry are of the crystallosymmetry includes two graphic If the plane includes two or more axes, it is called an axial plane of symmetry. like axes of symmetry, it is called a principalplane of symmetry ; also an axis of symmetry in which two or more like planes of symmetry meet is a principalaxis of symmetry. of the different classes,here and later,the center of t In describingthe symmetry not mentioned when its presence absence is obvious. symmetry is ordinarily or

halves which

are

MORPHOLOGICAL

GENERAL

III.

In

SYSTEM.

HEXAGONAL

RELATIONS

the

OF

19

CRYSTALS

Hexagonal Division there are four like planes meeting at angles of

of these three are axial planes of symmetry; the vertical their intersection-line being 60",

crystallographic axis;the fourth to these. There also three are rightangles plane (a the of the other diagonalplanes of symmetry three first set in the meeting of vertical axis,arid making with them 30". angles Further, there is one principalaxis of hexagonal symmetry; this is the vertical crystallographic axis; at rightanglesto it there are also six binary The in sets of three each. last two agonal axes. are Fig.30 shows a typicalhexthe of with basal See also Fig.37 and same. a projection crystal, Figs.220-227. principalplane) is at

32

Miorosoinmite

In the

Cabito

Trigonal or

Rhombohedral

Division

Chrysolite of this system there

are

three

at angles of 60" in the vertical axis. planes of symmetry intersecting Further,the forms belonging here have a vertical principalaxis of trigonal and three horizontal axes of binary symmetry, coincidingwith symmetry, the horizontal crystallographic axes. Fig. 31 shows a typicalrhombohedral crystal,with its basal projection. See also Figs.243-269. IV. ORTHORHOMBIC SYSTEM. Three unlike planes of symmetry meeting the of at 90", and their the intersection-lines graphic crystalloposition fixingby with axes. Further,three unlike axes of binary symmetry coinciding w ith its the last-named orthorhombic 32 shows crystal, axes. a typical Fig. basal projection. See also Fig. 38 and Figs.298-320. V. MONOCLINIC SYSTEM. One plane of symmetry which contains two of the crystallographic axis of binary symmetry, normal to this Also one axes. axis. See Fig. 33; also and plane coincidingwith the third crystallographic Fig.39 and Figs.333-347.

like

"

No plane and no axis of symmetry, but symmetry solelywith respect to the central point. Figs.34 and 40 show typical triclinic crystals.See also Figs.359-366 VI.

TRICLINIC

SYSTEM.

20

CRYSTALLOGRAPHY

26. The relations of the normal classes of the different systems are further and symmetry by the illustrated both as regards the crystallographic axes 35-40. The exterior form is here that bounded accompanying figures, by faces each of which is parallelto a planethrough two of the crystallographic lines. indicated by the central broken Further, there is shown, within axes this,the combination of faces each of which joinsthe extremities of the unit lengthsof the axes. 34

Axinite

Pyroxene

The full understanding of the subjectwill not be gained until after a study of the forms of each system in detail. Nevertheless the student will do well to make himself familiar at the outset here illustrated.

with

35

most

relations

37

Isometric

It will be shown

the fundamental

Tetragonal later that the symmetry

clearlyand easilyexhibited by the in Art. 39 et seq.

use

Hexagonal

of the different classes can be of the different projections explained

MORPHOLOGICAL

GENERAL

RELATIONS

OF

21

CRYSTALS

the different sysModels. Glass (or transparent celluloid)models illustrating tems, having the forms shown in Figs.35-40, will be very useful to the student,especially relations as regards symmetry. in learningthe fundamental They should show within,the or more simple crystallographic axes, and by colored threads or wires,the outlines of one Models of wood are also made in great variety and perfectionof form; these are forms. of crystallography. to the student in mastering the principles indispensable 27.

"

Monoclinic

Orthorhombic

Triclinic

It will appear Forms. Hemihedral 28. So-called and Holohedral later that each crystal form * of the normal class in a given system embraces all the faces which have a like geometricalpositionwith reference to the such a form is said to be holohedral (from bXos,complete, crystallograpfeic axes; and Mpz, face). On the other hand, under the classes of lower symmetry, a certain form, while necessarily having all the faces which the symmetry of as the correspondingform allows,may yet have but halfas many called on this account the normal class ; these half-faced forms are sometimes hemihedral. Furthermore, it will be seen that,in such cases, to the given holohedral form there correspondtwo similar and complementary hemihedral which forms, called respectively positiveand negative (or right and left), togetherembrace all of its faces. "

41

43

Octahedron

Positive Tetrahedron

Negative Tetrahedron

In the normal A singleexample will help to make the above statement intelligible. " holohedral" form with all class of the isometric system, the octahedron (Fig. 41) is a the possiblefaces at equal which are alike in that they meet the axes eightin number In the tetrahedral class of the same distances. system, the forms are referred to the same defined in Art. 19 (and more fullylater)calls for crystallographic axes, but the symmetry but four similar faces having the positiondescribed. hedral/' These yielda four-faced,or "hemihedron, form, the tetrahedron. Figures 42 and 43 show the positiveand negative tetrawhich together,it will be seen, embrace all the faces of the octahedron, Fig. 41. "

"

*

The

use

of the word/orw

is defined in Art. 37

22

CRYSTALLOGRAPHY

In ut

certain classes of stilllower symmetry

a

given crystalform

one-quarter of the faces belongingto the correspondingnormal

have

may

form, and,

same method, such a form is sometimes called tetartohedral. kinds of hemihedral (and tetartohedral) development of the various possible forms under a given system has played a prominent part in the crystallography of the past, but it leads to much less complexity and is distinctly

after the The

of the symmetry

the direct statement

simple than

in each

The

case.

latter

followed in this work, and the subjectof hemihesystematically drism is dismissed with the brief (and incomplete)statements of this and the followingparagraphs. In several of the systems, forms 29. Hemimorphic Forms. occur method

is

"

the classes of lower symmetry than that of the normal characterized by this : that the faces present are only those under

class which

are

belongingto one axis of of extremity an symmetry (and crystallographic axis) Such forms are convenientlycalled hemimorphic (half-form).A simple example under the hexagonal It is obvious that hemimorphic system is given in Fig. 44. .

forms 30.

have

Molecular

no

center

Networks.

of symmetry. "

Much

light has

cently re-

the relations existing between thrown upon the one the different types of crystals, on hand, and of of crystals, the other, these to the physicalpropertied on the various of consideration of the methods possible by of the of the molecules which are crystals grouping This subject,very early supposed to be built up. J. D. Dana), treated by Haiiy and others (including Zincite discussed at Frankenheim and later by was lengthby More Bravais. recentlyit has been extended and elaborated by Sohncke, Wulff, Schonflies, Fedorow, Barlow, and others. All solid bodies,as stated in Art. 7, are believed to be made up of definite molecules. Of the form of the physicalunits,called the physical,or crystal, molecules nothingis definitely known, and though theoryhas something to say about their size,it is enough here to understand that they are almost infinitely small,so small that the surface of a solid e.g., of a crystal may appear to the touch and to the eye, even when assisted by a powerful microscope, as smooth. perfectly The molecules are further believed to be not in contact but separatedfrom if in contact, it would be impossibleto explainthe motion to another one which the sensible heat of the body is due, or the transmission of radiation motion of the ether, (radiantheat and light)through the mass by the wave is believed to penetrate the body. which When from the state of a liquidor a gas to that of a solid, a body passes under such conditions as to allow perfectly free action to the forces acting between the molecules, the result is a crystal of some definite type as regards that the The simplesthypothesiswhich can be made assumes symmetry. form of the crystalis determined by the way in which the molecules group themselves togetherin a position of equilibriumunder the action of the intermolecular forces. the molecules vary in magnitude and As, however, the forces between direction from one of to type crystal another, the resultant grouping of the molecules must also vary, particularly as regardsthe distance between them been

'

"

"

"

24

CRYSTALLOGRAPHY

for This is found to be true in the study of crystals, then II, nn, and so on. those whose all bears forms are, in nearly the common some position cases, simple relation to the assumed axes; forms whose position is complex are usuallypresent only as small faces on the simple predominating forms, that So-called vicinal forms, that is,forms taking is,as modifications of themforms to which they approximate very the place of the simple fundamental are closelyin angularposition,

exceptional.

Orthorhombic

Point System

tion the numerical rela(2) When a varietyof faces occur on the same crystal, existingbetween them (that which fixes their position)must be rational and, as stated in (1),a simplenumerical ratio is to be expectedin the common This, as explainedlater, cases. is found by experienceto be a fundamental law of all crystals.Thus, in Fig.47, starting with a face meeting the section II would be in mm, b and a; nn would

common face,and for it the ratio is 1 : 2 in the directions be also common with the ratio 2:1. (3) If a crystalshows the natural easy fracture,called cleavage,due to a minimum of cohesion,the cleavagesurface must be a surface of relatively faces. great molecular crowding,that is,one of the common fundamental or This follows (and thus gives a partial,though not complete,explanationof cleavage)since it admits of easy proof that that plane in which the points closest together is farthest separated from the next molecular are plane. Thus in Fig 47 compare the distance separatingtwo adjoiningplanesparallel to bb or aa, then two parallelto Illustrations of the above II,nn, etc mm, will be found under the specialdiscussion of the subjectof cleavage. a

32.

of Molecular

Kinds

described molecules.

shows

RELATIONS

MORPHOLOGICAL

GENERAL

that

there

OF

CRYSTALS

25

The discussion on the basis just Groupings. fourteen are possibletypes of arrangement of the "

with the seven classes defined t he normal classes of the six systems in Art. 25 as representing respectively with also that of the trigonal (orthe agonal rhombohedral) division of the hexOf the fourteen, system. metric three groupings belong to the isosystem (theseare shown, for in Fig. 48 from sake of illustration, Groth; a, cube lattice;", cubecentered lattice; c, face centered These

agree

as

to their

symmetry

Isometric

cube

lattice) ; two each to the

one

system;

two

to the

hexagonal and the rhombohedral; four

to the

Lattices

tetragonal;

monoclinic,and

one

to the orthorhombic

to the triclinic.

the theory fails to explainthe exabove outlined, istence of the classes under the several systems of a symmetry lower than that and later by of the normal class. It has been shown, however, by Sohncke admits of the extension. that The and Schonflies theory Barlow, Fedorow, idea supposed by Sohncke is this: that,instead of the simple form shown, the be conceived of as consist of a double system, one of which may network may if to other one relative the as to side,or (2)as if pushed (1) having a position if rotated in both as rotated about an axis,or finally as (2)and displaced (3) makes it in of the The impossibleto develop it as subject complexity (1) here. It must suffice to say that with this extension Sohncke concludes that has been further extended to 230 This number there are 65 possible groups. the stillremains true that these fall into 32 it other authors named, but by observed groups of forms all the and thus distinct types as regardssymmetry, described under the several systems, have a theoretical crystals, among In its simplestform, as

explanation, A completeunderstandingof this subjectcan Literature. only be gained careful study of the many papers devoted to it. An excellent and very clear summary of the whole subjectis given by Groth in the fourth edition of his Physikalische 1905, and by Sommerfeldt, in his PhysiKrystallographie, kalische Kristallographie, 1907. 33. X-Rays and In 1912, while attempting to Crystal Structure. and light,Dr. Laue, of the between character a i n X-rays similarity prove Universityof Zurich conceived the idea of using the ordered arrangement of " the molecules or atoms of a crystal diffraction grating for their analysis a as By placinga photographicplatebehind a crystalsection which in turn lay in the path of a beam of X-rays he found that not only did the developed in show dark its center where the direct pencilof the X-rays had a plate spot hit it but it also showed a largenumber of smaller spots arranged around the formed in a regulargeometricalpattern. This pattern was center by the interference of waves which had been diffracted in different directions by the he succeeded in proving that molecular structure of the crystal. In this way of the class to same X-rays belong phenomena as lightbut with a much shorter wave The lengths experiment showed indeed that the wave length. the layersof between of the X-rays must be comparable to the distances molecular particles of crystals. Another, and, from the crystallographic point the furnishing of a of view, a very important,result of this investigation was "

by

a

"

"

26

CRYSTALLOGRAPHY

method for the study of the internal structure of crystals.The positionof smaller dark spots in the Laue photographs corresponded to that of various planes existingin the crystalnetwork parallelto possiblecrystal faces and their arrangement indicated the symmetry of the crystal. of Laue and his colleagues another fruitful Followingthese investigations of crystalstructure method of investigation of devised means by X-rays was of X-rays meets the by W. H. and W. L. Bragg. In this method the beam section with and acute the of incidence reflection of crystal varying angles the rays is studied. The reflected from the surface of not the X-rays are section like lightrays but because of their short wave lengthspenetrate the crystalsection and are reflected from the successive layersof its molecular In studying the reflection phenomena we structure. have to consider the each other of these different wave effect upon the from trains originating different layers of the crystal. In general these various reflected waves would be in different phases of vibration and so would tend to interfere with each other with the consequent cessation of all vibrations. But with a certain the different of incidence and reflection it would that flected reangle happen the would from the on same crystal phase of possess rays emergence therefore reinforce each other. vibration and would This angle would vary with the wave lengthof the X-ray used (forit has been found that the wave lengthof X-rays varies with the metal that is used as the anticathode in the X-ray bulb) and with the spacingbetween the molecular layersof the mineral used. It is also obvious that there might be other angles of incidence at which the successive wave trains would each differ in phase by two or even whole wave more flected lengthsfrom the precedingone and a similar strong rethe beam obtained. the of use a angles By specialX-ray spectrometer If the be accuratelymeasured. at which these reflections take place can character of the X-ray used is therefore kept constant these anglesof reflection the between t he the data for calculating distance sive succesgive necessary molecular layersin the particular mineral used and for the direction ular perpendicularto the surface used for reflection. The spacingof the moleclayerswas found to vary with different substances and in different directions in the same substance and by making a series of observations it has been possibleto arrive at some conclusions as to the interesting very character of the molecular structure of certain minerals as well as to the pounds. relationship existingbetween the structures of different but related comThe possibilities in attack these methods of are great lying very and unquestionablymuch will information concerningcrystalstructure new the and An be available. the soon excellent summary methods of employed " " results already obtained will be found in X-rays and Crystal Structure by W. H. and W. L. Bragg, 1915. the

GENERAL

MATHEMATICAL

RELATIONS

OF

CRYSTALS 34. Axial Ratio, Axial Plane. have been The crystallographic axes defined (Art.22) as certain lines, usuallydetermined by the symmetry, which and in the determination of used in the description of the faces of crystals, are their positionand angular inclination. With these objectsin view, certain "

MATHEMATICAL

GENERAL

lengthsof these

assumed

are

axes

RELATIONS

as

OF

units to which

27

CRYSTALS

the

occurringfaces

are

referred. lettered a, b, c, to correspond to the scheme in The axes are, in general, Fig.49. If two of the axes are equal,they are designateda, a, c; if the three In one system, the hexagonal,there are are equal,a, a, a. 49

four axes, lettered a, a, a, c. Further, in the systems other

than the isometric, one the unit to which the other are referred;hence the lengths of the axes axes express for sulphur (orthorhombic, axial ratio. Thus t he strictly see Fig.49) the axial ratio is of the horizontal

axes

a

rutile

For a

: c

=

:

b

is taken

: c

=

as

0'8131

:

1

:

1'9034.

it is (tetragonal) 1

:

0'64415,

or,

simply,

c

=

0'64415.

is called an axial plane, The plane of any two of the axes and the space included by the three axial planesis an octant, since the total space about the center is thus divided by the three axes into eightparts. In the hexagonal system, however, Orthorhombic where there are three horizontal axes, the space about CrystalAxes the center is divided into 12 parts,or sectants. 35. Parameters, Indices, Symbol. Parameters. The parameters of a plane consist of a series of numbers which express the relative intercepts of that plane upon the crys"

axes. tallographic They are lished given in terms of the estabunit lengths of those For example, in Fig. axes. 50 let the lines OX, OY, OZ

be taken as the directions of the crystallographic axes, and let OA, OB, OC represent their unit lengths, designated

(alwaysin the same the letters a, b, c. interceptsfor the

order)by Then

the

plane (1) OK, OL; for the plane (2)ANM they are But in terms OA, ON, OM. of the unit lengths of the these give the following axes

HKL

are

OH,

parameters, and

(1) (2)

la

2c.

It is to be noted that since

and the two planes HKL the same, hence crystallographically these two sets of parameters are considered to be identical. Obviously each of them may be changed into the other by multiplying(ordividing)by 4.

MNA

are

parallelto each other and

28

CRYSTALLOGRAPHY

Indices and Symbol. Simplified and abbreviated expressions which have been derived from the parameters of a crystalform are commonly used to These are known indices. axes. as give its relations to the crystallographic of derivingindices have been devised and A number of different methods in use several are at present. The so-called Miller indices are most widely be will used in this work.* and Below, a description exclusively employed of the other important systems of indices is given togetherwith the necessary directions for transformingone type into another. be derived from the parameters of any form by The Miller indices may and clearingof fractions if necessary. For instance taking their reciprocals take the two sets of parameters as given above.

(1) \a

:

|6

and

\c,

:

(2)

case

:

|6

:

2c.

la

:

|6

:

ic.

obtain

By inversion of these expressionswe (1) 4a : 36 : 2c, and In the

la

(2)

to clear of

(2)it is necessary (2) 4a : 36 : 2c. of

fractions, giving

The letters indicatingthe The indices of this form then are 4 a : 3 6 : 2 c. different axes are commonly dropped and the indices in this case would be the different axes on written simply as 432, the intercepts being indicated by are the order in which the numbers given. A generalexpressionfrequentlyused for the indices of a form belonging is hkl. In the to any axes crystalsystem which has three crystallographic becomes hkil. If the parameters hexagonal system, which has four axes, this of a form be written so that they are fractions with the numerators always the same will become the correspondingindices. as unity then the denominators The

generalexpressionin this

would

case

therefore be

T

r

rl K

7L

"

symbol of a given form is the indices of the face of that form which The symbol is comaxes. monly simplestrelations to the crystallographic used to designatethe whole form. the relations between paramVarious examples are given below illustrating eters The

has the

and

indices.

fe }a

16 16 26 006

la

GO6

la

la la

la

Miller's Symbol

Parameters

"

16 26 006

}

lcl

2c/ ooci ooc ooc

)

=

%a

:

kb

=

=

=

:

Ic

=

221

:

%c

=

212

:

jc

=

201 210

\a

:

"

:fc

=

ja

:

"6

:

"c

=

100

in behind on the a axis,or If the axial interceptsare measured left on the 6 axis,or below on the c axis, they are called negative,and signis placed over the correspondingnumber of the indices;as

*In method

the hexagonal system of Miller.

the

-\b

:

minus

Indices

Parameters

-\a -io

to the a

\c

indices used

=

are

221 201

those adapted by Bravais

after the

MATHEMATICAL

GENERAL Different Systems The above. preceded by a number

of 'Indices.

RELATIONS

The

Weiss

indices

OF

are

the

29

CRYSTALS

same

as

the

parameters

representedby the letters a, b and c, each being indicatingthe relative interceptof the face in question upon that pyramid face might be represented particularaxis. For instance, a possibleorthorhombic be converted indices may into the Miller indices by inversion la : 26 : fc. The Weiss as In the Naumann and clearingof fractions, the above symbol becoming then 213. indices the unit pyramidal form is indicated by O in the isometric system where the three crystal differ in their unit lengths. unit lengths or by P where the axes all have the same axes mPn For other forms the indices become (ormOn) in which m gives the interceptupon the of the horizontal axes vertical axis,c, and n the interceptupon one (a or 6),the intercept To which the other at horizontal axis horizontal axis always unity. being particular upon be indicated by a mark refers may it as n for the b axis,ft or n' for the over this number If the interceptm or n is unity it is omitted from the indices. The pyramid face a axis. would therefore in the Naumann notation be represented by used as an example above modified J. D. Dana the Naumann |P2. Other examples are given in the table below. He indices by substitutinga hyphen for the letter P or O and i for the infinity sign,oo the only parameter differing pyramid form simply by 1. When designated the fundamental the vertical axis,it was from unity was which referred to the interceptupon that one written alone; for example the pyramid face having the parameter relations of la : 16 : 2c and Dana indices are easilyconverted into the The Naumann would be indicated by 2. in the proper Miller indices by arranging them tions. order,invertingand then clearingof fracmethod of deriving indices. This has the Goldschmidt has proposed another advantage that the indices for any particularface can be derived directlyfrom the position of its pole on the gnomonic projection. The first number gives the linear positionof the pole in respect to the left to right medial line of the projectionand in terms of the unit second figure similarlygives the distance of the projection (seeArt. 84). The pace stitute positionof the pole in reference to the front to back medial line. These two figurescondescribed

different

are

axes

.

should be the same the of the face. If the two numbers Goldschmidt indices are easilyconverted into the Miller indices figureand clearingof fractions and eliminatingany oo sign. indices for the hexagonal the Miller and the Miller-Bravais

the Goldschmidt is omitted. The by adding 1 as the third The relations between system are given in Art.

indices

second

EXAMPLES

OF

169.

INDICES

ACCORDING NOTATION

TO

VARIOUS

SYSTEMS

OF

Indices. The study of crystalshas established of Rational the axes the interceptson for the the general law that the ratios between different faces on a crystalcan always be expressedby rational numbers. 36.

Law

"

1 : V2, etc. be 1:2, 2:1, 2:3, 1 : oo, etc., but never These ratios may be either whole the values of hkl in the Miller symbols must Hence always numbers or zero. If the form whose interceptson the axes a, 6, c determine their assumed is well chosen,these numerical unit lengths the unit form as it is called In the Miller symbols, values of the indices are in most cases simple. very 0 and the numbers from 1 to 6 are most common. in The above law, which has been established as the result of experience, fact follows from the consideration of the molecular structure as hinted at in "

"

an

earlier paragraph

(Art.31).

30

CRYSTALLOGRAPHY

includes all the faces which form in crystallography the to relative have a like position The full planes,or axes, of symmetry. after will be of this a study of the several It appreciated meaning systems. will be seen that in the most generalcase, that of a form having the symbol unit axes at unequal (hkl),whose planes meet the assumed be forty-eight like faces in the isometric lengths,there must system * (seeFig.121),twenty-fourin the hexagonal(Fig.226), sixteen in the tetragonal(Fig.187),eightin the orthorhombic (Fig.51),four in the monoclinic,and two in the triclinic. In the first four systems the faces named yieldan enclosed solid, and hence the form is called a closed form; in the remaining 37.

Form.

A

"

systems this is not true, and such forms in these and called open forms. Fig. 298 shows a crystal other cases are bounded by three pairsof unlike faces;each pair is hence an Figs.52-55 show open forms. open form. The unit or fundamentalform is one where parameters correspond unit lengths of the axes. to the assumed Fig. 51 shows the unit pyramid of sulphur whose symbol is (111);it has eight similar faces,the positionof which determines the ratio of the axes given in Art. 34. two

52

53

Basal Pinacoid

Prism

(001)

(110)(/i/cO)

54

Dome

Dome

(101),(MM) *

The

normal

(Oil),(OW) cla,ssis referred to in each

case.

32

CRYSTALLOGRAPHY

the point of intersection of crystal(i.e.

its

axes). From this crystallographic drawn to the successive faces of the crystaland the surface of the sphere. The continued until they meet pointsin which these normals touch that surface locate the poles of the respectivefaces and togetherform the spherical projectionof the crystal. The method of formation and the character of the is shown spherical projection in Fig. 57. It is to be noted that all lie the polesof faces which the in the same zone on i.e. faces whose tersectio incrystal, lines are mutually fall upon the same parallel, great circle on the sphere. TTulTls illustrated in the of the figure in the case a-d-a and a-o-d. versely, Conzone of course, all faces whose polesfallon the same great circle of the spherical lie in the projectionmust A face whose zone. same at the intersection falls pole of two or more great circles SphericalProjection(afterPenfield) indelies in two or more pendent zones, as for instance o(lll),in Fig. 57. The angular relations ing between the faces on the crystalare of course preservedin the anglesexistbetween their respective poles on the sphericalprojection. The angles between the poles,however, are the supplementary anglesto those between the faces on the crystal, The in Fig. 58. shown as those which are are supplementary angles commonly measured and recorded when studying a crystal,see Art. 230. The sphericalprojectionis very useful in getting a mental pictureof the relations existingbetween the various faces and zones but because of a crystal upon its nature does not permit of the close study and accurate measurements that may be made on the other described below which are made on projections plane surfaces. 41. The StereographicProjection. The stereo* graphicprojectionmay be best considered as derived from the sphericalprojectionin the followingmanThe plane of the projectionis commonly taken as the equatorial ner. of plane the sphere. Imaginary lines are drawn from the polesof the spherical projectionto the south pole of the sphere. The points in which these lines piercethe plane of the equator locate the polesin the stereographic projection. The relation between the two projectionsis shown in Fig. 59. common

center

normals

are

"

projection sioij

"[

GENERAL

OF

RELATIONS

MATHEMATICAL

33

CRYSTALS

projectionwithout the foreshortening stereographic Fig. 60 shows the same of Fig. 59. Commonly only the polesthat lie in the northern hemisphere, projection. includingthose on the equator, are transferred to the stereographic Certain facts concerningthe stereographic projectionneed to be noted. Its most importantcharac-*

ter is that all circles or arcs

on

projection

are

of true

arcs

cular cir-

spherical projectedas

the

circles on

the

stereographicprojection.* The poles of all crystal faces that are parallelto the vertical crystallogrator phic axis fall on the equaof the sphericalprojection and

occupy

oft 111

the

in the stereographic 010 positions projection. The

same

pole of a horizontal face of will fall on the center the stereographicprojection. All north and south meridians of the spherical as projectionwill appear straightradial lines in the stereographic projection ing of circles havarcs as (i.e. infinite radii). Other Relation between Sphericaland Stereographic Projections ical great circles on the spheras as projection, alreadystated,will be transferred to the stereographic 60. in shown of all these circular arcs. are Fig. Examples The angularrelations between the polesof the various faces are preserved in the stereographic projectionbut the linear distance correspondingto a of degree arc naturallyincreases from the center of the projectiontoward its This is illustrated in Fig. 61 where the circle represents a circumference. and the line A-B vertical section through the spherical represents projection the trace of the horizontal plane of the stereographic projection.A point 20" from N on the sphere is projectedto the point a on the stereographic In this way N is projectedto b,etc. a protractor a point45" from projection, be made of which angular distances from the center of the can by means Fig.62 representssuch stereographic projectioncan be readilydetermined. relation mathematical The which devised was a Penfield.f by protractor and its angular between the linear distance from the center of the projection value is seen by study of Fig.61. If the radius of the circle of the projection is taken as unity the distance from its center to any desired pointis equal to half of the anglerepresented. For instance the distance the tangent of one *

f

For proof of this statement see Penfield,Am. Jour. Sci.,11, 10, 1901. tained This protractor and the other protractors and scales used by Penfield ?pan be obversity, from the Mineralogical Laboratory of the Sheffield Scientific School of Yale UniNew Haven, Ct.

34

CR YSTALLO

GR

APH

Y

60

duo

a

dlio

01

a 010

a

Projectionof Stereographic

the Isometric

100

Forms, Cube, Octahedron, and Dodecahedron

61

the center to the point a is equivalentto the tangent of 10",to point c tangent of 35",etc. Fig. 63 represents a chart used by Penfield for making stereographic grees. projections.The circle has a diameter of 14 cm. and is graduated to deWith it go certain scales that are very useful in locatingthe desired pointsand zonal circles. These will be brieflydescribed later. from

the

MATHEMATICAL

GENERAL

RELATIONS

OF

CRYSTALS

35

of the principles of the stereographic detailed descriptions projection reader the is referred to the various books and of its use and the methods the titlesof which are given beyond. It is possible here to giveonly articles, important methods of construction used. a brief outline of the more For

62

StereographicProtractor

for

plottingStereographicProjections(afterPenfield; reduced one-half)

(1) To locate the poleofa facelyingon a known north and south great circle, of the proangular distance from the center or a point on the circumference jection tion protractor,Fig.62, or the tangent relabeinggiven. The stereographic The stated above, gives the proper distance. as poles labeled o (isometric be in this located octahedron),Fig.60, may way. of the arc of a great circle which is not a north (2) To locate the projection the equator. The and south meridian or projectionsof three points on the the be known. since must arc projectionof the circle will be stilla Then, tion be determined circular arc, its positioncan by the usual geometricconstrucfor a circle with three pointson its arc given. If,as is commonly the the great circle crosses the equator and the angle it case, the pointswhere it is possible to get the radius of the promakes with the equator are known jected from Scale No. 1, Fig.63. The location of such a desired arc directly in Fig.64. The arcs shown is shown in Fig.60 were also located in this arc .

its

way.

locate the

position of the poleof a facelyingon a known great circle, ference south a meridian, its anglefrom a pointon the circumthe known. of small vertical The projectedarc a of projection being cumferenc whose radius is the known angle,is drawn about the point on the circircle, and since all pointson this arc of the projection have the must requiredangular distance from the given point the intersection of this circle with the known great circle will give the desired point. The radius of the projectedarc of the small vertical circle can be determined by findingthe positionof three pointson the projectionwhich have the requiredangular distance from of the projectionand the point given on the circumference then obtainingthe center of the requiredcircle in the usual way. Or by the Scale obtained radius is of No. the use directly. It is 2, Fig. 63, required the of the circumference to be noted that the known projection, point on is not the actual center of while the stereographic of the small circle, center the projectedarc. The will lie outside the circumference on a concenter tinuation of the radial line that joinsthe given point with the center of the if the radius of the requiredarc is taken from projection.Therefore,even (3) To

which

is not

north

and

36

CRYSTALLOGRAPHY

II

s

i "a

E 3"

E

r3-

P

RELATIONS

MATHEMATICAL

GENERAL

OF

37

CRYSTALS

to establish at least one Scale No. 2, it will be necessary point on the reThese methods of construction are circle in order to find its center. of the pole n (isotrated in Fig.65, in which the positionis determined

Zed

Location

of the

arc

of

a

Projectionat great circle in the Stereographic above

a

givenangle

the equator

a

Oil

dllQ

Location

of

Projection n(211), in Stereographic pole of trapezohedron,

metric

trapezohedron)which polesa (isometric cube) and angle(35J")with a.

lies o

on

the

great circle passing through the

(isometricoctahedron),and makes

a

known

38

CRYSTALLOGRAPHY

(4) To locate the positionof the poleof a facegiven the anglesbetween it and two other faceswhose poleslie within the divided circle. Circumscribe about known the poles of the two points small circles with the proper radii and The two small circles the desired point will be located at their intersection. intersect in two points. In touch at only a singlepoint or they may may the requiredconditions. both pointswill meet The positions the latter case of the projectedsmall circles are readilyfound by drawing radii from the center of the projection through the two known poles and then layingoff on these radii pointson either side of the known poleswith the requiredangular these two distances. The center is then found between pointsin each case This line of this circle will then be everyand a circle drawn through them. where from the known of degreesaway the requirednumber quired pole. The reof the StereographicProtractor, pointsmay be found readilyby means Fig. 62, remembering that the zero point on the protractor must always lie at the center of the projection. This construction is illustrated in Fig.66, in which the pointss (isometric hexoctahedron),are 22" 12' and 19" 5' from the pointso (isometric octahedron),and d (isometricdodecahedron). It is be noted to here, also,that while the points o and d are the stereographic of the circles about centers them, the actual centers are points which are the center of the projection. out from farther somewhat

a

010

duo

a

Location

of two

loo

poles of hexoctahedron, s,

in

Projection Stereographic

the angle between two (5) To measure given points on the stereographic If the the two lie circumference of the projectionthe on projection. points read from of the circle. If they between them is the divisions angle directly lie on the same the angle is given by the use radial line in the projection, of In is other 62. it the StereographicProtractor, first to cases Fig. necessary which the two points lie. This is most find the arc of a great circle upon easilyaccomplished by the use of a transparent celluloid protractor upon Place this protractor over which the arcs of great circles are given,Fig. 67. the center of the projection the projection with its center coinciding with and turn it about Note the pointswhere until the requiredgreat circle is found. this circle intersects the circumference of the projection. Then place a small vertical circles are which second transparent protractor on given, Fig. 68, over the projectionwith its ends on the pointsof the circumference

40

CRYSTALLOGRAPHY

by drawing the radial line through N and A and measuring with the stereographicprotractor an angleof 90" from A to the pointB. The requiredarc will pass through this pointand the pointsp and pf which are each 90" away from the pointsat which the line A-N-B the divided circle. The crosses this great circle givesthe value of the on angle between x and y measured requiredangle at A. This is most 69 readilymeasured by the use of the transparentprotractor showing small circles, Fig.68. This is placedacross the projection from p to p' and the between x and angle y read directly from it.

Wiilfinghas described a stereographic net, which givesboth great and

from

the net to

a

small circles for every two degrees. Over this is placeda sheet of tracingpaper upon which the stereoIf the graphic projectionis made. is fastened at the of the center paper that it be so into turned can drawing various positionsin respect to the net below, the various stereographic great and small circlesneeded can be sketched directly the drawing. upon Or the requiredpointscan be transferred of three point dividers. separate drawing by means of the stereographic will be given later projection

Examples of the use under each crystal system.

70

no

^100 Relation between

42. The

Sphericaland Gnomonic

Projections

Gnomonic Projection. The characters of the gnomonic projection best be understood can by consideringit to be derived from the sphericalprojection (seeArt. 40). In the case of the gnomonic projection the plane of the projection is usuallytaken as the horizontal plane which "

,

GENERAL

MATHEMATICAL

RELATIONS

OF

CRYSTALS

41

lies tangent to the north pole of the sphere of the spherical aginary projection. Imlines are then taken from the center of the sphere through the poles of the crystalfaces that lie on its surface and extended until they touch the plane of the projection. The points in which these lines touch that plane constitute the gnomonic projection of the forms represented. Fig. 70 shows the relations between the spherical and gnomonic projections, using the same isometric crystalforms (cube,octahedron and dodecahedron) as ployed emwere to illustrate the principles of the StereographicProjection(Art.41). set of forms. Fig.71 shows the gnomonic projectionof the same

100

Gnomonic

Projectionof Cube, Octahedron

and

Dodecahedron

The

followingfeatures of the gnomonic projectionare important. All the sphericalprojectionbecome ferred on straightlines when transto tho gnomonic. The polesof a series of crystalfaces which belong in the same lie on a straight zone the gnomonic projection, on will,therefore, line. This primary distinction between the stereographic and gnomonic projections will be readilyseen by a comparison of Figs.60 and 71. The pole of a horizontal crystal face (like the top face of the cube) will fall at the center of the projection.The poles of vertical crystalfaces will lie on the plane of projection This is shown by a only at infinite distances from the center. consideration of Fig. 70. Such faces are commonly indicated on the projection which indicate the directions in by the use of radial lines or arrows great circles

which

their poles lie. This is illustrated in the

case

of the vertical cube

and

dodecahedron faces in Fig.71. Crystalfaces having a steep inclination with the horizontal plane must frequentlybe indicated in the same way.

42

CRYSTALLOGRAPHY

A simple relation exists between the linear distance from the center of the the projection and to a given point angular distance represented. This is shown in Fig. 72 where the circle is assumed to be a vertical cross-section of the sphere of the sphericalprojectionand the line A-B represents the trace of the plane of the gnomonic projection. It is evident from this figure

d'

B

that if the radius of the circle is taken as unity the linear distances N-a',N-b', etc.,are the tangents of the angles quently 20", 35", etc. Consein the gnomonic projectionthe distance of a givenpolefrom the center of the projection, mental consideringthe fundadistance 0-Ar, Fig. 72, to be unity,is equal to the tangent of the

angle represented.

In the

case

of the stereo-

graphic projectionthis distance is equal to the The stereographicscale,used half the angle,see Art. 41. tangent of one hi trie stereographicprotractor,Fig. 62, can therefore be adapted for use in the gnomonic projectionby taking the point on it reading at twice the of plotting,however, is to make desired angle. The a simplest method direct use of the tangent relation. The distance 0-Nt Fig. 72, is taken at convenient some length and then by multiplyingthis distance by the natural tangent of the angledesired the linear distance of the pole in question from

the

center

is obtained. projection

of the

Frequently

the distance 0-N is taken as 5 cm. In making a gnomonic projection drawn about a circle is commonly the center of the projection, known the fundamental with a as circle, radius equal to this chosen distance. Points th at have an angular distance of 45" with the center pointof the projectionwill lie on the circumference of this circle. Measurement

Commonly

also the

gnomonic

pro-

of

(Ai,A2) on

angle between any two poles the Gnomonic Projection

jectionis surrounded by a square border of two parallel lines on which is indicated the directions in which lie the poles that cannot the projectionbecause of the vertical or on appear inclined their of faces. These characters are shown in position steeply 71. Fig. To measure the angle between two poleson the gnomonic projection. In

MATHEMATICAL

GENERAL

let Ai and

RELATIONS

OF

CRYSTALS

43

A2 be

two pointsthe angle between which is desired. any line a straight through them or, in other words, find the direction of the zonal line upon which they lie. Next erect the line 0-A perpendicular to this zonal line and passingthrough the center 0 of the projection.On this line establish the point N, the distance A-N being equal to the hypothe distance A-P. thenuse of the righttriangleA OP or The point TV is known of the zone the angle-point The angle AiNAz is equal to Ai-Az. as the desired angle between the pointsAI and A2. In the case of zonal lines that pass through the center of the projectionthis angle-pointwill lie on circle at the terminus of the fundamental the circumference of a radius which is at rightanglesto the zonal line in question. In the case of vertical crystalfaces whose poleslie at an infinite distance the center of the projection is itselfthe angle-point.

Fig.73

First draw

explanationof the above method may be given as follows. In Fig. 74 let the circle vertical section through the sphere of the sphericalprojectionand the line a N-A the trace of the plane of the gnomonic projection. Let the line A-C represent the intersection of a zonal plane lying at rightangles to the plane of the drawing. The zonal line representingthe intersection of this zonal plane with the plane of the gnomonic projection would therefore be a straight line through point A which would be 74 ing. perpendicularto the plane of the drawThe angle between N O A any two poles mined lying on this zonal line would be deterby the angle formed by the lines drawn from these poles to the point C. consider this zonal line which Ifjwe passes through A perpendicularto the drawmg as an axis around which we revolve its zonal plane, the point may The

represent

C may be moved that it will lie'in so the plane of the gnomonic projection and fall at N, the distance A-N being The character of the equal to A-C. point C has not been changed by this the transfer and the point N becomes angle-point of the zonal line running through A and the angle between any two poles on this line may be determined by running lines from them to this point and measuring the included angle. The point N lies on the line running through O (centerof the gnomonic projection)and the distance A-N is equal to the hypothenuse, A-C, of the right triangleone side of which is equal to A-O and the other to O-C circle). (theraclius of the fundamental

zonal lines on the gnomonic projection. the anglebetween parallel Zone In Fig. 75 let the two lines 1 and Zone 2 represent two parallel zonal lines the angle between which is desired. Draw the.radial line trom the center of the projection, 0, at rightangles to these zonal lines intersecting The 0-P them at the pointsAI and A2. Make at rightanglesto 0-AiA2. The construction angle AiPAz will give the anglebetween the two zones. will be readilyunderstood if the figureis supposed to be turned on the line 0-AiAz as on an axis until the point P becomes the center of the spherical projection The broken arc now represents a vertical cross section of the sphere of the spherical projectionand the points"i and 02 the pointswhere the two zonal lines cross it. The angle at P is obviouslythe angle between To

the two The

measure

zones.

angle between Zone 2 and the prism zone, the line of which lies at the gnomonic projection, is given in Fig. 75 by the angle A%PN on infinity which

is the

same

as

44

CRYSTALLOGRAPHY

A gnomonic net, similar in character to the stereographic net described in Art. 41, is useful in plottingthe pointsof a projection in making measor urements it. The lines it the of straight represent upon upon projection the arcs

of

great circles of the spherical

while projection,

the

hyperbolacurves

represent those of the circles.

small vertical

The

gnomonic projectionis most commonly used in connection with the measurement of crystalanglesby of the two-circle goniometer. means This use will be explainedlater,see Art. 232. For more detailed descriptions of the principles and uses of the gnomonic projection the reader is referred to the literature listed below. References

on

Gnomonic

the

Stereographic and Projections.

In addition to the descriptionsof these of the angle between parallelprojectionsthat are given in many general the Gnomonic zones on crystallographictexts the following books Projection of value. and papers are Die Anwendung der stereographischen Projektion bei kristallographiBoecke, H. E. schen Untersuchungen, 1911. Die gnomonische Projektionin ihrer Anwendung auf kris-

Measurement

tallographische Aufgaben, 1913. Gnomonic Evans, J. W. Projectionsin two planes. Min. Mag., 14, 149, 1905. V. Uber 1887. Goldschmidt, Projektion und graphischeKristallberechnung, 1914. und Kristallzeichnung, Gossner, B. Kristallberechnung The Gnomonic of The Construction Hilton, H. Net, Min. Mag., 14, 18-20, 1904. Some Projections,Min. Mag., 14, 99-103, 1905. Crystallographic Applications of the Gnomonic Min. Mag., 14, 104-108, 1905. Projectionto Crystallography, Hutchinson, A. On a protractor for use in constructingstereographicand gnomonic of the sphere,Min. Mag., 15,94-112, 1908. projections The Gnomonic Palache, Charles. Projection. Amer. Min., 6, 67, 1920. Penfield,S. L. The StereographicProjection and Its Possibilities from a Graphical in CrystalOn the Solution of Problems Standpoint,Am. J. Sci., lography 9, 1-24, 115-144, 1901. of Graphical Methods based upon by Means Spherical and Plane Trigonometry. Am. J. Sci.,14, 249-284, 1902. On the Drawing of Crystalsfrom Stereographicand Gnomonic Projections, Am. J. Sci.,21, 206-215, 1906. On the Advantages of the Gnomonic Smith, G. H. H. tion Projecand its use in the Drawing of Crystals,Min. Mag., 13, 309-321, 1903.

43.

Angles between

Faces. The anglesmost veniently conwith the Miller symbols, and those given tween in this work, are the normal angles, that is,the anglesbethe polesor normals to the facts,measured arcs on of great circles joining the polesas shown on the stereo Chrysolite graphicprojection. These normal anglesare the supplements of the actual interfacial angles,as has been explained. "

used

The relations between these normal angles,for example in a given zone, is much simpler than those existing between the actual interfacial angles. Thus it is always true that,for a series of faces in the same angle between two end faces is equal to the zone, the normal of the angles of faces fallingbetween. Thus sum (Figs.76, 77) the normal angle of

GENERAL

MATHEMATICAL

RELATIONS

OF

45

CRYSTALS

of aw(100 A 110),ms(110 A 120), and s6(120 A 010). A 010) is the sum relation holds true in all the systems. Furthermore, it will be seen that,supposing oca! (Fig.77) is a plane of symmetry

06(100

the

orthorhombic

system,

the

A

110,

44.

in

77

am

or

as

angle

(Fig. 76), is half 110(rara'").Similarly 010 A 120(6s) is half the angle 120 A 120(ss')jagain, 100 A lll(ae) is the complement of half the angle 111 A 111(66')and 010 A lll(6e)the_compleof half the angle 111 A 111(60. ment Here, as throughout this work, the sign A is used to represent the angle between two faces,usually designated by letters. 100

the angle 110

This

A

of the Stereographic fcoio Projection to Exhibit the Symmetry. The symmetry of any classes may of the crystalline one be readilyexhibited by the help of the stereographic projection. The axes of binary,trigonal, tetragonaland hexagonal symmetry Use

010

ft

"

are represented respectively by the following signs: Further,a plane of stereographicProjection of Faces on Chrysolite by a full symmetry is represented Crystal,Fig. 76 while a dotted line (zone-circle), line indicates that the plane of symmetry is wanting. The positionof the is shown by arrows at the extremities of the lines. The axes crystallographic poleof a face in the upper half of the crystal (above the planeof projection) is representedby a cross; below by a circle. If two like one .

faces fallin a vertical zone a double within the sign is used, a cross circle. Figs. 91, 128, 140, etc., give illustrations. tween beRelations 45. General Planes

in the

Same

Zone.

Certain important relations between the indices of faces exist All in the same that lie zone. faces to belong to the same zone, tautozonal facesas they are called, tions intersechave their mutual must -

"Y

to parallel

a

given direction,

This direction is known the axis of the zone. as of this zonal axis can The position as be expressedby what is known

see

Art.

38.

symbol. Consider Fig.78, where is representedtwo crystalfaces, axes the crystallographic X, Y and Z. In the ABC, and CDE, intersecting to pass through both faces have been assumed for simplicity, illustration,

the zonal

46

CRYSTALLOGRAPHY

This, of course, is possiblesince any crystal its relative intercepts parallelto itselfwithout altering in the line C-W, which These two planes intersect in which they then the direction of the zonal axis for the zone becomes has been drawn which lie. Let the line 0"P parallelto this direction represent that axis. In the parallelogramof which it is the diagonal the edges have been taken as equal to the lengthof the edge 0-S and its parallel The point P on the zonal axis and therefore the direction distance 0-C. of the axis itselfis fixed by the three coordinates, 0-M, 0-R, and 0-S. By that the it is possible to prove of the consideration of similar triangles means be expressedby, values of these coordinates may point C on the plane may be moved the crystalaxes. on the

0-M

axis

(Ar

=

Z.

lq)a;0-R

-

(Ip

=

hr)b;0-S

-

=

(hq

-

kp)c,

6, c represent the unit lengthsof the three crystallographic axes, and (hkl)and (pqr)represent the indices of the two faces ABC X, Y, These kr CDE. are u expressions usuallysimplified by substituting Iq, vb and 0-S we. v hr, w hq kp, giving 0-M Ip ua, 0-R in question. The three figures[uvw] are said to be the symbol of the zone the o f the values of the three in or reciprocals coordinates, They represent the indices of a point,P, on the zonal axis. They may other words are and subtraction most readilybe obtained by a system of cross-multiplication the indices scheme. Write the of face twice in one following accordingto and the their proper order directlyunder them correspondingindices of the where

a,

and

Z

=

=

=

"

=

=

"

"

=

of each series. Then Cross off the first and last number tiply mulsecond face. the figuresjoinedby the cross see uct lines, below, and substract the prodof the two joinedby lightlines from that of those joined by heavy lines, working from left to right. The three numbers obtained will in their order correspondto u,.v and w. k

I

k

h

I

XXX P u

=

kr

"

Iq,v

=

Ip

"

hr,w

r

q =

hq

"

p

q

kp.

Since the zonal symbol for a given zone be obtained from the indices may two faces lyingin that zone it follows that the indices of every sible posface in that zone must have definite relations to the zonal symbol. For in a zone ing given face with indices (xyz), having the symbol [uvw]the followzonal known the must hold true. as equation, equation,

of any a

ux

-\-vy +

wz

=

0.

it can be readilyshown whether or not a given face can In this way lie in a certain zone. Further if [uvw]be the symbol of one and [efg] that of another intersecting zone it,then the point of intersection will always be the pole of a possible and crystalface. Its indices (hkl)must satisfythe equationsof both zones be obtained by combining them be had by taking the same result may or may and subjecting the symbols of the two zones them to the same sort of crossthemselves originally derived. multiplication by which they were

48

CRYSTALLOGRAPHY

48. with

Relations

the Axes.

the

between In

"

Indices of

and

Plane

a

the

X, Y, and Fig.80 let the three lines, axes crystallographic making any

Angle made Z

by it

represent three

angleswith each unit lengths. their represent with the these axes cutting Let and O-K 0-L. 0-p-P be a intercepts0-H, the plane at normal to the plane HKL intersecting the the surface of and sphericalproenveloping jection p Let hkl represent the indices of the at P. to the Since the line 0-p is normal given form.

80

other and let a, b and Assume face HKL any

c

the triangles plane HKL HOp, KOp and LOp are rightangles and the followingrelations hold true. -

The

angles HOp, KOp, and LOp

OL

=

7

=

"=

we By substituting

.

,

OP

h

This

deduced

KOp;

cos

cos

=

LOp.

arcs

PX, PY

and

PZ

and

OH

=

PY

n

=

PZ.

j cos I

equationis fundamental, and several of the relations given beyond from

^,

have, cos

=

=

=

to the angles repreequal,respectively, sented

are

sphericalprojectionby the

the

on

Qr

HOp;

cos

are

it. 81

no

The

most

useful Z

is that application

when

the axial

anglesare 90", as representedin Fig.

the normals to 100, 010, 001, respectively. Also if the face of the unit pyramid, that is,if its interceptson the axes are

81; then X, Y,

are

taken as a unit lengths

OH

=

a,

OK

=

b,

OL

=

plane

HKL

taken

as

is

the

c.

Then the lines HK, HL, KL give also the intersections of the planes 110, 101, Oil on to these the three axial planes, and their poles are hence at the points fixed by normals

GENERAL

lines drawn

O.

from

MATHEMATICAL

RELATIONS

It will be obvious

from

OF

49

CRYSTALS

this figure,then,that the

relations following

hold true:

These

values

are

tan

(100

A

110)

=

tan

(001

A

101)

=

tan

(001

A

Oil)

=

^; -

;

^-

often used later.

In the case of four faces in a Cotangent and Tangent Relations. the either between all the faces and which we know, angles concerning three faces and all the the indices of three of them, or the angles between indices,it is possibleby either a simple graphicalmethod of plottingor by the missingangle or indices. to determine ^calculation firstlet Fig.82 represent a cross section To illustrate the graphicmethod rhodonite of The the traces the a to zone crystal. prism perpendicular upon and of faces the the direction of the a(100) 6(010) provide drawing plane It is assumed that the positionof the third of the lines of reference X and Y. to its trace upon the plane of and a line drawn parallel face w(110) is known the two the drawing from the point X will give its relative intercepts upon These interceptsdo not correspond to the unit lengths lines of reference. these axes 6 since,rhodonite being triclinic, do not lie in of the axes a and the plane of the drawing but they represent rather the unit lengthsof these that plane. This makes ference, difforeshortened by projectionupon no as axes true will stillbe that all faces in the it since lying prism however, of rhodonite must interceptthese two lines in distances which will have zone of w(110). It is now rational relations to the lengthsof the intercepts sumed asthat a fourth face / has the indices (130) and its angular positionin its indices it must respect to the other faces in the zone is required. From X-X' Y-Y' ratio of 1 to ^. in the and lines of reference the two intercept Y-Y'. line joining Then X-X' and OZ Let OX 1 a on on f equal equal of of the direction the trace will the these two / upon plane of give points the anglesit will make with the other faces in the drawing and so determine 49.

"

zone

the

zone.

the other hand, the angles between / and the other faces in the the of trace of the zone position / upon the plane of the drawing known, could be found, and so its relative intercepts (and indices)upon the two lines of reference be determined.

If, on were

of calculation is used let P, Q, S and R be the poles of If the method four faces in a zone (Fig.83) taken in such an order * that PQ " PR and let the indices of these faces be respectively

Then

it may

S

R

P

Q

hkl

pqr

fs

xyz

uvw

be proved that cot

PS

cot

PQ

-

(P.Q)

cot PR =

-

cot PR

(Q.R)

(S.R) (P.S)

* In the applicationof this principleit is essential that the planes should be taken in inth" dices above ; to accomplish this it is often ne_cessaryto use the proper order, as shown etc. and correspondingangles,not of (hkl),but the face opposite (h k F), r

50

CRYSTALLOGRAPHY

where 1 X

hq

2

kr

kp

"

3 X

2X3

Iq

"

_

pv

qw

rv

"

yw

of these fractions reduces

to

be taken in its place. This formula is chieflyused in the monoclinic referred to under these systems. cases are

1

zv

ly

-

indeterminate

an

pw

"

3 X

"

kz

one

hr

"

ru

2X3

If

Ip _

qu

"

1

Ix

form,

hz

-

-,

then

one

of the others

must

and

triclinicsystems;

and

special

some

The for a rectangular zone, much simplified cotangent relation becomes between a pinacoidand a face lyingin a zone that is,a zone at rightangles 90". In Fig. 83 let P(hkl) and Q(pgr) to it so that the angle PR, becomes be two between faces lying in the zone a(100) and d(011) with the angle Pa and d Let 90". a Qa represent the angles between the two faces A Then the followingholds true. and the pinacoida. =

h

k

Pa

tan "*\s

or

the

Qa

tan

p

the faces P and Q lie in expressionbecomes

k .

P

r

q

tan

P6 Pb

tan

Q6

I

tan

PC

tan

Qc

k _

_

pinacoids6(010)or c(001)

I

.

q

h

___.

with the other

zones

h

I

:

_

pqr

If the zone in question lies between two pinacoidswhich are anglesto each other so that the indices of the faces P and Q become hkQ and

p#0, hQl and pOr

or

OH

and

tan

(100 (100

A

(001 (001

A

tan tan tan

tan tan

These

equations are plane or dome.

The

most

common

positionsof the

unit

the

ones

A

hkQ) pqQ)

k

p.

h

q

=

'

h

MM) pQr)

(001 A Qkl) (001 A Qqr)

either

have

Qqr, we A

right

at

r_

=

.

'

~

'

I

p

k =

r '

~

I

ordinarilyemployed

'

q

to determine

the symbol of any

and important applicationof this tangent principleis where faces 110, 101, Oil are known, then the relation becomes tan tan

tan

Also, tan

(100 A fe/cO) =k h' (100 A 110) (001 A MM) (001 A 101)

h

tan tan

tan

= ~

I'

tan

(010 (010

A

hkO)

A

110)

h =

(001 A 0/cQ (001 A Oil)

k'

=k ~

I

matic pristhe

MATHEMATICAL

GENERAL

the

Thus

half

the

84

represents

the

If

to

seen

distance

intersect

giving

O-Y, But

(104).

d

u,

the

c(001)

will

the and

angles as

shown

u

c

I

are

between

other

the

them

intercepts

on

proportional their

two

|

indices O-Y to

d

and

and

the and

the

I

the

i

and

(102) for

poles

at

lengths,

faces at

the the

axes

unit

axis

of

be

to

the

their

The

direction

plane

assumed

is

broken

ing represent-

the

the

intersect

the

The

show

to

been mined deter-

line

the

on

angles

poles

three

tangents that

of

below. tan

58"

10%'

=

1

tan

38"

5H'

=

.8056

=

%

tan

21"

56|'

=

.4028

=

i

=

1.6112

001

A

Fig.

have

c

their

upon

face

O-Y.

and

O-X

namely

of

it

(101)

and

I

axis

proportional

100

barite

a

the

figure. x

faces

the

of

51

CRYSTALS

102,

between

between

that

of

the

in

these

axes.

dome

faces

d,

point

a

of

distances

are

u,

crystallographic

a

c

assumed

positions

the

and

001,

angle

tangent

in

of zone

is

a,

from

traces

and

unit

faces

indicated

as

drawn

the

It

the

clearly

cross-section

macrodome

the

and

measured

twice

shown

are

c(001). the

is

base, the

OF

110.

A

a

showing and

lines

010

of

tangent

120

A

relations

last

which

between

a

of

tangent

crystal

100

angle

These

a(100)

of

the

of

tangent

the

between

the

times

2

|,

|, f,

angles

of

tangents

respectively

RELATIONS

110

203,

201,

302,

and

(here v

=

etc.,

Again,

101.

2

V

and

are

the

one-

52

CRYSTALLOGRAPHY

I. ISOMETRIC

(Regularor

SYSTEM Cubic

System)

embraces all the forms which are referred to SYSTEM 50. THE ISOMETRIC three axes of equal lengthsand at rightangles to each other. Since these it is customary to designatethem all by are axes mutually interchangeable the letter a. When placed in properlyorientated (i.e. 85 the commonly of accepted positionfor study) one has vertical the these and of two axes a position a3 which lie in the horizontal plane,one is perpendicular to the observer. The order in and the other parallel which the axes referred to in are givingthe relations -i of any face to them is indicated in Fig.85 by lettering ^^ a* them ai, 0% and as. The positiveand negative ends ox of each axis are also shown. There are five classes here included;of these the normal class,*which possesses the highestdegree of for the system and, indeed,for all crystals, symmetry Isometric Axes is by far the most of the other important. Two the pyritohearal and tetrahedral, also have numerous representatives classes, minerals. among "

1.

NORMAL

CLASS

(1). GALENA

Holohedral or (Hexoctahedral

TYPE

Class)

The symmetry of each of the types of solids enumer51. Symmetry. ated in the followingtable,as belonging to this class, and of all their combinations, is as follows. Axes of Symmetry. There are three principalaxes of tetragonalsymmetry which are coincident with the crystallographic and are times someaxes known the cubic axes since they are perpendicularto the faces of as the cube. There are three diagonalaxes of trigonal symmetry which emerge known These in the middle of the octants formed by the cubic axes. are as the octahedral axes since they are perpendicular to the faces of the octahedron. Lastly there are six diagonalaxes of binary symmetry which bisect the plane These are anglesmade by the cubic axes. perpendicularto the faces of the These dodecahedron and are known the dodecahedral axes. as symmetry in shown the Figs.86-88. axes are Planes of Symmetry. There are three principalplanes of symmetry intersections fix the posiwhich are at rightanglesto each other and whose "

*

It is called normal, as before stated,since it is the most common and hence by far the important class under the system ; also,more fundamentally, because the forms here included possess the highestgrade of symmetry possiblein the system. The cube is a possible form in each of the five classes of this system, but although these forms are alike geometrically, it is only the cube of the normal class that has the full symmetry as regards molecular structure which its geometricalshape suggests. If a crystalis said to belong to that it is included the isometric system, without further qualification-, it is to be understood Similar remarks apply to the normal classes of the other systems. here. most

ISOMETRIC

53

SYSTEM

In addition there are six diagonal tion of the crystallographic axes, Fig.89. which bisect the principalplanes, the angles between planes of symmetry

Fig.90 87

Axes of

Axes of TetragonalSymmetry

TrigonalSymmetry

Axes of Binary

Symmetry (DodecahedralAxes)

(OctahedralAxes)

(Cubic Axes)

90

PrincipalSymmetry

Planes

DiagonalSymmetry

Planes

projection accompanying stereographic with the (Fig.91), constructed in accordance in Art. the distribution shows 44, explained principles of the faces of the generalform, hkl (hexoctahedron)and hence represents clearly the symmetry of the class. Compare also the later. given projections The various possibleforms 52. Forms. this to class,and possessingthe belonging symmetry denned, may be grouped under seven The

"

types of solids. These

are

in the enumerated the simplest.

followingtable, comiQencing with

Symmetry

of Normal

Class,

Isometric System

54

CRYSTALLOGRAPHY Indices

1. Cube

Octahedron Dodecahedron 4. Tetrahexahedron 5. Trisoctahedron 6. Trapezohedron 7. Hexoctahedron

(100) (Ill) (110)

2.

3.

Attention

.'

(AfcQ) as, (310) (210); (320),etc. (hhl)as, (331) (221); (332),etc. (hll)as, (311) (211); (322),etc. (hkl)as, (421); (321), etc.

is called to the letters uniformlyused in this work

Mineralogy (1892) to designate certain of the isometric forms.* Cube: a. Octahedron: o. Dodecahedron: d. Tetrahexahedrons: Trisoctahedrons: p

Trapezohedrons:

m

Hexoctahedrons:

s

e

=

=

=

=

=

=

210; / 221; q 311; n 321; t

310; g 331; r 211; /3

=

=

=

=

=

320; 332; p

and

in Dana's

They

h

=

System of

are:

410. 441.

=

322.

421.

Cube. The in cube, whose general symbol is (100), is shown It is bounded to two of the axes. by six similar faces,each parallel Each face is a square, and the interfacial angles are all 90". The faces of the cube are parallel to the principal axial planesof symmetry. or 53.

"

Fig.92.

92

Cube

Octahedron

octahedron,shown in' Fig. 93, has the general by eightsimilar faces,each meeting the three Each at equal distances. face is an axes trianglewith plane equilateral_ anglesof 60". The normal interfacial angle,(111 A 111), is 70" 31' 44". in Fig. 94, 55. Dodecahedron. The rhombic dodecahedron,f shown has the generalsymbol (110). It is bounded by twelve faces,each of which of the axes two to the third axis. meets at equal distances and is parallel terfacial Each face is a rhomb with plane anglesof 7Q"" and 109 J". The normal into the six angleis 60". The faces of the dodecahedron are parallel or diagonal,planesof symmetry. auxiliary, 54.

Octahedron.

Dodecahedron

symbol (111).

The

"

It is bounded

"

.

*

The

usage

followed here (as also in the other systems) is in most

cases

that of Miller

(1852).

t The dodecahedron of the crystallographcris this fc of garnet. Geometricians reco commonly found on crystals by twelve similar faces; of these the regular (pentagonal) this solid is impossible th" portant. In crystallography to it. (SeeArt. 68.) mates

rhombic

shaped

faces

solids bounded imledron is the most

various

pyritohedronapproxi-

56

CRYSTALLOGRAPHY

It should be carefully noticed,further,that the octahedral faces replace the solid anglesof the cube, as regulartriangles equallyinclined to the adjacent cubic faces,as shown in Fig.95. Again, the square cubic faces replace the six solid anglesof the octahedron,being equallyinclined to the adjacent The faces of the dodecahedron truncate * the octahedral faces (Fig.97) .

in Fig. 101. twelve similar edges of the cube, as shown They also truncate the twelve edges of the octahedron (Fig.99). Further,in Fig. 98 the cubic faces replacethe six tetrahedral solid anglesof the dodecahedron,while the octahedral faces replaceits eighttrihedral solid angles(Fig.100). 102

101

Cube

and

Cube, Octahedron

Dodeca-

hedron

normal

The

interfacial

103

and

Octahedron,Cube

Dodecahedron

anglesfor adjacentfaces

100 A Cube on octahedron, ao. Cube on dodecahedron, ad, 100 A Octahedron on dodecahedron,od, 111 A

and

Dodecahedron

are

111

=

110

=

110

=

as

follows:

54" 44' 8". 45" 0' 0". 35" 15' 52".

less widelyfrom the or always deviate more 67. As explainedin Art. 18 actual crystals of the unequal development of like faces. Such crystals, ideal solids figured,in consequence definition of rightsymmetry to the three relatively therefore,do not satisfythe geometrical ditions principaland the six auxiliaryplanes mentioned on p. 53 but they do conform to the conof crystallographic symmetry, requiring like angular position for similar faces. of the faces do not actuallymeet Again, it will be noted that in a combination form many It is stilltrue, the axes within the crystal, as, for example, the octahedral face o in Fig. 95. if distances and since the the at meet would axes equal this face that produced; however, of each form, and the actual lengthsof the axes axial ratio is the essential point in the case of no importance, it is not necessary that the faces of the differentforms in a crystal are to will be seen actual axial lengths. The above remarks should be referred to the same apply also to all the other forms and combinations of forms described in the pages following.

The tetrahexahedron (Figs. 104, 105, 106) is isosceles triangle. Four each of which is bounded an by twenty-fourfaces, these faces of dron) togetheroccupy the positionof one face of the cube (hexahewhence the name The generalsymbol commonly appliedto this form. is (hkQ),hence each face is parallel while it meets the other of the axes to one at unequal distances which definite multiplesof each other. two axes are There kinds of edges,lettered A and C in Fig. 104; the interfacial two are angle of either edge is sufficient to determine the symbol of a given form forms are given on a later of the common (seebelow). The anglesof some 58.

page *

Tetrahexahedron.

"

(p.63). The words truncate,truncation, are with the adjacent similar faces.

used

only when

the

modifyingface

makes

equal

ISOMETRIC

There

be

may

interceptsof the

a

largenumber and

two

axes, (310),(210),(320),etc. The

of hence form

(530) in Fig. 106.

Fig. 105, and

57

SYSTEM

as tetrahexahedrons,

the ratio of the

of h to k

varies;for example (410) is in Fig. 104; (410) in shown (210)

All

the tetrahexahedrons fall in a zone As h increases relatively with a a dodecahedral to k the form approachesthe cube (inwhich h : k "x" : 1 or 1 : 0),while as it diminishes and more and becomes more nearly equal to k in value it approaches k. the dodecahedron; for which h Compare Fig. 105 and Fig. 106; also Figs. 125, 126. The specialsymbols belonging to each face of the tetrashould be carefully noted. hexahedron cubic face and

face. =

=

106

Tetrahexahedrons 107

Cube

and Tetrahexahedron

108

109

Octahedron and Tetrahexahedron

Dodecahedron and Tetrahexahedron

bevel * the twelve similar edges of the cube, as in Fig. 107; they replacethe solid anglesof the octahedron by four faces inclined on and also the tetrahedral the edges (Fig. 108;/ 310), solid angles of the dodecahedron by four faces inclined on the faces (Fig. The

faces of the tetrahexahedron

=

109; h

=

410).

The Trisoctahedron. trisoctahedron (Fig. 110) is bounded by and three twenty-four similar faces; each of these is an isosceles triangle, the common the positionof an octahedral face,whence together occupy name. Further, to distinguishit-from the trapezohedron (or tetragonal it is sometimes trisoctahedron. There are called the trigonal trisoctahedron), two kinds of edges,lettered A and B in Fig. 110, and the interfacial angle of the special correspondingto either is sufficient for the determination 59.

"

symbol. * The word bevel is used when two like faces replacethe edge of inclined at equal angles to its adjacent similar faces.

.a

form

and

hence

are

58

CRYSTALLOGRAPHY

Eacn forms are (221),(331),etc. The generalsymbol is (hhl)', common of the axes two at a distance less than unity face of the trisoctahedron meets and the third at the unit length,or (which is an identical expression*)it of the axes two at the unit length and the third at a distance greater meets noted. than unity. The indices belonging to each face should be carefully forms are given of the more The normal interfacial anglesfor some common on

a

later page. 112

Ill

Trisoctahedron

Cube

and

Trisoctahedron

Octahedron and Trisoctahedron

The trapezohedron 60. Trapezohedron. f (Figs.113, 114) is bounded or by twenty-foursimilar faces,each of them a quadrilateral trapezium. It certain relation to the octahedron,whence also bears in appearance a the trisoctahedron. sometimes of There two are employed, tetragonal name, kinds of edges,lettered B and C, in Fig. 113. The generalsymbol is hll\ forms are common (311),(211),(322),etc. Of the faces,each cuts an axis at a distance less than unity,and the other two at the unit length,or (again, identical expression) of them intersects an axis at the unit lengthand one an the other two at equal distances greater than unity. The indices belonging The normal interfacial angles for to each face should be carefullynoted. of the common forms are given on a later page. Another name for this some "

form is icositetrahedron. of these forms with the cube, octahedron,etc., 61. The combinations It will be seen should be carefullystudied. (Fig.Ill) that the faces of the trisoctahedron the solid replace angles of the cube as three faces equally inclined on the edges;this is a combination which has not been observed on crystals. The faces of the trapezohedron appear as three equal triangles equallyinclined to the cubic faces (Fig.115). Again, the faces of the trisoctahedron bevel the edges of the octahedron, inclined to the faces Fig. 112, while those of the trapezohedron are triangles at the extremities of the cubic axes, Fig. 119; m(311). Stillagain,the faces of the trapezohedronn(211) truncate the edges of the dodecahedron (110), in shown this be from the zonal as can Fig. 118; proved to follow at once *

Since

la : 16 \a : %b : {c in Art. 35. It will be seen later that the =

:

2c.

The

student

should

read

the again carefully

planations ex-

name trapezohedron is also given to other solids whose trapeziums conspicuouslyto the tetragonal trapezohedron and the trigonal trapezohedron.

t

faces

are

ISOMETRIC

relations the

form

59

SYSTEM

(Arts.45, 46), cf. also Figs.125, 126. The positionof the faces of m(311), in combination with o, is shown in Fig. 119; with d in

Fig. 120. 114

113

Trapezohedrons form both It should be added that the trapezohedronn(211) is a common is in trisoccombination. The alone and in combination; m(311) common tahedron alone is rarelymet with,though in combination (Fig.112) it is not uncommon.

115

Analcite.

Cube

Analcite. Trapezohedron Garnet. Trapezohedron and and Octahedron Dodecahedron

and

Trapezohedron 118

119

Garnet. Dodecahedron and Trapezohedron

62.

Spinel. Octahedron and Trapezohedron

Magnetite. Dodecahedron and

Trapezohedron

The hexoctahedron. Figs. 121, 122, is the general form in this system; it is bounded similar faces,each of by forty-eight which is a scalene triangle, and each intersects the three axes at unequal

Hexoctahedron,

"

60

CRYSTALLOGRAPHY

in forms are s(321),shown The generalsymbol is (hki)\ common of the individual faces, as The indices Fig. 121, and "(421), in Fig. 122 shown in Fig. 121 and more fullyin the projections(Figs.125, 126), should be carefully studied distances.

edges lettered A, B, C (longer, edges are needed to middle, In Fig. 124 the of fix the symbol bevel the dodecahedral faces of the hexoctahedron edges,and hence for this has the specialsymbol (321). The hexoctahedron form h k + 1; the form s in combination alone is a very rare form, but it is seen with the cube (Fig 123, fluorite)as six small faces replacingeach solid angle. Fig. 124 is hexoctahedron

The

has

three kinds

of

Fig. 122; the anglesof two of these unless the zonal relation can be made use

shorter)in

=

common

with garnet. 123

Fluorite Cube Hexoctahedron

and

Garnet and

Dodecahedron Hexoctahedron

Isometric forms, by Pseudo-symmetry in the Isometric System. development in the direction of one of the cubic axes, simulate tetragonal More and of greater interest, forms. forms simulatingthose of are common, rhombohedral in the direction of an or by extension, symmetry by flattening; octahedral Both these cases illustrated later. Conversely,certain axis. are rhombohedral forms resemble isometric octahedron an in angle. 65. Stereographic and Gnomonic The Projections. stereographic projection,Fig 125, and gnomonic projection, Fig. 126, show the positions of the poles of the faces of the cube (100),octahedron dron (111),and dodecahealso the tetrahexahedron the trisoctahedron (110); (210), (221),the trapezohedron(211),and the hexoctahedron (321). 64.

"

"

ISOMETRIC

SYSTEM

61

126

110

010 H

Stereographic Projectionof (110), Tetrahexahedron hedron (321))

Isometric Forms (Cube (100),Octahedron (111),Dodecanedron (210),Trisoctahedron (221),Trapezohedron (211), Hexocta-

between two cubic note the prominent zones Finally, of planes; for example,the zone faces includinga dodecahedral face and the faces of all possibletetrahexahedrons. Again, the zones from a cubic face (as 001) through an octahedral face (as 111) passing through the trisoctahedrons, as 113, 112, 223, and the trapezohedrons 332, 221, 331, etc. Also the from one dodecahedral zone face,as 110, to another, as 101,passing through 321, 211, 312, the figures shown At the same etc. time compare these zones on with the same zones A study of the relations illustrated in Fig. 127 will-^efound useful. already described. From it is seen in the zone that any crystalface falling between the cube and dodecahedron the cube and octahedron tetrahexahedron; any face fallingin the zone between the the in between and zone face to falling a belong trapezohedron; any and octahedron dodecahedron must belong to a trisoctahedron,further any face falling outside these three zones must belong to a hexoctahedron. must

belong to must

a

62

CRYSTALLOGRAPHY

126

"321

821

120

321

Gnomonic

Projection of Isometric

(110),Tetrahexahedron hedron

Forms

(Cube (100),Octahedron

(210),Trisoctahedron

(111),Dodecahedron (221),Trapezohedron (211),Hexocta-

(321))

128

UOO)

Symmetry

of

Pyritohedralclass

64

CRYSTALLOGRAPHY

the normal class,so that the lower grade of symmetry described In studying the forms here present thoroughly understood. in matter of this and illustrated in the followingpages, symmetry, especially the mind. before be of the normal should that continually relation to class, It will be observed that the faces of both the pyritohedron(Fig.129) and the diploid(Fig. 135) are arranged in parallelpairs,and on this account

jection(Fig.91) for be

these forms

have

been

sometimes

called

Further,those

hemihedrons. parallel

call this cases as preferto describe these hemihedrism. hemihedrism or pentagonal type parallel-faced because The pyritohedron(Fig.129) is so named 68. Pyritohedron. It is solid bounded a it is a typicalform with the common pyrite. species, by twelve faces,each of which is a pentagon, but with one edge (A, Fig.129) longerthan the other four similar edges (C). It 4s often called a pentagonal of closelythe regulardodecahedron dodecahedron, and indeed it resembles geometry, in which the faces are regular pentagons. This latter form is, however, an impossibleform in crystallography. authors

of hemihedrism

forms

who

"

129

130

Pyritohedrons

Showing

Relation

between

Pyritohedron and Tetrahexahedron

The generalsymbol is (MO) or like that of the tetrahexahedron of the each face is parallelto one normal class. Hence of the axes and meets the at unequal distances. other two axes Common forms are (410),(310),(210), (320),etc. Besides the positivepyritohedron,as (210),there is also the complementary in Fig. 130; the symbol is here (120). negative form * shown Other common forms are (250),(230),(130),etc.

positiveand negative pyritohedronstogether embrace twenty-four faces,having the same positionas the twenty-four like faces of the tetrahexahedron The

of the normal class. The relation between the tetrahexahedron is pyritohedron shown in Fig. 131, where the alternate faces of the tetrahexahedron (indicatedby shading) are extended to form the faces of the pyritohedron. 69. Combinations. The faces of the pyritohedron replace the edges of the cube as shown in Fig. 132; this resembles Fig. 101 but here the faces make unequal angles with the two adjacent cubic faces. On the other hand, when the pyritohedronis modified by the cube,the faces of the latter truncate the longeredges of the pentagons. the

and

"

*

The negative forms in this and similar cases the same the positiveform, but are then as e(210) and e4 (120).

have

sometimes

distinguished by

distinct a

times someletters,

subscriptaccent,

as

ISOMETRIC

Fig. 133 shows Fig. 134 these

SYSTEM

65

the combination of the pyritohedron and octahedron,and forms are equally developed. The resultingcombination bears a close similarity to the icosahedron, or regulartwenty-faced solid of geometry of the twenty faces,the Here, however eight octahedral are the twelve others equilateraltriangles, belongingto the pyritohedron are isosceles triangles. m

two

132 134

Cube

and

Pyritohedron

Octahedron

and

Pyritohedron 70.

Octahedron

and

Pyritohedron

Diploid. The diploidis bounded by twenty-four similar faces, meeting the axes at -unequal distances;its general symbol is hence forms are s(321),2(421), (hkl),and common The form (321) is shown etc. in Fig. 135; the symbols of its faces, as should giveii, be carefully studied. As seen in the figure, the faces are or quadrilaterals trapeziums; moreover, they are grouped in pairs,hence the common name diploid. It is also sometimes called a dyakisdodecahedron. The complementary negative form bears to the relation as the positiveform of Fig. 135 the same negative to the positivepyritohedron. Its faces have "

each

the symbols 312, 231, 123, in the

front octant, and

similarlywith the proper negativesignsin the others. The positiveand negative forms togetherobviously embrace normal derived

all the

faces

of the

hexoctahedron of the Diploid class. be considered to be diploid can from the hexoctahedron by the extension of the alternate faces of the latter and the omission of the remaining faces,exactlyas in the case of the pyritohedron and tetrahexahedron (Art.68). In Fig. 136 the positivediploidis shown in combination with the cube. Here the three faces replaceeach of its solid angles. This combination form resembles that of Fig. Ill, but the three faces are here unequally inclined two adjacent cubic faces. Other combinations of the diploidwith the upon cube,octahedron,and pyritohedronare given in Figs.137 and 138. 71. Other If the pyritohedral Forms. type of symmetry be appliedto that this symmetry calls for to two of the axes, it is seen planes each parallel This cube cannot be six of these,and the resulting form is obviouslya cube. distinguished geometricallyfrom the cube of the normal class,but it has its mon characteristic molecular symmetry. own Corresponding to this ijbis comnate to the alterto find cubes of pyritewith fine lines (striations) parallel edges,as indicated in Fig. 139. These are due to the partialdevelopThe

"

66

CRYSTALLOGRAPHY

if pyritohedralfaces (210). On a normal cube similar striations, cubic face. each to both sets of edges on present,must be parallel of

ment

136

Cube

and

Cube, Octahedron Diploid

Diploid

Cube, Diploid and Pyritohedron

and

Similarlyto the cube, the remaining forms of this namely, (111),(110),(hhl),(Ml),have pyritohedralclass, the same as the octahedron, geometricalform,respectively, dodecahedron,the trisoctahedrons and trapezohedronsof the normal class. In molecular structure, however, these forms are distinct, each having the symmetry described in Art. 67. ^2"

Pyrite. Striated Cube of

some

A^g*68"

common

The following tables contain the forms.

angles

PYBITOHEDRONS.

Angle on a(100) 14" 2J' 18

26

21 26

48 34

30

57|

33 36 38

41 52

39

3 48

Angle on o(lll) 456 33f 43 5| 41

22

39 37 36

14 37

36 35 35

48" 4i 45" 35f

DlPLOIDS. Cf. Fig. 135. 421 532 531 851 321 432 431

3.

321

Edge A A 321, etc. 51" 45|' 58 14| 60 56| 63 36f 64 37" 67 42^ 72 4|

TETRAHEDRAL

321

Edge B Edge C A 321, etc. 321 A 213, etc. 25" 12"' 48" 114' 37 51f 35 20 19 27f 19 27f 12

6

53

55i

31 43 22

0| 36^ 37 J

38 26

12i m

43

3

CLASS

(3). TETRAHEDRITE

Tetrahedral (Hextetrahedral,

and

73. Typical Forms and Symmetry. that from which it derives its name,

"

Hemihedral The is the

TYPE

Class)

typicalform

of this

shown tetrahedron,

in

class, Figs.

ISOMETRIC

141,

142.

150,

151.

There

SYSTEM

also three other distinct

are

67

forms, shown

in

Figs. 149,

The

symmetry of this class is as follows. There are three axes of binary symmetry which coincide with the crystallographic There are also axes. four diagonalaxes of trigonalsymmetry which coincide with the octahedral There are six diagonal planes of symmetry. There is no center of symmetry.

axes.

The shows

stereographicprojection (Fig. 140) the

general form

distribution

of

the

faces of

the

and thus (hkl),hextetrahedron,

exhibits the symmetry of the class. It will be that the like faces are all grouped at once seen in the alternate octants, and this will be seen to be characteristic of all the forms peculiar The relation between to this class. the symmetry here described and that of the normal class must be carefully studied. In distinction from the pyritohedralforms in parallel whose faces were pairs,the faces of and the analogous solids are the tetrahedron Symmetry of Tetrahedral Class inclined to each other, and hence they are sometimes spoken of as inclined hemihedrons,and the type of so-called hemihedrism here illustrated is then called inclined or tetrahedral hemihedrism. The tetrahedron,*as its name is a four74. Tetrahedron. indicates, at equal distances. Its faced solid,bounded by planes meeting the axes the faces of form is 141) positive (Fig. generalsymbol (lll)_,_and_the_four These correspondto four of the faces have the symbols 111, 111, 111, 111. the of the normal class (Fig.93). The relation between of the octahedron 143. in two forms is shown Fig. "

Positive Tetrahedron

Negative Tetrahedron

Showing Octahedron

Relation between and Tetrahedron

triangle;the of the four faces of the tetrahedron is an equilateral the regular is The tetrahedron 16". (normal) interfacial angle is 109" 29' must be it so placed triangularpyramid of geometry, but crystallographically and one is vertical. axis of edges, opposite middle the that the axes points join Each

hedron, of the five regularsolids of geometry,which include also the cube, octaThis is one the last as already the and two, icosahedron; the regularpentagonaldodecahedron, crystals. noted, are impossibleforms among *

68

CRYSTALLOGRAPHY

the positivetetrahedron possibletetrahedrons: (111), has alreadybeen described, and the negative form and symmetry, but the tetrahedron, having the_same_geometrica_l

There

two

are

designatedby

the letter o, which

indices of its four faces are 111, 111, 111, 111. This second form is shown Fig. 142; it is usuallydesignatedby the letter o,. These two forms are, as stated above,identical in geometrical shape,but they may be distinguished in many to reveal the molecular cases by the tests which serve structure, the etching-figures; also in many cases particularly by pyro-electricity (see under boracite,p. 306), Art. 438. It is probable that the positiveand ence negative tetrahedrons of sphalerite (seethat species)have a constant differin this particular, it possible which makes to distinguish them on crystals from different localitiesand of different habit. in

144

145

146

\/

Positive and Negative Tetrahedrons

Cube

If both tetrahedrons This is geometricallyan

and

Tetrahedron

Tetrahedron

and

Cube

present together,the form

in Fig. 144 results. when the two forms are equally developed, but crystallographically it is always only a combination of two unlike forms, the positiveand negative which can be distintetrahedrons, guished as alreadynoted. are

octahedron

147

Tetrahedron

and

Dodecahedron

The

angles

tetrahedron

in

Fig. 145. shown in Fig

Boracite. Cube, Dodecahedron with Positive and Negative Tetrahedrons

combination with the cube replacesthe alternate solid The

cube modifying the tetrahedron truncates its The normal angle between adjacent cubic and tetrahedral faces is 54" 44'. In Fig. 147 the dodecahedron is shown modifytet"hedr"n' whlle m FlS- 148 the cube is the predominating form with the positive and negative tetrahedrons and as

edges as

in

146.

fnL -tPl?S^1Ve

dodecahedron.

ISOMETRIC

75.

SYSTEM

gg

Other Typical Forms. There three other distinct are types of solids in this class, having the general symbols (hhl),(hll), and (hkl) The firstof these is shown in Fig 149; here the symbol is 221). There are twelve faces each a quadrilateral belonging to this

by

-

form,distributed as determined

the

tetrahedral type of symmetry. They correspond to twelve of the faces of the trisoctahedron, namely, all those falling in alternate octants I his type of solid is sometimes called a tetragonal tristetrahedron, or a deltoid dodecahedron It does not occur alone among but its faces are crystals, observed modifying other forms

Tetragonal Tristetrahedron There

is also

Hextetrahedron

complementary negativeform, correspondingto

a

form, related

Trigonal Tristetrahedron

to it in

tetrahedron.

belong to the other

the precisely

same

way

Its twelve faces are those set of alternate octants.

as

the

the

negativeto the

tive posipositive

of the trisoctahedron which

152

Tetrahedrite

Sphalerite

Boracite

Another form, shown in Fig. 150, has the generalsymbol (hll), here (211); it is bounded distributed after manded the type deby twelve like triangularfaces, by tetrahedral symmetry, and correspondingconsequentlyto the of the faces of the alternate octants of the form (hU) the trapezohedron normal tristetrahedron called a trigonal class. This type of solid is sometimes or trigondodecahedron.* It is observed both alone and in combination, "

"

* It is to be noted that the tetragonaltristetrahedron has faces which resemble those of the trapezohedron (tetragonaltrisoctahedron), although it is related not to this but to the tristetrahedron trisoctahedron (trigonaltrisoctahedron). On the other hand, the faces of the trigonal resemble those of the trisoctahedron,though in fact related to the trapezohedron.

70

ALLO

CR YST

GR

APH

Y

it is much than the with the species tetrahedrite; more common especially form Fig. 152 (hhl). There is here again a complementary negativeform. the positive form n(211) with the positivetetrahedron, and Fig. 153 shows the form m(311) with a(100),o(lll),and d(110). In Fig. 154, the negative form 71X211)is present. in Fig. 151. The fourth independent type of solids in this class is shown here (321),and is bounded It has the generalsymbol (hkl), by twenty-four faces distributed accordingto tetrahedral symmetry, that is,embracing all hexoctahedron. the faces of the alternate octants of the forty-eight-faced hexakistetrahedron. The of faces the remaining The positivehextetrahedron,0(531),is shown in Fig. 154 octahedron, and dodecahedron, also the negative trigonal called

is sometimes

This form

a

complementary

hextetrahedron

or

the

(hkl) embraces

negative form

hexoctahedron. with the cube, tristetrahedron nt (21 1 ) be applied in the case 76. If the tetrahedral symmetry of planes each that there must be six such faces. to the two axes, it will be seen parallel to the cube both of the normal and They form a cube similar geometrically in its molecular structure,as be readily can pyritohedralclass but differing .

(Art.438). Similarlyin the case proved, for example, by pyro-electricity of the planeshaving the symbol (110),there must be twelve faces forming a rhombic the relation dodecahedron to the like geometrical same bearing form of the normal class. The same is true again of the planeshaving the positionexpressedby the generalsymbol (hkQ); there must be twenty-four of them and they togetherform a tetrahexahedron. In this class, there are also seven therefore, types of forms, but only four of them are geometricallydistinct from the correspondingforms of the normal 77.

class.

Angles.

forms TETRAGONAL

"

The

followingtables contain

the

angles of

mon com-

TRISTETRAHEDRONS.

Angle on o(100) 50" 14J' 48 47

Angle on o(lll) 10" If 15 47| 19 28|

111

1\

46

TRIGONAL

some

:

22

0

TRISTETRAHEDRONS.

Angle on o(100) 19" 28i' 22 25 29 35 43

Angle on o(lll) 35" 15f '

0

32 29 25

14i 29| 15f 18f

19 11

44

29f 14" 28" 25|

HEXTETRAHEDRONS.

Cf. Fig. 151. 531 321 432

431

321

Edge A A 312, etc. 27" 39|' 21 47i 15 5i 32 12J

EdgeB 321

A

57" 69 82

67

312

EdgeC etc.

7i' 4i 4f 22f

321

231, etc. 27" 39f 21 47i 15 5" 15 56| A

Angle on o(100) 32" 18f 36 42

42

38

19|

If

Angle on o(lll) 28" 33fr 22 15 25

124

13* 4

72

CR

GR

YSTALLO

APH

Y

and halite. It is usually shown by the distribution of the moniac, sylvite, small modifying faces,or by the form of the etchingfigures.Fig. 158 shows 10' 12). a crystalof cupritefrom Cornwall (Pratt)with the form 2(13'

5.

TETARTOHEDRAL

(5). ULLMANNITE

CLASS

Pentagonal Dodecahedral (Tetrahedral Symmetry and TypicalForms.

80.

The

"

TYPE.

Class)

fifth remaining

possibleclass

under the isometric system is illustrated by Fig. 160, which represents the bution the to twelve-faced solid corresponding general symbol (hkl). The distriin the projection, of its faces is shown called a Fig. 159. This form is sometimes dodecahedron. It is tetrahedral-pentagonal have one-fourth faces to as the as seen many hence there are form (hkl)in the normal class, all four similar solids which together embrace These four the faces of the hexoctahedron. as solids,which are distinguished right-handed and negative)and left-handed (posi(positive

circular polarization.The the class are (besidesthe

remaining forms of cube

and

rhombic

dodecahedron) the tetrahedrons,the pyritoheSymmetry of Tetartohedral Class drons,the tetragonal and trigonaltnstetrahedrons; geometricallythey are like the solids of the same names already This class has no plane of symmetry described. and no center of symmetry. of binary symmetry There are three axes normal to the cubic faces,and four of normal the faces of the tetrahedron. to axes trigonalsymmetry 160

This

is illustrated by artificialcrystalsof barium

tium nitrate,stronchlorate,etc. Further,the speciesullmannite, which sometimes shows pyritohedraland again tetrahedral forms, both having the same composition,must be regarded as belonging here. group

nitrate,sodium

MATHEMATICAL 81.

Most

of the

OF

THE

ISOMETRIC

SYSTEM

problems arisingin the isometric system can be solved the sphereof projection(Fig.125) without the use

trianglesin right-angled formulas.

RELATIONS

at once of any

by the special

ISOMETRIC

SYSTEM

73

It will be remembered that the angles between a cubic face of a tetrahexahedron, 310, 210, 320, etc can be

face,as 100, and

the adjacent

obtained at once, since the

this angle is equal to

"

o

in general

or

-"-"-"

6

"

tangent of '

r

h tan

(hkO

A

100)

=

~

162

ac

k

6c

ft

Z

c

Z

1

=

2

=

90

=

a"c 26" 34'

=

(100) A

(210)

This relation is illustrated in Fig. 162, which also shows the method of graphically the angle between one determining the indices of a tetrahexahedron, of its faces and an adjacent cube face being given. Since all the forms of a given symbol under different specieshave the same angles,the tables of angles alreadygiven are very useful. and similar angles may These be calculated immediatelyfrom the sphere,or often more article. simply by the formulas given in the following 82. Formulas. (1) The distance of the pole of any face P(hkl) from the cubic faces is given by the followingequations. Here Pa is the distance between (hkl)and (100); Pb is the distance between (hkl)and (010); and PC that between (hkl)and (001). in the various specialcases, for (hkQ), These equationsadmit of much simplification "

etc.: (hfd),

(2) The distance between the poles of followingequation,which in specialcases

any

faces P(hkl) and Q(pqr) is givenby the also be more less simplified: or

two

may

hp + kq+

Ir

cosPQ (p* calculation of the supplement interfacial or normal anglesfor the several forms follows: The angles A and B are, as before,the supplementsof the interfacial Trisoctahedron. angles of the edges lettered as in Fig. 110.

(3) The

may

be

accomplishedas "

V cos

A

+

2hl.

2

,2

= ,

9/,2_/2

,

(Fig.149), tetragonal-tristetrahedron

For the

Trapezohedron (Fig.113).

C

B and

cos

B

cos

B

=

=

the supplement anglesof the edges as lettered in

are

the figure. cos

For the

B

= T0

,

^70

J

(Fig.150), trigonal-tristetrahedron

Tetrahexahedron

cos

C

cos

B

=

cos

C

=

(Fig.104). cos

A

"*

= ,

2

.

^2

74

CR YST

GR

ALLO

APH

Y

hk

h2 k2 "' ^2 _^_fc2 "

129), cos Forthepyritohedron(Fig. Hexoctahedron

A

=

A

=

C

=

^rqrp*

(Fig.122). I2

-

cos

cos

/+y;v

For the diploid(Fig.135),

^

B

cos

A

=

;2;^ + ;8;

-

M

,

M

,

n;

cOS

c

cos

C

cos

B

=

=

/;y;p",","" h2

For the hextetrahedron

83. To of its

(Fig.151),

-

2kl

=

h2 +

k2 +

I2

determine the indices of any face (fcfel) of an isometric form, given the position the stereographicprojection. As an illustrative example of this problem the hexoctahedron (321)has been taken, It is assumed that the angles 100 A 321 36" 42'

pole on

=

ISOMETRIC

22" 12' are 111 A 321 these measurements have

75

SYSTEM

given. The

methods by which the desired pole is located been described on page 38 and are illustrated in Fig. 163. Having located the pole (hkl)a line is drawn through it from the center O of the projection. This line O-P represents the intersection with' the horizontal plane (which is the plane of the horizontal crystalaxes, a and 6) of a plane which is normal to the crystalface (hkl) Since two planes which are at rightanglesto each other will intersect a third plane in lines that are at rightangles to each other,it follows that the plane of the hexoctahedral in a line at rightangles to O-P. face will intersect the plane of the horizontal axes If, be taken as representingunity on the a axis and the line therefore,the distance 0-M will represent the interceptof be drawn the distance 0-N at rightangles to O-P M-P-N in this case in value. the 6 axis. 0-N is found to be f 0-M the face in question upon the two horizontal axes The interceptsupon plottingof the are, therefore la, |6. The interceptupon the c axis is shown in the upper left hand quadrant of the figure. The angular distance from 0 to the pole (hkl)is measured by the stereographicprotractor as 74" 30'. This angle is then laid off from the line representingthe c axis and the line representing The distance O-P. is transferred from the lower part of the pole (hkl)is drawn. the right triangle, the vertical side of which is the construct the figure. Then we can (the intersection of the plane which is normal to c axis,the horizontal side is this line O-P the crystalface with the horizontal plane) and the hypothenuse is a line lying in the face and therefore at rightangles to the pole of the face. This line would intersect the c axis relation may be shown by startingthis last line The same at a distance equal to 30-M. from a point on the c axis which is at a distance from the center of the figureequal to 0-M. In this case the intercepton the horizontal line O-P would be at one third its total length. By these constructions the parameters of the face in question are shown to be la, |6,3c,

and from

=

.

giving (321)as its indices.

the indices of the faces of teometac 84. To determine their poles on the gnomonic projection. As an illustrative m Fig projectionof ^ometric lower right hand quadrant of the gnomonic re at ""* and ( lines O-M The been taken and reproduced in Fig. 164. each other and may representthe horizontal axial to these two of the projectionlines are drawn perpendicular^ pole relations to rational have lines these that the interceptsmade upon seen -

forn^

?3^^^^^"

2 126

76

CRYSTALLOGRAPHY

since

we

alike

and and

45"

point

readily

poles

consideration

the to

O-M

lines

the

find

To

distance.

and

The

165.

O-N

of

to

distance of

the

of

be

|,

the

this

lines

the

|,

it

the

to

is

true

from

and

2

upon

is

drawn 3

only

is

all

are

center

That

f, 1,

5,

axes

intercepts

from axes.

represented,

face

any

different

the

intercepts

found

are

indices

Miller

the

length

unit

crystallographic

the that

(i.e. the

O-R

the

Fig.

of

follows

it

distance

equal

must

which

in

system

other,

each The

projection)

by

seen

isometric

with

identical.

are

the

of

different unit

the

interchangeable O-N

O-M

with

dealing

are

the this

times

to

necessary

165

of

Plane

the

take

clear

its

from

of

fractions,

parallel

to

the

the

position

horizontal

axes.

of

the

indices of

the The

required

vertical be

may

pole

and

and

relative indices

axes

yields

312, the

obtained

by

dropping

pole

1

a

as

and the

indices

pole taking

which any

the

formed

third

upon

number

with

gives

lies

to

these will

axes

at

in

if

In

the

on

necessarily

give be

0.

the

the

case

gnomonic that

line

representing will

lines

| \ 1, which,

question.

radial

place

ct2,

necessary The

312.

infinity

lines axes

then

expression

the

on

the

and

a\

and indices

the

face

the

point

two

figure

face

of

of

the

upon third

"a2, which

perpendiculars

intercepts

a

hexoctahedrqn lai

at

axis,

while

add

the

exa'mple the

clearing

the

numbers

for

intercept

its

from

drawn

order

proper

Take

pole

lines

two

on

projection, to

the

of

their

face

again, a

in

fractions.

of

drawn

of

intercepts

numbers

these

Projection

Gnomonic

points the

first

two

two

TETRAGONAL

II. TETRAGONAL THE

85.

TETRAGONAL

77

SYSTEM

SYSTEM

SYSTEM

includes all the forms

which

are

referred

rightanglesto each other of which the two horizontal axes each other in length and interchangeableand the third,the to are equal vertical axis,is either shorter or longer. The horizontal axes are nated desigthe letter the vertical axis by by c (seeFig. 166). The lengthof a; the vertical axis expresses properlythe axial ratio of a : c, a being uniformly orientated and their oppositeends taken as equal to unity. The axes are designatedby plus and minus signsexactlyas in the case of the Isometric

to

three

at

axes

System. in this system. Of these the normal class is classes are embraced and important among minerals; two others have several representatives, and another a singleone only. It may be noted that in four of the in the remaining classes the vertical axis is an axis of tetragonalsymmetry; axis is of it three an binary symmetry only.

Seven

common

1.

CLASS

NORMAL

TYPE

(6). ZIRCON

Bipyramidal (Ditetragonal

or

Holohedral

Class)

class of the The forms belonging to the normal Symmetry. axis of tetragonal tetragonalsystem (cf Figs.170 to 192) have one principal with the vertical coincides which the of name system) symmetry (whence of binary symhorizontal also four axes There are metry, c. crystallographic axis, axes coincide with the horizontal crystallographic of which two first the between the angles the other while two are diagonal axes bisecting 86.

"

.

two. 167

166

eta

Symmetry

Axes of TetragonalMineral, 1 : 178 Octahedrite a : c

Further horizontal

symmetry

Class

plane of symmetry, the plane of the principal also four vertical planes of There are axes. crystallographic make axis c and vertical the crystallographic which pass through they

have

one

anglesof 45" with each other. axes crystallographic

The

of Normal

TetragonalSystem

=

other two

are

known

as

and

Two are

zontal of these latter planes include the horiaxial planes of symmetry. known as

diagonalplanesof symmetry.

78

CRYSTALLOGRAPHY

The The

symmetry in the

is shown 87.

planes of symmetry

and

axes

Forms.

this system

"

shown

in

Figs.168 and 169. generalform, hkl,

the distribution of the faces of the

projection, Fig. 167. stereographic under The various possibleforms as

are

and

are

the

normal

class of

follows: Symbols

1. Base 2. 3.

(001) (110) (100) (hkO)as, (hhl)as, (hQl)as, (hkl)as,

basal pinacoid of the firstorder of the second order

or

Prism Prism

Ditetragonalprism Pyramid of the firstorder 6. Pyramid of the second order 7. Ditetragonalpyramid 4.

5.

169

168

Symmetry

(310); (210)f (320),etc. (223); (111); (221),etc. (203); (101); (201),etc. (421); (321); (122),etc.

of Normal

Class,TetragonalSystem

The 6ase is that form which 88. Base or Basal Pinacoid. includes the two similar faces which are parallel_to the plane of the horizontal axes. These faces have the indices 001 and 001 respectively; it is an "open form," as they do not inclose a space, consequentlythis form can occur bination only in comwith other forms. Cf. Figs. 170-173, etc. This form is always lettered c in this work. "

170

171

OQL

172 001

4-

i 100

010

no

First Order

Prism

Second

Order

Prism

First and Second Order Prisms

89. Prisms. Prisms,in systems other than the isometric, have been defined to be forms whose faces are parallel to the vertical axis (c) of the while they meet the two horizontal axes; in this system the fourcrystal, faced form whose planes are parallel both to the vertical and one horizontal "

80 As

CRYSTALLOGRAPHY

alreadystated,the a

form

pyramid

name

whose

is

metric) given (insystems other than the iso-

of the axes; in this system the form whose planesmeet horizontal axis while parallel the axis c and one to the other is also called a pyramid. The pyramids of this class are strictly double pyramids (bipyramidsof some authors). 94. Pyramid of First Order. A pyramid of the firstorder,is a form whose eightsimilar faces intersect the two horizontal axes at equal distances It has the general symbol (hhl). It is and also intersect the vertical axis. the terminal edges,and a pyramid with equal interfacial anglesover square of the faces replace the horizontal, the first order prism and or basal,edges the solid anglesof the second order prism. If the ratio of the vertical to the horizontal axis for a given firstorder pyramid is the assumed axial ratio for the species, the form is called the fundamentalform, and it has the symbol 174. The indices of its_faces_ oned in order are: me Above (lll)_as in_Fig. 111, 111, 111, 111; below 111, 111, 111, 111. to

planes

all three

meet

"

176

175

177

in in

First Order

Zircon, First Order and Pryamid

Pyramid

Zircon, First Order Prism and Pyramids

Prism

Second Apophyllite, Order Prism and First Order Pyramid

Obviously the anglesof the firstorder pyramid, and hence its geometrical widely with the length of the vertical axis. In Figs. 174 and vary 182 the pyramids shown have in both cases the symbol (111) but in the first case (octahedrite) c 1.78,while in the second (vesuvianite), 0.64. c For a given speciesthere may be a number of second order pyramids, in positionaccordingto the ratio of the intercepts varying the vertical upon and horizontal axes. Their symbols, passingfrom the base (001)to the unit thus be (115),(113),(223),(111),(332),(221), (110),may prism (441),etc. In the generalsymbol of these forms h diminishes, as (hhl), the form approximates and more more nearly to the base (001),for which h 0- as h increases, the form passes toward the firstorder prism. In Fig. 176 two pvramids of this order are shown, p(lll) and w(331). 95. Pyramid of Second Order. The pyramid of the second order is the iorm, .big.178, whose faces are parallelto one of the horizontal axes while meeting the other two axes. The generalsymbol is (hOl) These faces replace the basal edges of the second order prism (Fig. 179),and the solid anglesof the firstorder prism (cf.Fig. 180). It is a square pyramid since its' aspect,

=

=

=

"

.

basal

section

is

a

square,

and

the interfacialangles

over

the four terminal

TETRAGONAL

81

SYSTEM

and below, are equal. The successivejaces of the form (101) follows: Above below 101, Oil, 101, Oil; 101, Oil, 101, Oil. the horizontal and vertical axes If the ratio of the intercepts on is the the symbol is (101),and the form is desigaxial ratio of the species, assumed nated of by the letter e. This ratio can be deduced from the measurement either one of the interfacial angles(y or z, Fig.178) over the terminal or basal of second a number edges,as explainedlater. In the case of a given species,

edges,above are

as

180

Order

Second

Rutile, First

Second Order Prism and Pyramid

Pyramid

Order

Second and mids Pyra-

and

Prisms

pyramids may occur, varying in the ratio of the axes a and c. Hence of such forms whose symbols may be, for there is possiblea largenumber tioned example, (104),(103),(102),(101),(302),(201),(301),etc. Those menfirst come nearest to the base (001),those last to the second order prism (100); the base is therefore the limit of these pyramids (hQl)when 0. 1 and I Fig. 186 h 0, and the second order prism (100) when h shows the three second order pyramids w(105),6(101),g(201).

order

=

=

=

183

182

Pyramid

and

Cassiterite First and Second Order

Vesuvianite

Vesuvianite First Order Prism,

First Order Pyramid and First and Scond Order

Base

Pyramids

Prisms

of a given first Thus I "h to Jor ( ratio as it order pyramid as in Fig. 183 has the same This etc. is obvious of (221), (201) of (111); the terminal edge truncates positionas the correspondingedge of the each face has the same because 101; also Figs. 186, 191, other form (see Fig. 183, when " - 111 and e the truncates 105). Again, if a first order pyramid where r 115, u h for I to is half second order pyramid,its ratio A

second

pyramid truncatingthe pyramidaledges

order

,

=

=

=

pyramidal edges of

a

given

CRYSTALLOGRAPHY

82

that of the other form; that is,(112)truncates the pyramidal edges of (101); (111) of (201), etc. This relation is exhibited by Fig. 186, where p(lll) the zonal equationsprove the the edges of 0(201). In both cases truncates relations stated. 186

185

184

m

Vesuvianite Order Second and amid Prisms,First Order Pyrand Base

First

Apophyllite Order Prism, Ditetragonal Prism, First Order Pyramid and Base

Octahedrite Order mids, PyraFirst Order Prism, Three Second Order Pyramids and Base

Second

Two

First

The ditetragonal pyramid, or double eightDitetragonalPyramid. of each whose form sixteen is similar faces meets the the pyramid, This is the most of the three axes at unequal distances. generalcase symbol is equal to 0. That there are where h, k, I are all unequal and no one (hkl), sixteen faces in a singleform is evident. Thus, for example, for the form (212) the face 212 is similar to 122, the two lateral axes being equal (not, however, to 221). Hence there are two like faces in each octant. Similarly the indices of all the faces in the successive octants a s are, therefore, follows: 96.

"

sided

Above

212

122

122

212

212

122

122

212

Below

212

122

122

212

212

122

122

212

187

DitetragonalPyramid

188

Zircon First and Second Order Prisms, First Order

189

Cassiterite

190

Rutile

Pyramid, Ditetragonal Pyramid This form is common zirconoid. It is shown

in

with the specieszircon,and is hence often called Fig. 187- It is not observed alone,though some-

a

TETRAGONAL

times,

as

In

form.

in

SYSTEM

Figs. 188 (x 311) and 189 (z 321), it is the predominating Fig. 190 two ditetragonal pyramids occur, namely, /(313) and =

=

Z\OZ\.), 97.

83

-g-

In

addition

to the

perspectivefiguresalready of given, a basal projection (Fig. 191) is added the crystal of octahedrite already referred to (Fig. 186) ; also a stereographic (Fig. 192) and gnomonic with the faces of (Fig. 193) projectionsof the same the forms w(22l) and These exhibit $(313) added. well the general relations of this normal class of the here is to be tetragonal system. The symmetry the with to similar note"l first, zones 100, respect 001, 100 and 010, 001, OH); also,to the other pair of similar zones,

110, 001, 110, and

110, 001,

110.

Octahedrite

192

no

010*

:010

11

StereographicProjectionof Octahedrite

CRYSTALLOGRAPHY

84

193

110

110\_221

\UO

4* Gnomonic

Projectionof Octahedrite 2.

HEMIMORPHIC IODOSUCCINIMIDE

CLASS

(7).

TYPE

(Ditetragonal Pyramidal or Holohedral Hemimorphic Class) This class differs from 98. Symmetry. the normal class only in having no horizontal plane of symmetry; hence the forms are hemimorphic as defined in Art. 29. It is not known to be represented minerals,but is shown among the crystalsof iodosuccinimide. Its symon "

Symmetry are

of

Hemimorphic

distinct forms,001

Class

*" stereographicpro" P6^ Sf"lufor^ed Here the two basal planes

jection (Fig.194). and 001; the prisms do not

differ

geometricallyfrom

TETRAGONAL

85

SYSTEM

those of the normal class, though distinguished by their molecular structure; further,the pyramids are no longer double pyramids, but each form is represented by one half of Figs. 174, 178, 187 (cf.Fig. 44, p. 22). There are hence six distinct pyramidal forms, correspondingto the upper and lower halves of the first and second order pyramids and the ditetragonal pyramid. 3.

TRIPYRAMIDAL

CLASS

(8). SCHEELITE

TYPE.

(TetragonalBipyramidal or Pyramidal Hemihedral

Class)

and Symmetry. The forms here included have Typical Forms plane of symmetry only, that of the horizontal crystallographic axes, axis of tetragonalsymmetry and one axis) (the vertical crystallographic The distinctive forms are the tetragonalprism (hkO) and normal to it. pyramid (hkl)of the third order,shown in Figs.196, 197. The stereographicprojection,Fig. 195, 195 99.

"

one

of the class and the exhibits the symmetry distribution of the faces of the generalform (hkl). Comparing this,as well as the figures with those of the normal immediately following, class,it is seen that this class differsfrom it in the absence of the vertical planesof symmetry of symmetry. and the horizontal axes and Pyramid of the Third 100, Prism The Order. typical forms of the class, above as stated,are a square prism and a are distinguished pyramid, which square respectivelyfrom the square prisms a (100) in Figs.170 and 171 and and m(110), shown from the square pyramids (hOl) and (hhl) y third order." of Figs. 174 and 178 by the name "

Tri-PyramidalClass

"

198

197

196

120

100

Third

Order

Prism

Third

Order

Pyramid

derived from half the faces forms of the normal class by taking only one the ditetragonal therefore of the latter and the omission of the remaining faces. There are which and right, each designatedleft in forms two case, complementary tragonal diteand (Fig.173) the of p rism faces ditetragonal include all the The

third order

prism and pyramid

may

together pyramid (Fig.187) of the normal

be considered

class.

as

CRYSTALLOGRAPHY

.

The

indices of the faces of the two

complementary prisms,as (210),are:

Left: 210, 120, 210, Right: 120, 210, 120, The

indices of the faces of the

Left: above

Right: above

120. 210.

correspondingpyramids, as (212),are:

212, 122, 212, 122; 122, 212, 122, 212;

below below

212, 122, 212, 122, 212, 122,

122. 212.

Fig. 198 givesa transverse section of the prisms a(100) and m(110), also the prism of the third order (120). Figs.196, 197 show the rightprism (120) and pyramid (122)of the third order. that is,the base The other forms of this class, Forms. 101. Other and also the square ra(110); mids pyrac(001); the other square prisms,a(100) like the correspondingforms of the (hQl)and (hhl)are geometrically The class shows therefore three types of class already described. normal .class. called the is hence and tripyramidal pyramids square 102. To this class belongs the important speciesscheelite;also the unless it be that they are rather isomorphous speciesstolzite and powellite, 199 shows wulfenite a with classed be Fig. typicalcrystalof to (p. 87). "

201

199

Scheelite

Scheelite

Meionite

a basal section of one similar;these illustrate well the the forms characteristics of the class. Here are e(101),p(lll), and the third-order pyramids 0(212),s/131). Fig. 201 represents a meionite crystal withr(lll),and the third-order pyramid 2(311). See also Figs.203, 204, in which the third-order prism is shown. described (seeArt. 28) as showing The forms of this class are sometimes hemihedrism. pyramidal

and Fig.200 scheelite,

4.

PYRAMID

AL-HEMIMORPHIC

(TetragonalPyramidal

CLASS or

Hemihedral

(9). WULFENITE

TYPE

Hemimorphic Class)

The fourth class of the tetragonal system is closely vertical axis of tetragjustdescribed. It has the same onal but is there horizontal of no The forms symmetry, plane symmetry. hemimorphic in the distribution of the faces (cf.Fig. 202). are, therefore, The mineral species probspecieswulfenite of the Scheelite Group among ably belongshere,although the crystalsdo not always show the difference

103. Symmetry. related to the class

"

CRYSTALLOGRAPHY

88

class by the the first order pyramid of the normal There latter. therefore of the are faces alternate the development of only and the known as forms positive negative possibletwo complementary is unit sphenoid (111),and positive sphenoids. The generalsymbol qf_the_ while the negative sphenoid its faces have the jndices:111, 111, 111, 111, occur the complementary forms together,if has the symbol (111). When two unlike sets of faces, the having s olid, though resulting developed, equally from the first order pyramid (111). geometrically be distinguished cannot ered

as

derived from

208

TetragonalScalenohedron

Sphenoid

which belongs to this class, the deviation in In the specieschalcopyrite, angle and in axial ratio from the isometric system is very small,and hence the unit sphenoid cannot by the eye be distinguishedfrom a tetrahedron 0'985 (instead (compare Fig.209 with Fig. 144, p. 68). For this speciesc of 1, as in the isometric system),and the normal sphenoidalangle is 108" 40', Hence instead of 109" 28',the angle of the tetrahedron. copyrite a crystalof chalwith both the positiveand negative sphenoids equally developed closelyresembles a regularoctahedron. In Fig. 210 the second order pyramids e(101)and z(201)and base c(001) also present. are =

209

Chalcopyrite 106. Tetragonal Scalenohedron. The sphenoidal symmetry yields another distinct type of form, that shown in Fig. 208. It is bounded by and hence is called a tetragonalScalenohedron; eightsimilar scalene triangles, the general symbol is (hkl). It may be considered as derived from the class by taking the alternate pairs of ditetragenalpyramid of the normal "

TETRAGONAL

89

SYSTEM

faces of the latter form.

The faces of the complementary positive and negative therefore embrace all the faces of the ditetragonal pyramid. This in combination in chalcopyrite, but is not observed pendently. indeappears In Fig. 211 the form s(531)is the positive tetragonalscaleno-

forms form

hedron. Other

107.

Forms. The other forms of the class, namely, the firstand the ditetragonal prisms,, prism, and the firstand second order pyramids (hhl)and (MM), are geometricallylike those of the normal class. The lower symmetry in the molecular structure is onlv revealed by special as investigation, by etching.

second

"

order

6. TRAPEZOHEDRAL

CLASS

(11). NICKEL

(TetragonalTrapezohedralor

SULPHATE

TrapezohedralHemihedral

TYPE

Class)

class under The trapezohedralclass is analogousto the plagiohedral isometric system; it is characterized by the absence of any plane or center of symmetry; the vertical axis,however, is an axis of tetragonalsyi: and perpendicularto this there are four axes of binary symmetry. metry, This symmetry and the distribution of the faces of the generalform (hkl) 108.

the

-

213

212

Symmetry

of

TrapezohedralClass

TetragonalTrapezohedron

Fig.212, and Fig. 213 givesthe stereographicprojection, tragonal trapezohedron.It may be derived from the ditesolid,a tetragonal resulting faces the alternate pyramid of the normal class by the extension of There two complementary forms called right-and leftform. are that of pyramid of the normal handed which embrace all the faces of the ditetragonal enantiomorphous, and the salts belongingto forms are These two class.

are

shown

in the

this class show

Nickel

circular

sulphateand

polarization. a

few

other artificialsalts belong

TETARTOHEDRAL

7.

CLASS

in

this class.

(12)

or SphenoidalTetartohedral Class) (TetragonalBisphenoidal

class under

this

seventh and last possible The Symmetry. of symmetry, but the vertical axis is an axis center system has no plane nor The symmetry and the distribution of the faces of the of binary symmetry. 109

"

90

CRYSTALLOGRAPHY

generalform (hkl)are shown is known the solid resulting as

c projection (Fig.214), and stereograph] It be derived order. third the can a sphenoidof of the normal the ditetragonal from pyramid class by taking only one quarter of the faces

in the

of that

There

form.

are

therefore four

which

plementary com-

respectively ) and left distinguishedas right ( + and (+ and ). These four togetherembrace all the sixteen faces of the ditetragonal pyramid. forms

are

"

"

.

characteristic forms of this class of the the third order are ](hkty, prism of the first positiveand negative sphenoids second order of the (111),and also those artificial order (101). It is said that an compound, 2CaO.Al203.SiO2, crystallizesin this class. other

The

the

Symmetry

of Tetartohedral

Class

RELATIONS

MATHEMATICAL

OF

SYSTEM

TETRAGONAL

THE

It appears of the seven from the discussion of the symmetry llOo Choice of Axes. classes of this system that with all of them the positionof the vertical axis is fixed. In either set classes 1, 2, however, where there are two sets of vertical planes of symmetry, the axial planes and the other the diagonal planes. The choice between these be made may two by the habit of the possiblepositionsof the horizontal axes is guided particularly and the relations of the given speciesto others of similar form. With occurring crystals tation crystalcharacters have been described it is customary to follow the oriena specieswhose given in the originaldescription. of the Axial Ratio,etc. The followingrelations serve 111. Determination to connect the axial ratio,that is,the length of the vertical axis c, when a 1, with the fundamental angles (001 A 101) and (001 A 111): "

"

=

tan For

(001 A

101)

-

tan

c;

same rectangular zone (cf.Fig. 214) are:

faces in the cases

(001

A

the tangent

tan

(001

tan

(001 A

hOl) 101)

tan

(001 A

OfcQ

A

111)

X

principle applies. The

most

portant im-

h = ~

I

'

k = "

tan

(001 A Oil)

tan

(001

A

I h

hhl) = ~

tan

For the

(001

A

111)

'

l'

prisms tan

(010

A

fcfcO) =

"

tan

(100

A

hkQ]

=

"

112. It will be noted that in the stereographicprojection(Fig. Other Calculations. 214) all those spherical trianglesare right-angledwhich are_ formed by great circles (diameters) which meet the prismaticzone-circle 100, 010, 100,_010. Again, all those formed by 100 and great circles drawn between 100, or 010 and 010, and crossingrespectivelythe zone-circles 100, 001, 100, or 010, 001, 010. Also, all those formed by great circles drawn 110 and 110 and crossing the_zone-circle between 110 and 110 110, 001, 110, or between and crossingthe zone-circle 110, 001, 110. These sphericaltrianglesmay hence be readilyused to calculate any angles desired; for the pole of any face,as hkl (say 321), and the pinacoids 10_0, example, the angles between The terminal angles (x and z, Fig. 187) of the ditetragonalpyramid, 212 A 212 010, 001. (or 313 A 313, etc.),and 212 A 122 (or 313 A 133, etc.), also be obtained in the same can The zonal relations give the symbols of the poles on the zones way. 001, 100 and 001, 110 for the given case. For example,the zone-circle 110, 313, 133, 110 fneets 110, 001, 110 at "

TETRAGONAL the

pole 223,

"

and

SYSTEM

91

the calculated angle 313 A 223 is half the angle 313 A 133 If a laree tO ** Calculated" "* ^ tt is more Convenient to use a formula

"

given bek"wr 113.

Formulas.

"

expressed directlyin

It is sometimes convenient to have the normal interfacial angles of the axis c and the indices h, k, and I Thus

terms

'

These

also be expressed in the form

may

P" '"-

(2) For

PQ

"

"

|Ti

tan2 PC

the poles of any

"

=

v

:

two

faces (hkl),(pqr),we

on

Angle on w(110) 30"57f

410

14"

310

18

26

26

34

210

26

34

18

26

21'

have

in general

-^ "

[(# + k2)c2+ I2][(p2-f o2)c2+ rz]

"

0(100)

"

"2

The above equations take a simpler form for specialcases for hkl and the angle of the edge y of Fig. 187. 114. Prismatic The angles for the commonly Angles. follows* are as

Angle

"

/C2C2

the distance between

cos

',

=

"-

often occurring; for example,

occurringditetragonal prisms

Angle

on

o(100)

Angle

on

530

30" 57*'

w(llO) 14" 21'

320 430

33

11

36

41J 521

8

18| 7|

115. To determine, by plotting, the axial ratio, : c, of a tetragonalmineral from the a As an illustrative example it has been stereographic projection of its crystal forms. that the angles between the faces on the crystal assumed of rutile, representedin Fig 180, and from been measured these measurements have the poles of the faces in one octant In determining the axial ratio of a located on the stereographicprojection,see Fig. 215. thing,the length of the c axis,since the length of tetragonalcrystal(or what is the same the a axes the indices of some are always taken as equal to 1) it is necessary to assume It is customary to take a pyramid which is prominent upon the crystals pyramidal form. that it is the fundamental unit pyramid of either the firstor of the mineral and assume or second order and has as its symbol either (111) or (101). In the example chosen both a dent firstorder and a second order pyramid are present and from their zonal relations it is evithat if the symbol assigned to the firstorder form be (111) that of the second order be (101), In order to determine the relative length of the c axis in respect to form must to plot the interceptof the length of the a axis for rutile therefore, it is only necessary In the case of the second order pyramid it is only the axes. either of these forms upon left hand quadrant of Fig. 215) in to construct a rightangle triangle(see upper necessary which the horizontal side shall equal the length of the a axis,(1),the vertical side shall represent the c axis and the hypothenuse shall show the proper angle of slope of the face. the center of the projectionand the pole e(101) is measured The by the angle between making that angle with the line representingthe protractor and a line drawn stereographic then be at right angles to this pole. Its The hypothenuse of the trianglemust c axis. vertical side of the w hen expressed in relation to the distance the triangle, interceptupon (0-M) which was chosen as representingunity on the a axis,will therefore give the length to be 0.644. In rutile this is found the positionof the pyramid of the first order s(lll) value is obtained when is first drawn at rightangles to the radial line 0-P the line M-P-N In this case drawn through the pole s(lll). The triangleto be plotted in this case has the distance be at rightangles to the O-P the length of its horizontal side. Its hypothenuse must as in the first as the pole to (111). The intercepton the c axis is the same line representing

of the

c

The is used.

case.

axis. same

CRYSTALLOGRAPHY 216

H010

TETRAGONAL

93

SYSTEM

To determine, by plotting, the indices of any face (hkl) of a tetragonal form from position of its pole on the stereographic projection. The solution of this problem is under the -Isometric System, see p. 74, except that the like that given in a similar case interceptof the face on the vertical axis must be referred to the established unit length of is exactly the reverse method of the that axis and not to the length of the a axis. The used in the problem discussed directlyabove. one the axial ratio,a : c, of a tetragonalmineral To determine, by plotting, from the 117. As an illustrative example consider the crystal gnomonic projection of its crystalforms. of rutile,Fig. 180, the poles to the faces of which, are shown plotted in gnomonic projection The in Fig. 216. pyramids of the first and second order present are taken as the and O-N with the symbols, s(lll) and e(101). The lines O-M unit forms represent the 116.

the

the distance from the center O to the circumference of horizontal axes az and a\ and and O-N circle is equal to unity on these axes. The interceptson O-M the fundamental made by the polesof e (101)or the perpendiculars drawn from the poles of s(lll) give the In this case this distance,when unit length of the vertical axis,c. expressed in terms of the assumed length of the horizontal axes (which in the tetragonalsystem always equals two

1) is equal to

0.64.

This repthe above relation is true is-obvious from a consideration of Fig. 216. resents vertical section through the spherical and gnomonic projection including the a The horizontal axis,02. slope of the face e(011) is plotted with its interceptson the a2 and c axes and the positionof its pole in both the sphericaland gnomonic projectionsis It is seen shown. through the two similar trianglesin the figurethat the distance from the intercept be the same as the center to the pole e(011) in the gnomonic projectionmust And the vertical axis c. represent unity on c. as e is a unit form this must of the face e upon

That

118.

To

the indices determine, by plotting,

positionof its pole on the gnomonic is being considered whose Unaxial ratio is known. der these conditions draw the perpendicularsfrom pole in question to the the two lines representing Then horizontal axes. these lines off on space to the distances equivalent bering length of the c axis,remembe that it must expressed in terms of the length of the horizontal which in turn is equal axes the to the distance from of the projection center of the to the circumference circle. Give fundamental the intercepts of the lines from the pole of drawn the face to the axes a\ of the in terms and a2 length of the vertical axis, add a 1 as the third figure clear of and if necessary fractions and the required indices are the result. This

of any

face

of

a

from

tetragonal form that in this

projection. It is assumed

case

the

mineral

a

217

is illustrated in Fig. 217, is the lower right which hand quadrant of the gnomonic projection of the the rutile forms shown on drawn

e

as

"-

dttetragonalpyramid ,(321),Perpendiculars h

sr

from

its

pole

.intera

94

CRYSTALLOGRAPHY

be readily the indices of the face in question. The indices of a prism face like "(310)can the Isometric System, Art. 84. described under manner as obtained in exactly the same p. 75.

III.

SYSTEM

HEXAGONAL

includes all the forms which referred SYSTEM are in at common a plane intersecting to four axes, three equal horizontal axes anglesof 60",and a fourth,vertical axis,at rightanglesto them. of distinct sections are here included, each embracing a number Two themselves. classes related among They are called the Hexagonal Division The symmetry of the former, and the Trigonal(orRhombohedral)Division. about the vertical axis,belongs to the hexagonal type, that of the latter to 119.

the

The

HEXAGONAL

trigonaltype.

Miller (1852)referred all the forms of the hexagonalsystem to three equal axes parallel at equal angles,not rhombohedron, and hence intersecting to the faces of the fundamental 90". This method (furtherexplained in Art. 169) had the disadvantage of failingto bring between the normal hexagonal and tetragonaltypes, both characterized out the relationship by a principalaxis of symmetry, which (on the system adopted in this book) is the vertical

different symbols to faces which axis. It further gave are crystallographic crystallqnatural to employ the three rhombohedral for trigonal axes graphicallyidentical. It is more forms only, as done by Groth (1905),who includes these groups in a TrigonalSystem; but this also has some disadvantages. The indices commonly used in describinghexagonal the Miller-Bravais indices,since they were forms are known as adopted by Bravais for use used by Miller in the other crystalsystems. from the scheme with the four axes

There are five possibleclasses in the Hexagonal Symmetry Classes. the most Of these the normal class is much Division. important,and others are also of importance among minerals. two crystallized In the Trigonal Division there are seven hedral classes;of these the rhomboof the Calcite is class or that and Type, by far the most common, three others are also of importance. and The 121. Axes taken is Symbols. position of the four axes shown in Fig.218; the three horizontal axes called a, since they are equal are and the vertical axis is c, since it has a different length, and Interchangeable, being either longer or shorter than the horizontal 218 The lengthof the vertical axis is expressed axes. in terms of that of the horizontal axes which in turn is always taken as unity. Further,when it is desirable 120.

"

"

between the horizontal axes distinguish designated"i, a2, a3. When properly orientated one of the horizontal axes (a2)is parallel to the observer and the other two make angles of 30" either side of the line perpendicular to him. to

they

may

be

The

axis to the left is taken as ai, the one to the The as and a3. positive negative ends of ^e axes in Fig. 218. shown are The general be expressed in a position of any plane may that applicable in the other systems, viz.-

right

Hexagonal Axes manner

analogous

to

1111

h^'-k^'-i"*''!*' .

The correspondingindices for a given plane are refer to the axes named in the above scheme.

;

then h, k, i,I; these always Since it is found convenient

96

CRYSTALLOGRAPHY

The

order.Fig.220, includes prism of the first

six

faces,each one of which at adjacent horizontal axes

two meets to the vertical axis and parallel It has hence to the third horizontal axis. equal distances,while i^isparallel the the generalsymbol (1010)and is uniformlydesignatedby the letter m; indices of its six faces taken in order (seeFigs.220 and 229, 230) are:

is

10TO, OlTO, TlOO, 1010,

lIOO.

0110,

221

T"~~

"First Order

Prism

2110

i 1120

Second

Order

--1210

Prism

Dihexagonal Prism

Order. The Second of the second order, prism to the vertical axis,and Fig.221, has six faces,each one of which is parallel the at the unit distance, the three horizontal axes, two alternate axes meets intermediate axis at one-half this distance;or, which is the same thing,it the last-named axis at the unit distance,the others at double this meets The distance.* generalsymbol is (1120) and it is uniformly designatedby the letter a; the indices of the six faces (seeFigs.221 and 229, 230) in order 126.

Prism

of

the

"

are:

1210, 2110,

1120,

1120,

1210,

2110.

first and second order prisms are not to be distinguished geometrically each other since each is a regularhexagonal prismwith normal interfacial angles of 60". They are related to each other in the same as way the two prismsra(110)and a(100)of the tetragonal system. The relation in positionbetween the firstorder prism (and pyramids) on the one hand and the second order prism (and pyramids) on the other will be understood better from Fig. 223, representing section of the two prisms parallel a cross to the base c. 127. Dihexagonal Prism. The dihexagonal prism, Fig. 222, is a twelve-sided prism bounded of which is parallel by twelve faces,each one to the vertical axis,and also meets two adjacent horizontal axes at unequal distances, the ratio of which always lies between 1 : 1 and 1:2. This has two and prism edges,lettered x unlike_ y, as shown in Fig. 222. The generalsymbol is (hkzO)and the indices of the faces of a givenform, as (2130),are: The

from

"

*

Since lai

:

la-j:

"

|a3 :

a"c

is equivalentto 2ai

:

2a2

:

"

Ia3

:

HEXAGONAL

2130, 2130,

1230, 1230,

97

SYSTEM

1320, 1320,

2310, 2310,

3210,

3120,

32lO, 3l20.

Pyramids of the First Order. Correspondingto the three types of prisms justmentioned, there are three types of pyramids A pyramid of the first order,Fig. 224, is a double six-sided pyramid (or by twelve similar triangularfaces above and six bipyramid)bounded six which have the same below positionrelative to the horizontal axes as the faces of the first order prism,while they also intersect the vertical axis above The generalsymbol is hence (hOhl). The faces of a givenform, and below. are: as 1011), 128.

"

"

"

Above Below

1011, 1011,

0111, 0111,

1101, 1011, 1101,, 1011,

0111, 0111,

1101.

lIOl.

given speciesthere may be a number of pyramids of the firstorder, in the ratio of the intercepts the horizontal to the vertical axis, on differing between the base (0001) and the faces of the unit and thus forming a zone prism (1010). Their symbols, passing from the base (0001) tojthe unit prism (1010),would be, for example, 1014, 1012, 2023, 1011, 3032, 2021, In Fig. 228 the faces p_and u are firstorder pyramids and they have etc. in As shown 0.4989. the symbols respectively (1011) and (2021),here c the faces of the first order pyramids replacethe edges of the first these cases order prism. On the other hand, they replacethe solid anglesof the second order prism a(112Q). On

a

=

226

224

First Order

Pyramid

Second

Order

Pyramid

DihexagonalPyramid

The pyramid of the second order Pyramids of the Second Order. the twelve similar faces including (Fig.225), is a double six-sided pyramid 129.

"

which have the same positionrelative to the horizontal axes as the faces vertical axis. They of the second order prism,and which also intersect the of the form the faces of indices have the generalsymbol (h'h-2h-l). The

(1122)are: Above Below

1122, 1122,

1212,

1212,

2112, 2112,

1122, 1122,

1212, 1212,

2112. 2112.

between the faces The faces of the second order pyramid replacethe edges Further,they replacethe solid angles of the second order prism and_thebase. a .numbe on a singlecrystal: ber of the first order prism m(1010). There may base the c(0( between zone a forming order pyramids of second

98

CRYSTALLOGRAPHY

order prism a(1120),as, naming them in order: JL124, 1122, 2243, 1121, etc. In Fig. 227, s is the second order pyramid (1121). The 130. Dihexagonal Pyramid. dihexagonal pyramid, Fig. 226, is a double twelve-sided pyramid, having the twenty-four similar faces embraced under the general symbol (hk'd). It is bounded by twenty-four similar two zontal also the vertical and each meeting adjacent horimeeting axis, faces, the ratio of which lies at unequal distances, between axes always Thus the form (2131)includes the followingtwelve faces in 1 : 1 and 1:2. the upper half of the crystal:

the

the faces_of

second

"

2131, 2131,

1231, 1231,

1321, 2311, 3211, 3121, 1321, 2311,

3211,

3121.

similarlybelow with I (here 1) negative,2131,etc. The dihexagonal because a common form with the species pyramid is often called a berylloid beryl. The dihexagonalpyramid v(2131)is shown on Figs.224, 225. 131. Combinations. of the Fig. 227 of beryl shows a combination And

"

227

Beryl and prism m(1010) with the_first base_c(0001) order pyramids p(10ll)and the second order pyramid s(1121) and the dihexagonal pyramid tt(2Q21); p(2131). Both the last forms lie in a zone between m and s, for which it is that k I. The basal projection of a similar crystalshown in Fig.228 is very instructive as exhibitingthe symmetry of the normal hexagonal class. This is also true of the stereographic and gnomonic projectionsin Figs.229 and 230 of a like crystalwith the added form true

=

0(1122).

2.

HEMIMORPHIC

(DihexagonalPyramidal 132.

CLASS or

(14). ZINCITE

TYPE

Holohedral Hemimorphic Class)

This class differs from Symmetry. the normal class only in having no horizontal plane of principalsymmetry and no horizontal axes of binary symmetry. It has,however, the same six vertical planes of symmetry at meeting anglesof 30" in the vertical crystallographic axis which is "

2110

0110

1100

1010

CRYSTALLOGRAPHY

100 axis of

an

is

There

hexagonal symmetry.

center

no

is exhibited

symmetry

of symmetry. The in the stereographic

Fig. 231. projection, The

forms

belonging to this are planes, 0001 here distinct forms, the positive and 0001, (upper) and negative (lower) pyramids of each of the three types; also the three prisms, last do not differ geometricallyfrom which class. An the prisms of the normal example in zincite,Fig. 44, of this class is found lodyrite,greenockiteand wurtzite are p. 22. Forms.

133.

Symmetry

of

3.

Hemimorphic Class

-

-

the

class

two

basal

also classed here.

CLASS

TRIPYRAMIDAL

(Hexagonal Bipyramidal

(15).

Pyramidal

or

APATITE

TYPE

Hemihedral

Class)

This class is important because and Symmetry. speciesof the ApatiteGroup, apatite,pyromorphite, The typicalform is the hexagonal prism (hklO)and each designatedas of the third order. These the hexagonal pyramid (hktl), in Figs.233 and 234 may be considered as derived forms which are shown the correspondingdihexagonalforms of the normal from class by the omission the faces of the latter. of the of one half other forms of the They and class have only one plane of symmetry, the plane of the horizontal axes, and axis of hexagonal symmetry (the vertical axis). also one

Typical Forms

134.

"

it includes the common mimetite,vanadinite.

The

symmetry

is exhibited

in

the

stereo-

graphicprojection(Fig.232). It is seen here, in the figuresof crystalsgiven,that,like as the tripyramidal class under the tetragonal faces the of the general form (hk~l) system, of the possible half are planesbelonging present to

above

each sectant, and further that those and below fall in the same vertical

zone.

135. Order.

Prism

and

Pyramid

of

the

Third

The prism of the third order (Fig. under the 233) has six like faces embraced general symbol (hkiQ) and the form is a regular hexagonal prism with anglesof 60",not to be "

,

if alone,from the Symmetry of Tripyramidal Class distinguished geometrically, cf. hexagonal prisms; Figs.220, 221, The six faces of the right-handedform (2130) have the indices p. 96. other

2130, The

faces of the

3210,

2l30, 1320, 32lO.

complementary left-handed form have the indices:

1230, As

1320,

23lO, 3120, 1230, 2310, 3l20

alreadystated these two dihexagonalprism (Fig.222).

forms

togetherembrace

all the faces of the

HEXAGONAL

233

Third

The

Order

SYSTEM

101

234

Prism

Third

pyramid is also

Order

236

Pyramid

regulardouble

a

hexagonal pyramid of the third

order, and in its relations to the other hexagonalpyramids of the class (Figs. 224, 225) it is analogous to the square pyramid of the third order met with in the correspondingclass of the_tetragonalsystem (see Art. 100). The faces of the

right-handedform (2131)are: Above 2131, 1321, 3211, 2131, 1321, 3211. Below 2131, 1321, 3211, 2131, 1321, 3211. There is also a complementary left-handed form, which with this embraces all the faces of the dihexagonalpyramid. section of Fig.235 shows The cross in outline the positionof the first order prism, and also that of the righthanded prism of the third order. The prism and pyramid justdescribed do not often appear on crystals as predominatingforms,though this is sometimes the case, but commonly these faces are present modifying other fundamental forms. Forms. of the class are geometri136. Other The remaining forms cally the base (0001); the firstorder prism like those of the normal class, viz., the first order pyramids (hQhl); (1010); the second order prism (1120);_ ture, structheir molecular order pyramids (h'h'2h'l). That and the second is class this to the of readilyproved,for however, corresponds symmetry In this it was shown that example,by etching. way pyromorphite and mimetite belonged in the same with group with apatite(Baumhauer),though crystals This class the typicalforms had not been observed. of Tripyramidalbecause its forms is given its name include three distinct types of pyramids. in Fig. 137. A typicalcrystalof apatiteis given_ and the third order pjism ft(2130), It shows 236. also the third order pyramids, M_(2131), n_(3141); the first order pyramids r(1012),z(1011),"/(2021), the order second pyramids K1122), s(1121); the base c(0001). the prism w(1010), and Apatite finally, "

4

CLASS

PYRAMIDAL-HEMIMORPHIC

(Hexagonal Pyramidal

or

(16). NEPHELITE

Pyramidal Hemihedral

TYPE

Hemimorphic Class)

the the hexagonal division, fourth class under class,is like that just described,except that the pyramidal-hemimorphic 138.

Symmetry.

"

A

CRYSTALLOGRAPHY

102 forms

are

hemimorphic.

The

singlehorizontal plane of symmetry

is

absent,

This symmetry but the vertical axis is stillan axis of hexagonal symmetry. projectionof Fig.237. The typicalform would is shown in the stenographic The half of Fig. 234 of the pyramid of the third order. be like the upper (Kg. speciesnepheliteis shown by the character of the etching-figures Groth after Baumhauer) to belong here. 237

Symmetry

of

Class Pyramidal-Hemimorphic

TRAPEZOHEDRAL

5.

Nephelite

CLASS

(17)

(HexagonalTrapezohedralor TrapezohedralHemihedral

Class)

The last class of this division is the trapezohedral 139. Symmetry. agonal class. It has no plane of symmetry, but the vertical axis is an axis of hexsymmetry, and there are, further,six horizontal axes of binary symmetry. The symmetry and the distribuThere is no center of symmetry. tion of the faces of the typicalform (hkll)is shown in the stereographic projection (Fig.239). The typicalforms may be derived from the dihexagonal pyramid by the omission of the alternate faces of the latter. There are two the right and left hexagonal trapezohedroris as (see possibletypes known "

239

/

V

240

o,{"

(--AA-H V ? % / Symmetry

Fig.240),which in this class show

of Trapezohedral Class

are

Hexagonal Trapezohedron

salts falling enantiomorphous,and the few crystallized polarization.A modification of quartz known as

circular

104

CRYSTALLOGRAPHY

mineral is the rare of this class known only representative This in 242. crystalshows benitoite,a crystalof which is represented Fig. the hexagonal_prism of_thesecond the trigonalprisms m(1010) and ^(0110), order,a(1120),the trigonalpyramids,p(1011]and Tr(Olll);6(0112)and the hexagonal pyramid of the second order, x(2241) zones.

The

2.

(19). CALCITE

CLASS

RHOMBOHEDRAL

Scalenohedral (Ditrigonal

or

Rhombohedral

Hemihedral

TYPE .

Class)

The typicalforms of the rhomand Symmetry. 142. Typical Forms and the scalenohedron 244) rhombohedron (Fig. (Fig. bohedral class are the with the These forms, projections, 259). 243 Figs. 243 and 269, illustrate the symmetry I three ! characteristic of the class. There are these are diangoal planes of symmetry only; horizontal crystallographic and to the axes intersect at anglesof 60" in the vertical crystallographic axis. This axis is with these forms there axis of trigonal symmetry; an are, further,three horizontal axes diagonal to the of binary symmetry. crystallographicaxes also Fig.245 et seq. Compare Fig. 244, 269 with Fig. 229, p. By comparing Fig. it that all the faces in half will be seen 99, Symmetry of Rhombohedral is hence This group the sectants are present. Class metric analogous to the tetrahedral class of the isosystem, and the sphenoidal class of the tetragonalsystem. 143. Rhombohedron. is Geometrically described,the rhombohedron It six rhomb. has six like like each lateral a a solid bounded by faces, edges forming a zigzag line about the crystal,and six like terminal edges, three The vertical axis joinsthe two above and three in alternate positionbelow. trihedral solid angles,and the horizontal axes jointhe middle points of the oppositesides,as shown in Fig. 244. "

".--" -^

"

Positive Rhombohedron

246

245

244

Calcite

Negative Rhombohedron

Positive Rhombohedron Hematite

The generalsymbol of the rhombohedron faces of the unit form (1011)have the indices:

Above, lOll, IlOl, Olll;

is

(hQhl),and the successive

below, OlIT, Toil, llol.

HEXAGONAL

105

SYSTEM

The

varies widely as the angles geometricalshape of the rhombohedron change, and consequently the relative lengthof the vertical axis c (expressed of the horizontal axes, a in terms the 1). As the vertical axis diminishes, rhombohedrons become more and more obtuse or flattened; and as it increases and more A cube placed with an octahedral axis acute. more they become vertical is obviously the limitingcase between the obtuse and acute forms where the interfacial angle is 90". In Fig. 244 of calcite the normal rhombohedral angle is 74" 55' and c while of this for 246 hematite 0-854, Fig. 94" is and 1-366. 246-251 other c show drons rhomboheFurther,Figs. angle of calcite, (0554),/(0221),M(4041), and p(16-0-16-l) namely, I (0112),"/" ; in the ratio of J, f 2, 4, 16, to that of the fundahere the vertical axes mental are of Fig. 244, whose angle determines the (cleavage)rhombohedron =

=

=

,

value

of

c.

247

249

261

250

254

253

Figs.247-252,Calcite

Figs.253-254,Gmelinite

To positive every and Negative Rhombohedrons. Positive identical and form, inverse be complementary an there rhombohedron may Thus in the_alternate sectants. geometrically,but bounded by faces falling 245 has in shown Fig. rhombohedron (0111) unit the the negativeform of

144.

"

the faces:

Above,

Olll, 1011, 1101;

below, 1101, 0111,

1011.

fully (Figs.269, 270) should be careThe positionof these in the projections 250 are to referred 246, Figs.244, Of the figuresalready studied. 251 Fig. rhombohedrons; and Figs. 245, 247, 248, 249 negative, positive, forms. both shows bohedrons that the two complementary positiveand negative rhombe It will seen the faces of the like all of given axial length togetherembrace two When these the first order. double six-sided hexagonal pyramid of form is geometrically the .identical developed equally are rhombohedrons of 254 r(1011), gmelimte illustrated is Fig. by with this pyramid. This .

,

CRYSTALLOGRAPHY

106

p(0111)and by Figs.284, 285, p. 113,of quartz, r(1011),3(0111).* In each double hexagonal pyramid (in Fig. a the form, which is geometrically case of the two unit rhombohedrons, combination 254 with c and m), is in fact a the two forms a difference in size between and negative. Commonly positive form taken the the posias tive be observed, as in Figs.253 and 286, where may if distinction this cannot be rhombohedron predominates. But even be rhombohedrons distinguished can b y always etching, two the established, of quartz, by pyro-electrical phenomena. or, as in the case the faces of the posiof rhombohedrons tive and the between the base first (0001) edges rhombohedrons the faces the of the Also replace negative order prism (1010). between and the that (0001) forms, edges is, alternate edges of the same

145. Of the two rhombohedrons

series,or

zones,

replacethe

(0110) (compare Figs. 253, 254, etc.). Fig. 255 shows the rhombohed_ron with the prism a(1120). Fig. 256 the same in combination with the base. the two forms happens to approximate to 70" 32' the angle between When This is illustrated the crystalsimulates the aspect of a regularoctahedron. 71" and the also 69" here oo crystalresembles 22', co 42', by Fig. 257; truncated with 55). octahedron Fig. 99, (cf. edges p. closelyan =

=

257

255

Coquimbite

Figs. 255, 256, Hematite

258

Eudialyte

the positiveand negative 146. There is a very simple relation between it which is The form of one series rhombohedrons important to remember. which truncates the terminal edges of a given form of the other will have one axis of the latter. This half the intercept on the vertical crystallographic Thus (0112), ratio is expressedin the values of the indices of the two forms. the terminal truncates edges of the positiveunit rhombohedron (1011); the terminal of truncates (2025). Again (1011) (1014) (0112),_(1015) edges_of the edges of (0221),(4041) of _(0221), This is illustrated by etc. basal proFig. 252 with the forms r(1011)and /(0221). Also in Fig.258,_a jection^ of the of truncates 2(1014) edges e(0112);c(0112) r(1011); r(1011)

truncates

of s(0221). 147. Scalenohedron. The shown in Fig. 259, is the scalenohedron, generalform for this class correspondingto the symbol hkll. It is a solid, bounded by twelve faces,each a scalene triangle. It has roughly the shape of a double six-sided pyramid, but there are two sets of terminal edges,one obtuse than the other, and the lateral edges form a zigzagedge around more the form like that of the rhombohedron. It may be considered as derived from the dihexagonalpyramid by taking the alternatingpairs of faces of "

*

the less so as a convenient illustration in this case, none Quartz serves the fact that it belongsto the trapezohedralclass of this division.

ing notwithstand-

HEXAGONAL

107

SYSTEM

It is to be noted that the faces in the lower half of the form do that form. with those of the upper half. Like the rhombohefall in vertical zones drons, the scalenohedrons be either positiveor negative. may The positiveforms correspond in position to the positive not

rhombohedrons The

and

conversely. positivescalenohedron (2131),Fig. 259, has the

indices for the several Above Below For

the

lowing fol-

faces:

2131, 2311, 3211, 1231, 1321, 3l21 1231, 1321, 3121, 2131, 2311, 3211. complementary negative scalenohedron (1231)the

indices of the faces Above Below

1231, 2311,

"an

are:

1321, 3211,

3121,

2131,

2311,

1231, 1321, 3l2l,

32ll. 2131.

of Scalenohedrons to Relation Rhombohedrons. It was that the scalenohedron in X above general has a series of Q bcaler like the rhombohedron. It lateral is edges obvious, further, zigzag rhombohedron there will be series or for every of scalenohedrons a that zone lateral edges. This is shown in Fig. 262, where the scalenohedron having the same 148.

"

noted

,

260

261

262

,

263

Figs.260-263, Calcite

Figs.266, 267, Spangolite*

Figs.264, 265, Corundum

w(2l3l)bevels

267

266

265

264

the lateral edges of the fundamental

rhombohedron

r(10Tl);the

same

hedron Further,in Fig.263, the negativescalenoThe relation rhombohedron /(0221). of the lateral negative edges 3(1341) bevels the be shown to be, for example, for the may of the indices which must exist in these cases See also the prok, etc. jections, k + l\ again for /(0221),h + 21 h rhombohedron r(lOTl), Further, the positionof the scalenohedron may be defined with Figs. 269, 270. y (2131) For example in Fig. 262 the scalenohedron reference to its parent rhombohedron. r(1011). Again in Fig. 263 has three times the vertical axis of the unit rhombohedron

would

be true of the scalenohedron

(3251),etc.

=

-

re

(1341) has twice the vertical axis

of

/(0221).

the next illustration. the of value the destroy *

Spangolitebelongs properlyto

(hemimorphic)group,

but

this fact does not

108

CR

149.

Other

Forms.

"

YSTALLO

GR

APH

Y

class of the The remaining forms of the normal division are rhombohedral geometricallylike gonal those of the correspondingclass of the hexathe base division c(0001); the viz._, "

prisms ra(lOlO),a(1120),(teO);also the second of these order pyramids, as (1121). Some in forms shown the accompanying figures. are For to

further illustrations reference

typicalrhombohedral

be made

may

tite, hemaas calcite, species,

etc.

With

respect to the second order pyramid, it alone interestingto note that if it occurs in it is n Fig. 264, (as 2243) impossibleto whether it has the say, on geometricalgrounds, Calcite trigonalsymmetry of the rhombohedral type of the hexagonal type. In the latter case, the hexagonal symmetry is

=

or

2110

ml

1120

1010 m

Calcite

the form

might be made a first order pyramid by exchanging the axial and diagonalplanes of symmetry. The true symmetry, however, is often indi-

HEXAGONAL

cated,as

with

109

SYSTEM

corundum, by the

on_ other

occurrence

faces,as r(1011)in Fig.265

hedral rhombocrystals_^)f

(herez 2241, co 14-14-28-3). Even if rhombohedral faces are absent (Fig.266), the etching-figures (Fig.267) will often serve to_ reveal the true trigonalmolecular symmetry; here o (1124),p (1122). 150. A basal projection of a somewhat complex crystalof calcite is given in Fig.268, and stereographic and gnomonic projections of the same forms in Figs. 269 and 270; both show well the symmetry in the distribution =

=

=

=

270

ra(10lO); rhombohedrons, the forms are: prisms,a(l_120), scalenohedrons. e(0112), /(0221); positive, r(lOll),negative, positive,

of the faces. Here

3.

RHOMBOHEDRAL-HEMIMORPHIC CLASS

(20). TOURMALINE

Pyramidal or (Ditrigonal Symmetry.

rhombohedral

Trigonal

Hemimorphic Class)

Hemihedral 151.

TYPE

"

A

number

species,as

of

prominent

tourmaline,

pyrarto a hemimorphic class the symmetry For them

belong gyrite,proustite,

under this division. in the groupingof the faces differs at the two extremities of the verticalaxis. The forms have three diagonal planes of symmetry the same at meeting angles of 60" in the vertical axis,

Symmetry of Rhombohedral-Hemimorphic Class

110

CRYSTALLOGRAP

is

which

axes

axis

an

of

of

Cf.

of symmetry.

center

There

trigonalsymmetry.

symmetry,

as

zontal however, no horiclass,and there is no

are,

in the rhombohedral

Fig. 271.

In this class the basal planes (0001) and (0001) the two other characteristic forms are trigonal also the four trigonal prisms ra(1010)and ra/0110) of the first order series; first order pyramids, correspondingrespectively to the three upper and three lower faces of a positiverhombohedron, and the three upper and three lower faces of the negative rhombohedron; also the hemimorphic the four ditrigonalpyramids, order second hexagonal pyramid; finally, and lower faces respectively of the positive correspondingto the upper illustrate these forms. and Figs. 272-275 negative scalenohedrons. Fig. 274 is a basal section with r/0111^ and e/1012) below. 152.

are

Typical

Forms.

"

The

distinct Jorms.

.

274

272

275

Figs.272-275, Tourmaline 4.

CLASS

TRI-RHOMBOHEDRAL

(21). PHENACITE

(Rhombohedral or Rhombohedral

Tetartohedral

TYPE

Class)

This class,illustrated by the species dioptase, Symmetry. It is phenacite,willemite,dolomite,ilmenite,etc., is an important one. characterized by the absence of all planes of 153.

"

276

symmetry, but the vertical axis is stillan axis of trigonalsymmetry, and there is a center of symmetry. 154. order

Fig.276.

TypicalForms.

of the class

;.._..,.

Cf. are

The distinctiveforms the rhombohedron of the second "

and

the hexagonal prism and rhombohedron, each of the third order. The class is thus characterized by three rhombohedrons of distinct types (each + and ), and hence the name given to it. The second order rhombohedron be derived may

v_...

-

^

by taking one half the faces of the normal of the hexagonal second pyramid order. Class Tri-Rhombohedral There will be two complementary forms known as positiveand negative. For example, in a given case the indices of the faces for the positiveand negative forms are: Symmetry

Positive

of

(above) 1122, 2112, 1212; Negative (above) 1212, 1122, 2112;

(below) 12l2, Il22, 2ll2 (below) 2112, 1212, 1122!

112

CRYSTALLOGRAPHY 280

loio

1100

10J50

shows

(+r,

of the third ojder the distributionof the faces of the four rhombohedrons unit to the faces of the hexagonal prism (1010). +/, r, "I) relatively "

PHENACITE

TRAPEZOHEDRAL

5.

CLASS

TYPE

(22). QUARTZ

TYPE

(TrigonalTrapezohedralor TrapezohedralTetartohedral Class) This class includes,among 157. Symmetry. minerals, the species The forms have and of cinnabar. no plane symmetry and no center quartz the vertical axis is,however, an axis of trigonalsymmetry, of symmetry; of binary symmetry, coincidingin also three horizontal axes and there are direction with the crystallographic axes; cf. Fig. 281 "

281

282

283

o

\ r *

Symmetry

of TrapezohedralClass

TrigonalTrapezohedrons

HEXAGONAL

158.

Typical Forms.

"

The

113

SYSTEM

characteristic form

of the

cJass

is the

trigonaltrapezohedron shown in Fig. 282. This is the general form corresponding to the symbol (hkil), the faces being distributed as indicated in the accompanying stereographic projection(Fig.281). The faces of this form correspondto one quarter of the faces of the normal dihexagonalpyramid, Fig.226. There are therefore four such trapezohedrons, two called positive, respectively right-handed(Fig.282) and left-handed (Fig.283),and two similar negative forms, also right-and left-handed (see the scheme given in Art. 160). It is obvious that the two forms of Figs.282, 283 are enantiois a strikingcharacter of the species morphous, and circular polarization to the class elsewhere discussed. as belonging The indices of the six faces belongingto each of these will be evident on consultingFigs.281 and 229 and 230. The complementary positiveform (r and I) of a given symbol include the twelve faces of a positivescalenohedron, while the faces of all four as already stated include the twenty-four faces of the dihexagonalpyramid. Corresponding to these trapezohedrons there are_two ditrigonal prisms, as respectively right-and left-handed, (2130)and (3120). The remaining characteristic forms are the right-and left-handed trigonal prism a(H20) and_a(2110);also the right-and left-handed trigonalpyramid, half as one (1122)and (2112). They may be derived by takingrespectively of the faces the of the hexagonal prism of the second order (1120)or sponding correpyramid (1122); these are shown in Figs.221 and 225. The Forms. 159. Other other forms of the class are geometrically class. They are the base c(0001),the hexagonal like those of the normal as firstorder prism ra(1010),and the positiveand negativerhombohedrons the from These be cannot geometrically distinguished (1011) and (0111). "

normal 160.

forms. The

forms alreadyremarked

Illustrations.

"

of this class

are

best

in

shown

the

often appear 106),simple crystals

(p. speciesquartz. As r(1011)and 2(0111) hexagonalsymmetry, the rhombohedrons ence In however, a differ285). cases, many 284, (Figs. being equallydeveloped be observed,and more comin molecular character between them can

to be of normal

284

288

285

Figs.284-288, Quartz

predominatesin size; the distinction monly one rhombohedron, r(1011), like Fig. 286, show crystals, out by etching. Some always be made

can as

with a rightpositive modifying faces the righttrigonal pyramid *(ll2l), and rotate called right-handed are as z(5161). Such crystals trapezohedron,

114

CRYSTALLOGRAPHY

of lighttransmitted in the direction of the vertical the plane of polarization axis to the right. A crystal,like Fig. 287, with _thelefttrigonalpyramid as x(6151),is called left-handed, trapezohedrons, left s(2111)and one or more and as regardslighthas the oppositecharacter to the crystalof Fig. 286.

complex right-handedcrystalwith several positive several positiverighttrapezohedronsand the N. left trapezohedron, negative shows the distribution of the faces of the four The followingscheme agonal to the faces of the unit hextrapezohedrons(+r, -\-l,"r, "I) relatively prism (lOlO);it is to be compared with the correspondingscheme, of the negaof the phenacitetype. _In the case tive given in Art. 156, of crystals authors preferto make forms some the faces 2131, 1231, etc.,right,and 3121,1321, etc.,left. shows

Fig. 288

a

more

negative rhombohedrons,

and

TYPE

QUARTZ

161.

the Trigonal as (23) is known class. It has one plane of symmetry that of the horizontal axes, and one axis of trigonalsymmetry the vertical axis. There is no center of symmetry. Its characteristic forms the three and are of the three correspondingtypes of types trigonalprisms trigonalpyramids. Cf. Fig. 289. This class has no known representation Other

Bipyramidal

Classes.

or

"

The

next

class

Trigonal Tetartohedral

"

"

crystals.

among

The

or

last class (24) of this division is known the Trigonal Pyramidal as TrigonalTetartohedral Hemimorphic class. It has no plane of symmetry 289

Symmetry and

no

of

center

The

TrigonalBipyramidal Class

290

Symmetry

Trigonal Pyramidal Class

of symmetry, but the vertical axis is an axis of trigonalsymmetry. all hemimorphic, the prisms trigonalprisms,and the are

forms

pyramids hemimorphic trigonalpyramids. sodium

of the

periodatebelong to this class.

Cf.

Fig. 290.

The

crystalsof

HEXAGONAL

MATHEMATICAL

SYSTEM

RELATIONS

OF

115

HEXAGONAL

THE

SYSTEM.

The positionof the vertical crystallographic axis is fixed in all since it coincides with the axis of hexagonal in the symmetry hexagonal division and that of trigonalsymmetry in the rhombohedral division. The three horizontal axes also fixed in direction except in the normal are class and the subordinate hemimorphic class of the hexagonal division;in these there is a choice of two positions according to which of the two sets of vertical planes of symmetry is taken as the axial set. 163. Axial and The axial element is the length of the vertical Angular Elements. axis,c, in terms of a horizontal axis,a; in other words, the axial ratio of a : c. A single measured but the prismatic)may angle (in any zone be taken as the fundamental angle from which the axial ratio can be obtained. The angular element is usually taken as the angle between tfhe base c(0001) and the unit first order pyramid (1011),that is,0001 A 1011. The relation between this angle and the axis c is given by the formula of Axis. 162. Choice the classes of this system "

"

(0001

tan

The

vertical axis is also easilyobtained tan

These

relations become

lOll) X

A

from

(0001

(0001

1122)

A

follows:

as

-Xc;

=

2i

(0001

tan

h'h'2h'l)

A

=

order pyramid, since

c.

=

hOhl) X-^3

A

c.

=

the unit second

general by writing them tan

Vs

-

I

X

"

c.

In general it is easy to obtain any requiredangle between the polesof two faces on the sphericalprojection either by the use of the tangent (or cotangent) relation,or by the In practicemost of solution of sphericaltriangles, or by the applicationof both methods. the trianglesused in calculation are right-angled. The tangent relation holds good in any zone 164. Tangent and Cotangent Relations. For example: from c(0001)to a face in the prismatic zone. "

tan

(0001 A

hOhl)

tan

(0001

lOll)

=h.

tan

2h h'h'2Ji'l)

(0001 A

_

l"

"

In

the prismatic zone,

A

the cotangent

dihexagonalprism, hklQ, as

I

'

(0001

tan

formula

takes

a

1122)

A

simplifiedform; for example,lor

a

(2130) :

cot

(1010A M*0)

cot

(1120

A

feHO)

=

=

^ ML "

of the angles (lOlOA hkiO) and (1120 A MnO) is equal to 30". sum to any generalform, applying Further, the last equations can be written in a more 0001 to 0110, where the 1010 and a face in the zone pyramid (hkil)in a zone, first between pyramid, in a zone 1010 and this face is known; or_again,for the same angle between 1120 and this face 0001 to 1010, the angle between between 1120 and a face in the zone is example (cf._Fig. 229, p. 99), if the first-mentioned zone being given. For The

lOlO'/iEZ-OlIl and

the second cot

is

llSfrAHMOll, then

(10TOA hM)

=

cot

(lOlOA Olll)

^

and

"

"

cot

Also

"

"

.

for similarly

(1120

A

Mil)

lOll)

=

cot

(1120

=

cot

(1010A 0221)

A

.

j-"p

other zones, cot

(1010A MB)

"

.

f-" etc.

116

CRYSTALLOGRAPHY

(1120

cot

Other

165.

For

(1) and

in

a

2021) "~7""

(1120 A

cot

=

.

etc.

The followingsimple relations Angular Relations. hexagonalpyramid of the firstorder, "

tan

\ (lOTlA OlTl)

tan

\ (hOhl

Vj,

where

tan

"

",V|, where

tan

",=

=

sin "

=

sin

=

are

of

frequent

use:

c,

general

(2) For

a

(3) For

a

Qhhl)

A

hexagonalpyramid of the 2 sin

\ (1122

A

order,as (1122),

second

I2l2)

and

sin ",

=

^-c.

tan

"

c.

=

rhombohedron sin "

in

hkil)

A

(lOTlA TlOl)

=

Vf,

sin

a

sin

a,

where

=

a

(0001

A

(0001

A

lOTl);

general hhOl)

sin \ (hOhl A

=

Vf

where

,

=

a,

The zonal equations,described in Arts 45, 46, apply here as only that it is to be noted that one of the indices referringto the horizontal the third,i,is to be dropped in the calculations and only the other three axes, preferably in which the faces (hkil), (pqft)lie are employed. Thus the indices (u, v, w) of the zone given by the scheme 166.

Relations.

Zonal

"

in other systems,

I

XXX where

u

=

kt

Iq,

"

v

lp

=

ht,

"

w

hq

=

kp.

"

example (Fig.226) the face n lies in the zone mv, IOTO'2131 and^also in the zone For the_first the values obtained are: 2021. zone u I, w 1; for the 0, v 2. second zone, e !,/=!, 0 Combining these zone symbols according to the usual For

au, 1120

'

=

=

=

=

=

scheme 1

0

\

The

face 167.

n

has, therefore,the indices 314i,since further i (h + k). The following formulas in which unit length of the c equals the =

Formulas.

vertical axis

are

"

"

sometimes

useful:

(1) The_distances from the polesof the faces (see Fig. 229) of the pole of any face (hkil) (10TO), (0110),(1100),and (0001) are given by the followingequations, (k + 2h)

c cos

(hkil)(1010)

=

4c2

+

c cos

(M#) (OlTO)

_

4c2 c

(hkil)(TlOO)

+ k2 + hk) (/i9-

(h

-

k)

=

(As

hk)

(hkil)(0001) v

by

hk)

(2k + h)

4c2

cos

k2 +

=

+

cos

(h2+

(2) The distance (PQ) between the equation

3?2 +

the poles of

4c2 anv

(A2+ two

fc24-

faces

A/c)

P(hkil)and Q(pqrt) is given

HEXAGONAL

W, +

PQ

cos

=

117

SYSTEM

2c2

(hq + pk + 2hp + 2kq)

-7=

v [3J2+ 4c2 (h2+ k2 to give the value (3) For specialcases the above formula becomes simplified;it serves of the normal angles for the several forms in the system. They are as follows: (a) Pyramid of First Order (hQhl),Fig. 224:

X

cos

(terminal)

(6) Pyramid of Second cos

Y

Order

Z

cos

(basal) =

3/2

(h'h'2fcl), Fig. 225:

(terminal)

cosZ(basal)-P + 4^

=

P +

4W'

: (c) Dihexagonal Pyramid (hkil)

Q/2

X

cos

Y

cos

Z

cos

(d) Dihexagonal Prism cos

X

=

-

",

(seeFig.226)

=

O~2

I

/J,2 _|_ ]fZ

^2+J(^

fc2

3l2 +

2hk

2c2

(2h2+

4^

fr,+

.

3. +

(basal)

.

"

;

-

k2)

-

". +

M.)

k2 +

hk)

'

=

3/2 +

4c2

(h2+

(hkiQ),Fig. 222: 2hk

2ft2 +

^^^

(axial)

(diagonal)

Y

cos

.

2

(h*+

-

A;2+

(1011):

(e) Rhombohedron

X

cos

(f) Scalenohedron

(seeFig. 226)

(terminal)

=

(hkil): 2c (2A:2 + cos

cos

X

Y

(seeFig.259)

-

3/2 3Z2 +

Cft.

(seeFig. 259)

2hk

=

2c2

==

"

+

2c2

(W +

(2h* (h*+

4**

k* +

hk)

commonly occurringdihexagonalprisms with the The angles for some 168. Angles. table: in the following iven owng risms order second are given first and prisms n "

w(1010) 8" 57'

5160

The

Miller Axes

61

10 13

53^

19

3140

54

5270

16

6

16 13

54

2130

19 23

10

53^

3250

24i

5490

26

19{

4150

169.

a(1120) 21"

and

Indices.

forms

The

of the

6

referred three equal taken which were to the edges of the unit parallel of the positiverhombohedron

hexagonalsystem

by Miller to oblique axes

291

a

species. Fig.

2l2.

have the indices, 100,221,010,122,001,

291

represents

with the rhombohedron of the Miller axes shown. position gonal for hexaThis choice of axes forms has the grave objection the that in several cases form are faces of the same resented repby two sets of different indices;for example the faces of .the pyramid of the first order however, disappearsifthe This objection, such

would

were

set of

a

118

CRYSTALLOGRAPHY

Miller axes and indices are used only for forms in the Rhombohedral Division,that isfor forms It is belonging to classes which are characterized by a vertical axis of trigonalsymmetry. agonal believed,however, that the mutual relations of all the classes of both divisions of the hexthemselves (as also to the classes of the tetragonal system), both system among morphologicaland physical are best brought out by keeping throughout the same axes, The Miller method has, however, been adopted by a namely those of Fig. 218, Art. 121. of authors and consequently it is necessary number to give the followingbrief description.

110

(1120)

0210) Oil

(1010)

Miller and Miller-Bravais Indices Compared

Fig.292 shows in stereographicprojectionthe common hexagonal-rhombohedral forms .vith their Miller indices and in parentheses the corresponding indices when the faces are referred to the four axial system. It will be noted that the faces of the unit positiverhomhave the indices 100, 010, and 001 and those of the negative unit rhombohedron bohedron have 221, 122, 212. These two forms togethergive the faces of the hexagonal pyramid_of the firstorder (seeabove). The hexagonalprism of the first order is represented by 211, etc.,while the second order prism has 101, etc. The dihexagonal pyramid has also two sets of indices (hid)and (efg) ; of these the symbol (hkl)belongs to the positivescalenohedron and In this as it is true that in other cases (efg) to the negative form. 2h + 2k e 2h k + 21, g h + 2k + 21. For I,f example, the faces of the form 201, etc.,belong in the Rhombohedral Division of this system to the_scalenohedron (2131) while the complementary negative form would have the indices 524, etc. The relation between the Miller-Bravais and the Miller indices for any form can be =

-

=

-

=

-

120

CRYSTALLOGRAPHY 2

e

Determination 172.

To

=1,70

of the indices for

the determine,by plotting, 295

294

v

on

calcite

indices of hexagonal forms, given the positionof then: poles on the gnomonic projection. To illustrate this problem of the gnosectant one monic projection of the important forms of beryl, Fig. 228, is reproduced in The directions Fig. 295. of the three horizontal dicated inaxes, ai, 02 and "3 are by the heavy lines. From the polesof the faces perpendicularsare drawn to these three axes. It will be noted that the various intercepts made the axes by these upon lines have simple rational relations to each other. One of these interceptsis chosen as having the length of 1 (this length will be equivalent to the unit length of the c crys-

tallographic axis, see below) and the others are then given in terms of it.

ORTHORHOMBIC

SYSTEM

121

The indices of each face are obtained directly by taking these intercepts the three upon their proper horizontal axes in order and by adding a 1 as the fourth figure If necessarv of the clear of the second fractions,as in case order pyramid, 1122. 173.

To

determine

the axial ratio of

a hexagonal mineral from the gnomonic projection projectionof the beryl forms,Fig. 295, may be used as an illustrative example. The radius of the fundamental circle, a, is taken as equal to the and is given a value of 1. Then the length of the fundalength of the horizontal axes

The

of its forms.

in the

same

gnomonic

manner

in the

as

IV.

case

of the tetragonalsystem,

ORTHORHOMBIC (Rhombic

Axes. Crystallographic

Art. 117, p.

SYSTEM

Prismatic

or

see

System)

The orthorhombic system includes all the referred to forms which three axes at are right 296 anglesto each other,all of different lengths. be taken as the of the three axes Any one may Of the two horizontal axes the vertical axis,c. longer is always taken as the b or macro-axis * and orientated is parallelto the observer. The when a or brachy-axisis the shorter of the two horizontal and is perpendicular to the observer. The length axes of the b axis is taken as unity and the lengthsof the other axes are expressed in terms of it. The for instance,is a : b : c 0*815 axial ratio for barite, 174.

"

=

:

TOO

:

1*31.

Fig.

296

the

shows

crystallographic

for barite.

axes

(25).

CLASS

1. NORMAL

(OrthorhombicBipyramidal 175.

Symmetry.

of the orthorhombic

"

The

TYPE

Holohedral

or

Class)

Orthorhombic

Axes

(Barite)

forms

system

BARITE

are

of the normal class characterized by three which directions

axes are

of

binary symmetry,

coincident with

297

There also are axes. crystallographic at unlike planes of symmetry right lographic anglesto each other in which lie the crystalthe

three

axes.

The

symmetry

of the

class is exhibited in

accompanying stereographicprojection, Fig.297. This should be compared with Fig. 91 (p.53) and Fig.167 (p.77),representing

the

classes of the of the normal the symmetry isometric and tetragonal systems respectively. metric that while normal isoIt will be seen developed alike in the crystalsare three axial directions,those of the tetragonal

Symmetry

of Normal Class Orthorhombic System

*

are

The

from

type have direction

a

of

like development only in the horizontal axes, and two

the

(and also used in this system ( prefixesbrachy-and macroand long. short, Greek M"KPOS, the words, ppaxvs,

in the triclinicsystem)

122

CRYSTALLOGRAPHY

of the orthorhombic type are unlike in the three even axial directions. Compare also Figs.92 (p.54), 171 (p.78) and 298 (p.122). The various forms possiblein this class are as follows : 176. Forms. those

"

Indices

jr"^

1. 2. 3. 4. 5. 6. 7.

Macropinacoid or a-pinacoid Brachypinacoidor 6-pinacoid Base or c-pinacoid Prisms Macrodomes

.

(100) (010) (001) (hkO) (hQl) (OfcZ)

Brachydomes Pyramids

(hkl)

defined on p. 31, a pinacoid is a form whose faces are parallelto two of In general, as whose faces are parallelto the vertical the axes, that is,to an axial plane; a prism is one * (or horizontal prism)is one whose axis,but intersect the two horizontal axes; a dome of the horizontal axes, but intersect the vertical axis. A pyramid to one faces are parallel is a form whose faces meet all the three axes. These not only in the orthorhombic used in the above sense terms are system, but also in the monoclinic and triclinicsystems; in the last each form consists of two planes only.

The macropinacoidincludes two faces,each of which 177. Pinacoids. both to the macro-axis b and to the vertical axis c; their indices parallel are respectively100 and 100. This form is uniformly designated by the called the a-faceor the a-pinacoid. letter a, and is convenientlyand briefly The two i ncludes brachypinacoid faces,each of which is parallelboth to the brachy-axisa and to the vertical axis c; they have the indices 010 and 010. This form is designatedby the letter 6; it is called the b-faceor the b-pinacoid. The base or basal pinacoidincludes the two faces parallel to the plane of the horizontal axes, and having the indices 001 and 001. This form is designated by the letter c; it is called the c-faceor the c-pinacoid. Each of these three pinacoidsis an open-form,! but together they one make the so-called diametral prism, shown in Fig. 298, a solid which is the analogue of the cube of the isometric system. Geometricallyit cannot be from the cube, but it differs in having the symmetry unlike in distinguished "

is

299

300

120-

-

110

120 n

\

Macro-,Brachy-

and Basal Pinacoids

the three axial directions; this may be shown acter by the unlike physicalcharof the faces, a, 6, c, for example as to luster, striations, etc.; or, again, by the cleavage. Further,it is proved at once This

by opticalproperties.

*

From

the

J feee p. 30.

Latin domus, because

resembling the

roof

of

a

house;

cf. Figs. 301, 302.

ORTHORHOMBIC

123

SYSTEM

diametral

prism, as juststated,has three pairsof unlike faces. It has three to the axes edges,four in each set, parallelrespectively a, 6, and c; it has, further,eight similar solid angles. In Fig. 298 the dimensions are made to correspond to the relative lengthsojkthe chosen arbitrarily axes, that a crystalof this shape givesno informabut the student will understand tion of

kinds

to these values.

as

The prisms proper include those forms whose faces are to the vertical axis,while they intersect both the horizontal axes; parallel their generalsymbol is,therefore, (hkQ). These all belong to one type of rhombic prism, in which the interfacial anglescorrespondingto the two unlike vertical edges have different values. The unit prism, (110),is that form whose faces intersect the horizontal ratio in correspondingto the accepted axial ratio of axes lengthshaving a in other the words, the angle of this unit prism fixes a : b for given species; This form is shown in combination the unit lengthsof the horizontal axes with the basal pinacoidin Fig.299; it is uniformly designatedby the letter The four faces of the unit prism have the indices 110, IlO,TlO,iTO. m. There cepts is,of course, a largenumber of other possibleprisms whose internot to their unit the horizontal axes are proportionate lengths. upon 178.

Prisms.

"

.

follows: macroprisms, whose faces lie between those of the macropinacoid and the unit prism, brachyprisms those of the brachypinacoid and the unit prism. A with faces between macroprism has the generalsymbol (hkQ)in which h " k and is represented These

may

be divided

into two

classes

as

by the form Z(210),Fig. 300. A brachyprism has the generalsymbol (hkQ) with h " k and is representedby n(120),Fig. 300. 302

301

303

101

Macrodome

Brachydqme

and and

Brachypinacoid

Pyramid

Macropinacoid

forms whose The macrodomes are Brachydomes. vertical axis intersect the while macro-axis they b, are is The (hOl). hence the angle axis generalsymbol the horizontal c and a; This form is a : c. of the unit macrodome, (101),fixes the ratio of the axes the with is form) brachypinacoid. it an in Fig.301 combined shown (since open the base c(001)and the macropinacoid between In the macrodome zone of macrodomes having the symbols, be a large number a (100) there may taken in the order named, (103),(102),(203),(101),(302),(201),(301);etc. 179.

faces

Macrodomes, to parallel

"

the

Figs.318 and 319 described later. to the brachy-axis,a, The brachydomes are forms whose faces are parallel c and 6; their generalsymbol is (0/cZ). while they intersect the other axes with a(100) in The angle of the unit brachydome, (Oil),which is shown b : c. the of the ratio axes determines Fig.302, between c(001) and 6(010) includes the forms The brachydome zone (021),(031),etc. Cf. Figs.318 and 319. Cf.

(013),(012),(023),(Oil),(032),

124

CRYSTALLOGEAPHY

spoken of as horizontal prisms. The propriety obvious, since they are in fact prisms in geometrical makes which form; further,the choice of positionfor the axes less is in the more or them narrower arbitrary, domes, instead of prisms sense, as alreadyexplainedelsewhere. The pyramids in this system all belong to one 180. Pyramids. type, the double rhombic pyramid, bounded by eightfaces,each a scalene triangle. This form has three kinds of edges,x, y, z (Fig.303),each set with a different the axial ratio. of these angles suffice to determine interfacial angle; two The symbol for this,the generalform for the system, is (hkl). be divided into three groups The pyramids may correspondingrespectively to the three prisms just described,namely, unit pyramids, macropyramids, and br achy pyramids. characterized by the fact that their intercepts The unit pyramids are on have the same the horizontal axes ratio as those of the unit prism; that is, the assumed axial ratio (a : b) for the given species. For them, therefore, the generalsymbol becomes (hhl). There may be different unit pyramids on crystalsof the same species vertical and with different intercepts the these form a zone of faces axis, upon would lyingbetween the base c(001)and the unit prism m(110). This zone include the forms, (119),(117),(115),(114),(113),(112),(111). In the symbol of all of the forms of this zone h k, and the lengthsof the vertical the in axes are hence, example given,^, \, ", J, f J of the vertical axis c of the unit pyramid. The macropyramids and brachypyramidsare related to each other and to the unit pyramids, as were the macroprisms and brachyprisms to themselves and to the unit prism. Further,each vertical zone of macropyramids (or ratio for the horizontal axes brachypyramids),having a common (or of h : k in the symbol), belongs to a particular acterized macroprism (or brachyprism) charratio. Thus the macropyramids (214),(213),(212), by the same vertical zone between the base (001) and (421),etc.,all belong in a common the prism (210). Similarlythe brachypyramids (123),(122),(121),(241), vertical zone between etc.,fall in a common (001) and (120). 181. Illustrations. The following figures of barite (304-311) give Both

sets

of domes

often

are

of this expressionis

"

=

,

"

305

306

307

Barite Crystals

excellent illustrations of crystals of a typicalorthorhombic species, and show also how the habit of one and the same The speciesmay axial ratio vary. for this species is a : b : c 0'815 : 1 : 1'314. d is the macrodome Here =

ORTHORHOMBIC

125

SYSTEM

(102)and

o the brachydome (Oil); m is,as always,the prism (110). Figs. and 309 are described as tabular j| c; Fig.308 is prismaticin habit in the direction of the macro-axis (6),and 310, 311 prismaticin that of the

304-307

brachy-axis(a). of native sulphur show Figs.312-314 series of crystalsof pyramidal a habit with the dome n(011),and the pyramids p(lll),s(113). Note n truncates the terminal edges of the fundamental pyramid p. In generalit should 314

Sulphur Crystals 315

316

317

Figs. 316-318, Topaz

Staurolite

that a macrodome truncating the edge of a pyramid must the same ratio oth:l', thus, (201) truncates the edge of (221),etc. have Ji. Similarlyof .the brachydomes: (021)truncates the edge of (221),etc. 319-321. Figs. the shows Again, Fig. 315, of staurolite,

be remembered

pinacoids6(010), c(001), the prism m(110), and the macrodome r(101). are prismatic crystals of Figs. 316-318 topaz. Here m is the prism (110); I and n the prisms (120),(140); d and p are the are macrodomes (201) and (401);/and y are the brachydomes (021)and (041); i,u, and o are the pyramids (223),(111),(221). 182. Basal, stereographic, Projections. and gnomonic projections are given in Figs. of the 319-320a, on pp. 125,126,127 for a crystal speciestopaz. Fig.319 is the basal projection -

-

Topaz

CR YST

126

ALLO

GR

APH

Y

in *ig. 318. Figs.320 and 320a of the crystalshown forms these of present upon and gnomonic projections

give the stereographic it.

110

ProjectionTopaz Crystal Stereographic

2.

HEMIMORPHIC

CLASS

(26). CALAMINE

TYPE

(OrthorhombicPyramidal Class) of the orthoThe forms 183. Class Symmetry and Typical Forms. rhombic-hemimorphicclass are characterized by two unlike planes of symmetry and one axis of binary symmetry, the line in which they intersect; there is no center of symmetry. The forms are therefore .hemimorphic,as defined in Art. 29. For example, if,as is usuallythe case, the vertical axis to the is made the axis of symmetry, the two planesof symmetry are parallel those like and pinacoidsa(100) 6(010). The prisms are then geometrically of the normal class,as are also the macropinacoid and brachypinacoid; but the two basal planesbecome independent forms,(001)and (001). There also two are macrodomes, (101) and (101),or in general(hQl)and (MM); and t wo similarly sets,for a given symbol, of brachydomes and pyramids. The general symmetry of the class is shown in the stereographicprojec"

.

Y

APH

GR

CR YSTALLO

128

of struvite, represent Fig 321. Further, Figs.322, of calamine, and 323, forms are "(301), i(031), present In of this class. Fig.322_the typicalcrystals 0(011). in Fig.323 they are 8(101),"i(101), t"(12l); tion

TYPE.

(27). EPSOMITE

CLASS

SPHENOIDAL

3.

BisphenoidalClass) (Orthorhombic 184. Symmetry

Typical

and

Forms.

"

325

324

forms The class of the

the

of

remaining

system, the

ortho-

acterized class,are charrhombic-sphenoidal unlike tangular recof axes binary symmetry coincide with the cryswhich tallographic axes, but they have no plane and no center of symmetry (Fig. 324). The general form hkl here has four faces only, and the correspondingsolid is a

by

three

rhombic the

sphenoid, analogous to sphenoid of the tetragonal

system. The complementary of

Symmetry

Class Sphenoidal

Epsomite

itive pos-

and

negativesphenoids are enantiomorphous. Fig. 325 represents a typicalcrystal,of epsomite, with the positivesphenoid, z(lll). Other crystalsof this species often show but usually unequally both positiveand negative complementary forms developed. ,

"

RELATIONS

MATHEMATICAL

OF

SYSTEM

ORTHORHOMBIC

THE

As explainedin Art. 175, the three crystallographicaxes are 186. Choice of Axes. be made of them but any one fixed as regards direction in all orthorhombic crystals, may the vertical axis,c; and of the two horizontal axes, which is the longer (6) and which the the fundamental, be determined until it is decided which faces to assume as snorter (a) cannot "

or

unit,pyramid, prism, or

domes.

choice is generallyso made, in a given case, as to best bring out the relation of the crystalsof the speciesin hand to others allied to them in form or in chemical composition, the cleavageparallelto the fundamental in both respects; or, so as to make form; or, as or other considerations. habit of the crystals, or suggestedby the common The axial elements are given by the ratio of the 186. Axial and Angular Elements. lengthsof the three axes in terms of the macro-axis,b, as unity. For example, with barite the axial ratio is The

"

a

:

6

: c

=

0'81520

:

1

:

1'31359.

The the three pinacoids and angular elements are usually taken as the angles between the unit faces in the three zones between them. Thus, again for barite,these elements are '

100

A

110

=

39" 11' 13",

001

A

101

=

58" 10' 36",

001

A

Oil

=

52" 43' 8".

of these anglesobviously determine the third angle as well as the axial ratio. The of the axial ratio depends upon to be attempted in the statement the accuracy from which this ratio has been deduced. character of the fundamental measurements There is no good reason for giving the values of a and c to many decimal places if the probable of the measurements amounts to many minutes. In the above the measurements error case within a few seconds. It is convenient,however, (by Helmhacker) are supposed to be accurate to have the angular elements correct, say, within 10", so that the calculated angles obtained from them will not vary from those derived direct from the measured angles by than 30" to 1'. more Two

degree of

ORTHORHOMBIC

axes

187. Calculation of the Axes. with the angular elements : tan

(100

A

110)

=

a,

"

The

129

SYSTEM

following simple relations (cf Art. 48) connect .

tan

(001

A

Oil)

=

c,

tan

(001

A

101)

=

the

-

These

to give either the axes from the 'angularelements, equations serve It will be noted that the axes not angular elements from the axes. are needed for simple purposes of calculation, but it is stillimportant to have them, for example to use in comparing the morphological relations of allied species. In practice it is easy to pass from the measured angles,assumed as the from basis of calculation (or deduced the observations by the method of least squares),to the angular elements, or from either to any other angles by the applicationof the tangent principle(Art.49) to the pinacoidalzones, and by the solution of the right-angledsphericaltriangles given on the sphere of projection. Thus face hkl lies in the three zones, 100 and Qkl,010 and hOl, 001 any For example, the positionof the face 312 is fixed if the positions and hkO. These of two of the poles,302, 012, 310, are known. last are given, respectively, by the equations Stibnite tan f x tan (001 A 101), (001 A 302) \ X tan (100 A 110). tan (001 A 012) \ x tan (001 A Oil) tan (100 A 310) or

the

=

=

=

m'

:010

StereographicProjection Stibnite Crystal

CRYSTALLOGRAPHY

130

188 Fig. 326 represents a crystalof stibnite from Japan and Fig. 327 Example. ra(110) and of its forms, p(lll), r(343),77(353),co3(5-10'3), the stereographicprojection fundamental: taken as were measured angles 6(010). On this the following 1' 0", 7777'(353 A 353) =55" "

7777'" (353

353)

A

99" 39' 0".

=

out with27" 30|' are known 40" 10*' and 353 A 053 the angles 353 A 010 * the 010'053'353 angle yields The calculation. right-angledsphericaltriangle the angle at 010, which is equal to (001 A 101). also hence A 053); and A (001 053) (010 tan c. Also, since f X tan (001 A 053), and tan (001 A Oil) But tan (001 A Oil)

Hence,

=

=

=

=

(001

A

101)

=

--,

the axial ratio is thus known, and

of the angular elements.

two

(001 A 110) can be calculated independently, for the angle is equal to (010 A 350) and tan (010 A 350) x f triangle001'053'353 (010 A 110),the complement of (100 A 110). be used to check the value of a already Then since tan (100 A 110) a, this can with the occasional solution of a rightof the The further use tangent principle obtained. either the fundamental desired angle from angles to give any angled trianglewill serve elements. from the angular direct,or measured be readily calculated if two face can Again, the symbol of any unknown the face for the For ured meashand. at example, tolerable are suppose co, angles of accuracy The

third angular element

in the

001

at

=

=

angles to be 6co

The

(010

(001 (001

tan

But :

30" 15', coco'(hkl A

=

hkl)

the ratio of k

A

Okl)

A

Oil)

73" 34|'

tan

45"

16" 25' 20", and

=

k =

_

'

~

be rational and

I must

:

tan

51" 32'.

=

Okl)

solution of the triangleb'u'Okl gives the angle (010 A

tan

10

hkl)

A

I

30^' the number

derived

agrees

closelywith

most

3.

be calculated from the same Again, the angle (001 A hOl) may now this the ratio of h to I is derived since From value 59" 38 f obtained. tan

tan

(001 (001

A A

hOl

) 101)

tan

59" 38f '

tan

45" 43J'

the

h _

=

=

=

triangleand

'

I

This ratio is nearlyequal to 5 : 3, and the two values thus obtained give the symbol 5'10'3. If,however, from the triangle001' Okl'u,the angle at 001 is calculated,the value 26" 42f From this the ratio h : k is deduced, since is obtained,which is also the angle (010 A MO).

The

value of

gives the

-r

same

tan

(010

A

tan

(010

A

110) hkO)

tan

45" 12f

tan

26" 42f

k = "

~

is hence closelyequal to 2; this combined

symbol

' ~

h

with that firstobtained

f

=-

=

-5-

J

5" 10*3.

than usually complex calls for fairlyaccurate This symbol being more measurements. is can best be judged by comparing the measured How accurate the symbol obtained angles the symbol. For example, in the given case with those calculated from the calculated 30" 16',coco'(5'10-3)51" 35'. The correctness anglesfor u(5'10'3)are 6"(010 A 5'10'3) of the value deduced is further established if it is found that the given face falls into =

prominent

=

zones.

It will be understood further that the zonal relations, explained important part in all calculations. For example, in Fig. 326, if the

on

pp.

45-47,play an

of r were known, unit could be obtained from a singleangle (as br),since for this zone h I. 189. Formulas. Although it is not often necessary to employ formulas in calculations, few are added here for sake of completeness. Here a and c in the formulas are the lengths

symbol

=

"

a

of the two

*

The

axes

a

student

and

c.

in this

as

in every

similar

case

should

draw

a

projection,cf. Fig. 327

(not necessarily accuratelyconstructed),to show, if only approximately, the relative position of the faces present.

ORTHORHOMBIC

(1) For the distance in general:

between

131

SYSTEM

the pole of any

face P(hkl) and

the pinacoidsa, 6, c,

we

have

cos2 Pa

cos2 P6

cos2

=

=

cos2

(Md

A

(Md

A

(Md

A

100) 010)

=

he2 +

k2a?c2 +

I2a?

Me*

+

A;2a2c2+

Pa?

+

/c2a2c2+

=

'

Pa? cos2 PC

(2) For

=

cos2

the distance (PQ) between

001)

=

_ '

We2

the poles of any

hpc2 + kqa?c2+ PQ

cos

two

I2a?

faces (Md) and

(par)

Ira2 '

=

V(h2c2 + ,

"2a2c2 +

+ ?2a2c2+ r2a2] Z2a2][p2c2

the axial ratio of an orthorhombic To determine, by plotting, having given crystal, In order to solve this problem it is necessary stereographicprojectionof its forms. indices be given or the position that the positionof the pole of a pyramid face of known tration For illusdome and a brachydome. of both a macroof the faces of a prism and one or that a crystalof barite,such as represented in Fig. 305, has been it is assumed the goniometer and the polesof its faces plotted in the stereographic tion. projecmeasured on The lower righthand quadrant of this projectionis shown in Fig. 190.

the

The

328. are

forms

common

present on

ones

crystals

and

ite bar-

have

given the symbols, ro(110), d(102), o(011), c(001). The ratio of a : 6 be determined can readily from the position of the A radial pole m(110). been

line

of

is drawn the face

to

the

and

the end

Oil

pole

then

perpendicularerected it from

102

a

111

to

of the line b crysThe

representing the tallographicaxis. intercept of this

dicular perpen-

the line senting reprethe a axis,when expressed in terms of the assumed unit length of the b axis,gives the length It is to be noted of a. that the fact that this line in the present case on

passes

very

nearlythrough

the pole 111 is wholly accidental. The length of the vertical axis can the determined from be

position of the pole of either d(102) or o(011).

given^n8 the upper hand quadrant figure. If the

of

leftthe

Determination

of the Axial Ratio for Barite

brachydome, o(011),is used the sloping line that

.

gives

,

the

,. inchnA.

the horizontal line equivalentto the length on a distance tion of the face is started from the unit length of that axis. .on the c axis will equal of the 6 axis, or 1, and its intercept line the of trianglemust be made equal base the used is of d(102) If the

position the intercept on length of the a axis as already established and Tatter's unit length. of the

however,

to the unit

equal

?

the

c

axis

will

132

CRYSTALLOGRAPHY

of the pyramid face,111, The problem could have been wholly solved from the position in this case is also construction The the been had on crystal. if that form present illustrated. crystal, 191. To determine, by plotting,the indices of a face upon an orthorhombic

given the position of iis the stereographic pole upon projectionand the axial ratio

329

To illustrate it is assumed position of the

of the mineral. this problem the

that

stereographic pole in the projectionof the face o, Fig. 329, upon a topaz crystal is First draw known. line through the e

a

pol o

radial Next

.

perpendicular to this the line, starting it from erect

a

selected

distance 1

the

on

as

senting repre-

b

crystalloThe intercept

graphic axis.

the line axis when of the expressed in terms unit length of the b axis is This is equivalentto 0'53. the established unit length of the a axis and therefore the parameters of the face o the horizontal crystalloon of

this line

upon

the representing

graphic axes

are

a

la, 16.

Next

is transferred the distance O-P into the upper left-hand quadrant of the figure. The of the normal to the face is determined by measuring with a protractor the angular position O and o. The line giving the slope of the face is next drawn perpendicudistance between lar the line representingthe vertical axis determined. to this normal and its interceptupon This distance when expressed in terms of the length of the 6 axis is 0'95. This is twice the established length of the c axis (0'476) and consequentlythe third parameter of the face o is 2c. This givesthe indices 221 for the face. 192. To deter the axial ratio of

mine, by plotting, an

orthorhombic

crystalhaving given the gnomonic To illustrate projectionof its forms. this problem the gnomonic projectionof the crystalof topaz alreadygiven in Fig. 320a will be In Fig. 330 one used. quadrant of this projection is reproduced. From each pole lines are drawn lines perpendicular to the two representingthe a and b crystalIt will be found lographicaxes. in this that the intercepts made

2"

upon the a axis have rational relations to each other. The same is true of the intercepts upon the 6 axis. The interceptsupon the two however, are axes, irrational in respect to each other. A convenient interceptupon each axis is chosen as 1 and the other interceptsupon that axis are then expressed in terms of this length. Of way

MONOCLINIC

133

SYSTEM

with a known mineral, whose forms have alreadyhad indices assigned to them, the interceptthat shall be considered as 1 is fixed. If we take r as equivalent to the radius of the fundamental circle of the projection, the 6 crystallographic axis and p that upon the q as equal to the chosen interceptupon be derived from the following the axial ratio can a axis,then expressions: course

proof of

b

r

c

q

.

a c

is similar to these relationships

r

p

that

alreadygiven under the Tetragonal 117, p. 93. the indices of a face upon 193. orthorhombic an determine, by plotting, crystal, of the its the eral. pole gnomonic projectionand the axial ratio of the minposition upon given method of construction in this case is the reverse The of that given in the problem the same as given under the Isometric and Tetragonal Systems, above and is essentially In the case of an orthorhombic mineral the intercepts of the perpendicuArts. 84 and 118. lars in must be expressedin each case drawn from the poleof the face to the a and b axes be determined from the terms of the unit intercepton that axis. These values,p and q, can equationsgiven in the precedingproblem. The

System,

Art. To

V.

MONOCLINIC

SYSTEM

(Obliqw System) Axes. 194. Crystallographic referred to three forms which are unequal axes, having one of their "

The

monoclinic

system includes all the 331 i

axial inclinations oblique. designated as are The axes clino-axis inclined or follows: the tical is a; the ortho-axis is b, the verThe acute angle axis is c. and c is repthe axes a resented between by the letter (3; the anglesbetween a and b and b and c

right angles. See Fig. 331. When properly orientated the are

inclined axis,a, dopes dawn .toward zontal the observer, the b axis is horiand observer to the and parallel 1. NORMAL

S^Omi^^W1 the

c

axis

CLASS

or (Prismatic

vertical.

(28). GYPSUM Holohedral

TYPE

Class)

class of the In the normal of symis there one plane metry monoclinic system of axis binary symmetry normal and one The plane of symmetry is always the to it. metry plane of the axes a and c, and the axis of symto this coincides with the axis b, normal and that of plane. The positionof one axis (6) (a and c) is thus the plane of the other two axes may fixed by the symmetry; but the latter axes in this plane. Fig.332 different positions 195.

occupy

Symmetry on

of Normal

the

Class

snows

planeof symmetry.

Symmetry.

"

jected protypicalstereographicprojection, actual of the an 348 are projections Figs.347,

the

134

CR YST

ALLO

GR

APH

Y

crystalof epidote;here,as is usual,the plane of projectionis normal to the prismaticzone. The various forms * belonging to this class,with their 196. Forms. in the particularly followingtable. As more explained symbols, are given two faces only,and a pyramid four only. includes later,an orthodome "

Symbols

3.

Orthopinacoidor a-pinacoid Clinopinacoidor 6-pinacoid Base or c-pinacoid

4.

Prisms

5.

Orthodomes..

6.

Clinodomes.

1.

2.

(100) (010) (001) (hkO) ' (/^

.

7.

197. Pinacoids. and the basal plane. "

The

pinacoidsare

the

orthopinacoid,clinopinacoid,

(100),includes the two faces parallelto the plane of orthopinacoid, b and the vertical axis c. They have the indices 100 and 100. This form is designatedby the letter a, since it is situated at the extremity of the a axis; it is hence convenientlycalled the a-faceor a-pinacoid. The (010),includes the two faces parallelto the plane of clinopinacoid, that the is, plane of the clino-axis a and the axis c. They symmetry, The have the indices 010 and 010. is designatedby the letter clinopinacoid the called is and or b-face b-pinacoid. 6, The base or basal pinacoid,(001),includes the two terminal faces,above to the plane of the axes and below, parallel a, 6; they have the indices 001 The is base and 001. designatedby the letter c, and is often called the c-faceor c-pinacoid.It is obviouslyinclined to the orthopinacoid,and the normal angle between the two faces (100 A 001) is the acute axial angle 0. The

the ortho-axis

333

335

101

Ortho-, Clmo and

The

Basal

Prism and Basal Pinacoid

-

Pinacoids

diametral

prism, formed

I

Orthodomes and

Clinopinacoid

by these three pinacoids,taken

Fig.333, is the analogueof the cube in the isometric system. by

three

sets

four similar to the axis On

of unlike

faces; it has

edges parallelto

b, are

of two

the generaluse

sets.

of the terms

four

similar

together,

It is bounded

vertical

edges; also the axis a, but the remaining edges,parallel Of its eightsolid anglesthere are two sets of

pinacoid,prisms,domes, pyramids,

see

pp.

31, 122.

136

CRYSTALLOGRAPHY

0-589, ft

74"

=

=

p(101) is figures see

orthodome;

an

p.

b

orthoclase

(aj

2/(201)are

Since

: c

the

Of

0'659

=

:

orthodomes

1

:

other

340-342

(Fig.340) c and x happen to make the prism m, the combination

edge crystal.

is the are

represent

: c

1'092

=

:

1

:

forms.

Fig. 336 prism (110);

unit

for

pyramids;

other

crystals of

common

is

=

is

a

often

simulates

an

orthorhombic

342

341

340

b

64"). Here z (130) a prism; clinodome; 0(111) a pyramid. nearly equal angles with the vertical

n(021)

of

:

typicalmonoclinic

0'555, ft ;

(a

pyroxene

forms, m w(lll), 0(221), s(lll)

Again, Figs.

475.

#(101) and

of

"

prism.

diametral

the

shows

Figs. 336-339 o(100) A c(001)) show

Illustrations.

202.

Orthoclase

monoclinic

crystal,epidote,prismatic in the direction of the ortho-axis; the forms are a(100), c(001), r(101) and w(Ill). Fig. 344 the unit pyramid is flattened ||6(010); it shows of gypsum /(111) with the unit prism w(110). Fig. 343

shows

a

Epidote 203.

Epidote

Projections. Fig. 345 shows a projection of a crystal of epidote to the prismatic zone, and a plane normal p. 531) on Fig. 346 of a similar crystal on one a plane parallel to 6(010); both should be carefully studied, as also the stereographic and gnomonic projectionsof the same The Figs. 347, 348. species, symbols of the prominent faces are given in "

(cf.Fig. 897,

the latter

figures.

Stereographic of EpidoteCrystal Projection

210 IV

10211

211

a

Gnomonic

100

of EpidoteCrystal Projection

(137)

138

CRYSTALLOGRAPHY

2.

(29). TARTARIC

CLASS

HEMIMORPHIC

ACID

TYPE

(SphenoidalClass) 204.

The

class is characterized by a singleaxis monoclinic-hemimorphic of binary symmetry, the 350 axis 6,but 349 crystallographic it has no plane of symmetry. ^ It

X.

^^"

7^

is illustrated

by the stereographicprojection (Fig. 349) made a plane parallelto upon 6(010). Fig. 350 shows a common

form

of

tartaric

acid; sugar crystalsalso belong here. The hemitinctly morphic character is dis-

Symmetry of Hemimorphic Class artificialsalts

3.

Tartaric

Acid

belonging here often exhibit CLASS

CLINOHEDRAL

in shown the distribution of the clinodomes and pyramids; corresponding to this the marked pyroelectrical mena. pheno-

(30). CLINOHEDRITE

(Domatic or Hemihedral

TYPE

Class)

205. The monoclinic-clinohedral class is characterized by a singleplane to the clinopinacoid, of symmetry, parallel 6(010),but it has no axis of symmetry. This symmetry is shown in the stereographic projectionmade upon the forms parallel to 6(010), a planeparallel therefore, Fig.351. In this class, to the 6 axis,viz.,c(001),a(100),and the orthodomes, are represented by a 353

Symmetry

of Clinohedral

Class

Clinohedrite

singleface only. The other forms have each two faces,but it is to be noted that,with the singleexceptionof the clinopinacoid6(010),the faces of a to each other. The name given form are never parallel given to the class is based on this fact. Several artificialsalts

but the only belong here in their crystallization,

MONOCLINIC

139

SYSTEM

known

minerals is the rare representativeamong clinohedrite silicate, of a (H2CaZnSiO5),* complex crystal which is shown in two positions in Figs. As seen in these figures, the crystalsof the group 352, 353. have a hemimorphic aspect with respect to their development in the direction of the vertical axis,although they cannot properly be called hemimorphic since this is not an axis of symmetry. The forms in Figs.352 shown 353 are as follows: pinacoid,b (010);_ prisms,w(110), Wi(IlO), Z(130); fc(3_20), n_(120), orthodomes, e(10_l), pyramids, p(lll), Pi(lll), tf(lll),r(331), ei(l_01); s(551),*(771),w(531),o(131),z(131),y(121). It is to be noted that crystalsof the common speciespyroxene (alsoof and s how this habit in the distribution of their segirite titanite) occasionally faces,but it is not certain that this may not be accidental^ MATHEMATICAL

RELATIONS

OF

SYSTEM

MONOCLINIC

THE

of Axes. It is repeated here (Art. 196) that the fixed positionof the establishes the direction of the plane of the a and c crystallographic and also of the axis b which is the symmetry axis and lies at rightangles to this plane. axes The have varying positionsin the symmetry c axes, a and however, may plane according to which faces are taken as the pinacoids a(100) and c(001),and which the unit pyramid, 206.

Choice

"

plane of symmetry

domes.

prism, or

The axial elements are the lengthsof the axes Angular Elements. of the unit axis b, that is. the axial ratio,with also the acute angle of for orthoclase the axial elements are: inclination of the axes a and c, called /3. Thus Axial

207.

a

and

c

and

"

in terms

:

a

The

angular elements

b

: c

usuallytaken

are

the three

/3; also the angles between unit orthodome

prism 110, the

0'6585

=

:

001

A

100

001

A

101

:

0'5554

0

63" 56f.

=

as the angle (100 A 001) which is equalto and pinacoids100, 010, 001, respectively,

the angle the unit Thus, again,for

101) and the unit clinodomeOll.

(101 or

orthoclase,the angular elements

1

are:

100 63" 56f , 50" 16"', 001

=

=

A

110

=

A

Oil

=

30" 36"'. 26" 31'.

relations connecting axial and angular elements are given in mathematical which in the following equations a, b, and c represent the unit lengths of the respective The

208.

axes. crystallographic

(10"

tan a

A

110)

=

(001

tan

or

tan

(100

A

110)=

a.

Qr

tan

(001

A

Oil)

c

sin 0;

(1)

sin /3;

(2)

/3

sin

A

Oil)

=

=

.

sin.tf a

sin ?

-

.

(001

tan cos

A

101) (001

tan

0

.

.

(m

101)

A

101)

A

a

+

c

.

cos

(3) a. ("

(001

tan

=

"

sin 0 + These

cos

A

101)

:

0

.

"

.

tan

relations may

(001

tan UCkU

(001 ^vyv/i

101)

A /\

J.WA/

"

101)

A

be made

or Ul

=

more

a

generalby writing in

-

c

.

the several

0

cos

cases

"

i

in

(1)

MO

for 110

and

^

in (3)

a

for a;

in (2)

hOl for 101

and

OW

c

j-

for Oil

and

Before;

for c..

,

38, 115, ,889.

140

CRYSTALLOGRAPHY

Also c

sin (001 A

101)

sin

A

101)

sin (001 A =

=

a

and

more

(100

(TOO A

sin

101); TOl)'

generally h

sin (001 A

hOl)

I

sin (100 A

hOl)

tan

0

c

hQl)

sin (001 A =

'

~ ~

a

(TOOA hQl)

sin

also that

Note

=

and

a

tan

f

=

c,

347) between the zone-circles (001, 100) and (001, 110); also f is "f"is the angle (Fig. and (100,Oil). between 001) (100, angle All the above relations are important and should be thoroughly understood. 209. The problems which usually arise have as their object either the deducing of the of 6(= 1), from three axial elements, i.e.,the angle /3 and the values of a and c in terms where

the

measured angles,or the findingof any required interfacial angles from these elements or from the fundamental angles. The simple relations of the preceding article connect the angular and axial elements, be solved * either by the solution of spherical and beyond this all ordinary problems can the aid of the cotangent (and tangent) relation. of the or by on sphere projection, triangles all great circles on 010 cut the zone circles 010, 001, 010

sphere of projection(see circle 100, 001, 100 at right also those from as obliquely, the

noted, in the first place,that projection,Fig. 347) from stereographic

It is to be

the

angles,but those from 100 cut the zone circle 100, 010, 100. cuttingthe zone 210. Tangent and Cotangent Relations.

001

The simpjetangent relation holds good for all circle 100, 001. 100; in other words, for the prisms, of pyramids in which the ratio of h : I is constant (from 001 to clinodomes, and also zones hOl or to "(M). Thus it is stilltrue, as in the orthorhombic system, that the tangents of the angles of the prisms 210, 110, 120, 130 from 100 are in the ratio of * : 1 : 2 : 3, or, more that generally, from

zones

010

the

poleon

to any

tan tan

(100 (100

A

A

"

zone

MO) 110)

k

tan

h

tan

(010 (010

=

~~

hkO) 110)

A A

h _ ~

k'

Also for the clinodomes the tangents of the angles of 012, Oil, 021 from 001 are in the A^similarrelation holds for the tangents of the angles of pyramids in ratio of \i : 1 : 2, etc. the zones mentioned, as 121, 111, 212, etc. from 100 to a clinodome, or from 001 to a For zones other than those mentioned as tion general cotangentformula given in Art. 49 must be employed. This relaprism, the more for certain common is simplified cases. For any zone startingfrom 001, as the zone 001, 100, or 001, 110, or 001, 210, etc.; if 001 and those two faces in the given zone two angles are known, viz.,the angles between which fall (1) in the zone 010, 101, and (2) in the prismatic zone 010, 100; then the angle be calculated. between 001 and any other face in the given zone can

Thus, Let or

" "

or

Then zone

001

A

101

001 001

A

111 212

A

=

=

=

PQ PQ PQ

and

001 001

"

001

A A A

100 110 210

=

=

=

PR, PR, PR,

etc.

for these,or any similar cases, the angle (PS) between 001 and any face in the given (as201, or 221, or 421, etc.,or in general hQl,hhl,etc.)is given by the equation cot PS

cot PR

-

l_ = ~

cotPQ For

the corresponding zones value; but here

same

PQ or

*

any as

=

from

001

A

001

A

001

cot

-

to

TOl, PR Til,etc.,

100,

=

PR to

h

110,

001

A

001

A

to

210, etc.,the expressionhas the

TOO, PS TlO,etc.,

=

001

A

hOl,

001

A

hhl,etc.

The generalformulas,from which it is possibleto calculate directly the angles between face and the pinacoids,or the angle between any two faces whatever,are so complex to be of littlevalue.

MONOCLINIC

If,however,

100

is the

141

SYSTEM

and starting-point, 100

or

100

A A

101 111

100

A

001

100

A

Oil

PR, PR, etc.,

then the relation becomes cot

PS

cot

PQ

-

-

cot PR cot

PR

To determine,by plotting, 211 the axial elements of a monoclinic crystal eiven the As an example of this problem stereographjcprojection of its forms. that orthoclase crystalsimilar to the one shown in Fig 341 has been measured an of its faces located on the stenographic projection, of the a axis The Fig. 354. the angle 0 is given or of the stenographic protractor the directlyby measuring, by means angular distance between the poles of a(100) and c(001). In the present case the a(100) iirmt does not actuallyoccur form the crystal, p is measured on 64" If thp basp as the crystalit will be usualfy of some present upon possibleto locate its positionby mean^

"t[fassumld andThe pol?s inclination

zone

the

circle on

which

oiemto the base

it must "^

he

In the present case the great circle of the zone of m'(TlO), t0 ba"k llne (Z"ne "f the orthodomes)at ^ point of

mllO

fc'oio*

6010

a

Determination

of Axial Elements

100

of Orthoclase

from

Projection Stereographic

from the be readily determined can the lengths of the a and b axes ratio between the of the center from O-P projection line radial Draw the positionof the pole,m(110). This represents a line at rightangles to O-P. From the end of the b axis draw to m(110). and the distance O-R horizontal the plane with face of the the intersection prism of the a axis. The distance of the prism upon the horizontal projection gives the intercept foreshortened somewhat distance that but is axis the of a unit O-R therefore is not the length because of the inclination of that axis. The construction by which the true length The line R-O-S-T represents the horizontal in Fig. 355. of the a axis is obtained is shown As the from Fig. 354. projectionof the a axis upon which the distance O-R is transferred a perpendicufound be lar dropping 'a axis by can the prism face is vertical its interceptupon of this last from R to intersect the line which represents the a axis. The inclination The

142

CRYSTALLOGRAPHY

The length of the line is found by use of the angle ft,which has been already determined. expressed in terms of the b axis (TOO) was found to be 0'66. a axis when be found best from the inclination of the ?/(201) face. This The length of the c axis can face will intersect the negative end of the a axis and the upper end of the c axis at either the center of the projection,O, Fig. 354, and the \a, Ic or la, 2c. The angle between this angle the position of the stereographicprotractor. From pole y is measured by means The line representingthe slope of of the normal to y, as shown in Fig. 355, is determined. the negative unit length of at rightangles to this normal, startingfrom the face is drawn found to be equal to I'll,which, as the inclined a axis. The intercepton the c axis was it is equal to 2c, would give the unit length of the c axis as, 0'55. from the inclination of the pyramid The length of the c axis could also be determined lem face,o(Tll). The method of construction would be similar to that described in the probbelow. the indices of a face upon monoclinic a 212. To determine crystal,having given the

positionof

its

pole upon

the

stereographicprojectionand

the

axial elements

of the

eral. min-

face o on orthoclase will be used to illustrate the problem. First,see through the pole o and a perpendicular S-T erected to it, Fig. 354, a radial line is drawn section startingfrom the unit length of the b axis. It is to be noted that the point T is the interTransfer the distance of the face o with the horizontal projectionof the a axis The

pyramid

Determination O-S

to the horizontal

of Axial

line in Fig. 355

and

Elements, etc.

of Orthoclase

locate the positionof the normal

to

o

by the

angle, Fig. 354, between O and o. The line givingthe slope of the face can then be drawn from the point S (Fig. 355) perpendicular 'to the normal. This line intersects the line representing the vertical axis at a distance equal to its unit length. Two section points of interof the pyramid face with the plane of the been determined, have now a and c axes A line joiningthese two points will namely Ic and T. give the intersection of the two planes and the point where it crosses the line representingthe a axis will therefore give the intercept of the pyramid upon that axis. This is also found to be at the unit length and

therefore the indices of o must be 111. 213. To determine, the axial elements of a monoclinic by plotting, crystal,having given the gnomonic projectionof its forms. The construction by which this problem is solved is shown in Fig. 356. The poles of the unit forms (101),(Oil),(001) and (111) are located tor pyroxene) and the zonal lines drawn. (in this case The to is

angle /S

complementary

144

CRYSTALLOGRAPHY

is called the c axis (cf.Fig.357),a second axis lies in the front-totoward the observer,and is back plane,slopingdown 357 The called the a axis. remaining axis is designated as the b axis. Usually the a and b axes chosen that are so the a axis is the shorter and, like in the orthorhombic called the brachy-axis. In that system, is sometimes the 6 axis is longer and is known the macroas case But this is not invariablytrue; thus with rhoaxis. donite 1*073 : 1. of a :b ratio The the angle b and c is called a, that between the axes between a Triclinic Axes and c is 0, and that between and b is 7 (Fig.357). a relation between the values of It is to be noted that there is no necessary less be than and one 90"; this is determined by greater or may a, p, 7, any forms. choice of the fundamental the tion and

=

1. NORMAL

CLASS

(31). AXINITE

(Holohedralor Pinacoidal 216.

by

center

Class)

The normal class of the triclinic system is characterized of symmetry, the point of intersection of the three axes, This symmetry is shown in plane and no axis of symmetry.

Symmetry. a

TYPE

"

but

there is no

the

accompanying stereographicprojection(Fig.358). 358

of Normal

Symmetry 217.

Class

Triclim'cPinacoids

Forms. Each form of the class includes two faces,parallelto another and symmetrical with reference to the center of symmetry. This is true as well of the form with the general symbol (hkl)as of one o" the specialforms, as, for example, the a-pinacoid(100). "

one

Hence,

shown

in the

followingtable,the four pjismaticfaces 110, TlO, forms, namely, 110, 110, and 110, 110. The same is true of the domes._Further, eight corresponding pyramidal _any faces,as, for example, 111, 111_,_111,_111, 111, _1_11, 111, 111 belong to four distinct forms, namely, 111, 111; 111, 111; Hi, lll;-in, 111, and similarlyin as

__

10, 110 include two

general.

TRICLINIC

various types of forms

The

145

SYSTEM

given in the following table:

are

Indices

Macropinacoid or a-pinacoid Brachypinacoid or 6-pinacoid Base or c-pinacoid

'

(100) (010) (001)

"

Prisms

{ ", W

MacrodomeS

(P) (g

I(MO)

BrahydomeB

Pyramids I

(hkl)

\(hkl) table it is assumed that the axial ratio is such that a " the names would be interchanged. brachy- and macro-

In the above true

were

b.

If the opposite

the two precedingsystems make it the discuss in detail various forms individually, as unnecessary except of crystals illustrated in the case belongingto certain typicaltriclinicspecies. be mentioned, however, that Fig. 359 shows the diametral prism, It may bounded is which by three sets of unlike faces,the pinacoidsa, 6, and c. This is the analogue of the cube of the isometric system, but here the like faces,edges,and solid anglesinclude only a given face,edge,and angle,and that oppositeto it. A typicaltriclinic crystalis shown 219. Illustrations. in_Fig.360 of axinite. Here a (100) is the macropinacoid; m(110)_and M(110) the two unit prisms; s(201)a macrodome, and z(lll) and r(lll)two unit pyramids. The axial ratio is as follows: The

218.

explanationsgiven under

to

"

a

:

b

: c

=

0'49

:

1

:

0'48, a

=

82"

54',ft

=

91"

52',7

=

131" 32'.

which is allied to of rhodonite, a species Figs.361, 362 show two crystals it in and habit. Here the faces and which approximatesto angle pyroxene, 361

362

Rhodonite

are:

6(010),c(001); prisms m(110), M(lTO); pyramids a(l_00), Pina_coids illustrations are given by Fig.363 of albite and The symbols of the faces,besides the pinacoidsand

Further

thite.

Fig.364 of the

unit

anor-

prisms,

CRYSTALLOGRAPHY

146

364, prisms /(130), z(130); domes Fig. 363, z(101); _Fig. *(207),t/(201),e(021),r(061),n(021); pyramids m(lll), a(lll), o(lll), are

as

follows:

365

363

"0104

"010

mllO

a

100

MllQ

StereographicProjectionof .

In

an

Axinite

Crystal

Fig.364 of anorthite the similarityof the crystalto on slightexamination (cf.Figs.340, 341),and

clase is evident

one

of ortho-

careful

study

TRICLINIC

SYSTEM

147

with the measurement of anglesshows that the Hence in this case the choice of the fundamental

Fig. 365 graphic

and

correspondenceis very close planes is readilymade. represents a crystal of axinite; Figs.366 and 367 its stereognomonic projections. 367 M110

6010-4

K110

a

Gnomonic

2.

ASYMMETRIC

CLASS

Projectionof

an

Axinite

(32). CALCIUM

100

Crystal THIOSULPHATE

TYPE

(Hemihedral Class) Besides

220.

the

normal

class of the triclinic system there is another

neither possibleclass,possessing symmetry with respect to a plane,axis nor center; in it has one face only. This class finds a given form of artificialsalts. number a examples among calcium of is these One thiosulphate (CaS2O3.6H2O); as yet no mineral speciesis

368 "

^-

*"

" ..

This is the most be included here. general of all the thirty-twotypes of forms and classified according to their symmetry known

comes

to

if the classes are arranged first, therefore, the degree of symmetry to according

\

in order

This class is one of those them. characterizing whose crystals circular polarization. show may This is true of eleven of the classes which have Symmetry been described in the preceding pages.

of

Asymmetric

Class

148

CRYSTALLOGRAPHY RELATIONS

MATHEMATICAL

TRICLINIC

THE

OF

SYSTEM

of It is obvious,from what has been said as to the symmetry 221. Choice of Axes. be chosen the pinacoids,or as may this system, that any three faces of a tricliniccrystal the faces which fix the positionof the axial planes and the directions of the axes; moreover, or pyramids which further fix there is a like libertyin the choice of the unit prisms,domes "

the lengthsof the axes. in hand is allied in form or composition to other species, whether of the crystal When the choice of the the problem and makes different systems, this fact simplifies the same or This is well illustrated, as alreadynoted,by the triclinicfeldspars forms easy. fundamental in angleto the allied monoclinic albite and anorthite,Figs.363, 364) which are near (e.g., of the pyroxene (Figs.361, 362), the triclinic member species orthoclase. Rhodonite group, is another good example. and where varied habit makes different exists, In other cases, where no such relationship there is but littleto guide the choice. This is illustrated in the case orientations plausible, have been assumed of axinite (Fig.360),where at least ten distinct positions by different authors. axial elements The of a triclinic crystal are : 222. Axial and Angular Elements. (1) the axial ratio,which expresses the lengths of the axes a and c in terms of the third axis,6; and (2)the anglesbetween the axes a, 3, 7 (Fig.357). There are here five quantities which obviouslyrequirethe measurement of five independent angles to be determined between the faces. The angular elements are usually taken as the angles between the pinacoids and, in addition,those between each pinacoidand the unit face lyingin the zone of the other pinacoids; that is, "

100

also or,

am

instead,any

one

or

aM,

A

010,

ac,

110, all of these, 100

A

100

A

110,

100

A

001,

010

A

001

A

101,

001

A

001; Oil;

001

A

101,

001

A

Oil.

be,

Of these six anglestaken, one is determined when the others are known. 223. The mathematical relations existing between the axial anglesand axial ratio, the on one hand, and the angles between the faces on the other,admit of being drawn out with great completeness,but they are necessarily complex and in general have littlepractical In fact,most of the problems likely value. to arise can be solved by means of the triangles of the sphericalprojection, togetherwith the cotangent formula connecting four planes in the same zone (Art.49, p. 49); this will often be laborious and may requiresome ingenuity but in generalinvolves no serious difficulty. In connection with the use of the cotangent it is noted be to that in certain commonly occurringcases formula, its form is much fied; simpliof these have alreadybeen explained under the monoclinic some system (Art.210). The formulas given there are of course equallyapplicablehere. 224. The firstproblem may be to find the axial elements from measured angles. Since these elements include five unknown quantities,viz.,the three axial angles a /3 7 and the lengthsof the axes of b, five measured a and c in terms angles are required, as already

stated.

Fig. 369 represents the crystallographic of the triclinic mineral rhodonite axes The of the three axes are joined by lines forming three trianglesthe angles of

positive ends which

are

very

important.

In the

for instance, which triangle,

has the b and c axes for of its sides since the length of the b axis is taken as I'O,it is only to know necessary the angle a and either or ?r p in order to determine the length of the c axis. In the triangle that has the a and b axes for two of its sides it is necessary to know the value of 7 and either a or T in order to determine the lengthof the a axis. And lastly in the triangle formed between the a and c axes, if the lengthof either of two

of the other

can

be determined from

the angle " and

either'f orT " "S*? ^af a

TRICLINIC rhodonite forms "i{ ^*k ?ho*jD" the, 370, has of

bee^me^ural and^e

poles

great

circles which the same

SYSTEM

o(100),6(010),c(001) and

represent

a

see

Fie

371

connect

100

as

projection, Fig. 371, identical with be proved as

p(lll), stereogr^hic'p

the faces plotted in the

these those shown in the the triangles built upon crystallographic With axes, Fig.369. the anglesbetween the different crystal faces known by measurement, it is easy, by the formulas of spherical to calculate the value trigonometry, of these other angles and from them obtain the axial ratio. That the anglesshown on the stereographic

poles are

149

are

those in Fig.369 may follows. Let Fig. 372 vertical section cut

through the sphericalprojectionof in rhodonite such to a as way include the 6 and c crystallographic The triangle, axes. which has these two sides and axes as the three angles a, -K and p, lies therefore in the plane of the figure. The mals noraioo to all faces parallelto the i.e. the c axis, prism zone, would lie in a plane at rightangles to that axis. This plane would intersect the sphere of the spherical 372 projectionin a great circlewhich is representedon the stereographicprojection, Fig. 371, by the divided circle. On Fig. 372 this great circle would in orthographicprojection as the appear line C-C' lying at rightangles to the c axis. In the same all faces lying way to the b axis, i.e.the zone parallel (100)(101)-(001),would have their normals in a plane which would be foreshortened to the line B-B' in Fig. 372. Since the lines C-C' and B-B' at right are to the c and b axes angles respectively the angle between them must equal the axial angle, a. This same angle will therefore on the stereographic appear projection,Fig. 371, between the great circles of the two zones, the faces of which are parallel respectivelyto the c and b axes. Further the normals to all faces which intersect the b and c axes at their unit lengthswould lie in a plane at right angles to the line b-c, Fig. 372. This plane would appear in orthographicprojection On the stereographic as the line P-P'. be projection,Fig. 371, this would represented the zonal circle passing through (100), (111), as 373 B-B' and P-P' (Oil),(100). The angle between will by construction equalV and that between C-C' and P-P' will equal p. These same angleswill appear therefore in the stereographicprojectionbetween the the circles. In the same corresponding zone way identityof the anglesj, a, T, 0, n and v in Figs.369 and 371 can be proved. the necessary With number of these anglesgiven the formulas required for the calculation of the axial lengthsare given below. The angles T',a',t"',

//,if'and p' are the correspondinganglesto in the adjacentquadrants,see Fig. 373.

T, o-, etc..

150

CRYSTALLOGRAPHY

sin

T

sin

"r

sin T'

sin

a

sin v'

v

sin

c

sin TT'

-w

c _

_ _ _

_

_

~

~

~~

sin a'

'

b

sin

'

sin M'

M

sin

"

b

sin p'

p

'

and the pyramid hkl (not the unit form) If the anglesgiven are between the three pinacoids the correspondinganglesbe represented hkl if for That the face similar. the relations are is, circles 100, 001 and 100, 010 the zone by TO, ffo, etc.,where TO, "TO are the angles between be expressedin the general relations these circle and the zone may 001, hkO, respectively form k a sin TO' sin TO a_ _

_ ~

sin

o-o

sin

vn

'

sin

o-0

sin

VQ

b'

h

h,

c

he

I

la

""

"

MO

sin MO'

TTO

sin TH/

sin

htt sin sin

Thus

PO

become

sin

sin

sin

It is also to be noted

2_a

a^

_

3c

sin

2c

XQ _

_

sin

36

180"

=

A,

-

ft

sin

a

MO

^

b

po

are

A

=

B

+

*"

180"

=

B,

-

180"

=

7

-

C,

pinacoidal sphericaltriangle IOO'010'OOI

the angles in the polesrespectively.That is,

A, B, C

I,

that a

where

v0

_

|6

(TO

c

b

_

sin p0'

for the face 321 the formulas TO

k I

c _

_

=

P

+

TO

PO

=

^+M

=

^

+

/io=

C

=

T-f-"r

=

T0

+

"r0=

A

=

at

these

(180" a); (180" -0); (180" 7).

=

-

-

Also 180"

-

TT' +

P'

TTO'4- PO'

=

=

".

the faces or calculation,the angles between Hence, having given, by measurement the ab(100 A 010),ac(100 A 001) and 6c(010 A 001), which are the sides of this triangle, anglesA, B, C are calculated and their supplements are the axial angles a, /3,7 respectively. Stillanother series of equations are those below, which give the relations of the angles and axial angles. By means of them, with the sine formulas given /*, v, p, etc.,to the axes above, the angularelements (and other angles) can be calculated from the axial elements. sin )8

a

tan fj.

"

+

c

a

T

=

c

cos

a

b +

a

tan

;

'

cos

a

2 sin a

P'

sm

P

a '

c

2 sin

b

+

a

=

cos

a

7 '

cos

90";

7

if their

sum

is greater than

sin w'

?r

= **

sin (p 2 sin ,

sin

=

7

These equationsapply when M + v, etc.,is less than is negative. 90" the sign in the denominator 207. The following equations are also often useful. tan

8

cos

6 sin

7'"

"

r"

b +

.

c

tan

'

sin

a

tan

"

+

a

;

-

,

6

,

sin 8

"

a

= ,

=

v

/3

cos

b sin tan p

c

tan

;

"

;

"

,,

p')

-

fj.sin

'

sin (TT

TT')

-

//

2 sin

sin v'

v

_ _

sin (n 2 sin

sin

n'}

"

sin T'

T

2 sin

tan

sin (T

T')

-

(v

v')

"

sin "r'

a

'

sin ("r

a')

-

Also, a

+

7r+p=/3+M the

+

y

=

7+r

+

(r

=

180".

The calculation, from angular elements or from the assumed fundamental angles,either (1) of the angular position of any face whose symbol is given, or

measured

(2) of the

152

CRYSTALLOGRAPHY

l'93c. ;. By dividingthese numbers by 1'55 we get the interceptsexpressed in terms of the 0'71a,16, l'24c. h of the 6 axis,consideringthat as 1*0. The interceptsthen become length T114 : 1 : 0'986, these are compared with the axial ratio of rhodonite, a : b : c When The indices of x are therefore 321. the parameters of the face are found to be fa, 16, 2c. of a triclinic crystalhaving given the the axial elements 227. To determine,by plotting, that the posiTo illustrate this problem it is assumed tions gnomonic projectionof its forms. of the poles of the faces,(100),(010),(001),(101),(Oil) and (111) On rhodonite are If this figureis compared with the stereographicprojectionof the known, see Fig. 376. forms given in Fig.371, it will be seen that the angle between the zones same (100)-(101)(100)-(111)-(011)and (001) and (100)-(111)-(011)is equal to TT, that between the zones (010)-(011)-(001)and (010)-(111)-(101)is equal (100)-(110)-(010)is equal to p, between The method to v and between (010)-(111)-(101)and (010)-(110)-(100)is equal to Mbe measured was -by which the angles between these various zones explained in Art. may From these angles triangles ^2, p. 43, and is illustrated by the construction of Fig. 376. in terms be readilyconstructed to give the lengths of the a and c axes of the 6 axis, can with its length taken as equal to 1 '0. =

228. To determine, by plotting, the indices of the forms of a triclinic crystal, having given the positionof other poles upon the gnomonic projection. The method for the solution of this problem is similar to that alreadydescribed under the previous systems. The difference lies in the fact that the lines of reference upon which are plotted the intercepts to them from the polesof the faces make of the lines drawn obliqueangles with each other

These

reference lines

interceptsfrom which study of the gnomonic

MEASUREMENT 229.

measured

taken as the zonal lines the indices are determined are

are

(OOl)-(lOl)and

(OOl)-(Oll)and the from the pole of (001) A projectionof axinite, Fig. 367, will illustrate this problem.

OF

THE

Contact-Goniometers. of instruments by means "

measured

ANGLES

OF

CRYSTALS

The interfacial angles of crystals are which are called goniometers.

MEASUREMENT

OF

THE

COntact"

This

ANGLES

or

OF

153

CRYSTALS

hand-goniometer one

form

of which

is

contact-goniometerconsists of a card on which is printeda semicircular graduated to half degreesat the center of which is fastened a

arc

celluloid arm which may be turned to any desired position. The method of of the goniometer is illustratedin Fig.377. The bottom of the card and

use

"77

PenfieldContact Goniometer,Model

B

the blackened end of the celluloid arm are brought in as accurate contact as possiblewith the two crystalfaces,the anglebetween which is desired. Care must be taken to see that the planeof the goniometeris at rightanglesto the the two faces. Another model of the contactintersection between of edge has swiveled two arms togetherand separate from the goniometer,Fig.378, of the arms is obtained The and then by means crystalangle graduated arc. the them the angle between them measured graduated arc. by placing upon liesin such a position This latter type is employed in cases where the crystal of the former.* to prevent the use as * devised by S L. Penfield and can be These simple types of contact-goniometerswere Laboratory of the Sheffield Scientific School of obtained by addressing the Mineralogical Yale University,New Haven, Ct.

CRYSTALLOGRAPHY

154

faces

whose

in the

is useful contact-goniometer

The

not

are

polished;the

well

case

of

measurements

largecrystalsand those with it,however, are

378

Penfield

seldom

within

accurate

where crystals,

the faces

a

Contact

Goniometer,

quarter of are

smooth may

379

Model

A

a degree. In the finest specimens of and lustrous, accurate results far more be obtained by means of a different

instrument, 230.

called

the

ometer. reflectinggoni-

Goniometer. This instrument devised was type by Wollaston in 1809. It has undergone extensive modifications and improvements since that time. Only the perfectedforms that in are common use to-day will be described. The principle underlyingthe construction

Reflecting

-

of

of

the

understood

379),

reflecting goniometer will be by reference to the figure(Fig.

which

represents

a

section

of

a

crystal,whose angle, abc, between the faces ab, be, is required. Let the eye be placed at P and the point M be a source of light. The eye at P, looking at the face of the crystal,be, will observe a reflected image of in

the

that fn.

direction of Pn.

the lo

image is seen effect this,the

same

m,

The

crystalmay

reflected by

crystal must

be so changed in its position the next face and in the same direction, be turned around, until abd has the now

OF

MEASUREMENT

THE

ANGLES

OF

CRYSTALS

155

of the number therefore, present direction of be. The angle dbc measures, be measured degrees through which the crystalmust be turned; it may by which turns with the crystal. attachingthe crystalto a graduated circle, This angle is the supplement of the interior angle between the two faces,or is the normal in other words angle,or angle between the two poles(seeArt. the angle needed 43, p. 44). The reflecting goniometer hence givesdirectly

the system of Miller here followed. A form Goniometer. 231. Horizontal of reflectinggoniometer well for in Fig. 380. The measurements accurate is shown particular adapted Fuess. form of instrument here figured* is made by

on

"

One-circle

Reflection

Goniometer

The central stands on a tripod with levelingscrews. instrument which the d, plate, turns, carrying axis,o, has within it a hollow axis,6, with the uprightsupport of which is the verniers and also the observingtelescope, carries the graduated which shown at B. Within b is a second hollow axis,e, the tangent screw, circle, /, above, and which is turned by the screw-head,0; B, the screw, c, being for the observingtelescope, fine The

a,

serves

as

a

adjustment

for this purpose raised so as to bind b and e together. The tangent screw, 0, the third is a fine adjustment for the graduatedcircle. Again, within e is which the central h within rod, is and axis,h, turned by the screw-head, i, trivances conand centering the with adjusting carries the support for the crystal, the lowered fc, raised by or be screw, rod This can below. mentioned The

figurehere used

is from

the catalogueof Fuess.

CRYSTALLOGRAPHY

156 so

as

to

to the bring the crystal

proper

height "

that

is,up

to the axis of the

telescope; when this has been accomplished,the clamp at p, turned by a take placeindependof h can ently set-key,binds s to the axis,h. The movement these two for measurement axes is are the but after ready of g, crystal is at The /. the C, telescope supported signal bound set-screw, togetherby The mounted is of the the on of crystal tripod. legs firmly attached to one The the plateis clamped by the screw, v. centering the plate,u, with wax, other each to at slides (one of these is rightangles apparatus consists of two and the screw, a, which works it;the end of the other in the figure) shown is seen at a'. The adjustingarrangement consists of correspondingscrew the other at rf; in the figure, shown of them, r, one two sections, cylindrical is The circle on / center. have a common graduated to degrees the cylinders and quarter degrees,and the vernier givesthe readingsto 30". of lightis placed behind the collimator tube which is A brilliant source Openings of various size and character are provided at the top of the support C. end of this tube in order to modify the size and shape of the at the rear monly combeam of lightthat is to be reflected from the crystalfaces. The most made tact used opening is one by placingtwo circular disks nearly in conthem an with each other leavingbetween hour-glassshaped figure. The removable with several L tube is telescopeswith lenses provided telescope and hence are which have different angular breadths and magnifying powers suitable for observingfaces varying in size and degree of polish. At the front be thrown into or of the tube L there is a lens which is so pivotedthat it may of lens this liesin axis the tube it of When the of axis the the out telescope. with which the into the telescope a converts crystal low-power microscope this lens the telescopehas a long-distance focus Without be observed. may face can be seen. of lightreflected from the crystal and only the beam is brieflyas follows. The littleplate u is removed of use of the instrument method The of some the crystalto be measured. faces of it is fastened by means wax should be placed as nearlyas possiblevertical to the surthat is to be measured face zone of this plate. It will usuallyfacilitatethe subsequent adjustment if a prominent face be placed so that it is parallelto one in this zone of the edges of the plate u. This plate with the attached crystalis then fastened in place by the screw v. During the preliminary adjustments of the crystalthe small lens in front of the tube L is placed in its axis and the It is usually better also to make crystalobserved through the microscope thus formed. k these first adjustments outside the dark room in daylight. By means of the screw-head the central post is raised or lowered until the center of the crystallies in the plane of the of the two slidingtables controlled by the screw-heads a and a' telescope. Next by means the crystalis adjusted so that the edge over which the angle is to be measured coincides with the axis of the instrument. This adjustment is most easilyaccomplished by turning the central post of the instrument of these slidingplates lies at rightangles to until one the telescopeand then by turning its screw-head bring the intersection in questionto coincide with the vertical cross-hair of the telescopetube. Then turn the post until the other plateliesat rightanglesto the telescopeand make a similar adjustment. Then in a similar of the tipping screws manner the faces by means x and y bring the intersection between to a positionparallelwith the vertical cross-hair of the telescope.By a combination of these adjustments this edge should be made to coincide with the vertical cross-hair and to remain stationarywhile the crystalis revolved upon the central post of the instrument. the instrument Next is taken into the dark room and a lightplaced behind the collimator tube, and the crystalturned until one of the faces is seen through the tube L to be brightly illuminated. Then the littlelens in the front of this tube is raised and the reflection of the beam of light,or signalas it is called,should lie in the field. If the preliminary adjustments the horizontal accurate were cross-hair will bisect this signal. In the majority of cases, however, further slightadjustments will be necessary. Before the angles between the faces can be measured their various signalsmust all be bisected by the horizontal crosshair. When these conditions are fulfilledeach signalin turn is brought into place so that The

and the

upon

MEASUREMENT

OF

THE

ANGLES

OF

157

CRYSTALS

is bisected also by the vertical cross-hair and its angular positionread by of the means The difference between graduated scale and vernier. the angles for two the normal angle between them. In making these readings care must be taken that the plate which the graduated circle is engraved is turned with the on central post. In order to do this only the screw-head be used unless, is wise,the two screw-heads i and g must as a have been previouslyclamped togetherby means of I. For the accurate adjustment of the

it

LeTgfves

signals on

the

vertical cross-hair the tangent

anglesmeasured th"

a?i of the

it is important to note character of the signal. It is

different faces and

232.

number

or

Theodolite-Goniometer.

practicaladvantages and

/3 is used.

screw

In making

a

record of the

accuratelythe face from which each signalis derived

frequentlyhelpfulto

make

a

sketch of the outlines

letter them. "

A

form

at present in wide

of goniometer * having many has two independentcircles use

381

Two-circle

Reflection

Goniometer

and

is commonly known the two-circle goniometer. It is used in a manner as of this type were analagousto that of the ordinarytheodolite. Instruments devised and Goldschmidt. Other independentlyby Fedorow, Czapski models have been described since. In addition to the usual graduated horizontal and collimator, circle of Fig. 380, and the accompanying telescope a second graduated circle is added which revolves in a plane at rightangles to the first. Fig.381, after Goldschmidt,givesa cross-sectional view of one of * Fedorow, Universal or Theodolit-Goniometer, Zs. Kryst., 21. 574, 1893; 22, 229, 1893; Czapski, Zeitschr. f. Instrumentenkunde, 1, 1893; Goldschmidt. Zs. Kryst.,21, 210, of Goldschmidt, On the method 1892; 24, 610, 1895; 25, 321, 538, 1896; 29, 333, 589, 1898. A see Palache, Am. J. Sc.,2, 279, 1896; Amer. Mineral, 6, No. 2, et seq., 1920. simplifiedform of the theodolite-goniometeris described by Stober, Zs. Kryst., 29, 25, 1897; 64,442.

158

CRYSTALLOGRAPHY

It will serve to illustrate the essential the earlier machines devised by him. instrument. features of the is attached at the end of the axis (h) of the The crystalto be measured of suitable centeringand vertical circle and so adjusted by means tipping to this axis and devices that a given plane, called the polar plane, is normal the axis of the horizontal circle. In using the instrument, lies directlyover the position instead of directlymeasuring the interfacial anglesof the crystal, of of each face is determined independentlyof the others by the measurement what its angular co-ordinates, or might be called its latitude and longitude. and p of Goldschmidt) measured, respecThese co-ordinates are the angles("f" tively, in the vertical and horizontal circlesfrom an assumed ian, poleand meridwhich are fixed,in most cases, by the symmetry of the crystal. In practice that its prismaticzone the crystalis usually so mounted is perpendicular the basal plane to the vertical circle. A plane at rightanglesto this zone, i.e., in the first four systems, is known the polar plane and its positionwhen as the signalinto the telescope establishes the zero reflecting positionfor the horizontal circle. The positionof a pinacoid,usuallythe 010 plane,in the prism zone establishes the zero positionfor the vertical circle. For example, for the pyramid 111, the angle "f"(measured on with an orthorhombic crystal, the vertical circle) is equal to 010 A 110 and p (measured on the horizontal is equal to 001 A 111. circle) Goldschmidt has shown that this instrument is directly applicableto the and of of indices methods system calculation and projectionadopted by him, which admit of the deducing of the elements and symbols of a of given crystal with a minimum labor and calculation.* Fedorow has also shown strument, that this inwith the addition of the appliances devised by him, can be most convenientlyused in the crystallographicand optical study of

crystals. The followinghints as to the methods of using this instrument may helpful. prove The telescope and colhmator tube are convenient placed at some angle each to other (usually about 70") and then clamped in position. The find the polar posinext step is to tion of the horizontal circle, the positionat which a crystalplane lyingat rightangles i.e., to the axis of the vertical circle will throw the reflected beam of lighton to the cross-hairs of the telescope. Obviously the plane under these conditions must be normal to the bisector of the angle between the axes of the collimator and telescope, the line B-P Fig 382. The method by which this polarpositionis found is as follows: Some reflectingsurface is mounted the end of the post h, Figs. 381, upon small inclined 382, making some angle to the plane normal to that post. Then by turning the instrument in both the hori*

See

Goldschmidt's

Krystallographische Winkeltabellen

les

9Q

gystem bT his, "TT"a"e a-?" rec*ulre(i author's

wnrV work ooserveu

The.same

"/

-11

giving

all

upon

atlas der

f"* all known

(432 pp., Berlin, 1897). species. See also Zs. Kryst.,

1913 Krystallformen,

previouslypublished crystalfigures together with tnem.

et seq., a

is a monumental

discussion of the forms

160

CRYSTALLOGRAPHY

After these adjustments have been completed the crystal is turned about both the it successivelyreflects the signal horizontal and vertical planes so that each face upon made in each case. horizontal and vertical readings are The into the telescope. The forms tions. present can then be readilyplotted in either the stereographicor gnomonic projecFig. 383 shows how the forms of a simple crystalof topaz could be plotted in the from the "f"and p angles obtained from it the two circle gonistereographicprojection ometer For each face the vertical circle angle, "",is plottedon the divided measurements. the positionof 6(010)givingthe zero point while the horizontal circle angle is plotted circle, the positionof c(001)givingits zero radial line from the center of the projection, on a point. "

COMPOUND

OR

TWIN

CRYSTALS

Crystals. Twin crystalsare those in which one or more positionwith reference to the other parts regularlyarranged are in reverse to consist of two or more often or crystals part parts. They appear externally form of a cross and sometimes have the star. or symmetricallyunited, They of part of the faces, also exhibit the compositionin the reversed arrangement Twin

233.

"

386

384

Thenardite

Columbite

Fluorite

in the striae of the

the surface,and in re-enteringangles; in certain cases by an examination in polarized examples of typicalkinds of twin crystals, and many others are given on the pages following. To illustratethe relation of the parts in a twin Figs.387, 388 are crystal, given. Fig. 387 shows a regularoctahedron divided into halves by a plane to an octahedral face. If now parallel the lower half be supposed to be revolved 180" about an axis normal to this plane,the twinned octahedron of Fig.388 results. This is a common type of twin in the isometric system, and the method here employed to describe the positionof the parts of the crystalto one another is applicable to nearlyall twins. 234. Distinction between It is Twinning and Parallel Grouping. important to understand that crystals, or parts of crystals,so grouped as to parallelpositionswith reference to each other occupy that is,those whose similar faces are parallel are not called twins; the term is appliedonly where the crystalsor parts of them are united in their reversed positionin accordance with some deducible mathematical law. Thus Fig. 389, which represents a cluster of partial crystals of analcite,is a case of parallel grouping simply (seeArt. 252); but Fig.407 illustrates twinning,and this is

compound

structure can only be surelydetected light. The above figures(Figs.384-386) are

"

"

"

COMPOUND

true

of

Fig. 416 also.

OR

Since

TWIN

161

CRYSTALS

though in these

the axes remain parallel in position. positionof the parts of a twinned crystal can be best described as justexplained,by reference to that line or called the twinning-axis, axis a revolution of 180" about which would serve to

the similar faces (and planes of symmetry) 235. The relative Twinning-Axis.

are

cases

reversed

"

388

Twinned

Octahedron

Analei'te

to the other,or in other words, which would bring the twinned part parallel of the parallel cause to the other. one partsto take a twinned positionrelatively The that is,either twinning-axisis always a possiblecrystallineline axis or the normal to some a possibleface on the crystal, crystallographic the fundamental forms. of one common usually It is not to be supposed that ordinarytwins have actuallybeen formed by such a revolution of the parts of crystals, for all twins (exceptthose of secondary of Art 242) are the result see regularmolecular growth or enlargeorigin, ment, like that of the simple crystal. This reference to a revolution, and an the forms. of describing axis of revolution, is only a convenient means In certain rare of certain pseudo-hexagonalspecies,a cases, particularly "

120" about a normal to the base has been assumed to observed. complex group The plane normal to the axis of revolution is 236. T winning-Plane. axis and plane of twinning bear the same The called the twinning-plane. in the in their reversed position;consequently, relation to both individuals are symmetricalwith reference to the majority of cases, the twinned crystals revolution

of 60"

or

explain the

"

twinning-plane. to a possible The twinning-plane parallel occurring is,with rate exceptions, face on the givenspecies, frequentor fundamental and usuallyone of the more The forms. only in the triclinicand monoclinic systems, exceptionsoccur where the twinning-axis is sometimes one of the obliquecrystallographic axes, a and then the plane of twinning normal to it is obviously not necessarily in albite. true is conspicuously crystallographic plane; this 237. Composition-Plane. The plane by which the reversed crystals This and the twinning-plane monly united is the composition-plane. are very comcoincide;this is true of the simple example given above (Fig.388), "

be conceived to take place the revolution may which the semi-individuals are the and by plane twinning-axis) not coinciding,the two planesare generallyat united are identical. When is parallelto the the that composition-plane is, other rightangles to each Still below. this again,where the of are axis of revolution. given Examples where

the

plane

about

which

(normal to the

"

CRYSTALLOGRAPHY

162

tact they interpenetrate,the conexceedinglyirregular.In such but always, a definite position, cases its loses significance. the composition-plane parts have often no rectilinear Thus in quartz twins the interpenetrating manner in most the throughout the mass, irregular boundary, but mingle in the character of variations by abrupt showing this composite irregularity in found internal crystals, This irregular structure, quartz many the surfaces. of polarized light;also the common kinds, is well brought out by means even acid. by etching with hydrofluoric than the definite signification has sometimes a more The composition-plane former in whereas the cases, many twinning-plane. This is due to the fact that is fixed, the twinning-axis maybe exchanged (andtwinning-plane) 390 for another line (and plane)at rightanglesto each, respectively, since a revolution about the second axis will also satisfythe 7v ' * An example of this conditions of producingthe requiredform. is furnished by Fig. 390, of orthoclase; the composition-plane is here fixed namely, parallelto the crystalface,6(010). to this be either (1) parallel But the axis of revolution may is then consequently the to a (100),which face and normal twinning-plane,though the axis does not coincide with the be taken as axis;or (2)the twinning-axis crystallographic may then the and vertical twinning-plane axis, coincidingwith the face. In other simpler to it is not a crystallographic normal Orthoclase sequence principleholds good, generallyin concases, also,the same of the possiblemutual interchangeof the planesof twinning and the true twinning-planeis evident,since it is composition. In most cases the crystalof simple mathematical face on ratio. to some parallel

crystalsare

not

regularlydeveloped,and

where

be be interrupted, or surface may may the axis and plane of twinning have, as

"

c

'

"

__

two twinning-axes at right 238. An interesting example of the possiblechoice between anglesto each other is furnished by the speciesstaurolite. Fig. 439 shows a prismatictwin The measured from Fannin Co., Ga. angle for bb was 70" 30'. The twinning-axisdeduced be normal to the face (230),which would then be the twinning-plane. Or, from this may be taken, which would instead of this axis,its complementary axis at rightangles to it may in this speciesit happens that the faces,130 Now equallywell produce the observed form. and 230 (over100),are almost exactlyat rightangleswith each other,and, according to the latter supposition,130 becomes the twinning-plane,and the axis of revolution is normal to it. Hence, either 230 or 130 may be the twinning-plane,either suppositionagreeingclosely with the measured angle (which could not be obtained with great accuracy). The former method of twinning (tw. pi.230) conforms to the other twins observed the species,and on hence it may be accepted. What is true in this case, however, is not always true, for it will seldom happen that of the two complementary axes each is so nearly normal to a face of the crystal. In most of the two axes conforms cases one to the law in being a normal to a possibleface,and the other does not, and hence there is no doubt to which is the as true twinning-axis. Another The common interestingcase is that furnished by columbite. twins of the speciesare similar to Fig. 385, p. 160, and have e(021) as the twinning-plane;but twins also occur like Fig. 434, p. 169, where the twinning-plane is g(023). The two faces,021 and 023, are nearly at rightangles to each other,but the measured angles are in this case exact to prove that the two kinds cannot be referred to one sufficiently and the same law.

239.

Contact-

and

Penetration-Twins.

"

In

contact-twins,when

mally nor-

formed, the two halves are simple connate, being united to each other by the composition-plane;they are illustrated by Figs. 385, 388, etc. In actual crystalsthe two parts are seldom symmetrical, as demanded by but one theory, preponderateto a greater or less extent over the other; may

in

only

COMPOUND

OR

small

portionof the

TWIN

163

CRYSTALS

second

individual in the reversed in nature in this positionmay the often are obliterated the mal abnorre-entering angles respect. Moreover, by of other of the and often one or developments parts, only an indistinct line of the faces marks the division between the -two individuals. on some Penetration-twins are those in which two or more interpenetrate, complete crystals have as it were crossing through each other. Normally,the crystals a common center, which is the center of the axial system for both ; practically, cases

some

exist.

a

Very great irregularities observed are

in

occur. contact-twins, great irregularities Examples of twins of this second kind are given in the annexed figures, and Fig.393 of chabazite. Fig.392 of tetrahedrite, Figs.386 and 391 of fluorite, in the pages of the species Other examples occur following, as, for instance, in nature staurolite (Figs.438-441),the crystalsof which sometimes occur with almost the perfectsymmetry demanded by theory. It is obvious that and penetration-twinsis not of great importcontactthe distinction between ance, drawn between them. and the line cannot always be clearly

however,

as

393

392

Chabazite

Tetrahedrite

Fluorite

distinction of paragenicand metagenic The Paragenic and Metagenic Twins. often so Yet the forms are than crystallography. belongs rather to crystallogeny is important. distinction of the notice brief that distinct a obviously had its beginning in a nucleal compound In ordinary twins, the compound structure compound in its very origin; and whatever molecule, or was opment in the develthese are 394 only irregularities in the result, inequalities at in others,the crystalwas But such a nucleus. from change in itself or in first simple; and afterwards,through some 240.

"

twins

the

condition

of the material

suppliedfor

its increase,

received

new

ot continuation,in a reversed position. This mode layers, the of the to result origin subsequent twinning is metagenic,or a ot it is form is paragenic. One crystal; while the ordinary mode attained had a length of middle The 394. portion illustrated in Fig. or

a

simultaneously geniculated and then became half an inch or more, often repeated in are These geniculations at either extremity. into one another, and the ends of the crystalare thus bent rutile, forms.

Rutile

and occasionally produce nearly regularprismatic presentedby the successive This metagenic twinning is sometimes especia quartz crvstals, as in some in crystal, a of deposition layers beingof oppos exceedinglythin, amethyst, the inseparablelayers, crystalsof the triclmic feldspars, similar manner, In kinds. a composition, oscillatory osc to often made up of thin platesparallel 6(010) by to the edge accordingly,is finelystriated parallel

are albite,etc., "., and the face c(001), _-

and Repeated Twinning, Polysynthetic precedingparagraph one case of repeatedtwinning 241.

of the

"

been

In

the

mentioned, that

versed rein grouping repetitionor parallel parallel is of kind This twinning lamellae. successive crystalline

feldspars;it is

positionof

Symmetrical. has

a

case

of

164

CRYSTALLOGRAPHY

cases often called polysynthetic being extremely twinning,the lamellae in many lines (striations) face or a crystal on thin,and givingrise to a series of parallel in many cases surface of cleavage. The triclinic feldsparsshow thetic polysyna twinning and not infrequentlyon both c(001)and 6(010),cf. p. 172. It is also observed with magnetite (Fig.474) pyroxene, barite,etc. Another kind of repeatedtwinning is illustrated by Figs.395-400, where reversed individuals are not parallel.In these cases the axes the successively twins of lie in the as o r a prismatic however, aragonite, they zone, may, may In all such cases the be inclined to each other, as in Fig. 397 of staurolite to tends circular o f the when the forms, twinning produce repetition angle the two axial systems is an aliquotpart of 360" (approximately). between of three individuals (hence called Thus consisting six-rayedtwinned crystals, with chrysoberyl(Fig.395),or cerussite (Fig.396),or staurolite occur trillings), (Fig.397),since three times the angle of twinning in each case is not far from in the octahedrons of gold and 360". occur Again,five-fold twins,or fivelings, ,

397

Spinel

Rutile

Phillipsite

spinel(Fig 398), since 5 X 70" 32' 360" (approx.). Eight-foldtwins,or of rutile (Figs. eigktlings, 399, 413) occur, since the angleof the axes in twinned positiongoes approximatelyeighttimes in 360". Repeated twinning of the symmetrical type often serves to give the compound crystalan apparent symmetry of highergrade than that of the simple and the result is often spoken of as a kind of individual, pseudo-symmetry (Art.20) cf. Fig. 431 of aragonite,which represents a basal section of a pseudo-hexagonal crystal. Fig.400 of phillipsite (cf.Figs.452-454) is an inter=

,

EXAMPLES

OF

IMPORTANT

METHODS

OF

165

TWINNING

estingcase, since it shows how a multipletwin of a monoclinic crystalmay simulate an isometric crystal(dodecahedron). Compound crystalsin which twinning exists in accordance with two laws not of common at once excellent example is afforded by are an occurrence; staurolite, Fig. 441. They have also been observed with albite, orthoclase, in other

and

cases.

When there is reason to believe that the Secondary Twinning. twinning has been produced subsequentlyto the originalformation of the it is said to be crystal,or crystalline as, for example, by pressure, mass, Thus calcite the of limestone a often show such grains secondary. crystalline lamellae. The observed (||c, same are secondary twinning occasionally 001) in pyroxene crystals.Further, the polysynthetictwinning of the triclinic feldsparsis often secondary in origin. This subjectis further discussed on a later page, where it is also explainedthat in certain cases twinning may be in a crystal individual produced artificially e.g., in calcite (seeArt. 282). 242.

"

"

EXAMPLES

OF

IMPORTANT

METHODS

OF

TWINNING

few exceptionsthe twins of the normal the octahedral axis,and an kind, twinning-axis system are to an octahedral face; in most the twinning-planeconsequentlyparallel cases, also,the latter coincides with the composition-plane.Fig. 388, p. 161,* 243.

Isometric

class of this

401

Galena

System. of

"

With

one

402

Hauynite

403

Sodalite

common shows this kind as appliedto the simple octahedron; it is especially a with the spinelgroup of minerals,and is hence called in general spinel-twin. *

the faces noted that here and elsewhere the letters used to designate line. subscript by a distinguished are parts of crystals

It will!be

the twinned

on

166

CRYSTALLOGRAPHY

Fig.401 is a similarmore complex form; Fig.402 shows a cube twinned by this in the direction form but shortened method, and Fig.403 representsthe same hence and the anomalous of the octahedral axis, aspect of a triangular having pyramid. All these cases are contact-twins. A simple followingthe same Penetration-twins, law, are also common. in of fluorite is shown case Fig. 391, p. 163; Fig. 404 shows one of galena; and Fig.405 is a repeated octahedral twin of haiiynite, Fig.406 a dodecahedral twin of sodalite. 244.

In the

class of the isometric system pyritohedral

in Fig. 407 are ot the type shown penetration-twins common (thisform of pyriteis often called the iron and cross). Here the cubic axis is the twinning-axis, obviously such a twin is impossible in the normal

class.

Figs.408 and 409 show analogousforms with parallel for crystalsbelonging to the tetrahedral axes class. The peculiar development of Fig. 408 of Pyrite tetrahedrite is to be noted. Fig.410 is a twin of the ordinary spinel type of another tetrahedral species,sphalerite;with it, and sometimes complex forms with repeated twinning are not uncommon t win lamellae noted. polysynthetic are 408

409

Tetrahedrite

245.

410

Eulytite

Tetragonal System.

Sphalerite

The most method is that where common face of the pyramid,e(101) It is especially characteristicof the speciesof the rutile group viz.,rutile and cassiterite:

the

"

is parallel to twinning-plane

a

.

"

411

413

Cassiterite

also

the similarly

Zircon

allied

specieszircon.

Rutile

This

is illustratedin

Fig.411, and

CRYSTALLOGRAPHY

168

the individuals both right-or both left-handed but parallel, with 2(0111). The to and coinciding then parallel r (]0ll) symmetrical, axes

hence

re-

422

421

420

un-

Figs. 419-426, Calcite and the parts are suitingforms,as in Fig.428, are mostly penetration-twins, often very irregularly united,as shown by dull areas (z)on the plus rhombohedral face (r); otherwise these twins are recognized by pyro-electrical phenomena. In Fig. 429 the twinning-planeis a(1120) the Brazil law the individuals respectively right-and left-handed and the twin symmetrical with reference to an a-face;these are usuallyirregular in penetration-twins; "

"

these twins

r

and 427

r, also

z

and

z, coincide

These

428

twins often show, in

con-

429

Figs. 427-429,Quartz the phenomenon vergingpolarizedlight, that pseudo-twinsof quartz are common

of "

Airy'sspirals.It may be added that is,groups of crystals which

EXAMPLES

OF

IMPORTANT

METHODS

OF

169

TWINNING

less complex twinninglaw, or nearly conform to some more grouping is nevertheless only accidental 430 249. Orthorhombic In the System.

but

where

the

431

"

orthorhombic

the commonest is that where the twinning is face of a of a prism twinning-plane 60", or nearly60". This is well shown with the In accordance speciesof the aragonitegroup. with the principle stated in Art. 241, the twinning after this law is often repeated, and thus forms with pseudoresult. hexagonal symmetry Fig. 430 shows a simple twin of aragonite;Fig.431 \ shows a basal section of an aragonitetriplet Aragonite which although it resembles a hexagonal prism reveals its twinned character by the striations on the basal plane and its composite prism faces due to the fact that the prison by irregularities matic angle is not exactly 60". With witherite (and bromlite),apparent but the true complex twinning is revealed hexagonal pyramids are common, in polarized noted later. as light, Twinning of the same type, but where a dome of 60" is twinning-plane, is common with arsenopyrite (tw.pi.e(101)),as shown in Figs.432, 433; also method

system

of

434

Columbite

Arsenopyrite

Fig.434 of

columbite,but compare Fig.385 and remarks in Art 238, Another manexample is given in Fig.395 of alexandrite (chrysoberyl) Chrysolite, .

435

ganite,humite, Another

are

common

436

437

Marcasite

Arsenopyrite

other specieswith which this kind of twinningis common. of twinningis that where the twinningis parallel method

170

CRYSTALLOGRAPHY

prism of about 70J",as shown in Fig.435. With this method not infrequently occur (Figs.436, 437). symmetricalfivelings staurolite illustrates three kinds of twinning. In Fig.438 the The species 45" 41',the crystalscross twinning-planeis (032),and since (001 A 032) nearly at rightangles. In Fig.439 the twinning-planeis the prism (230). In then crossing at anglesof about Fig.440 it is the pyramid (232); the crystals occur (seeFig.397),and indeed more complex forms. In 60",stellate trillings Fig.441 there is twinningaccordingto both (032)and (232). to

a

face of

a

=

440

Staurolite 441

Staurolite

Struvite

In the hemimorphic class, twins of the type shown in Fig.442, with c(001) the twinning-plane, to be noted. are 250. Mpnoclinic System. In the monoclinic system, twins with the vertical axis as twinning-axis is this illustrated 443 of are common Fig. by augite ; and Fig.445 of orthoclase (seealso Fig.390, (pyroxene), Fig.444 of gypsum,

as

"

443

444

445

y

Augite p.

Gypsum

Orthoclase

162). With the latter speciesthese twins are called Carlsbad twins (because in the trachyteof Carlsbad,Bohemia) ; they may be contact-twins

common

EXAMPLES

OF

IMPORTANT

METHODS

OF

171

TWINNING

(Fig.390),or irregular penetration-twins(Fig.445). In Fig.390 it is to be c and x fall nearlyin the same plane. In Fig.446, also of orthoclase, the twinning-plane is the clinodome (021), and since (001 A 021) 44" 56^',this method of twinning yieldsnearly prisms. These twins are called Baveno twins (from a prominent square at Baveno, Italy) locality ; they are often repeated (Fig.447). In Fig.448 a noted that

=

446

447

448

Orthoclase

twin

Manebach

is

shown; here the twinning-planeis c(001). Other rarer been noted with orthoclase. Polysynthetictwinning with c(001)as twinning-planei" common with pyroxene (cf.Fig.461, p. 173). with monoTwins of the aragonite-chrysoberyl type are not uncommon clinicspecies, having a prominent 60" prism (ordome), as in Fig.449. Stellate types of

twinning have

An and with chondrodite clinohumite. in Fig.450; here the pyramid (122)is the at angles 59" 21',the crystals and since (010 A 122) cross twinning-plane, fall nearly in a common of nearly_60";further,the orthopinacoids zone, since the orthodome is In 9'. 451 90" the twinning-plane Fig. (100 A 122)

twins

after this law

are

analogous twin of pyroxene

common

is shown

=

=

449

Wolframite

(101)

and harmotome Phillipsite

450

Pyroxene

461

Pyroxene

exhibit multiple twinning, and the crystals

cruciform fourlingwith pseudo-symmetry. Fig. 452 shows a the side face. the twinning shown by the stnations on c(001) as twinning-plane, nearly This is compounded in Fig. 453 with twinning-plane(Oil),making as twinning-plane with ra(110) further repeated prisms, and this square often

show

172

CR YST

ALLO

GR

APH

Y

Fig.400, p. 164, resemblingan yieldsthe form in Fig.454, or even dodecahedron, each face showing a fourfold striation.

251.

Triclinic

454

453

452

System.

"

isometric

Phillipsite The most interestingtwins of the triclinic the feldspars.Twinning with 6(010) as the

those shown by is especially twinning-plane very common, polysynthetictwinning yielding the striations on the face c (orthe correspondthin parallel shown by ing lamellae, and also clearlyrevealed in polarizedlight. This is cleavage-surface), known the albite law (Figs.455, 456). Another as important method (Fig. is the that of the law; 457) twinning-axisis the crystallographic pericline axis b. Here the twins are united by a section (rhombic section)shown in the and further explainedunder the feldspars.Polysynthetic figure twinningafter this law is common, and hence a cleavage-mass show two sets of striations, may the surface parallel to c(001)and the other on one to 6(010). on that parallel The angle made by these last striations with the edge 001/010 is characteristic of the particular triclinicspecies, noted later. as

system

are

455

456

457

Albite

Twins 458

of albite of other rarer types also occur, and further twins similar to the Carlsbad,Baveno, and Manebach twins of orthoclase. Fig. 458 shows twinning according to both the albite and Carlsbad types. REGULAR

GROUPING

OF

CRYSTALS

252. Parallel Grouping. with the subConnected ject of twin crystalsis that of the parallelpositionof associated crystals of the same species,or of different "

species. Albite

Crystals of the same speciesoccurringtogetherare commonly in parallelposition. In this way large

very

EXAMPLES

OF

IMPORTANT

METHODS

OF

173

TWINNING

of calcite, as crystals, are quartz, fluorite, sometimes buiJt up of smaller grouped together with corresponding faces parallel. This in crystals as they lie on parallelgrouping is often seen the supporting rock. On glancingthe eye over a surface covered with crystals a reflection from face will often be accompanied by reflections from the corresone ponding individuals

face in each of the other crystals, showing that the crystalsare throughout similar in their positions. With many forms result from the growth of species, complex crystalline

parallelpartial crystals in the direction of the crystallographic axes,

or

axes

of symmetry.

459

460

Thus

dendritic

ing forms,resemblingbrancho ften of icacy, vegetation, great delwith gold,copper, are seen and other species, argentite, especially those of the isometric tem. sysThis is shown in Fig. 459 (ideal),and again in Fig. 460, the twinned where and flattened cubes (cf. Fig. 403, p. 165) are grouped in directions corresponding octahedral to the diagonalsof an Co face which is the twinning-plane. 253. Parallel Grouping of Unlike Species. Crystalsof different species in the to often show same tendency parallelism mutual position. This is similar in form true most or less closely frequentlyof specieswhich are more of orthoclase, surface and composition. Crystalsof albite, implantedon a sometimes an are example of 461 462 this;crystalsof amphibole and (Fig.461), of zircon pyroxene rious and xenotime (Fig.462),of vaalso at kinds of mica, are times observed associated in parallel "

position. The

same

relation of

position

where connection in composition, the crystalsof rutile as tabular on crystalsof hematite, of the former the vertical axes the horizontal with coinciding z ircon Xenotime latter. of the enclosing Crystals of axes Amphibole enclosing in parallel in position parallel calcite have been observed whose pyroxene position rhombohedral faces had a series in all position;sometimes three parallel them, of also

occasionallyoccurs

there is no

quartz crystals upon each rhombohedral face, entirelyenvelop on quartz crystals,one form to pseudo-twins(rather with unite re-entering angles the calcite,and the of chalcopyrsphenoidal Parallel calcite. growths of quartz after trillings) such

ite upon structure

in crystal the similarity are common, the tetrahedral sphalerite of chalthe of the crystals position of the two speciescontrolling

copyrite.

174

CRYSTALLOGRAPHY

OF

IRREGULARITIES

produce

should

only equal,but

unmodified when by extrinsic causes, crystallization, of exact geometricalsymmetry, the anglesbeing not and the dimensions in the the homologous faces of crystals

of

laws

The

254.

CRYSTALS

forms

also

directions of like axes. hardly be considered

This other

symmetry than

an

is,however, ideal

so

that it can

uncommon

perfection. The

various

possible

to the kinds of symmetry, and the relation of this ideal geometricalsymmetry in been discussed Arts. 14 and 18 et actual crystallographic symmetry, have often the fundamental forms a nd are distorted, generally Crystals very seq. with the possible so completelydisguisedthat an intimate familiarity are is requiredin order to unravel their complexities.Even the irregularities

rather widely. vary anglesmay occasionally be treated of crystalsmay under several heads: The irregularities 1, and tions dimensions; 2, Imperfectionsof surface; 3, VariaVariations of form and impurities. ofangles;4, Internal imperfections

IN

VARIATIONS

1.

FORMS

THE

AND

DIMENSIONS

CRYSTALS

OF

The variations in the forms of crystals, Distortion in General. their in character, other certain faces in distortion, words, or, may be irregular being largerand others smaller than in the ideal geometricalsolid. On the be symmetrical, other hand, it may givingto the distorted form the symmetry of a group or system different from that to which it actuallybelongs. The 255.

former

"

case

is the

rule,but

common

IrregularDistortion.

the latter is the

more

interesting.

As

stated above and on p. 13, all crystals less extent accidental variation from the show to a greateror an or irregular if not accompanied by change in This distortion, ideal geometricalform. has no particular the interfacial angles, and does not involve any significance, deviation from the laws of crystallographic symmetry. Figs.463, 464 show of quartz ; they may distorted crystals be compared with the ideal form, Fig. 284, p. 113. Fig.465 is an ideal and Fig.466 an actual crystalof lazulite. 256.

463

"

464

Quartz The

correct ol this

465

466

Lazulite

identificationof the forms

on a difficult crystalis rendered much more prevailingdistortion, it results in the entire obliteration of when especially urtain laces by the enlargement of others. In deciphering the distorted crystalline forms it must be remembered that while the appearance of the crystalsmay be entirely altered, e intertacial angles remain the same; alike that is moreover, like faces are physically

because

"

176

CRYSTALLOGRAPHY

a The dodecahedron lengthenedin the direction of a trigonalsymmetry axis becomes If shortened in the same tion, direcsix-sided prism with three-sided summits, as in Fig. 470. kind (Fig.471). Both resemble rhombohedral it becomes a short prism of the same in garnet. When lengthened in the direction of one of the cubic forms and are common becomes (Fig.472), and a square prism with pyramidal summits axes, the dodecahedron axis it is reduced to a square octahedron, with truncated shortened along the same angles

(Fig.473). The trapezohedronelongated in the direction of an octahedral (trigonal)axis assumes rhombohedral symmetry. (trigonal) If the elongationof the trapezohedrontakes placealong a cubic axis,it becomes a double planes are obliterated eight-sidedpyramid with four-sided summits; or if these summit double pyramid. a complete eight-sided by a farther extension,it becomes tetrahexahedron and hexoctahedron show distortion Similarlythe trisoctahedron, may Further examples are to be found in the other systems. kind. of the same

2.

IMPERFECTIONS

OF

THE

SURFACES

[OF

CRYSTALS

The parallel 258. to OscillatoryCombinations. Striations Due lines and such furrows on the surfaces of crystalsare called strice or striations, surfaces are said to be striated. Each littleridgeon a striated surface is inclosed by two narrow planes less regular. These more or planes often correspond in positionto different faces of the crystal,and these ridges have been formed by a continued that give rise, oscillation in the operationof the causes when actinguninterruptedly, this the surfaces to enlarged faces. of a By crystal are means, with a succession of narrow marked in parallel lines, planes meeting at an the ridgesreferred to. angleand constituting This combination of different planesin the formation of a surface has been termed The combination. horizontal striations on oscillatory prismatic of of this crystals quartz are examples combination,in which the oscillation has- taken place between the prismatic and rhombohedral faces. Thus of quartz are often tapered to a point,without the usual pyramidal crystals terminations. Other examples are the striations on the cubic faces of pyriteparallelto the intersections of the cube with the faces of the pyritohedron; also the striations on magnetite due the octahedron to the oscillation between and dodecahedron Prisms of tourmaline are monly comvery bounded vertically by three convex surfaces, combination owing to an oscillatory of the faces in the prismaticzone. 259. Striations Due to Repeated Twinning. The striations of the basal plane of albite and other triclinicfeldspars, also of thexrhombohedral surfaces of some have been explainedin Art. 241 as calcite, due to polysynthetic twinning. This is illustrated by Magnetite Fig.474 of magnetitefrom Port Henry, N. Y. (Kemp.) 260. Markings from Erosion and Other Causes. The faces of crystals often uneven, are have the crystalline or structure developed as a consequence of etchingby some chemical agent. Cubes of galena are frequently thus uneven, and crystalsof lead sulphate or lead carbonate (anglesite) (cerussite)are sometimes present as evidence with regard to the cause. Crystals of numerous other species, of corundum, spinel, even quartz, etc.,sometimes show the same result of partialchange over the surface often the "

or

"

"

"

incipient

IRREGULARITIES

OF

177

CRYSTALS

process tendingto a final removal of the whole crystal. Interesting been have made by various authors on the action of solvents investigations the actual different structure of the crystalsbeing developedin minerals, on This method of this way. etching is fullydiscussed, with illustrations in

stage in

a

place (Art.286). markings on the surfaces of crystalsare not, however, always to be such depressions, ascribed to etching. In most cases well as the minute as the faces having the form of low pyramids (so-called elevations upon vicinal of the m olecular are a of the original part prominences) growth crystal,and to show the successive stages in its history. They often serve be imperfections may from disturbed an o r of interrupted arising development the form,the faces being the result of completed crystalline perfectlysmooth and even free from disturbingcauses. action Examples of the markings referred to of most minerals,and conspicuously the crystals the rhomboon occur so on another The

,

hedral faces of quartz. with angular elevations more often marked less or combination. due to oscillatory Octahedrons of fluorite which have for each face a surface of minute cubes,proceeding common are Sometimes from an oscillationbetween the cube and octahedron. tion examinaan of such a crystalshows that though the form is apparentlyoctahedral, octahedral faces present at all. Other similar cases there are could be no of

Faces

crystalsare

distinct,which

are

mentioned. Whatever

their cause, these minute markings are often of great importance true molecular symmetry of the crystal. For it follows from that like faces must be physically alike the symmetry of crystallization that is,in regardto their surface character;it thus often happens that on all as

revealingthe

"

the or perhapsfrom all localities, givenlocality, is alike. There much uniformityon roughened planes are same in this the faces of quartz crystals respect. result from surfaces may 261. Curved (a) oscillatory combination; in the independent molecular condition producing curvatures or (6) some cause. laminae of the crystal ; or (c)from a mechanical kind have been alreadymentioned (Art.258). surfaces of the first Curved in the lower in Fig.475, of calcite; of this nature is seen curvature A singular the

of crystals

a

speciesfrom etched

a

or

476

476

Calcite

part

of a scalenohedral form form. with the prismatic

traces

Beryl

Diamond are

apparent which

was

in

bination comoscillatory

178

CRYSTALLOGRAPHY

have all the faces convex. This of the second kind sometimes which almost of of diamond are spheres. is the case in crystals (Fig.476), some is less of curvature, in which all the faces are equally convex, The mode and surface is opposite than that in which a convex parallelto a common of dolomite and siderite are surface. Rhombohedrons correspondingconcave of frost on windows and the usually thus curved. The feathery curves in The alabaster winter other are of examples. pavements flagging-stones the Mammoth rosettes from Cave, Kentucky, are similar. Stibnite crystals curved and twisted forms. show very remarkable sometimes is of mechanical A third kind of curvature origin. Sometimes crystals been broken had if they transverselyinto many pieces,a slight as appear displacementof which has given a curved form to the prism. This is common in tourmaline and beryl. The berylsof Monroe, Conn., often present these

Curvatures

interruptedcurvatures, as representedin Fig.477. with a deep pyramidal depressionoccupyCrystalsnot infrequentlyoccur ing the placeof each plane,as is often observed in common salt,alum, and sulphur. This is due in part to their rapidgrowth. VARIATIONS

3.

IN

THE

ANGLES

OF

CRYSTALS

262. The greater part of the distortions described in Arts 256, 257 occasion no change in the interfacial angles of crystals. But those imperfections such that produce convex, cause curved,or striated faces necessarily of heat or pressure variations. Furthermore, circumstances under which formed sometimes have resulted not only in distortion the crystalswere may variation in angle. The presence of impuritiesat the of form, but also some time of crystallization may also have a like effect. Still more important is the change in the angles of completed crystals which is caused by subsequent pressure on the matrix in which they were or formed, as, for example, the change which may take place during the more less complete metamorphism of the inclosing rock. The change of composition resultingin pseudomorphous crystals(see Art. 273) is generallyaccompanied by an irregular change of angle,so that the pseudomorphs of a speciesvary much in angle. In generalit is safe to affirm that,with the exceptionof the irregularities sequent from the subarisingfrom imperfectionsin the process of crystallization, or alluded in variations and the are changes to, angles constancy rare, of angle alluded to in Art. 11 is the universal law. In cases where a greater or less variation in angleis observed in the crystals of the same the cause for this can speciesfrom different localities, usuallybe found in a difference of chemical composition. In the case of isomorphous that an exchange of correspondingchemically compounds it is well known equivalentelements may take place without a change of form, though usually accompanied with a slightvariation in the fundamental angles. The effect of heat upon the form of crystals is alluded to in Art. 433. 4.

263.

INTERNAL The

IMPERFECTIONS

AND

INCLUSIONS

transparency of crystalsis often destroyedby disturbed crystallization;

by impuritiestaken

crystallization; or, again,by

from the solution during the process of up the presence of foreignmatter resultingfrom

IRREGULARITIES

OF

179

CRYSTALS

partialchemical alteration. The general name, is given to any inclusion, whatever its origin. These inclusions foreignbody inclosed within the crystal, are they may be gaseous, liquid, extremely common; or solid;visible to the unaided eye or requiringthe use of the microscope. is a common Rapid crystallization explanation of inclusions. This is illustrated by quartz crystalscontaininglargecavities full or nearly full of water (in the latter case, these showing a movable bubble); or, they may contain sand or iron oxide in largeamount. In the case of calcite, tion crystallizafrom a liquidlargely with a foreign as quartz sand, may charged material, in which the impurity makes result in the formation of crystals up as much as

of the whole

two-thirds

limestone, and 264.

mass;

this is

seen

in the famous

Fontainebleau

in that from similarly

Liquid

and

other localities. Inclusions. Attention

Gas

early called by minerals,as quartz, In later years this subjecthas been thoroughly etc. topaz, beryl,chrysolite, studied by Sorby, Zirkel, Vogelsang,Fischer,Rosenbusch, and others. The of the liquidcan often be determined,by its refractive power, or by nature determination of the critical point in the case of specialphysicaltest (e.g., In examination. the observed chemical of the cases or majority by CO2), liquidis simply water; but it may be the salt solution in which the crystalwas in the case of quartz, liquidcarbon especially formed, and not infrequently, These first dioxide (CO2), as liquidinclusions are proved by Vogelsang. the in in the marked as cavityof a movable such, presence cases, by many Brewster

the

to

of gas.

bubble

as liquids,

water

presence

"

Occasionallycavities contain and

was

of fluids in cavities in certain

liquidcarbon

two

dioxide,the

stance subinclosinga bubble of the same Interesting iments exper(cf. Fig.478). gas be made with sections showing such can mixture inclusions (cf.literature, p. 181). The of gases yielded by smoky quartz,meteoric iron, of heat, and other substances,on the application has been analyzedby Wright.

latter

then as

the cavities appear to be empty; if they then have a regularform determined by of the species, the crystallization they are often In

cases

some

called negativecrystals.Such cavities are a on of secondary origin, as remarked

monly com-

later

Beryllonite

"pase.

infinite in solid inclusions are almost The Inclusions. be referred to a nd can their variety. Sometimes they are large and distinct, the which to the scales of gothiteor hematite, as mineral species, known common is a very is due. Magnetite peculiarcharacter of aventurine feldspar 265.

Solid

"

for example, in the Pennsbury mica; minerals,appearing, staurolite and gmelinite quartz is also often mechanically mixed, as in inclose foreignmaterial,such the other hand, quartz crystals very commonly other minerals. tourmaline, rutile,hematite,asbestus,and many as chlorite, (Cf.also Arts. 266, 267.) of material; consist of a heterogeneous mass The inclusions may granite; or the in a porphyntic in orthoclase crystals seen graniticmatter of berylor crystals coarse feldspar, quartz, etc.,sometimes inclosed in large

impurity in

many

,

spodumene, occurringin graniteveins.

,

""

,

180

CRYSTALLOGRAPHY

microscopic crystalsobserved as but more sometimes be referred to known inclusions may species, generally The is doubtful. term their true nature microlites, proposed by Vogelsang, is often used to designatethe minute inclosed crystals; they are generallyof and often very remarkable in their needlelike form, sometimes quiteirregular, of them are exhibited in Fig.484 and Fig. arrangement and groupings; some individuals belong to known the minute Where 485, as explainedbelow. etc. f or are microlites, example,feldspar called, speciesthey is used those minute term to cover an by Vogelsang Crystallites analogous but may be conforms which have not the regularexterior form of crystals, sidered matter and true between Some intermediate crystals. as amorphous of the forms are shown in Figs.479-483; they are often observed in glassy has been given to volcanic rocks,and also in furnace-slags.A series of names such as globulites, varieties of crystallites, margarites,etc. Trichite and is derived from introduced by Zirkel;the former name belonite are names in obsidian. like that in Fig.483, are common i",hair; trichites, 266.

Microlites, Crystallites. The "

479

480

481

482

Crystallites The microscopicinclusions may also be of an irregular glassynature; this kind is often observed in crystals which have formed from a molten as mass, lava or the slagof an iron furnace. 267. SymmetricallyArranged Inclusions. In general,while the solid inclusions sometimes i n the occur quite irregularly crystals, they are more evident reference to the symmetry of the form, generallyarrangedwith some shown in the following or external faces of the crystals.Examples of this are "

484

Augite (Zirkel)

486

Leucite

(Zirkel)

Garnet

inclosingquartz (Heddle)

figures.Fig. 484 exhibits a crystalof augite,inclosingmagnetite,feldspar etc. nephelitemicrolites, a Fig. 485 shows a crystalof leucite, species

and

IRREGULARITIES

whose

tion of

OF

181

CRYSTALS

crystalsvery commonly inclose foreignmatter, a crystalof garnet, containing quartz.

Fig.486 shows

a

sec

487

Andalusite

Another

striking example is afforded by andalusite (Fig.487),in which the impuritiesare of considerable extent and remarkably to yield symmetrical figuresof various forms. Staurolite arranged, so as tributed. occasionally shows analogous carbonaceous impuritiessymmetrically disinclosed carbonaceous

The magnetite common inclusion in muscovite,alluded to above, an as always symmetricallydisposed,usually parallelto 488 the directions of the percussion-figure (Fig.491, p. 189). The asterism of phlogopiteis explained by the presence of symmetricallyarranged inclusions (cf, Art, 368). is

of symmetrically shows an interesting case arranged The alteration. due to chemical originalmineral, spodumene, from Branchville,Conn., has been altered to a found to the substance apparently homogeneous eye, but the structure shown in Fig. 488. under the microscope to have Chemical analysisproves the base to be albite and the inclosed lithium silicate (LiAlSO4) called to be a hexagonal mineral eucryptite. It has not yet been identified except in this

Fig.

488

inclusions

Eucryptite in Albite

form. LITERATURE

of the most important works on the subject of microscopic inclusions are referred be made to the work of Rosenbusch reference may (1904); a fuller listof papers on also that of Zirkel and others mentioned pp. 3 and 4. Brewster. Many papers, publishedmostly in the PhilosophicalMagazine, and the Edinburgh Phil. Journal,from 1822-1856. Mineralien in krystalliBlum, Leonhard, Seyfert,and Sochting. Die Einschlusse von Some

to

here;

for

sirten Mineralien. Sorby. On the

Haarlem,

1854.

(Preisschrift.) etc. of crystals,

structure microscopical papers).

Q.

J. G.

Soc.,14, 453,

1858

(and other Sorby and

other On the structure of rubies,sapphires,diamonds, and some Butler. Proc. Roy. Soc.,No. 109, 1869. minerals. Labradorite. Pogg. Ann., 120, 95, 1863. Reusch. Arch. Neerland, 3, 32, 1868. Vogelsang. Labradorite. Freiburg in Br., 64 pp., mineralogische Studien. Kritische-microscopische Fischer.

Ite Fortsetzung, 64 pp., 1871; 2te Forts.,96 pp., 1873 Kosmann. Hypersthene.Jahrb. Min., 532, 1869; 501, 1871. Ber. Ak. Wien, 60 (1)996, 1869. Labradorite. Schrauf. 1875. Vogelsang. Die Krystalliten.175 pp., Bonn, in der Flussigkeitsemschlusse Natur gewissen die Ueber Geissler. and Vogelsang 1869 Mineralien. Ann, 137, 56, 257,

1869;

Pogg.

J. Chem. Soc.,1, 137; 2, 237, 1876, 1, 241, 2, etc. Liquid CO2 in cavities, 1877 150, 271, 1877; also,Proc. Roy. Soc, 26, 137, 1881. Ber. Ak. Miinchen, 10, 241, 1880; 11, 321, Gumbel. Enhydros.

Hartley.

_

1881 Smoky quartz (CO.). Am. J. Sc 21,203, J. fee, 21, 209, Am in quartz. Gases smoky Wright. Mm. MM., t, 2W-, 18M. Rutley. Notes on Crystallites. Zs. Kr, 27, 505, 189b. der Krystalliten, Vater. Das Wesen Hawes.

A. W.

l?

CEYSTALLOGBAPHY

182

CRYSTALLINE

AGGREGATES

of minerals that occur The greater part of the specimens or masses of imperfectcrystals.Many specimens be described as aggregations may whose structure appears to the eye quitehomogeneous, and destitute internally to be composed of crystalline be shown can grains. of distinct crystallization, included all the remaining varieties are Under the above head, consequently, 268.

minerals. of structure among individuals may be: The individuals composing imperfectlycrystallized is columnar or fibrous. the structure in which case 1. Columns, or fibers, 2. Thin lamince,producing a lamellar structure. 3.

a granularstructure. Grains, constituting

A mineral Structure. umnar coland Fibrous a possesses of slender as some when it is made columns, amphibole. up in cyanite, the strucas ture the individuals are flattened like a knife-blade, When is said to be bladed. when the mineral is made The structure again is called fibrous up of fibres, of The fibres the or variety gypsum. satin-spar as in asbestus,also may may columnar and are gradationsbetween coarse not be separable.There many Fibrous minerals have often a silkyluster. fine fibrous structures. The following are properlyvarieties of columnar or fibrous structure : in various directions and the fibers or columns cross Reticulated: when to a net. resemblance having some produce an appearance Stellated: when they radiate from a center in all directions and produce wavellite. Ex. stilbite, star-like forms. the crystalsradiate from without center a Radiated, divergent: when Ex. stibnite. stellar forms. quartz, producing The of a mineral is lamellar structure Structure. 270. Lamellar The laminae may be curved or straight, when it consists of platesor leaves. and thus give rise to the curved lamellar and straight lamellar structure. Ex. varieties If of the wollastonite (tabular spar),some talc,etc. plates gypsum, the structure is said to be center about a common are approximatelyparallel the laminae are thin and separable, the structure is said to concentric. When is a striking be foliaceous or foliated.Mica example, and the term micaceous is often used to describe this kind of structure. 271. Granular Structure. The particles in a granular structure differ much in size. When when coarse, the mineral is described as coarse-granular; fine-granular;and if not distinguishable fine, by the naked eye, the structure is termed impalpable. Examples of the firstmay be observed in granularcrystalline ties varielimestone,sometimes called saccharoidal;of the second,in some of hematite; of the last,in some kinds of sphalerite. but from necessity, The above terms are indefinite, as there is every degree of fineness of structure among mineral species, from perfectlyimpalpable, through all possible shades,to the coarsest granular. The term phanero-crystallinehas been used for varieties in which the grainsare distinct, and cryptoin for which those not crystalline they are discernible, although an indistinct 269.

Columnar

"

structure

"

"

be proved by the microscope. structure can crystalline Granular minerals, when easily crumbled in the fingers, said to be friable. are f -272. Imitative The followingare Shapes. important terms used in the imitative forms of massive minerals. describing "

1 84

CR

crystals

Such the

assumption,

been

changed

agency,

does

form

the

after

the

quartz,

Mineralogy.

etc.

of

form

This

taken

by

all

these

In

cuprite, subject

of

Y

APH

their

and

it

or

another cases

existence

that

proof,

direct

has

the

disappeared

chemical the

is

by

mineral

has

through

compound substance

new

explained

original

is

some

which

to

said

the be

to

a

mineral.

orginal

illustrations

Common

of

compound;

new

been

place belong.

not

pseudomorph

in

the

into

GR

pseudomorphs,

admitting

often

its

and

called

are

YSTALLO

pseudomorphous limonite is

further

in

the

crystals form

discussed

of

in

are

pyrite, the

afforded

by

barite

in

chapter

on

the

chite malaform

Chemical

of

PART

274.

heads

The

II.

PHYSICAL

PHYSICAL

MINERALOGY

of minerals

CHARACTERS

fall under

the

following

:

I. Characters depending upon Cohesion and Elasticity viz.,cleavage, fracture,tenacity,hardness,elasticity, etc. II. Specific the or Gravity, Density compared with that of water. III. Characters depending upon Light viz., parency, color, luster, degreeof transetc. specialopticalproperties, IV. Characters Heat depending upon viz., heat-conductivity, change of form and of opticalcharacters with change of temperature, fusibility, etc. V. Characters and Magnetism. depending upon Electricity VI. Characters depending upon the action of the senses viz.,taste, "

"

"

"

odor, feel. 275.

General

It has been

Relation

stated on is the external

pp.

of

Physical Characters

to Molecular

7, 8 that the geometricalform

evidence

of

the

internal

of

molecular

a

Structure."

eral mincrystallized

structure.

A

full

knowledge in regard to this structure, however, can only be obtained by the study of the various physicalcharacters included in the classes enumerated above. Of these

characters,the specificgravity merely gives indication of the of the elements present, and further,of the state of molecular mass aggregation. The first of these points is illustrated by the high specific gravity of compounds of lead; the second,by the distinction observed,for gravity example, between carbon in the form of the diamond, with a specific with a specific of 3' 5, and the same chemical substance as the mineral graphite, gravity of only 2. of Class All the other characters (exceptthe relatively unimportant ones in words the other in direction in the to crystal; VI) generalvary according directions true it is that For of them all orientation. have definite a they identical have like physicalcharacters. which are crystallographically In regard to the converse lographica proposition viz.,that in all directions crystalbe a variation in the physicalcharacters, an there may dissimilar This propositionholds true for all important distinction is to be made. crystals,so far as the characters of Class I are concerned; that is,those in the cleavage,hardness, shown as depending upon the cohesion and elasticity, It is also true etc. the etching-figures, the planes of molecular gliding, atomic

"

and piezo-electricity. of pyro-electricity in the case with respect to the characters which in the It does not apply same way radiant heat),the change of volume with involve the propagationof light(and change of temperature; further,electric radiation,magnetic induction,etc. 185

186

PHYSICAL

MINERALOGY

Thus, although it will be shown that the opticalcharacters of crystalsare of their form, they do not show in agreement in generalwith the symmetry is It true, for example, that all directions all the variations in this symmetry. class under the isometric in a crystalbelongingto any true of its molecular is not cohesion,as may be this obviously system; in directions all a tetragonal crystalat right the shown Again, cleavage. by but this again is not true of axis vertical are the s imilar; to optically angles of These points are further elucidated under the description the cohesion. are

opticallysimilar but

the

specialcharacters of each

group.

DEPENDING

I. CHARACTERS

UPON

COHESION

AND

ELASTICITY \

Cohesion, Elasticity. The

cohesion is given to the force of name of and the same molecules the between one sequence body, in conexisting of which they offer resistance to any influence tendingto separate them, as in the breakingof a solid body or the scratchingof its surface. is the force which tends to restore the molecules of a body back Elasticity when a from which they have been disturbed, as into their originalposition, body has suffered change of shape or of volume under pressure. for crystalsof different The varying degrees of cohesion and elasticity minerals, or for different directions in the same crystal,are shown in the prominent characters: cleavage,fracture,tenacity,hardness; also in the and the etching-figures. or pressure-figures, percussion-figures gliding-planes, is the of mineral to 277. Cleavage. a tendency Cleavage crystallized less smooth surfaces. break in certain definite directions, or yieldingmore in value of cohesion the direction of easy It obviouslyindicates a minimum that is,normal to the cleavage-plane itself. The cleavageparallel fracture to the cubic faces of a crystalof galena is a familiar illustration. An phous amorshow no cleavage. can body (p.8) necessarily As stated in Art. 31, the consideration of the molecular of structure be a direction in which the molecules must crystalsshows that a cleavage-plane are closelyaggregated together; while normal to this the distance between successive layersof molecules must be relatively large,and hence this last is the direction of easy separation. It further follows that cleavagecan exist only parallel to some possibleface of a crystal, and, further,that this be one must of the common in cases fundamental forms. Hence where the choice in the positionof the axes is more less arbitrarythe presence of or mental. cleavageis properly regardedas showing which planes should be made fundaStill again,cleavageis the same in all directions in a crystalwhich identical. are crystallographically Cleavageis defined,(1) accordingto its direction, as cubic,octahedral, 276.

"

attraction

"

"

rhomobohedral,basal,prismatic,etc. Also, (2) according to the ease with it is obtained,and the smoothness of the surface yielded. It is said to be perfector eminent when it is obtained with great ease, affordingsmooth, lustrous surfaces, in mica, topaz, calcite. Inferior degreesof cleavage are as indistinct -or imperfect,interrupted, spoken of as distinct, in traces,difficult. These terms are sufficiently without further explanation. It may intelligible be noticed that the cleavageof a species is sometimes better developedin some

which

of its varieties than in others.

CHARACTERS

DEPENDING

UPON

COHESION

AND

187

ELASTICITY

278. Cleavage in the Different Systems. (1) In the ISOMETRIC SYSTEM, cleavage cubic,when parallelto the faces of the cube; this is the common case, as illustrated by it is also often octahedral galena and halite, that is,parallel to the octahedral faces as with fluonte and the diamond. Less frequently it is dodecahedral, or parallelto the faces of the rhombic dodecahedron,as with sphalerite. In the TETRAGONAL cleavageis often basal,or parallelto the basal plane, as SYSTEM, with apophylhte; also prismatic,or parallel to one (or both) of the square prisms as with rutile and wernerite; less frequently it is pyramidal, or parallel to the faces of the square pyramid, as with scheelite. In the HEXAGONAL cleavage is usuallyeither basal,as with beryl,or prismatic, SYSTEM, of the six-sided prisms, as with nephelite; parallelto one pyramidal cleavage,as with pyromorphite, is rare and imperfect. In the RHOMBOHEDRAL besides the basal and prismatic cleavages rhomboDIVISION, hedral cleavage,parallelto the faces of a rhombohedron, is also with calcite as common, and the allied species. In the ORTHORHOMBIC cleavage parallelto one or more of the pinacoids is SYSTEM, Thus it is basal with topaz, and in all three pinacoidaldirections with anhydrite. common. Prismatic with cleavage is also common, as barite; in this case the arbitraryposition assumed in describingthe crystalmay make this cleavageparallel to a "horizontal prism," "

is

"

or

dome. In the

MONOCLINIC cleavageparallelto the clinopinacoid, is common, with SYSTEM, as heulandite and euclase; also basal,as with the micas and orthoclase, orthoclase,gypsum, or parallelto the orthopinacoid; also prismatic,as with amphibole. Less frequently cleavage is parallelto a hemi -pyramid, as with gypsum.

In the the

TRICLINIC

SYSTEM,

it is usual

and proper

to

so

select the fundamental

form

as

to

make

cleavage directions correspond with the pinacoids. In some 279. cases cleavage which is ordinarilynot observed may be developed by a sharp blow or by sudden change of temperature. Thus, quartz is usually conspicuously free from cleavage,but a quartz crystalheated and plunged into cold water often shows and to the prism as planes of separation* parallelto both the + and rhombohedrqns well. is observed with great distinctness in Similarly,the prismaticcleavage of pyroxene thin sections,made by grinding,while not so readilynoted in largecrystals. that is,when the cleavage is parallelto a closed form When it is cubic,octahedral, dodecahedral, or rhombohedral (alsopyramidal in the tetragonal,hexagonal, and orthooften be broken from solids resembling crystalsmay out rhombic a systems) single crystalline" individual,and all the fragments have the same angles. It is,in general,easy of fluorite, to from a true distinguishsuch a cleavage form, as a cleavage octahedron crystalby the splinterycharacter of the faces of the former. The there is perfect 280. face of a crystalparallelto which Cleavage and Luster. cleavageoften shows a pearly luster (see p. 249),due to the partialseparationof the crystal the clinopinainto parallelplates. This is illustrated by the basal plane of apophyllite. coid of stilbite and iridescent play of colors is also often seen, as with An heulandite. sufficient to produce the prismatic colors by the separation has been calcite,when "

"

"

"

interference.

281. Gliding-planes. Closely related to the cleavage directions in the glidingare their connection with the cohesion of the molecules of a crystal molecules take of the which t o directions a may slipping or parallel planes, mechanical o f as the by under force, place pressure. application This may have the result of simply producing a separationinto layersin the given direction, commonly, there may be or, on the other hand, and more "

revolution of the molecules formed. are twinning-lamellce a

a

new

that secondary so twinning-position,

crystalof halite,or rock salt,be subjectedto gradual pressure face, a plane of separationis developed the direction of a dodecahedral Thus,

in

into

if

a

form. in the direction of another face of the same in and separation a crystal There six such directions of molecular slipping are Certain kinds of mica of the biotite class often show of this substance.

normal

to this and

hence

(Zs.Kr., 11, 608, 1886) and Judd gliding-planes(seeArt. 281). *

Lehmann

(Min. Mag., 8, 7, 1888^ regardthese

as

MINERALOGY

PHYSICAL

188

faces,which pseudo-crystalline

undoubtedly secondary in origin that sequently developed by pressure exerted sub"

are

been

is,have

to the

growth

of the

crystal(cf.Fig.489).

the base, c(001),normal to the plane of perfect In stibnite, cleavage,is a gliding-plane. Thus a slippingof the molecules made to take be place by their separation may without of perfect to the direction normal pressure in a plane (||c) cleavage (||6). A slender prismaticcrystalsupported near by a dull edge is readilybent, the ends and pressed downward without the parts beyond the direction in this or knicked, support being affected.

Secondary Twinning.

282.

-

-

other

The

case

where molecular in the precedingarticle, mentioned slippingis accompanied by a half-re volution (180") well illustrated (seep. 160 et seq.)jis twinning-position new

Biotite

of the molecules into a by calcite. Pressure upon of thin lamella of a number

tion result in the formacleavage-fragment may the to the parent mass, twinning-position ary Secondobtuse the rhombohedron, 0(0112). negative twinning-planebeing similar to these are often observed in natural cleavagetwinning-lamellaB in the grainsof a crystalline limestone,as and particularly of calcite, masses a

in

in thin sections under the microscope. also be produced (and are Secondary twinning-lamellse may of the triclinic feldspars, nature) in the case pyroxene, in quartz barite,etc. A secondary lamellar structure the lamellae observed been has by Judd, in which

observed

consisted of

often noted in 490

right-handedand left-handed portions.

be artificially a complete calcite twin may By the proper means Thus, if a cleavage-fragment of prismatic produced by pressure. in breadth, be placed in length and 3-6 mm. form, say fr-8 mm. with the obtuse edge on a firm horizontal support, and pressed by the blade of an ordinary tableknife on the other obtuse edge (at a, Fig.490), the result is that a portion of the crystalis reversed in parallelto the plane (0112) which in the position,as if twinned done, the twinning figurelies in a vertical position. If skillfully the re-entrant surface is perfectlysmooth, and angle corresponds Artificial Twinning in Calcite exactly with that required by theory.

often 283. Parting. The secondary twinning-planes described are which may directions of an easy separation convenientlycalled parting is a common basal parting of pyroxene be mistaken for cleavage.* The example of such pseudo-cleavage;it was long mistaken for cleavage. The basal and rhombohedral (1011)and the less distinct prismatic(1120) parting of corundum; the octahedral partingof magnetite (cf.Fig. 474, p. 176),are "

"

other

"

examples.

An

importantdistinction between cleavage and partingis this : partingcan exist only in certain definite planes that is, the surface of a twinning-lamelon la while the cleavagemay take placein any plane having the given direction. "

"

284.

with the Percussion-figures. Immediately connected called the planes are figures percussion-figures f produced upon "

"

"

*

The lamellar structure of a massive mineral,without twinning, may fracture which can be mistaken for cleavage. best obtained if the crystalplate under t The percussion-figures are supported upon a hard cushion and a blow be struck with a lighthammer rounded the slightly point of which is held firmlyagainst the surface. of

a

glidingcrystal

also be the

cause

a

investigationbe upon

a

steel rod

CHARACTERS

DEPENDING

UPON

COHESION

AND

ELASTICITY

189

section by a blow or pressure with a suitable point. In such cases, the method described serves to develop more less well-defined cracks whose orientation or varies with the crystallographic direction of the surface. Thus the upon cubic face of a crystalof halite a four-rayed, star-shapedfigureis produced with arms parallelto the diagonals that is,parallelto the dodecahedral faces. On an octahedral face a threerayed star is obtained. The in the case of the micas have percussion-figures "

been

often

investigated, and, as remarked later, they form fixingthe true orientation of a cleavage-plate outlines. The having no crystalline figure(Fig.491) is here a six-rayedstar one of whose branches is parallelto the clinopinacoid (6),the others approximately parallel to the intersection edges of the prism (m) and base (c).* Pressure upon a mica plateproduces a less distinct six-rayedstar^diagonal to that justnamed; this is called a pressure-figure. a

of

means

it is possibleto prove Solution-planes. In the case of many crystals, the existence in which chemical action takes place most or directions, structure-planes, readily for example, when a crystalis under great pressure. These directions of chemical weakness have been called solution-planes.They often manifest themselves by the of a multitude of oriented cavities of crystalline outline (so-called presence negativecrystals) in the given direction. in certain cases, as shown These solution-planes by Judd, are the same as the directions of secondary lamellar twinning, as is illustrated by calcite. Connected with this is the schillerization (seeArt. 369),observed in certain minerals in rocks (asdiallage, schillerspar). 285.

"

of certain "

with the general subjects Etching-figures. Intimately connected in relation cohesion to o f the are crystals, considered, figuresproduced faces; these are often called etching-figures. by etchingon crystalline This method of investigation, developedparticularly by Baumhauer, is of high of structure molecular the crystalfaces under importance as revealingthe examination,and therefore the symmetry of the crystalitself. The as by water in some cases, etchingis performed mostly by solvents, caustic mineral also at the or steam acids, alkalies, more by ordinary generally and hydrofluoric powerful in its acid; the last is especially a high pressure produced are in action,and is used frequentlywith the silicates. The figures the majorityof cases angulardepressions, 493 492 such as low triangularor quadrilateral run pyramids,whose outlines may allel parto some of the crystallineedges. In some the planesproduced can be cases referred to occurring crystallographic alike on faces. They appear similar and hence faces of crystals, to serve distinguishdifferent forms, perhaps in the two sets of as identical, appearance faces in the ordinary double pyramid of quartz; so, too, they reveal the cornon pound twinning-structurecommon Quartz,rightQuartz,lefthanded as handed crystal some crystal crystals, quartz and aragonite. 286.

"

here

* Cf. Walker, Am. J. Sc.,2, 5, 1896, and G. Friedel,Bull. Soc. Min., 19, 18, 1896. Walker found the angle opposite6(010) (x in Fig.491) to be 53" to 56" for muscovite,59" for lepidolite, 60" for biotite, and 61" to 63" for phlogopite.

190

MINERALOGY

PHYSICAL

in general corresponds to the symmetry form of the reveal thus the the given crystalbelongs. They trapegroup zohedral symmetry of quartz and the difference between a right-handedand calcite and left-handed crystal(Figs. 492, 493); the distinction between of distinctive character the dolomite (Figs. apatite,pyromorphite, 496, 497) ; etc.; the hemimorphic symmetry of calamine and nephelite(cf.Fig. 237, of by their form the monoclinic crystallization p. 102),etc.; they also prove muscovite and other micas (Fig.495).

Further, their to

which

formed on a basal plane (cleavage)of topaz by fused Fig. 494 shows the etching-figures of muscovite by hydrofluoricacid; Fig. caustic potash; Fig. 495, those on a cleavage-plate and Fig.497, on one of dolomite by dilute hydroface of calcite, 496, upon a rhombohedral chloric acid. 494

Topaz

497

495

Calcite

Muscovite

Dolomite

499

500

Spangolite The shape of the etching-figures crystalwith the nature of the may vary with the same solvent employed,though their symmetry For example, Fig. 498 shows remains constant. the figuresobtained with spangolite 601 502 by the action of sulphuric acid, Fig. 499 by the same diluted,and

Fig.

500

by

hydrochloric acid

of

different degrees of concentration.

Of

the

same

nature

as

the

etching-figures artificially produced, in their relation to the are on

Corundum

of the crystal, symmetry the markings of ten observed the natural faces of crystals. These sometimes are

secondary,caused by a natural etchingprocess, but are more rften an in the crystalline irregularity development of the crystal. The inverted triangular often seen on the octahedral faces of diamond depressions crystals are an example. Fig.501 shows natural depressions, rhombohedral C observed on corundum crystalsfrom Montana h1aracter' (Pratt). Fig. shows a twin crystal of fluorite with natural etching-figures (Pirsson) Fluorite

,,

-

192

PHYSICAL

MINERALOGY

Talc.

6.

2.

Gypsum

7.

3.

Caltite. Fluorite.

1.

4.

9. 10.

Apatite.

5.

Orthoclase.

Quartz. 8. Topaz.

Crystallinevarieties with smooth

surfaces

Corundum. Diamond.

should

be

taken

so

far

as

possible. is scratched by the knife-blade as easily If the mineral under examination calcite its hardness is said to be 3; if less easilythan calcite and more so In the latter case the mineral in question than fluorite its hardness is 3'5. itself scratch calcite. It need be scratched by fluorite but would would is attainable not that added be by the above methods, great accuracy hardly determination the of for of minerals,exactness is though, indeed, purposes as

quiteunnecessary. be noted that minerals of grade 1 have a greasy feel to the hand; those of grade 3 are grade 2 are easilyscratched by the finger-nail; scratched of rather rather readilycut, as by a knife; grade 4, easilyby the grade 6, barelyscratched by a difficulty; knife;grade 5, scratched with some they also scratch ordinaryglass. knife,but distinctlyby a file moreover, Minerals as hard as quartz (H. 7),or harder,scratch glassreadilybut are in littletouched by a file;the few speciesbelonging here are enumerated Appendix B; they include all the gems. Accurate determinations of the hardness of minerals 290. Sclerometer. in of of the best various ment instrube made use an one being by can ways, The mineral is placedon a movable with called a sclerometer. carriage, horizontal ; this is brought in contact with the surface to be experimentedupon a steel point(ordiamond point),fixed on a support above; the weight is then is and produce a scratch the carriage determined which justsufficient to move the surface of the mineral. on the hardness of the different faces of a of such an instrument By means It has been found given crystalhas been determined in a varietyof cases. that different faces of a crystal(e.g., cyanite)differ in hardness,and the same face may differ as it is scratched in different directions. In general,differences in hardness which show distinct cleavage; noted onlywith crystals are the hardest face is that which is intersected by the plane of most complete cleavage. Further,of a singleface,which is intersected by cleavage-planes, the direction perpendicularto the cleavage-direction is the softer,those to it the harder. parallel It should

those of

"

=

"

This subject has been investigatedby Exner (p. 194),who has given the form of the obtained as of hardness for the different faces of many are crystals. These curves follows: the least weight required to scratch a crystalline surface in different directions, for each 10" or 15", from 0" to 180", is determined with the sclerometer; these directions laid off as radii from a center, and the length of each is made proportional are to the weight fixed by experiment that is,to the hardness thus determined; the line connecting the extremities of these radii is the curve of hardness for the given face. The following ness table gives the results obtained * (seeliterature) in comparing the hardof the minerals of the scale from No. 2. corundum, No. 9, taken as 1000, to gypsum, Pfaff used the method of boring with a standard point, the hardness being determined by the number of rotations; Rosiwal used a standard powder to grind the surface,Jaggar employed his micro-sclerometer, the method being essentiallya modification of that of cwrves

"

*

The

numbers

are

here given

as

tabulated

by Jaggar.

CHARACTERS

Pfaff.

By

DEPENDING

UPON

COHESION

AND

193

ELASTICITY

of this instrument he is able to test the hardness of the minerals present the microscope. Measurements of absolute hardness have also been made by Auerbach. Holmquist has recently made hardness tests by the grinding many method. His results with regard to the minerals of the scale of hardness agree fairlywell with those ot Rosiwal below but show considerable discrepancieswith the results given obtained by the other methods. He, like Rosiwal, finds that topaz is lower in the scale than quartz. in

a

means

thin section

under

Pfaff, 1884

Rosiwal, 1892

Jaggar, 1897

1000

1000

1000

9.

Corundum

8. 7.

Topaz Quartz

459 254

6.

Orthoclase

191

5.

Apatite

4.

37'3

3.

Fluorite Calcite

6'20 470

15'3

2'68

2.

Gypsum

12'03

53'5

:...

Relation of Hardness to Chemical Composition. be stated * in regard to the connection between its chemical composition.

"

can

1.

Compounds

of the

152

149 287

40 25 1'23 75 '26

'34

291. and

138

heavy metals, as silver, copper,

'04

Some generalfacts of importance of a mineral the hardness

mercury,

lead,etc.,are

soft,their

hardness

seldom exceeding 2 '5 to 3. Among the compounds of the common metals,the sulphides (arsenides)and oxides of iron (also of nickel and cobalt) are for pyrite H. 6 to 6'5; for relativelyhard (e.g., hematite H. iron tantalate; 6, etc.);here belong also columbite,iron niobate;-tantalite, =

=

wolframite,iron tungstate. 2. The sulphides are mostly relativelysoft (exceptas noted in 1), also most of the carbonates,sulphates,and phosphates. 3. Hydrous salts are relatively soft. This is most the silicates distinctlyshown among the feldsparsand zeolites. e.g., compare 4. The conspicuously hard minerals are found chieflyamong the oxides and silicates; of them are compounds containing aluminium many e.g., corundum, diaspore,chrysoalumino-silicates. Outside of these the borate,boracite,is hard (H. beryl,and many 7);

"

"

=

also iridosmine. On the relation of hardness 292.

Practical

to

specific gravity,see Art. 302. Several points should be regarded

hi the trials of hardness: (1) If the mineral is slightlyaltered,as is often the case with corundum, garnet, etc., be impossiblewith the mineral itself; the surface may be readilyscratched when this would a trial with an edge of the latter will often give a correct result in such a case. to be scratched when the grains (2) A mineral with a granular surface often appears have been only torn apart or crushed. soft mineral may leave a faint white ridge on a surface,as of glass, (3) A relatively observed. which can be mistaken for a scratch if carelessly scratched by the edge of another of the same (4) A crystal,as of quartz, is often slightly speciesand like hardness. (5) The scratch should be made in such a way as to disfigurethe specimen as littleas

Suggestions.

"

possible. 293.

Tenacity. "

Minerals

may

either

be

malleable,or sectile, brittle,

flexible.

(a) Brittle; when

parts of

a

mineral

separate in powder

or

grains on

calcite.

attempting to cut

it,as (b) Sectile; when piecesmay be cut off with a knife without fallingto This character is under a hammer. powder, but still the mineral pulverizes intermediate between brittle and malleable, as gypsum. (c) Malleable; when under

a

hammer;

native

be cut off,and gold,native silver.

slices may

*

See

further in

Appendix

B.

these slices flattened out

194

PHYSICAL

MINERALOGY

(d) Flexible;when the mineral will bend without breaking,and remain bent after the bending force is removed, as talc. The tenacityof a substance is properlya consequence of its elasticity. of 294. at once the Elasticity. The elasticity -a solid body expresses resistance which itmakes to a change in shape or volume, and also its tendency to act. to return to its original If the shape when the deforming force ceases is not passed,the change in molecular position limit of elasticity is proportional is exactlyresumed; if to the force acting,and the former shape of volume this limit is exceeded,the deformation becomes permanent, a new positionof molecular equilibriumhaving been assumed; this is shown in the phenomena and of gliding-planes secondary twinning,already discussed. The magnitude of a given substance is measured of the elasticity by the coefficient of "

This is denned elasticity, or, better,the coefficientof restitution. for example, between the elongationof a bar of unit section

as

the relation,

to the force

actingto produce this effect;similarlyof the bending or twistingof a bar. The subjectwas early investigated by Savart; in recent years, acoustically of the elasticity of many stances subVoigt and others have made accurate measures and of the crystalsof the same substance in different directions. of an amorphous body isthe same The elasticity in all directions, but it changes in value with change of crystallographic direction in all crystals. distinction between elastic and inelastic is often made between the of the mica and allied minerals. species Muscovite, for example, is group described as while phlogopiteis much less so. In this case highlyelastic/' it is not true in the physcialsense that muscovite has a high value for the coefficient of elasticity; its peculiarity liesrather in the fact that its elasticity is displayedthrough unusuallywide limits. The

"

LITERATURE Hardness

Sklerometer. Programm d. Coin Realgymnasiums, 1833. Pogg., 80, 37, 1850. Grailich u. Pekarek. Ber. Ak. Wien, 13, 410, 1854. Pfaff. Mesosklerometer. Ber. Ak. Munchen, 13, 55, 1883. Sohncke. Halite. Pogg., 137, 177, 1869. Seebeck.

Franz.

Exner. Ueber die Harte der Krystallflachen, 166 pp. Vienna, 1873 Wiener. Akad.). Auerbach. Wied. Ann., 43, 61, 1891; 45, 262, 277, 1892; 68, 357, 1896. Rosiwal. Verb. G. Reichs.,475, 1896. T. A. Jaggar, Jr. Schroeder der van

(Preisschrift

Microsclerometer. Kolk.

Ueber

Am. J. Sc.,4, 399, 1897. Harte in Verland mit Spaltbarkeit,Verb.

Ak.

sterdam, Am-

8, 1901. Holmquist. Ueber den Relativen Abnutzungswiderstand der Mineralien der Harteskala. Geol. For. Forh., 33, 281, 1911. Die Schleifharte der Feldspathe,ibid., 36, 401, 1914. Die Hartestufe, 4-5, ibid., 38, 501, 1916. etc. Etching-figures,

Goldschmidt and Wright. Ueber Aetzfiguren, und Losungskorper. Lichtfiguren exhaustive references to the literature. N. Jb. Min. Beil-Bd.,17, 355-390, 1903.

With

Gliding-planes, Secondary Twinning, etc. )be," halite,calcite. Pogg. Ann., 132, 441, 1867. Mica, ibid., Gypsum, ibid., Ber. Ak., Berlin, p. 135. 440, 1873. 61\ vSoMfe' Pogg" Ann-' 138"337' 1869" Zs" G- Ges-"26" 137" 1874- Galena,

136, 130,632, 1869. ~

L., 1,

L6",

SPECIFIC

Baumhauer. 1

7" 898

Calcite.

GRAVITY

OR

RELATIVE

195

DENSITY

Zs. Kr., 3, 588, 1879. Jb. Min., 1,32, 1883; 2, 13, 1883.

Caldte"augite"stibnite" etc.

LiJ* JU?d" ^Structure

etc. Solution-planes Q. J. G. Soc.,41, 374, 1885; planes of corundum, Min. Mag., 11, 49 1895

1887.

Min.

Also

ibid.,

Mag., 7, 81,

Voigt. See below. Elasticity Savart. Neumann.

Ann.

Ch. Phys., 40, 1, 113, 1829; also in Pogg. Ann., 16, 206, 1829.

Pogg. Ann., 31, 177, 1834. Angstrom. Pogg. Ann., 86, 206, 1852. Calcite. Baumgarten. Pogg. Ann., 152, 369, 1874. Groth. Halite. Pogg. Ann., 157, 115, 1876. Coromilas. Gypsum, mica. Inaug. Diss.,Tubingen, 1877 (Zs.Kr., 1, 407, 1877) Reusch. Ice. Wied. Ann., 9, 329, 1880. Klang. Fluorite. Wied. Ann., 12, 321, 1881. Koch. Halite,sylvite. Wied. Ann., 18, 325, 1883. Alum. Zs. Kr., 10, 41, 1885. Beckenkamp. Voigt. Pogg. Ann., Erg. Bd., 7, 1, 177, 1876. Wied. Ann., 38, 573, 1889. Calcite, 39, 412, 1890. Dolomite, ibid.,40, 642, 1890. Tourmaline,ibid.,41, 712, 1890; 44, 168 Also papers in Nachr. Ges. Wiss. Gottingen. Tutton. The Elasmometer. CrystallineStructure

1891.

II. SPECIFIC

GRAVITY

OR

and

Chemical

RELATIVE

1910. Constitution,

DENSITY

295. Definition of SpecificGravity. The specific gravityof a mineral is the ratio of its density* to that of water at 4" C. (39'2"F.). This relative densitymay be learned in any case by comparing the ratioof the weight of a certain volume of the given substance to that of an equal volume of water; hence the specific is often defined the the as: divided gravity weightof body by the weight of an equalvolume of water. that the specific The statement gravityof graphiteis 2, of corundum 4, of that the densities of the minerals named are galena 7'5,etc.,means 2, 4, and 7'5,etc.,times that of water; in other words, as familiarly expressed,any volume of them, a cubic inch for example,weighs 2 times,4 times,7*5 times, etc.,as much as a like volume, a cubic inch, of water. Strictlyspeaking,since the densityof water varies with its expansionor contraction under change of temperature, the comparison should be made with water at a fixed temperature, namely 4" C. (39'2" mum F.),at which it has itsmaxisuitable If correction at should made a a highertemperature, density. be introduced however, since a high degree of by calculation. Practically, in is impracticable often to cases is called not for,and, indeed, many accuracy attain in consequence of the nature of the material at hand, in the ordinary work of obtainingthe specific gravityof minerals the temperature at which variations of temperature the observation is made can safelybe neglected. Common would seldom affect the value of the specific gravityto the extent of unit in the third decimal place. one "

Thus if a cubic centimeter of the unit volume. body is strictlythe mass density,4" C. or 39'2" F.) is taken as the unit of mass, the of mass of grams is given by the number (about 19) in a as gold body cubic centimeter; in this case the same number, 1.9,gives the relative density or specific gravity. If,however, a pound is taken as the unit of mass, and the cubic foot as the unit of that of gold about 1188 Ibs., and the of a cubic foot of water is 62'5 Ibs., volume, the mass 19. the second again, to is the of the first, ratio or, specific gravity *

The

densityof

of water density of any

a

(at its maximum "

"

196

MINERALOGY

PHYSICAL

to take into consideration the fact it is not necessary is less than its true weight of of a mineral that the observed weight a fragment by the weight of air displaced. calls for an accurate determination of the investigation the nature Where of the precautions to four decimal places), no one of the specific gravity(e.g.,

the

For

in

regardto

same

the

reason,

of

purityof material,exactness

weight-measurement,temperature,

values spoken of are needed in be neglected.* The accurate ular volume, the relation of molecthe consideration of such problems as the specific others. volume to specific gravity,and many of the SpecificGravity by the Balance. The 296. Determination of the given mineral with an direct comparison by weight of a certain volume

etc.,can

"

equal volume of water is not often practicable.By making use, however, of in hydrostatics, in water, in viz.,that a solid immersed a familiar principle in loses of the amount the which is of weight an buoyancy latter, consequence the the of volume water volume it displaces) (thatis, equalto the weight of an equal of the specific the determination gravity becomes a very simple "

process. The

ner; weight of the solid in the air (w) is firstdetermined in the usual manis found (w')] the difference between the weight in water these is the weight of a volume wf) weights that is,the loss by immersion (w that of the solid to water the quotientof of ; finally, equal 505 the first weight (w) by that of the equal volume of water is the determined as w') (w specific gravity(G). Hence,

then

"

"

"

"

w

.

w

"

w'

of obtainingthe specific A common method gravity of firm fragment of a mineral is as follows: First weigh the specimen accurately on a good chemical balance. from of the balance by a horseThen it hair, one suspend pan fine silk thread,or, better still, a by platinum wire, in a glassof water convenientlyplaced beneath, and take the weight again with the same care; then use the results above directed. The as platinum wire may be wound around the specimen,or where the latter is small it may be made at one end into a littlespiralsupport. 297. The of using an ordinInstead ary Jolly Balance. balance and determiningthe actual weight,the spiral balance of Jolly, shown in Fig. 505, maybe conveniently employed; this is also suitable when the mineral is in the form of small grains. The instrument consists of a spiral the Springor at lower end of which spring are suspended two pans Jolly Balance ^ and or baskets"' d, Fig. 505. Upon the movable stand -B rests a beaker filledwith water. in adjustWhen ment for readingthis stand has such a position in that the pan d is immersed the water while c hangs above it. Upon the uprightA there is a mirror upon which is marked The position a scale. of the balance at any time is obtained by so placingthe eye that the bead, m, and its reflection in the mirror coincide a

"

for'spedSfGravitv

*

Cf. Earl of

Berkeleyin

Min.

Mag., 11, 64, 1895.

SPECIFIC

GRAVITY

OR

RELATIVE

197

DENSITY

of the top of the bead upon then readingthe position the scale. The first in consists in the the o f the operation getting step position springalone,having in the water in the beaker. the pan d immersed Let this readingbe represented The mineral whose specific by n. gravityis to be determined is then placed the pan or basket, c, and the platform B raised until d is properlyimmersed on The positionof the bead m is again read. in the water. Let this value be the representedby NI. If from N\ be subtracted the number n, expressing to which the scale is stretched by the weight of springand pans alone, amount the difference will be proportionalto the weight of the mineral. Next, the in the water, and again the mineral is placed in the lower pan, d, immersed correspondingscale number, Nz, read. The difference between these readings The Nz) is a number proportionalto the loss of weight in water. (Ni and

"

gravityis then specific Nj-n .

It is obviouslynecessary to have the wires supportingthe lower pan to the same depth in the case of each of the three determinations.

immersed

If care is decimal places. A beam balance described by Penfield is and device for measuring the specific accurate another quite simple very make will clear its essential parts. in which illustrated is It 506, Fig. gravity. The beam is so balanced by a weight on its shorter end that it is very nearly in water. An exact balance in equilibriumwhen the lower pan is immersed beam is balanced this d. the When rider small once the is then obtained by

taken the specific gravitycan Balance. Beam 298. The

be obtained

accuratelyto

two

"

in the subsequentreadings. rider is kept stationaryand its position disregarded beam the balanced by another and in the upper pan The mineral is first placed outer end of the beam. be the will near rider of such a weight that its position 506

Beam

Balance

for

Gravity, "th Specific

Natural

Size (afterPenfield)

the beam. positionof this rider is then read from the scale engraved upon to the lower transferred is next mineral The Let this value be equal to Ni. rider back. againbrought into balance by moving this same pan and the beam the for formula obtaining The be represented by N2. The second reading may gravityis now: specific

The

Nl n

=

.

N^^"2

If the mineral is in the form gravitymay be obtained by use fragments,the specific 299.

Pycnometer.

"

of grains or small of the pycnometer.

198

PHYSICAL

MINERALOGY

and ends in This is a small bottle (Fig. 507) having a stopper which fitstightly with is The distilled bottle filled fine opening. water, the a tube with a very water the and removed overflowing carefully stopper inserted, The of the and then cloth water soft with 607 weighed. weight a this between last and difference the that is obviously weight firstdetermined. mineral The and of the bottle as together, is be determined is to also mineral whose density weighed. Lastly the bottle is weighed with the mineral in it and filled The described above.* with water as weight of the water is obviouslythe difference between displacedby the mineral this last weight and that of the bottle filledwith water plus The specific eral the weight of the mineral. gravityof the minis equalto its weight alone divided by the weight of the Where this method equal volume of water thus determined. is followed with sufficient care, especially avoidingany change be highly of temperature in the water, the results may Pycnometer accurate. be firstreduced to forms a porous mass, it may Rose that chemical it is to be noted that it has been shown by If the mineral

powder, but precipitates

substance in a less higherdensitythan belongs to the same also of This increase density characterizes, though to a finelydivided state. of in fine mechanical subdivision. It is explained state less extent, a mineral a by the condensation of the water on the surface of the powder. It is often found convenient 300. Use of Liquids of High Density. both in the determination of the specific gravityand in the mechanical separation to obtain pure material of fragments of different specific gravities(e.g., for analysis, or again in the study of rocks) to use a liquidof high density that is,a so-called heavy solution. One of these is the solution of mercuric solution. When iodide in potassium iodide,called the Sonstadt or Thoulet made it has a maximum with care density of nearly 3 '2,which by dilution have

uniformly

a

"

"

at will.

be lowered

may

the borotungstate often employed, is the Klein solution, solution, This maximum of 3*6. density again may be lowered cadmium, having a certain will at precautions. Still a third by dilution, observing necessary solution of much practical value is that proposed by Brauns, methylene iodide, which has a specific or less more gravityof 3*324. A number of other solutions, have also been suggested.! When is to be used of these liquids one practical, for the determination of the specific gravityof fragments of a certain mineral it must be diluted until the fragmentsjustfloat and the specific gravitythen obtained,most convenientlyby the Westphal balance (Art.301). When, on the other hand, the liquidis to be used for the separationof the minerals mixed together, the material is firstreduced fragmentsof two or more to the proper degree of fineness, the dust and smallest fragmentsbeing sifted A second

of

out, then it is introduced after another

*

Care

should

taken to prevent air-bubbles being included among the mineral be accomplished by placing the bottle under an air-pump and exhausting the air or by suspending the bottle for a short time in a beaker filledwith boiling water and then allowing it to cool again before weighing. t Johannsen, Manual of Petrographic Methods, p. 519 et seq., givesin detail an account of the various solutions, the methods of their preparation, etc.

particles. This

be

into the solution and this diluted until one stituent consinks and is removed. For the convenient application

may

MINERALOGY

PHYSICAL

200

trained to detect a difference of specific be soon It is to be noted that the hand may thus the difference between small in fragment a eravitv if like volumes are taken, even and a quartz small diamond a the difference between albite and barite,even "

calcite

or

be detected.

crystal,can

LITERATURE.

"

SpecificGravity

General:

Pogg. Ann., 14,474, 1828. Jenzsch. Pogg. Ann., 99, 151, 1856. Jolly. Ber. Ak. Miinchen, 1864, 162. Gadolin. Pogg., 106, 213, 1859. G. Rose. Pogg. Ann., 73, 1; 75, 403, 1848. Scheerer. Pogg. Ann., 67, 120, 1846. Jb. Min., 561, 932, 1873; 399, 1874, etc. Schroder. Pogg. Ann., 106, 226, 1859. Ber. Ak. Wien, 47 (1),292, 1863. Tschermak. derselben angenomGewicht Die Mineralien nach den fur das specifische Websky. 1868. 170 Werthen. Breslau, und pp. gefundenen menen Beudant.

etc.: Use of Heavy Solutions,

Sonstadt. Thoulet.

Chem. News, 29, 127, 1874. Bull. Soc. Min., 2, 17, 189, 1879. Bull. Soc. Min.,

Breon.

3, 46,

1880.

Rohrbach.

Jb. Min., Beil.-Bd., 1, 179, 1881. Bull. Soc. Min., 4, 149, 1881. Jb. Min., 2, 186, 1883.

Gisevius.

Inaug. Diss.,Bonn.,

Goldschmidt. D. Klein.

1883.

Jb. Min., 2, 72, 1886; 1, 213, 1888. Retgers. Jb. Min., 2, 185, 1889. Jb. Min., 2, 214, 1891. Salomon. Am. J. Sc.,50, 446, 1895. Penfield. Am. J. Sc.,32,425, 1911. Merwin. Brauns.

III.

DEPENDING

CHARACTERS GENERAL

PRINCIPLES

UPON OF

LIGHT

OPTICS

the opticalcharacters of minerals in general,and Before considering of the different systems, it those that belong to the crystals particularly of the more of optics is desirable to review briefly some important principles in the which questiondepend. phenomena upon

306.

more

specialreference is made to the works crystals, (translationby Jackson), Liebisch,Mallard, Duparc and Pearce, Rosenbusch on by Iddings),Iddings,Johannsen, Winchell, mentioned p. 3 also to the (translation text-books of Physics. various advanced For

of

a

fuller discussion of the opticsof

Groth

considered to be an electroof Light. magnetic Light is now the in to due a periodicJvariation energy given off by phenomenon This electrons. vibrating energy is transmitted by a series of periodicchanges that show all the characters of ordinarywave phenomena. The lightwaves, short as they are commonly called, wave-lengthsthat are of the possess certain correct magnitude to affect the opticnerves. Other similar waves with longer 307.

The

Nature

"

shorter wave-lengthsbelong to the same class of phenomena. Immediately the so-called violet" ultrabeyond the violet end of the visible spectrum come with stillshorter wave-lengthsand on beyond these we waves have the X-rays and the Of the radium. waves by gamma" produced rays have the waves that give having greater lengthsthan those of lightwaves we

or

"

"

CHARACTERS

DEPENDING

UPON

201

LIGHT

rise to the sensation of heat and the Hertzian waves used in wireless while varying enormously in their vibrations,

these the

order

same

the section be

may into

a

end

so

would

phenomena series

shown strikingly

spectrum

a

which when

and

obey the

same

laws.

The

proportion that

produces we

yard long and

the effect of lightbears to the whole say that if ordinarywhite light is broken up this then considered to be extended either on

include all known electro-magnetic waves five million miles in length. transmission of lightthrough interstellar to

as

be

The

of

of the

All of

wave-lengths,belong to

the entire spectrum

over

space, through liquidsand time been explained by the assumption that a medium, called the luminiferous ether,pervades all space, including the intermodular of material bodies. In this medium space the vibrations of assumed to take place. For the are lightwaves of the present work, purposes is it to consider closely however, the exact nature unnecessary of lightor the mode of its transmission. It will assist greatly, however,in obtaininga clear idea of the behavior of lightin crystalsif we assume that lightwaves are chanical mein nature and consist of periodicvibrations in an ether. all-prevailing 308. Wave-motion in General. A familiar example of wave-motion is given by the series of concentric waves which on a surface of smooth water has for transparent solids,

some

"

from

of disturbance, center the point where a pebble has been as These surface-waves are propagated by a motion of the waterdropped which is transverse to the direction in which the waves particles themselves to the next adjoining, travel;this motion is given from each particle and so Thus the particles of water at any on. one spot oscillate up and down,* while the wave moves on as a circular ridgeof water of constantlyincreasing diameter, but of diminishingheight. The ridge is followed by a valley, indeed both togetherproperlyconstitute a wave in the physicalsense. This is another followed and wave compound wave by another, until the original impulse has exhausted itself. Another familiar kind of wave-motion is illustrated by the sound-waves which in the free air travel outward from a sonorous body in the form of concentric spheres. Here the actual motion of the layersof air is forward and back that is,in the direction of propagationof the sound and the effect of the transfer of this impulse from one layer to the next is to give rise and rarefied shell of air,which together constitute to a condensed alternately of constantly decreasing sound-wave and which waves a expand in spherical in the motion air set of waves, continuallyincreases).Soundmass intensity(since and they travel at a rate of the voice, be several feet in length, as may of 1120 feet per second at ordinarytemperatures. 309. It is important to understand that in both the cases mentioned,as in free each be considered a of on wave wave-motion, case point given may every tend to go out. of disturbance from which a system of new waves as a center These individual wave-systems ordinarily destroyeach other except so far as is concerned. whole the onward This is further o f the as a wave progression to light-waves discussed and illustrated in its application (Art 312 and Figs. go

out

a

in.

"

"

509, 510). is to be considered as the resultant of general,therefore,a given wave obstacle in encounters an all these minor wave-systems. If,however, a wave in comparison with the length its path, as a narrow narrow one opening (i.e., In

*

to Strictlyspeaking,the path of each particleapproximatesclosely

a

circle.

202

PHYSICAL

of the

wave)

waves

seem

or

a

MINERALOGY

sharp edge,then the fact justmentioned since new waves about the obstacles,

to bend

explainshow start

centers. important applicationin the the phenomena of diffraction (Art.331). explaining This

principlehas

an

from case

them of

the as

waves, light-

be mentioned, since it is particularly of wave-motion 310. Stillanother case ful helpmay at one in giving a correct apprehension of light-phenomena. If a long rope, attached end, be grasped at the other,a quick motion of the hand, up or down, will give rise to a half which will travel quickly to the in one wave-form case a crest,in the other a trough forward other end and be reflected back with a reversal in its position; that is,if it went has reached the end. a it will return as a trough. If,just as the wave a hill-likewave, as and pass in the middle, but here for a brief be started, the two will meet second like one at rest, since it feels two equal and opposite impulses. This interval the rope is sensibly of the simple interference of two like waves later to be a case will be seen opposed in phase. Again, a double motion of the hand, up and down, will produce a complete wave, with Still and this again is reflected back as in the simpler case. crest and trough, as the result, "

"

again, if a series of like motions are continued rhythmically and so timed that each wave is an even passing in part of the whole rope, the two systems of equal and opposite waves will be the the two directions will interfere and a system of so-called stationary waves the rope seeming to vibrate in segments to and fro about the positionof equilibrium. result, Finally,if the end of the rope be made to describe a small circle at a rapid,uniform, will again result,but now the vibrations of of stationarywaves will be seen to the stringwill be sensiblyin circles about the central line. This last case of circularly vibrations by which the waves ized polarroughly indicate the kind of transverse of what lightare propagated, while the former case represents the vibrations of waves is called plane-polarizedlight. All these cases of waves obtained with a rope deserve to be carefullyconsidered and studied by experiment, for the sake of the assistance they give to an understanding of the complex phenomena of light-waves.

rhythmicalrate, a system

In the discussion that follows,in order to make 311. Light-waves. have been treated as if they the explanations simplerand clearer,lightwaves called the ether. consisted of mechanical disturbances in a material medium The vibrations in the ether caused by the transmission of a lightwave take place in directions transverse to the direction of the movement of the These When characters. oscillations have the ether wave. an following ticle parit moves from its original is set vibrating ing positionwith graduallydecreasThen velocityuntil the positionof its maximum displacementis reached. with graduallyincreasing velocityit returns to its original positionand since it is moving without friction it will continue in the same direction on past this point. Its velocitywill then again diminish until it has reached a displacement equal but oppositein direction to its firstswing,when it will start back and repeat the oscillation. The varying velocityof such an its course on oscillation would be the same that shown as by a particle moving around a circlewith uniform speed if the particle observed in direction was a lyingin the of the Under circle. these conditions the particle to move would appear plane forward and backward line with constantlychangingvelocity. alonga straight Such a motion is called simple harmonic motion. The motion of one ether particle is communicated to another and so on, quently, each, in order,fallinga littlebehind in the time of its oscillation. Consewhile the individual particles move only back and forth in the same line the wave disturbance moves forward. If,at a given instant of time,the of successive particles in their oscillations are plotted, such positions a curve, in Fig.508, will be formed. as shown harmonic Such a curve is known as a The oscillatory curve. of the particles is called a motion in a lightwave m otion it since itself The dismaximum periodic at regularintervals. repeats "

CHARACTERS

placement of

DEPENDING

from particle (distanceC-D, is its positionin

of the instant

vibration and direction in which

original positionof rest is called the amplitude Fig. 508). The phase of a particleat a given 608

the D

it is

/^

moving. distance

The

particleand

any

203

LIGHT

its

a

wave

the

UPON

between the next

/" /

is in a like positionr of like phase, as A \ i.e., is the wave-length;\~ and B and the time requiredfor this completed movement which

"

"

is the or

of

time

I/

j\l

"

Harmonic

Curve

vibration,

vibration-period.The

wave-system

therefore travels onward

the distance

The of the lightvaries wave-lengthin one vibration-period. intensity and the color, with the amplitude of the vibration, ticle, as explainedin a later arthe the is the of of the violet waves length depends upon length waves; about one-half the lengthof the red waves. vibrations are to be thought of as taking In ordinarylightthe transverse the of vibrations line propagation. In the above figure, place in all planesabout in one plane only are represented; lightthat has only one direction of vibration is said to be plane-polarized. transverse Light-waves have a very minute length,only 0'000023 of an inch for the velocity,186,000 miles yellow sodium flame, and they travel with enormous the from thus to the earth in about in second sun a lightpasses vacuum; per time of is conseThe quently one minutes. or oscillation, vibration-period, eight the traveled is distance it by light given by dividing extremelybrief; of

one

included.* of waves second by the number In an Wave-front. isotropicmedium, as air,water, or glass nous in which lightwould be propagatedin all directions about a lumithat is,one The in form. the the are waves with spherical same velocity point all which includes in this continuous is case the spherical, surface, wave-front time. ously Obviof the moment vibration at same their that commence particles of the wave-front diminishes as the distance of the source the curvature from an indefinitely great distance and when the lightcomes of lightincreases, Such surface. are waves (asthe sun) the wave-front becomes sensiblya plane

in

one

312.

"

"

"

usually called plane waves.

These

cases

are

illustrated by

Figs.509

and

510.

medium

being 0, Fig. 509 the luminous is spherical.It is ABC the G, as that is wave-front, obvious il isotropic, stated in Art. 309, the resultant also made clear by this figurehow, as briefly of all the individual impulses which go out from the successive points,as abc form wave-front, new a g, concentric with A, B, C, etc.,as centers, be at a great disto is the luminous supposed 510 body In G. ABC Fig. In

the

and

point is supposed to be

.

.

.

.

.

.

speed at which lighttravels the rapidityof vibration, of the tremendous About eight a fixed point,is extremely great. it through of as light passes or "frequency second. Ine such in a a point would through of violet light pass trillion waves hundred of a singlewave of this for the passage time of interval required the of extreme brevity of a sort may perhaps be realized better when it is said that one eight-hundred-trillionth is of the whole of historic time. second is a vastly smaller part of a second than a second Nature of Matter and Electricity,p. 157. and Troland, "The Comstock *

"On

account "

204

MINERALOGY

PHYSICAL

tance,

so

that the wave-front

is a plane surface. Here also the individual impulsesfrom A, B, etc., ab unite to form the wave-front /

F

AB

.

609

.

to parallel

313.

AB

.

.

F. .

.

.

Light-ray. "

The

study of

light-phenomenais,in certain cases, facilitated by the conception of a light-ray,a luminous and whose

line

point

drawn to

the

from

the

wave-front,

direction is taken to represent that of the wave

so

as

itself.

510

/ in Fig. 510 and diverging light-rays, Fig. 509 OA, OB, etc., are where these OB, etc., are parallel light-rays. In both cases, is normal to the waveis assumed the light-ray the medium to be isotropic, in a onward This is equivalentto saying that the light-wavemoves front. In

OA,

direction normal to the wave-front. that the " light-ray"has no real existence and is It must be understood to be taken only as a convenient method of representingthe direction of Thus when by appromotion of the light-wavesunder varying conditions. priate the is altered the curvature wave-front of of the means use (e.g., lenses) then for example,if from being a plane surface it is made sharplyconvex if at firstparallel, the light-rays, said to be made to are diverge. Again, the wave-front is made plane,the diverginglight-rays then said to be convex are

"

"

made

parallel. Wave-length. lengthof the waves

314.

Notwithstanding the very with great precision. can The visual part of the waves incandescent body, going out from a brilliantly the glowing carbons of an electric arc-light, be shown to consist of as may of widely varying lengths. They include red waves waves whose length is small

0*0007604

mm.

(about \

Color. White of light, they

of

"

nAA

oy,uuu

an

inch

Light. "

be measured

)and

waves

whose

length constantly

/

diminishes without break, through the orange, yellow,green, and blue to the whose minimum violet, length (0'0003968 mm.) is'about half of that of the red. The colo of lightis commonly said to depend upon its wave-lengthand will be so spoken of here. This is not strictly true, however, because, since the velocityof lightvaries with the medium through which it is traveling

CHARACTERS

DEPENDING

UPON

LIGHT

205

constant

under all conditions, it follows color must be differentin different media. rather the frequency is, therefore, with which the lightwaves reach the eye tLat determines the color sensation. Commonly a given color produced by the combination of several different wave-lengthsof light It monochromatic strictly only when it corresponds to one definite this is nearly true of the bright-yellow sodium line, though strictly this consists of two sets of waves of of

"fhtof the ^ave;1,engt.h It

mpL

same

t I

wave-length

TpeS

lengths.

different slightly

The

violet

effect of come

platinum

at

The

white

light"is obtained

if all the

from the red to the

waves

together to the eye simultaneously; for this reason a temperature of 1500" C. appears white hot"

a

piece of

"

radiation from the sources named, either the the sun, electric carbons the glowing platinum, includes also or longer waves which do not affect the eye, but which, like the light-waves, produce the effect of sensible heat when received an upon absorbing as one of lampsurface, black. There are also,particularly in the radiation from the sun, waves shorter than the which also do not affect the The former are eye. called infra-red, the latter ultra-violetwaves. The brightness of light

violet

depends

the plitude amupon of its vibrations

and

varies directlyas the of this distance. 315. Complementary Colors. The sensation of white light mentioned above is also obtained when to a given color square

-

-

"

,

i

.

that

^

\^

\r "*

T

V

*"*

x

\," n

*

\^ T"*

^X

M

/T*

1

is, light-waves of given wave-length is -

-

combined certain other a called so complementary color. Thus certain shades of pink and combined, as by the rapid rotation of a card on green which the colors form segments, produce the effect of white. Blue and yellow of certain shades are also complementary. For every shade of color in the spectrum there is another one here complementary to it in the sense defined. The most perfectillustration of complementary colors is givenby the examination in polarizedlight, of sections of crystals later explained. as 316. Reflection. When to the waves come lightboundary which medium from another,as a surface of water, or glassin air, separates one or returned back into the firstmedium. they are, in general,in part reflected The reflection of light-waves In Fig. is illustrated by Figs.511 and 512. MM is surface and the lighthere a plane surface the reflecting 511, waves have a plane wave-front (Abcde); in other words, the light-rays (OA, Ob, etc.)are parallel. It is obvious that the wave-front meets the surface from pointto pointto E. firstat A and successively These pointsare to be regarded as the centers of new wave-systems which unimpeded would be in all directions and at a given instant would have propagated outward Hence the comtraveled through distances equal to the lines Aa', Bb' etc. -

"

"

"

,

PHYSICAL

206

MINERALOGY

with

these

radii from

tangent fghkE to the circular arcs drawn wave-front. or reflected etc.,representsthe direction of the new ricallythe mon

But

A, B, geomet512

is angle eAE cident equal to fEA, or the inand wavereflected make angles equal fronts with the reflecting surface.

at A, is a normal If NA called the angle OAN is incidence the angleof the angle equal to NAF, the of reflection.Hence -

-

"

familiar law: The

angleofincidence is angle of reflection.

equal to the

Furthermore, the

"

cident in-

and reflected rays" both lie in the same plane .to the the normal with surface. reflecting the waves going out from it

Fig.512, where the luminous pointis at 0, at points, firstat the pointA and successively the plane mirror MM it is easy Here also A. the to farther of (and right as left) away B, C, D, etc., which have at their centers A, B, C, etc., to show that all the new impulses, at of rise is reflected series center whose to a 0',at a must togethergive waves surface the from to MM measured normal distance equally great on a O'A}. (OA the lines OA, OB, etc.,which are perpendicularto the wave-front, Now and the eye placed in the direction BE, represent certain incident light-rays, tion It follows from the construcCF, etc.,will see the luminous pointas if at 0' be proved by experiment that if BN, CN', etc.,are of the figureand can normals to the mirror the anglesof incidence, OBN, OCN' ',etc.,are equal to the anglesof reflection, NBE, N'CF, etc.,respectively.Hence the above law to this also. case applies If the reflecting surface is not plane,but, for example, a concave surface, that of a spherical as or parabolicmirror,there is a change in the curvature of the wave-front after reflection, but the same law still holds true. In

will meet

=

.

The proportion of the reflected to the incident lightincreases with the smoothness of surface and also as the angle of incidence diminishes. The intensityof the reflected for a given surface in the case of perpendicularincidence (OA, Fig.512). lightis a maximum If the surface is not perfectlypolished, will take place,and there will diffusereflection be no distinct reflected ray. It is the diffusely the reflected reflected lightwhich makes surface visible;if the surface of a mirror were absolutelysmooth the eye would see the reflected body in it only, not the surface itself. Opticallyexpressed,the surface is to be considered smooth if the distance between the scratches upon it is considerablv less (say one-fourth)than the wave-length of light. the

317. Refraction. When into another lightpasses from one medium there is,in general, increase in its decrease a nd this an or velocity, commonly results in the phenomenon of refraction that is,a change in the direction of propagation. The principles applicablehere can be most easilyshown in the "

"

MINERALOGY

PHYSICAL

208

sin

The

of refraction then is given by the expression,

law

n

=

^

-

The

of the angle of incidence bears

angleof refraction. of lightpassingfrom In the case 3in

^

sin

r

be,

=

refractive

/

follows:

as

sine

be

may

,

olll

formulated

,

or

-

index,

for

or

air into

ratio to the sine

glassthis

crown

ratio

consequently gives the

number

this

T608, and

constant

a

of glass. The above

kind

this

514

of the

found

is

value

of

to

the

relation holds true for of

given

any

wave-system

into

passingfrom another, whatever in

length wave-

medium

one

the

wave-

of the

point is

face. bounding surshape Fig. 514 the luminous be readily it can at 0, and

shown

that

front

or

In

the

wave-front

new

dium mepropagated in the second (of greater opticaldensity)

has

flattened

a

corresponding

this

fwhere ^4^

at 0'

and

curvature

to =

OA

a

center

). Here

"

the

v

fracted reOB, OC, are J3*andC, the corresponding refracted rays being BE and CF.

incident

rays

at

For

this

case

also the relation holds

good, sin

i

sin

i

sin

r

n

sinr

-,,

etc.

lenses,there is a medium, but the

If the bounding surface is not plane but curved, as in in the second of the wave-front change in the curvature

simplelaw, n

=

-

"

"

holds true

also,so long as the medium

here

is isotropic.

The relation between wave-length and refractive index is spoken of in Art. 328. 319. Relation of Refractive Index to Lightvelocity. The discussion stance of the precedingarticle shows that if n is the refractive index of a given subfor waves of a certain length,referred to air,V the velocityin air and v the velocity in the given medium, then "

V n

=

""

v

For two that

media

whose

indices

are

n\

and n\

nz

v% t

_

nz

it consequentlyfollows respectively,

v\

CHARACTERS

Therefore,The

DEPENDING

UPON

209

LIGHT

indices

of refractionof two given media for a certain inverselyproportionalto their relativelight-velocities. other words, if the velocity of lightin air is taken as equal to

length wave-

are

In

1 and

the

velocityof the same lightis found to be one half as great when passing through a given substance,the index of refraction, or n, of that substance when referred to air (n TO) will be equal to 2*0. 320. The refractive index Principal Refractive Indices. has, as value for every substance, stated,a constant is usual, to air (or as referred, be to a vacuum). it may In regard to solid media, it is evident from Art. 318 and will be further explained later that those which are isotropic, viz., amorphous substances and crystalsof the isometric system, can have but a singlevalue of this index. Crystalsof the tetragonaland hexagonalsystems two principal refractive indices, have, as later explained, e and co, corresponding to the velocities of light-propagation in certain definite directions in them. Further, all orthorhombic,monoclinic, and triclinic crystalshave similarly three principalindices, In the latter 'casesof so-called anisotropic a, |S,7. the refractive index is taken,namely, as the arithmetical mean mean media, =

"

Effect of Index of Refraction upon Luster, etc. The luster and of a transparent substance depend largely itsrefractive generalappearance upon index. For instance the peculiar by means aspect of the mineral cryolite, of which it is usuallypossible to readilyidentify the substance,is due to its low index of refraction. If cryolite is pulverized and the powder poured into it will disappearand apparently go into solution. of water It is a test tube in the but becomes invisible water because its index quiteinsoluble, however, of refraction (about 1*34)is near that of water (T335). The lightwill travel the same the with practically as cryolite velocitythrough through the water and consequently suffer littlereflection or refraction at the surfaces between the two. On the other hand powdered glasswith a higherindex of refraction than that of water conditions because of the white under the same appears reflection of lightfrom the surfaces of the particles. Substances having an unusually high index of refraction have an appearance tine which it is hard to define,and which is generally spoken of as an adamanbe best comprehended by examining luster. .This kind of luster may cerussite (n of 1*98). They have a 2*419) or (n specimens of diamond which is not metallic almost flash and a quality,sometimes appearance, for example, specimens possessedby minerals of a low refractive index. Compare, of cerussite and fluorite (n 1'434). The usual index of refraction for be said to range not far from 1*55,and givesto minerals a luster minerals may vitreous. which has been termed Quartz, feldspar,and halite show good 321.

"

=

=

=

examples

of vitreous luster.

minerals arrangedaccordingto their indices than those of the isometric system the other of refraction. For minerals is given here. the value (asdefined in precedingarticle) average Below

is givena list of

Water

common

1 335

Muscovite

1'434

Beryl

1523

Calcite

1'524

Topaz

1 "547

Tremolite

'

1 582 .......

...........

Fluorite .........

Orthoclase

1'582

...........

T601 ..........

.......

Gypsum

Quartz

.........

..........

1622 ...........

1 '622 .......

210

MINERALOGY

PHYSICAL

1626

Anglesite

T884

Aragonite Apatite

1 633

1

Barite

1640

Zircon Cerussite Cassiterite

Dolomite

........

........

952

...........

.......

1 633

T 986

........

.........

2'029 .......

...........

2'077

1'723

Sulphur Sphalerite

1750

Diamond

2 419

1 765

Rutile

Diopside Cyanite Epidote

T 685

Corundum Almandite Malachite

1*810

Cuprite

2849

1 880

Cinnabar

2 969

..........

........

2369

........

..........

........

..........

2 711 ...........

.......

..........

.......

'

........

........

That Chemical Composition, Density, and Refractive Index. 322. Relations between the chemical compositionof a substance,its specific gravity, definite relations exist between in many With the plagiohas been conclusivelyshown cases. and its index of refraction, clase feldspargroup, for instance,the variation in composition which the different members refractive index. Attempts show is accompanied by a direct variation in density and of mathematical these relations in the form to express statements. have been made most The two satisfactoryexpressions are the one proposed by Gladstone and Dale,* "

l-^ "

n2

the

constant, and

=

proposed

one

Lorentz

independently by

f and

Lorenz,t

~

"

In these

constant.

=

-.

is equal to the

n

refractive index and

mean

d to the

density.

originallyproposed for use with gases and solutions and for these bodievS have about equallywell. When serve attempts are made, however, to apply them solids the results are at the best only approximate." This is probably because to crystalline the formulas do not take into consideration the modifications that the crystal structure These

been

must

were

found

to

introduce.

Reflection.

Total

323.

Critical

stated in Art. 318 and expressedby the

Angle.

In

"

equationn

regard =

-

principle

pointsare

two

"

the

to

,

to be

if the anglei noted. 0",then sin i First, 0, and obviouslyalso r 0; in other words, when the ray of light(asOA, Fig.514) coincides with the perpendicular, no change of direction takes place,the ray proceedsonward (AD) but with a change of velocity. without deviation, into the second medium if 90",then sin i Again, the anglei 1,and the equationabove becomes =

=

n

=

-

or

"

sin

r

=

-.

=

Asn

mentioned. 48"

=

has

a

fixed value

for every

substance,it is obvi-

7i

that there will also be

ous

r

sin

T

=

"

the above

From

31'; for

diamond, sin r

=

correspondingvalue

a

glass (n

crown

^r"

table it is seen

-

and

r

=

=

of the

angle r

that for water, sin

1'608),sin

r

=

and

r

r

=

for the =

case

VT^H 1 OOO

38"

27'; for

24" 25'.

This fact,that for each substance at a particular value of the angle r~the angle i becomes equal to 90", has an important bearing on the behavior of denser into an optically lightwhen it is passingfrom an optically medium. rarer *

Phil. Trans.,153, 317, 1863.

t Wiedem.

Ann., 9, 641, 1880. J Wiedem. Ann., 11, 70, 1880. " E. S. Larsen, Am. Jour. Sci.,28, 263, 1909.

12) 145,

'28 J, 1907.

See also

Cheneveau, Ann.

Chem.

Phys.,

CHARACTERS

In

Fig. 515

we

between

a

travelingalong the path into

out

pass

the

that

assume

may

the surface

meet

DEPENDING

from

O-A

glass

at

211

LIGHT

coming from

various directions

the air at the point A.

will

air without

the

lightrays

block of glass and

Light

515

a

change in its direction but with increase in its velocity. If emerges

UPON

B

an

it

any

angle than 90" the ray on enteringthe air will be bent away the perpendicular and from the other

angle of deviation the

with will vary touched with the index of the ray

angle at which

the surface and

refraction of the glass. The same in law holds true in this case as the case of a ray enteringfrom the

air, except that the formula

reads

nows

n

=

"

where

"

.

szn

,

r

=

the

angle the

ray

in

v

air makes with the normal to the surface and i the anglethat the ray makes In Fig.515 the ray C-A within the glassto the same normal. will pass out But the angle i for the ray E-A into the air along the line A-D. 38" 27' and, as shown in the precedingparagraph, for glass,where n 1*608,the in 90" travel the the air will be and the will surface of the r angle along ray the in direction A-F. such which meets as glass Consequently any ray, G-A, the surface of the glassat an anglegreaterthan 38" 27',will be unable to pass at the surface,passingback into out into the air and will suffer total reflection the glassin the direction A-G', with angle GAG The angle angle GAG'. is known its critical at which total reflection takes placefor any substance as =

=

=

=

The of gem

phenomenon of total reflection is taken advantage practicesuch a stone According to common

stones.

of in the cutting is cut with a flat

The of inclined facets on the bottom. number reflected above is in a largemeasure totally back to the eye through the stone. from the slopingplanesbelow and comes of the and the consequent brilliancy The amount of lightreflected in this way cut stones increases with its index of refraction. Two exactlyalike,one gem and the other,perhaps,from quartz, would have very different from diamond

surface

on

lightthat

with the stone

top and

enters

a

from

517

516

Total

appearances

their lower

Reflection

due

in Fluorite

n

=

1.43

Total

to this difference in the amount

facets.

This

Reflection

of

principleis illustrated in

in Diamond

n

=

2.42

lighttotallyreflected from Figs.516 and 517. They

212

MINERALOGY

PHYSICAL

sections of two hemispheres cut, one from fmorite and the that lightfrom all directions is focused is It assumed diamond. other from each of surface hemisphere. All the lightthat meets the of the center plane on critical angle for the mineral will be than the this surface at an angle greater of the The shaded areas surface. the back spherical through totallyreflected reflected be and would so that in each of case show the amount light

represent cross

figures

clearlyillustrate the opticaldifference between

the two

substances.

In 324. Effect of Index of Refraction upon Microscopic Phenomena. the tions variaunder sections in thin microscope, the study of minerals,especially In Fig. in the index of refraction give effects which are of importance. of lens a compound microscope, that L is the objective 518 let it be assumed a is exactly focused upon point O, Fig. 518, A. If and that the instrument index of refraction is mineral of mean we now imagine that a section of some "

518

Cover glass br~~Sectionin balsam "

;

A-Glassslide be in focus,or as in placedunder the lens,Fig.518, B, the point O' will now Fig.518, C, where the mineral is supposed to have a high index of refraction, Thus the focus will be at O". it is that with two sections of equal thickness and with the lens in the same looks deeper into the mineral of one position, higherindex of refraction. Consequently,when there are two minerals in the same the one having a high and the other a low index of refraction section, in quartz, n the of zircon, n 1.55), (forexample,a crystal 1.95,embedded one having the higher index of refraction will apparently have the greater =

=

will appear to stand up in reliefabove the surface of the mineral index. The apparent relief is furthermore augmented by other to be explainedbelow. properties In preparingthin sections of minerals or rocks for study with the microscope is to make firsta flatsurface upon the mineral or rock the process, in brief, This flat surface is abrasive. by grindingit upon a platesuppliedwith some then cemented to a pieceof glassby means balsam and the reof Canada mainder of the mineral is ground away until only a thin film remains,which in The section is finally the best rock sections is not over 0'03 mm. in thickness. in balsam,n about 1'54,and over embedded it a thin cover glassis laid. In thickness

of lower

and

CHARACTERS

the

DEPENDING

UPON

213

LIGHT

preparationof a section the surfaces are not polished,hence, from the of the abrasive,they must be pitted and scratched and it may be

nature

that in

assumed

cross

section such

a

preparationwould

be somewhat

as

sented repre-

in

a thin section is examined Fig.518, D. When under the microscope the lightenters the section from below, having been reflected up into the microscope tube by an inclined mirror. Before it reaches the section it will have passedthrough a nicol prism and through a slightly converginglens. Let that the mineral at a, Fig. 518, D, is one it be assumed of mean refractive The index. convergent lightenteringthe section will pass with littleor no

refraction from the mineral into the balsam because their refractive indices are nearly alike. Hence the roughness of the surface of the section is not if polished. If there is a crack,as at 6, as apparent and the mineral appears much so lightpenetrates it that it is scarcelyvisible when the convergent lens is close to the object, but when the latter is lowered,and especially when the lightis restricted by the use of an irisdiaphragm inserted into the microscope total reflection tube, the nearly parallel rays of lightwill suffer some along the line of the crack and so make itvisible. On the other hand, if the mineral has a high index of refraction there will be innumerable placesall over the section where the surfaces are so inclined that the lightwill suffer total reflection in attemptingto pass from the optically dense mineral into the rarer the uneven Hence surface of the section due to its grindingis plainly balsam. visible. This effect is more pronounced if the convergent lens is lowered. The cracks that may exist in a mineral of high index of refraction are for the distinct than in a mineral of low index. much more reasons same Further, in one if a mineral of high index of refraction is embedded of low, c, Fig.518, D, there will be placesalongits outer edge where total reflection will take place, thus causingits outline to be dark and distinct. This effect combined with the roughened aspect of the surface and the apparent increase in thickness, of high described in the precedingparagraph,all tend to make a mineral as in relief. index of refraction stand out conspicuously of Refraction of the Indices of Mineral 325. Determination Grains The considerations of the preceding article sugunder the Microscope. gest of determiningthe indices of refraction of mineral grainsunder a means in a liquidof known index of refracthe microscope. If a grainis immersed tion it has a higher or lower index of whether it is possibleto determine of a series of liquidsof varying refraction than the liquidand by the use the refractive indices it is possibleto determine with considerable accuracy * A listof liquids in common such index of refraction of the mineral. usejfor with their indices of refraction is given below. purposes, 1 450-1 '475 Mixtures of refined petroleum oils and turpentine 480-1 clove oil 1 535 bromide or and ethylene Turpentine "

"

'

Clove oil and a-monobromnaphthalene Petroleum oils and a-monobromnaphthalene a-monobromnaphthalene and methylene iodide Sulphur dissolved in methylene iodide Mixtures of methylene iodide with iodides of antimony, arsenic and tin,also sulphur and iodof orm (seeMerwin)

1 540-1 1 475-1 1' 650-1

'

'

'

635 650 740

1 740-1

790

1 740-1

870

1 740-2

280

...

(seeMerwin) Methylene iodide and arsenic trisulphide formed from mixtures of piperineand Resin-like substances *

Acad.

Research, p. 98; Merwin, Jour. Wash. Wright, Methods of Petrographic-Microscopic Sc.,3, 35, 1913.

214

MINERALOGY

PHYSICAL

These fuse easily the tri-iodides of arsenic and antimony. film of the in thin thus embedded a and mineral grainscan be 1 '680-2 10 material be determined either b The indices of refraction of the test liquidscan hollow glass prism with th a the use of the total refractometer or by filling metho'ds mineral prisms, se with the and ordinary employed using liquid '

Art. 327.

should be preparedwhich for most purposes migh A series of these liquids in the indices of the different liquidsof 0*01 show differences conveniently For more exactingwork smaller differences betw.een the indices of the member kept in well stopperei of the series would be of advantage. If these are bottles and at least

protectedfrom periodsof time.

are

considerable once

a

the

lightthey will show

very

littlechange ove their indice

It is advisable,however, to check

year. to be

into uniform studied should be broken down sma] and then few is a diameter) a usually good grains place" (0'05mm. grains. index of refraction is the] slide. A drop of liquidwith a known a glass upon glass. Whei placedupon the grainsand the whole covered with a thin cover in a liquidof closelythe same index of refractio] a mineral grainis immersed it loses its sharpnessof outline and if the mineral is colorless and the corre spondence of the two indices exact it will quite disappear. Certain tests however, are commonly used to determine the relative indices of the minera and the liquidwhich with proper differences as small a care can distinguish and especialcare O'Ol or with practice small O'OOl. To make these test as as the condenser below the microscopestage should be lowered and, if the instru ment has a sub-stage iris diaphragm, this should be partly closed. Unde: these conditions the obliquityof the lightis reduced and only a small penci of lightcomposed of nearly parallel enters the section. Let Fig. 511 rays The

mineral

represent a mineral grair illuminated in this way wher immersed in a liquid o1 higher index of refraction The as light rays the} the from mineral intc pass the higher refractingliquic above will be bent awa^ from the perpendicular. In the opposite case, Fig. 520, where the mineral has the wil] higher index the reverse be true and the light rays will be bent toward the This will perpendicular. Grain with Low Refractive Grain with High Refractive in produce one case a Index immersed in Liquid Index immersed in Liquid illumination of the brighter of High Refractive Index of Low Refractive Index borders of the mineral grain and the in other a brighter illumination of its. center. difThis 519

520

_

ference

in

illumination is, however, commonly

detected used with

under a

high

only with difficulty. The

these power

circumstances.

objectiveand

_

so

__.

slightas

_0

to

^

be

tainly cer-

so-called Becke Test is commonly This consists in focusing the grain upon then slowlyraisingor lowering the micro-

216

PHYSICAL

MINERALOGY

possibleto determine the crystalorientation of a cleavage or structure and so obtain the index significant graindue to some all that can be determined but ordinarily for some direction, crystal particular the slide.

Sometimes

it is

index of refraction of the mineral. The Becke test can be often Sections. Test in Rock Becke of refraction of two used in a rock section to determine the relative indices Their contact plane should different minerals lyingin contact with each other.

is the

mean

The

326.

"

The to give clear results. positionof this plane by focusingon the surface of the section and then when of the dividing the microscopetube is lowered note whether or not the position If it remains the two minerals remains stationaryor moves. line between is vertical or the nearly so. plane a dividing moves only or little, stationary of lightenteringfrom below is that the cone Under these conditions assume focused at point O, Fig.522, lyingon the dividingplane between L (mineral with lower index) and H (mineralwith higher index). The lightrays 1-6 passing as they do from be

nearly vertical

can

be determined

in order

a mineral into one

522 12

11

10

7

8

9654

3 2

suffer

no

of lower

index higher will total reflection of

from the and all emerge section on the side of H. On the other hand, rays 7-12 from

part

attempting to pass H to L will only in pass

the

across

dividingplane while the will be others totally

12

lower

reflected and

add

to rays

1-6

themselves the

on

H will therefore side of H. show a brighter In illumination than L. the this case also when tube of the microscopeis raised the Becke line will be seen moving toward of higher mineral the index or when the tube is that of toward lowered

3456

index.

The best results will be obtained by using an objectiveof high a magnificationnd the condenser lens must be lowered. 327. Determination of the Index of Refraction by Means of Prisms or Plates. For the more of the indices of refraction of accurate determination minerals a natural or cut prism or plateof the mineral is used. In all cases, except minerals of the isometric system, the prism or plate used must have a "

certain crystallographic orientation. This matter, however, will be discussed the opticalcharacters of such minerals are given. For the present, we will assume that the mineral whose index of refraction is to be determined is isometric in its crystallization.There are two chief methods of determining the index of refraction by the use of a prism. 1. The Method of Perpendicular Incidence. This method, although not when

"

CHARACTERS

the

most

one

with,as it may for

necessary

have

a

plane

surfaces

prism

DEPENDING

UPON

217

LIGHT

generallyemployed, is an excellent one to become acquainted be used to advantage in some and from it the formula cases making the calculations is readilyderived. It is necessary to of the

mineral

meeting at

which

has two

small

angle. angle should be small enough so that the lightmay freelythrough the prism pass a

This

and

suffer

not

attempts

total reflection as it into the air. For instance fluorite in which n 1*434,the any out pass

to

with

=

prism angle 12',for at a this angle total reflection would take place. For a mineral of higher index the angle would have to be smaller still, with diamond, as 2 '419, where total n reflection would take place at 24" 24'. On the other results will be obtained Refraction of Light through a Prism accurate hand, more if the prism angle is fairlynear to the limit Method of Perpendicular Incidence for the mineral being used.* be

must

less than

44"

=

Let

Fig.523 represent the cross section of such a prism. Let a-b lightstrikingthe face of this prism at 90" incidence. It ray deviation in its path on enteringthe prism but will proceed with no diminished velocity until itreaches c. In passingout of the prism at from a denser to a rarer medium, the lightwill be deflected away normal to the surface,P-P', making a. deviation 5 in the direction of

a

represent will suffer somewhat this

point,

from

the

The data for index refraction under these of of the calculation the necessary conditions are the angle of the prism, a, and that of the deviation in It is easy to see from the figurethat a and a' are the path of the light, 5. o-d.

both parts of right-angled having the angle triangles bP'c in common, and a" is equal to a! because they are oppositeangles. The defined in Art. 317, is equal to a + 8 and the angle of as angle of incidence,

equal, for they

are

refraction is equal to

a.

the usual formula

Therefore

-

-

sin Sm

.a sin

=

n.

In order to make

determination

n

becomes

here

of the index of

refraction,

a

it is necessary therefore, The prism is mounted a

a

"

r

in the

measured

same

to

measure on

way

a as

angles,a and 5. one-circle reflection goniometer and its angle an angle upon a crystal. The instrument is these two

it is necessary For this purpose of a refractometer. the outer rim of the to note that the telescope and vernier are both fastened to instrument and move together. The graduated circle being clamped, the tube is firstmoved to the position T',Fig.524, so that the rays from telescope the lightsignalto the collimator tube,C, passingthe edge of the prism,cause beingclamped fallon the vertical cross-hair of the telescope. The inner T" and 60" to the telescope position of is next moved arc an exactly through then clamped. Next the prism is turned to the first positionso that the then

adapted

to the

uses

Circle

lightfrom C

is reflected from

its right-handface and the signals falls on the normal, N, to the prism face,must bisect turned through The prism is now T".

the cross-hair of T". In this position the angle between and the axes of C an

angle

of

exactly 60"

exactlyin line with

the

which its second position, axis of the collimator tube.

to

bringsthe When

normal

this has

AT been

218

PHYSICAL

MINERALOGY

accomplishedthe graduated circle is securelyclamped. The

telescopemay

be and undamped moved without alteringthe positionof the prism, and somewhere between T' and T" a position T'" will be where the refracted found the falls cross-hair on ray now

524

of the

The

telescope.

ment move-

of the

telescopefrom the position T"' back to T' gives the angle of deviation, or light 5, of the that has been refracted the by prism. In practice it is well to repeat the of a and both measurements several times d and to through all the operations go of shiftingthe positions of the prism and telescope. If white lightis for illumination the used T"f refracted at seen ray ray

will exact

as

appear

a

narrow

make determination a To

spectrum.

an chromatic mono-

light(sodium light be employed.

is best) must 2. Determination Method

of Index

of Refraction of PerpendicularIncidence

The

Method

Deviation.

the

imum of Min-

-

that

method

generallyemployed for determiningindices of refraction by the prisms. It depends upon the principlethat when a 525 beam of light,abed, Fig. 525,traverses a prism in such that the anglesi and i' a way

This is is most use

of

are suffers equal,the beam the minimum of amount deviation in its path of any

possiblecourse through the This fact be prism. may proven empirically by experimentation the refracorder to make a determination, the angle a of the prism is firstmeasured the on goniometer. The angle of the prism with this method be considerably may largerthan on

tometer.

In

when

the method

of

perpendicular

CHARACTERS

incidence is used. in the position

telescopeundamped

DEPENDING

".

UPON

219

LIGHT

W110

_,

526

and

moved until the refracted ray in it. Now, appears turn the central post with the prism it toward the leftand follow the signal on with the telescope. The position of minimum deviation is soon reached, when, on turning the prism,the signal to remain stationary for a moment seems and then to the right, moves away in which direction the prism is matter no A little practice is needed turned. to determine imum exactly the position of mindeviation and the measurement in a monochromatic be made should When the light. telescopeis properly at this placed point the graduated circle is clamped and the telescope turned until the direct signalfrom the collimator tube is fixed upon the vertical crosshair. The these two angle between as positionsof the telescopeis the same mula forthe angle of deviation, 5. The or for making the necessary lation calcufrom these measurements follows very simply from a comparison of Figs. 525 and 523. It may be imagined that Fig.525 is composed of two This results in doublingthe angles prisms like Fig.523 placed back to back. becomes 5 so that the formula now a and sn sn

8) -J-a

ciple of Total Reflection. This method is based upon the prindense into an optically that lightcannot always pass from an optically the critical angle,will suffer but at a certain angle,known as medium rarer varies with the index of for substance total reflection. The criticalangle any in 323. Art. refraction of that substance as explained Consequently if we the index of refraction of the calculate this criticalanglewe can can measure the measurement because is particularly useful This method substance. be which may be made upon quitesmall in area. can a single polishedsurface, the Total as of an instrument,known is made This measurement by means The essential 352. of which will be found in Art. a description Refractometer, is a hemisphere of glasswith a known, high index feature of this instrument surface of the hemisphere is plane and should be of refraction. The upper in horizontal a position. The mineral to be tested may accurately adjusted 3. The Method

"

surface upon it has been ground plane shape provided that some tween of high index of refraction is placedbeof A some liquid polished. drop the surface of the glasshemisphere and the flat surface of the mineral. substances and dispelthe thin layerof air that to unite the two This serves should have an index of refraction The liquid would otherwise separate them. As the liquid that of the mineral. the and of that between intermediate glass be of any and

220

MINERALOGY

PHYSICAL

surfaces the two substances in the form of a thin film with parallel be will balanced it enters as by whatever opticaleffect it has upon the light So the opticaleffect of the the oppositeeffect as the lightleaves the film. sphere liquidcan be ignored. Fig. 527 represents a cross section of such a hemithat it be Let it. now supposed by with a mineral platerestingupon lightis thrown upon the apparatus of a mirror a beam of monochromatic means from the direction of X. Rays 1 and 2 will suffer partialrefraction at the the dividing plane between 527 to and the mineral rays glass also 2' and 1' and partial 1" and 2". reflection to rays liesbetween

strikes the mineral at critical angle for the the of the glass and combination will in part be mineral and refracted at a 90" angle and

Ray

3

emerge

as

ray

3',just grazing

the surface of the hemisphere. The greater part of ray 3 will be reflected as ray 3". however Beyond this point,all the light be totally thus must reflected, If 4". the 4 to optical axis of a telescopeis now of Index of Refraction Determination brought to the direction 3", I. of Total Reflection, Method to be a marked what appears in the field of vision. One side will be illuminated by the shadow will appear total reflection of all rays beyond those of the critical angle while the other darker since side will be distinctly 528 here a considerable of amount the light passed out into the mineral. The angle between the of and the shadow the position of to the the surface normal will be hemisphere, /*, Fig. 527, the criticalangle for the combination of glassand mineral. As the index of refraction of the glassis known it is possible to calculate what the index of refraction of the be. mineral must If the mineral is plate transparent enough so that light may through pass it into the glass hemisphere another

Fig. is

so

method

used,

528.

The

as

illumination illustrated m

1' and

2' and

the direction X. Rays 1 and 2 will justgrazes the surface to 3'. Beyond into the hemisphere and a telescopeplaced with from

3 which

no lightwill pass along the line 3' will show

this point axis

to

Determination of Index of Refraction Method of Total Reflection, II.

reflectingmirror

arranged that the lightcomes

be refracted

its

of

be

may

in its field a dark

shadow.

The

contrast

CHARACTERS

between

DEPENDING

UPON

221

LIGHT

the

lightand dark portionsof the field, by this method of illumination, is so placed stronger than by the one firstdescribed. The telescope that the line of the shadow exactlydivides the angle between the diagonal cross-hairs of the eyepiece. The telescope is attached to a graduated circle from which the angleM can be directly read. With each of these instruments comes a table givingthe indices of refraction corresponding to the ordinarily different possible values of ju. This table can easily be converted into a curve plottedon co-ordinate paper in such a way that the index of refraction for a particular anglecan be read at a glance. Further,the calculation can be made having given the index of refraction of the glassof the hemisphere and the value of fjifor a specialmineral plate. Let n' equal the index of refraction of the glassof the hemisphere and // the criticalanglemeasured; then the index of refraction of the mineral,n, sin ju X n'.* 328. Dispersion. Thus far the change in direction which lightsuffers in is much

=

"

reflection and

It is further true that refraction has alone been considered. of refraction differs for lightof different wave-lengths,being if ordinary lightbe of this fact, greater for blue than for red. In consequence passed through a prism,as in Fig.525, it will not only be refracted,but it will also suffer dispersion be separatedinto its component colors,thus forming or the prismaticspectrum. This variation for the different colors depends directly their wavelengths; upon vibrations the red waves transverse their are slower,and are longer, it may be shown to follow from this that they suffer less change of velocity shorter and than the violet Waves, which are medium on enteringthe new the refractive index whose velocityof transverse vibration is greater. Hence for a given substance is greater for blue than for red light. The following determined by Schrauf : values of the refractive indices for diamond are the

amount

red (lithiumflame). yellow (sodium flame). 2*42549 green (thallium flame). most instrument 329. Spectroscope. The commonly used for the is familiar to all as the spectroscope. There analysisof the lightby dispersion 2-40845

2*41723

"

*

The

derivation

follows.

of this formula

From

the ordinary law for the index of

reached n

=

i

=

90" and sin i

--

=

same

svay

Therefore

1. -,

-

velocity of lightin in the

"

we

mineral

=

-

.

mineral

for the

Further,we

may

derive

n

highly refractingglassof the hemispherewhose

of lightin glass velocity n1, is known, the expression,

=

"

.

Further, we

denser medium) the glass (optically

from

of the lightattempting to pass the expression,

sin

sin 90"

1 _

sin

1

sin

n

n

n' =

-

M

or

"

n

n

=

sin

/n

X "'"

in the

case

into the mineral

(measuredon instrument).

/x

_

"

have

_

n

sin

refractive index,

sin 90"

velocity of lightin mineral of lightin glass velocity By substitutingthis becomes

or

the critical angle h

substitute and have

may

of lightin velocity

or

when

But

n-

re-

222

PHYSTCAL

MINERALOGY

of varietiesof spectroscopesmade, the simplestof which consists with two tubes of the instrument at the center of a glassprism mounted is received through pointingaway from it. The lightfrom the given source tube and made to fall as a plane-wave (thatis, slitin the end of one a narrow surface of a prism at the center. The one as a pencilof parallel rays ") upon the and the its produced is spectrum prism through by dispersed passage light is viewed through a suitable telescopeat the end of the second tube. which is ''white hot" (Art.314) If the lightfrom an incandescent solid of colors of the is viewed through the spectroscope,the complete band the from red the is yellow, through seen green, blue,to the orange, spectrum is examined, it is from incandescent the an violet. If,however, vapor light lines o f bands) to (or only,and these found give a spectrum consisting bright line the characteristic of it as (doubleline)of yellow in a definite position and lines series of the more complex bands, red,yellow,and sodium vapor; multitude of the bright lines due to iron green, characteristicof barium; and hot electric arc), on. so (inthe intensely vapor the surface of a new Of the light incident upon 330. Absorption. fracted medium, not only is part reflected (Art.316) and part transmitted and re(Art.317),but, in general,part is also absorbed at the surface and part also during the transmission. Physicallyexpressed,absorptionin this case the transformation of the ether-waves into sensible heat,that is,into means the motion of the molecules of the body itself. The color of a body givesan evidence of this absorption. Thus a sheet of because in the transmission red to the eye by transmitted light, red glass appears gether of the light-wavesthrough it,it absorbs all except those which tothe of of red. For the effect same reason a piece jasper produce because it absorbs part of the light-wavesat the red by reflected light, appears surface,or, in other words, it reflects only those which together give the shade of red. effect of this particular Absorptionin generalis selectiveabsorption;that is,a given body absorbs of a definite waves definitely, parts of the total radiation, particular or, more wave-length only. Thus, if transparent piecesof glassof different colors are held in succession in the path of the white lightwhich is passing into the spectroscope, the spectrum viewed will be that due to the selective absorption of the substance in question. A layerof blood absorbs certain parts of the Certain lightso that its spectrum consists of a series of absorptionbands. rare substances,as the salts of didymium, etc.,have the property of selective of this,a section of a mineral absorptionin a high degree. In consequence often them characteristic a containing gives absorptionspectrum. This latter property may be made of in testingcertain minerals,more use These give charthose that contain the rare earths or uranium. acteristic especially bands in be the tested absorption They may spectrum. by passing a strong white lightthrough a thin section of the mineral and observingthe of a direct vision spectroscope. Often a better resulting spectrum by means result will be obtained by illuminating the surface of the mineral and testing the reflected lightfor absorption bands. The lightwill have sufficiently of it absorbed. penetrated the mineral before reflection to have had some be made These tests can best by some which sort of a microspectroscope, will give a clear spectrum superimposed upon a scale of wave-lengths.* are

number

a

"

"

"

"

"

*'""

For

details of this method

66, No. 5, 1915.

of

testingminerals

see

Wherry. Smithsonian

Misc. Coll..

224

PHYSICAL

MINERALOGY

minerals,except those of the isometric system. The wide separationof the is a the phenomenon so striking, which makes refracted rays by calcite, two in of indices of in the values its difference of the refraction; large consequence the of its due double to it is other words, as technically strength expressed, its birefringence. or refraction, refraction also takes place in the anisotropicmedia 333. Double just the incident lightis perpenwhen in the majority of cases, even dicular mentioned, If the medium to the surface. belongs to the uniaxial class (seep. 253, retains its initialdirection normal to the surof the rays always face; et seq.), one less in is certain deviated or but the other, except more specialcases, both rays are usuallyrefracted and from it. With a biaxial substance,further, direction. In the case of both uniaxial and biaxial bent from their original media,however, it is stilltrue that the normal to the wave-front remains unreincidence. fracted with perpendicular in General. ference The of Waves 334. Interference subject of 'the interIt alluded to in Art. 331, requiresdetailed discussion. of light-waves, and beautiful to explainmany is one of great importance,since it serves common phenomena in the opticalstudy of crystals. spoken of in Art. 308, it is easily Referringagain to the water-waves that when two wave-systems, going out, for example, from two understood centers of disturbance near one another,come together,if at a given point the result is to givethe particle phase (ascrest to crest), they meet in the same in questiona double amplitude of motion. On the other hand, if at any point the two wave-systems come length togetherin opposite phases,that is,half a wavethe the to the of of crest one other,they corresponding trough apart, interfere and the amplitude of motion is zero. certain conditions, Under unite two sets of to form of double waves waves amplitude; on therefore, may interfere and ously Obvithe other hand, they may each other. mutually destroy "

indefinite number of intermediate cases lie between these extremes. an and of waveis true of the waves What mentioned is true also of sound-waves motion in general. A very simple case of interference was nection spoken of in conwith the discussion of the waves carried by a long rope (Art.310). 335. Interference of Light-waves. be Interference phenomena can most The studied in extreme the of cases are case satisfactorily light-waves. follows: If two waves of like length and intensity, and propagated in the as meet in the same of double same direction, phase,they unite to form a wave an intensity(double amplitude). This, as stated in Art. 311, will cause increase in the intensity of the light. If,however, the waves differ in phase and extinguish by half a wave-length,or an odd multipleof this, they interfere each other and no lightresults. For other relations of phase they are also "

said to

interfere, forming a

new

resultant wave,

in amplitude from differing

each of the component waves. In the above cases monochromatic waves lightassumed were (that is,those of like length). If ordinarywhite lightis used interference for certain wave-lengths may traction result with the consequent subof the correspondingcolor from the white lightand so give rise to various spectrum colors. 336. Illustrations of Interference. A simpleillustration is afforded by the brightcolors of very thin films or plates, as a film of oil on water, a soapbubble,and like cases,. To understand these,it is only necessary to remember that the incident light-waves and in part reflected in part from the upper are from the lower surface of the film or plate. The rays that are reflected from "

CHARACTERS

DEPENDING

UPON

LIGHT

225

the under surface of the very thin film (seeFig.530) having traveled a greater distance and with a different velocitywill,when they unite with those rays reflected from the upper surface,show in generala different phase. For some ular partic-

wave-length of lightthis difference is likelyto be exactly a half wave-lengthor odd multipleof this amount and so the some corresponding color will be eliminated (assuming that ordinarywhite lightis being used) and its complementary color will be It is to be noted that the phenomseen. ena of interference by reflection are what somefact is the that there complicatedby reversal of phase (that is, a loss of a half a wave-length) at the surface that of greater optical density from the rarer one. separates the medium actual Hence relation in phase of the two reflected rays, as AC, BD the posing (supthem of the same wave-length)is that determined by the retardation. due to the greater length of path traversed 531 by BD, togetherwith the loss of a A half wave-length due to the reversal of phase spoken of. As shown in the there are also two transmitted waves which also interfere in like manner. figure, A plano-convex lens of long curvature, restingon a plane glasssurface the hence and from at (Fig.531), separated it,except center, by a film of air of varyingthickness, reflected monochromatic givesby lighta dark center and about this a series of lightand dark rings,called Newton's rings. The dark is due

the the interference of the incident and reflected waves, a wave-length behind the former. The lightrings correspond in the same the two sets of reflected waves to the distances where meet phase,that is (notingthe explanation above) where the retardation of those having the longerpath is a half wave-lengthor an odd multipleof this (JX, center

to

later half

ringsfall between these and correspondto in oppositephase,the retardation being The ringsare closer togetherwith of this. a wave-lengthor an even multiple blue than with red because of the smaller wave-lengthof blue light. In each of the cases described the ringis properlythe intersection on the plane surface fX, fX, etc.). Similarlythe the points where

the two

waves

dark

meet

of like retardation. get,instead of the alternate lightand dark rings If the illumination was described above, a series of colored bands. originally by sodium lightthe positionof the dark ringsindicates where lightfor that When particularwave-length has been extinguishedthrough interference. white lightis used the conditions in respect to its component having the yellow sodium-lightwave-length have not changed and this lightwill stillbe of the In

cone

of rays

ordinarywhite lightwe

but now, instead of dark rings,we get rings having points, of illumination If was means by blue. color our original complementary from those have different had red the would dark a positions duced prorings light inated in sodium light. And again when white lightis used red lightis elimIn this way we at those pointsand its complementary color shows. the successive of colors the obtain a series of colored rings, each showing of times The series of the spectrum colors are repeateda number spectrum.

eliminated at the

the

same

226

PHYSICAL

MINERALOGY

due to successive interferences produced by differences of phase of J, 1J,2|, distinguishedas of the first, etc., wave-lengths. The different series are second, third,etc.,order; for a given color,as red,may be repeated a number The interference ringsfor different colored lightsare not evenly of times. spaced,the ringsshown in blue lightbeing,for instance,closer togetherthan of the spectrum bands for red. Consequently after three or four repetitions the different interference ringsbegin to overlapone another and the resulting fainter and less pure. colors become Ultimately this overlappingbecomes and white light, the so-called white of is lost of color that the effect so general the higherorders,is shown. means

most Another satisfactoryillustration of the interference of light-waves is given by of the diffraction gratingsspoken of in Art. 331.

of the compositionof two systems of light-waveswill be conOther cases sidered after some remarks on polarizedlight. 337. Polarization and Polarized Light. Ordinary lightis propagated by transverse vibrations of the ether which may take place in any direction as tion longas it is at rightanglesto the line of propagation. The direction of vibradisturbance of the ether is a is constantlychanging and the resulting A ray of ordinarylightwill be symmetrical,therefore, complex one. only to the line of its propagation. the other hand, as stated briefly in Art. 311, is on Plane-polarized light, propagated by ether-vibrations which take place in one plane only. The change by which ordinarylightis converted into a polarizedlightis called and the plane at rightanglesto the plane of transverse vibration polarization, is called the planeof polarization* Polarization may be accomplished (1)by reflection and by singlerefraction, and (2)by double refraction. 338. Polarization by Reflection and Single Refraction. In general, has suffered reflection light which 532 from a surface like that of polished less completely poor glassis more larized; that is,the reflected waves are propagated by vibrations to a largeextent limited to a singleplane, viz.,(as assumed) the plane normal to the plane of incidence, which last is hence the plane of polarization. Furthermore, in this case, the light transmitted and refracted by the is also in like reflectingmedium "

"

manner

partiallypolarized;that

the vibrations

are

more

or

is,

less limited

a single plane,in this case a plane at rightanglesto the former and hence with the planeof incidence. coinciding For instance, in Fig.532, let a-b represent incident lightray in which an takingplacein allpossibletransverse directions as represented

to

the vibrations "

*

plane of the

are

It is necessary to keep clear the distinctionbetween the plane of polarization and the the vibrations take place. All ambiguity is avoided in which by speaking uniformly

of the light. vibration-plane

CHARACTERS

by the

arrows,

x-x, y-y, and

lightwith

vibrations

DEPENDING

UPON

227

LIGHT

When

this ray strikes the polishedsurface will be reflected along b-c and x-x other vibrations near to x-x in direction will be shifted to this direction so that the reflected ray will be largelypolarized. In a similar the light having z-" manner vibrations will enter the the as transparent substance refracted ray b-d and other will be shifted to vibrations this direction so that the refracted is also ray largely polarizedand in a plane at right angles to that of the reflected Light reflected from a ray. at

6

polished and face

is

transparent

z-z.

parallelto

sur-

Brewster's

completely

not

Law

polarized but

there is an for every angle of incidence substance will be at its maximum. of polarization the amount This will happen, the angle between illustrated in Fig. 533, when as the reflected and refracted rays A B and AC equals90". It is evident from a consideration of at which

the

figurethat the angler is the complement of i\ hence the formula

becomes

in this

?

-

=

n

case

sin i "

cos

:

=

tan

i

n.

=

^

This law, established by Brewster, may The angleof incidence for maximum

be stated

as

follows

is that polarization

:

angle whose tangent

is the index

substance. For crown reflecting of refraction of-the glassthis angle If lightsuffers repeated reflections from a series is about 57" (seeFig.533) .

is more of thin glassplates, the polarization is complete,though its intensity the lightvery slightly. weakened. Metallic surfaces polarize Refraction. When 339. Polarization light in passing by Double is doubly refracted (Art.332) or divided into medium through a crystalline and in two sets of waves, it is always true that both are completelypolarized This be other. each at to can only subject planes satisfactorily rightangles crystalline explained after a full discussion of the propertiesof anisotropic factory givesthe most satismedia, but it.may be alluded to here since this principle end For this it is method of obtainingpolarized light. necessary that that so of the two wave-systems should be extinguished, only that one one This is accomplishedby due to a singleset of vibrations is transmitted. in natural absorptionin the case of tourmaline platesand by artificialmeans "

the nicol 340.

prisms of calcite. Light by

Polarized

Absorption. "

Light

passing through

a

transparent thin section of a tourmaline crystal the axis will be almost to the vertical crystallographic section being cut parallel in the demonstrated be This following can easily way. completelypolarized. Select a polishedfloor surface,or a table top and stand in such a positionthat Look at lightfrom a window is reflected from the polishedwood to the eye. the it first with tourmaline the this reflected lightthrough section,holding

stronglycolored

but

"

"

228

PHYSICAL

MINERALOGY

direction 'ofthe c crystalaxis in a horizontal positionand then turning the vertical. The lightpassinginto the tourmaline section until the c axis becomes section is in considerable part polarizedthrough its reflection from It will be the wood surface and possesses a horizontal vibration direction. is horizontal the section tourmaline the the of axis readily c noted that when practically transmits lightbut when this axis is vertical the section becomes The crystalstructure of the tourmaline is such that lightentering opaque. of which has its it is doubly refracted), one it is broken up into two rays (i.e., of the vibrations the other lie in the while the to c axis, vibrations parallel From the foregoingexperiment it is plane of the horizontal crystalaxes. the axis is readilytransmitted by to c obvious that the lightvibratingparallel the axial plane,is in horizontal the crystalbut that the other ray, vibrating is clear that the transUnder conditions it these mitted almost completelyabsorbed. lightbelongs almost wholly to one ray, the vibrations of which take place in a singledirection. In other words, the lighttransmitted by such a tourmaline section is polarized. available it is instructive to make are If two such sections of tourmaline Place them together,first with their the followingexperiment with them. section upon the other until to each other,and then turn one c axes parallel In the firstcase, the lightcomes at rightanglesto each other. these axes are through the sections because the vibration planes of the transmitted rays in In the second to each other. the two sections are parallel case, all lightis these two vibration planes are at rightangles to each cut off because now other,the lightthat did get through the firstsection being wholly absorbed in the second. 341. Polarized Lightby Double Refraction. Calcite,as already stated in an unusual degree the power to doubly refract light. in Art. 332, possesses calcite block of clear take If we (Icelandspar)and look at an image a cleavage line drawn the image will appear dot such on a pieceof paper, or as a throughit, in it make If and take card a double. we a pinhole,place the card upon rhombohedron of hold face a cleavage and, looking through the calcite, one will observe two brightdots. if we of light, Now it up againsta source we at the lightreflected from a polishedwooden look in the same surface, way will find that when a line bisecting described in the precedingarticle, we as the acute anglesof the rhombic face of the cleavageblock is horizontal one of these images is brightwhile the other is almost invisible. If we then turn the block so that the line bisecting the obtuse anglesof the rhombic face is horizontal the firstimage will fade while the second becomes bering bright. Rememthat the lightreflected from the polishedwooden surface is largely it becomes evident from this polarizedwith a horizontal vibration direction, experiment that the two rays into which the lightis broken up in passing through the calcite are polarizedand that their planes of vibration are at bisect the anglesof the rhombic rightanglesto each other and respectively face of the cleavageblock. As the double refraction of calcite is strong, it follows that the indices of refraction of the two rays show considerable differences. This fact is taken advantage of in constructing calcite a prism from in such a way of these as to wholly eliminate one rays and so, as only the other the the lightthat emerges. can come through prism,effectively polarizing ray The prism referred to above is called the Nicol Prism or simply the nicol. A full explanationof the nicol cannot be made at this time,as there would be of the a but a required knowledge opticalpropertiesof hexagonal crystals, "

CHARACTERS

DEPENDING

UPON

LIGHT

229

be given enabling one to understand its construction and descriptionmay In Fig.534 is represented a cleavagerhombohedron of calcite uses. with its edges vertical. Let d represent a point of lightunderneath the rhombohedron. Light coming from d will be broken into two rays whose paths the rhombohedron shown are through 535 As lines and the shown o e. by above, these two are polarized,with rays vibration directions as indicated .by the

double

arrows

in the

top view in

In the construction of a Fig. 534. nicol,the top and bottom surfaces of such a cleavage rhombohedron are ground and polished so that they make angles of 68" with the vertical edges. Then the block is cut in two along the diagonal a-/, as shown in Fig. 535. These two surfaces,after cemented are being polished, together of a thin layer of Canada by means

balsam.

Let

lightenters

us

the

assume

that

a

ray

of

prism from below, as

shown

in Fig. 535. It is broken up the rays o and The e. o ray travels with the slower velocity, has therefo'rethe higherindex of refraction, and shows a greater deviation from Nico1 Prism the original path. The Canada balsam has a lower index of refraction than ray a, which,therefore, when it strikes the layer of balsam, is attempting to pass from an optically dense into a rarer medium. The construction of the prism is such that this ray meets the layerof balsam at an angle greater than the criticalangle for.this opticalcombination and suffers therefore total reflection toward the side of the prism,and will be absorbed second by whatever fasteningholds the nicol. The e ray with almost the deviation from its no prism course. through original passes Its index of refraction and that of the Canada balsam are nearly the same, hence the ray suffers almost no deflection at this point and passes out of the face of the prism. The that emerges from a nicol light,therefore, upper is all and t o to the shorter one vibratingparallel belongswholly diagonal ray of the rhombic end surface. It should be noted,however, that some prisms made in a different way and that the above statement are concerningthe plane of vibration of the lightemerging from the prism may not always hold true. It is always wise to test the plane of vibration of a nicol by looking through it at the floor or a table top as previouslydescribed. The prism will show brightwhen its plane of vibration is horizontal, thus correspondingto the plane of vibration of the reflected light. of two 342. Analyzer. The combination Polariscope. Polarizer. which transparent mineral other polarizing contrivances,between or nicols,

into

"

in polarized be examined sections may lightis called,in general,a polariscope; the lower In any polariscope forms of which are described later. the common outside from the which t he other given polarizes light contrivance, prism,or the If these is is the the called prisms source analyser. polarizer; upper prism

230

PHYSICAL

MINERALOGY

said to be at rightangles to each other, they are their vibration-planes then the w ill be incident polarizer extinguished crossed;the lightpolarizedby under these conditions it is said to suffer extinction. by the analyzer; briefly, Interference of Plane-polarizedWaves. Colors. 343. Interference in polarizedlight minerals are examined sections of doubly refracting When obtained that are of great imporcertain interference effects are commonly tance. As shown in Art. 341, calcitewhen it doubly refracts lightalso polarizes In general, the two rays and in planesthat are at rightanglesto each other. minerals. this is true of sections of doubly refracting Consider,then,what mineral is placed in takes place when a generalsection of a doubly refracting and analyzerthe planes of vibration of the polarizer between a polariscope In Fig.536 let the rectangular outwhich are at rightanglesto each other. line and section. The double marked such show the arrows a o e represent in the The directions vibration section. of of direction two light possible from the polarP-P' represents the plane of vibration of lightwhich emerges izer vibrate when it below and A- A' shows the direction in which lightmust In the first case from the analyzer above. to be considered the emerges Ato P-P' directions o and e are taken as parallel A' and respectively.The to the direction lightthat enters the section from below must all vibrate parallel P-P'. It enters the mineral section and must vibrate there as the ray labeled o. There will be no ray in the mineral vibratingparallel to the direction be resolved into another at right to o cannot e, as a vibration parallel stillvibratingparallel anglesto it. The lightwill leave the section, therefore, to P-P' and enter the analyzerabove. It will, reflected however, be entirely in the analyzer at the'layer of balsam since only light to A- A', vibratingparallel which is at rightanglesto P-P', can emerge from the analyzer. Consequently, when such a section has its planesof vibration parallel to those of the polarizer and analyzer, the section will appear dark. The same reasoningholds true when the section is turned to a position at 90" from the first. Consequently with such a section there are four positionsat 90" to each other in which it appears dark during its complete rotation upon the stage of the At such the section,is said to be extinguished. polariscope. positions have

"

636

537

538

A'

-P'

P

Next

consider what happens when the vibration directions of the section at obliqueangles to those of the polarizer and analyzer. In Fig. 537 let o and e represent the directions of vibration in a section which makes are

some

obliqueangle.with the directions P-P' and A- A'. In Fig.538A let the line P-P' representthe direction and amplitude of the vibration of the lightenter-

232

MINERALOGY

PHYSICAL

be used to study the effects of polarizedlight orientation and may of the sections wedge) of different thicknesses. Take the on plates(short and analyzerwithout combination of polarizer of a polariscope, simplestform

of known

539 A

Quartz Wedge it so that the vibration planesof the instrument are crossed. with ordinary lightand on the stage of the instrument place a to the plane of vibration of the quartz wedge with its X direction parallel polarizer.The lightin enteringthe quartz will vibrate parallelto the X direction and without changing its plane of vibration will pass through the quartz and up into the upper nicol where it will suffer total reflection. Hence will appear dark throughout its length. A similar the wedge in this position result will be obtained when the X direction of the wedge is placed parallel to the vibration plane of the analyzer. But if the wedge is turned so that its X direction makes an angle of about 45" with the plane of vibration of the polarizerthe wedge will exhibit a series of beautiful interference colors, arrangedin transverse bands, the nature of which will be discussed in a later paragraph. If the wedge is turned from this 45" positionthe colors become less and less brilliant as the positionof extinction is neared. i As preliminaryto another experiment, paste a narrow strip of paper, P-P, Fig.539, B, on the top, but to one side,of a quartz wedge. Place this the stage of a polariscope(withoutlenses)and illuminate with diffused on sodium light. When the wedge is examined under these conditions it will be found that it shows extinction when its vibration directions are parallel to those of the polariscope but at the 45" positionit will show transverse dark bands upon number of these bands will depend upon the a yellow field. The thickness of the wedge; usually there will be two or three,although for this to have a longerand proportionally thicker wedge experimentit is interesting than those commonly supplied, to have more bands appearing. Mark so as the strip of paper the position of each band, as illustrated in Fig.539, B and on number at the band nearest the thinner end of the wedge. The them, starting number 1 band marks the place where the faster of the two rays, into which the quartz breaks up the sodium light, has gained exactly one wave length in its phase over the slower ray. At the point marked 2 the gain is two wavelengths,

lenses,and

arrange

Illuminate

etc.

In 540

explainingthe phenomenon

in which

it is assumed

justdescribed,reference is made to Fig. is the plane of the polarizer and A- A1

that P-P'

CHARACTERS

DEPENDING

UPON

233

LIGHT

is the plane of the analyzer,and

a quartz wedge is between them at such an of the direction that the vertical to C-C'. If we angle crystalaxis liesparallel explainthe action of lightin the wedge in a purelymechanical way we may say, let the amplitude of vibration of an ether particlebefore the lighthas entered the wedge be represented in the figureby the line 0-p. The vibration may be likened to that of a pendulum', swinging back and forth from p to p'. If the to the ether impact, or disturbance,of an ether particleis communicated particlesof the quartz when it is at 0 at the middle of an oscillation from to r parallel one to C-C' and the p to p',there will result two disturbances, The amplitude of the vibrations repreother to s at rightangles thereto. sented of forces, cated by 0-r and 0-s are determined by the parallelogram as indiDuring the passage of these two rays by the dotted lines in the figure.^ through the quartz the one whose vibrations are representedby s-s' travels the faster and it is assumed that the thickness of the quartz wedge at the place under consideration is such that,on emerging,this ray is justone wave-length ahead of the one whose vibrations are parallel to r-r'. Now, when one ray is ahead of another be three one or wavelength (it two, exactly any exact may of wavelengths) the conditions are such,that,at the middle of the number of the ray s-s' is juststartingfrom 0 to s, vibration,when an ether particle be juststarting r-r' from 0 to r. will the Now o f ether sider conan particle ray in the directions the simultaneous 0 to effects the impacts produced by the o f the calcite the ether constituting analyzer. particles s and 0 to r upon of the A* vibration from s' to s acting at 0 will displacethe ether particles at r' 0 will to r acting calcite to a and a'. Likewise a vibration from displace of these resulting to p and p'. Two the ether particles namely disturbances, 0-"j' and 0-p',are easily disposedof,for being in the plane P-P' their effects turbances in the nicol. The other disbalsam cannot pass beyond the layer of Canada from the 0-ff and 0-p are both in the plane A- A' and can emerge at Oare acted upon but since the ether particles simultaneouslyby forces nicol, disturbance can take of equal magnitude acting in opposite directions no From the above it dark. section is the conditions these under and place

540

641

\ P\

tween mineral is observed besection of a doubly refracting a follows that, when angle vibration oblique planes making some crossed nicols with its

234

PHYSICAL

MINERALOGY

with the vibration planesof the nicols, complete interference will take place for some particularwave-length of lightwhenever the two polarizedrays phase. correspondingto this color emerge from the section in the same It is well to consider next the effects that result when, with the planesof vibration of the nicols crossed,lighttravels through such thicknesses of the the other half wave-lengthover f or some quartz wedge that one ray gains-J-, of an oscillation second ray. Let it be supposed,Fig.541, that at 0, the middle to the ether particles from of a p to p',the impact is communicated the axis of which lies to direction parallel quartz section the vertical crystal from 0 to r and There will result two disturbances in the quartz, one C"Cr. the section the phases of the two rays After traversing the other from 0 to s. half wave-lengthso that when the direction of the firstoscillation differ by one is from 0 to r, that of the other will be from 0 to sf. The impulse 0-r gives rise in the analyzer to two disturbances 0-p and 0-p'. The impulse Of these disturbances 0-s' results in the two displacementsO-a- and 0-a'. extend 0-a' the not and do of Canada balsam of the analyzer, 0-p' beyond layer while 0-p and 0-a, both of equal magnitude and vibratingin the plane A- A', additive and giverise to a disturbance and the sensation of light. Hence, are there are areas in the experiment with the quartz wedge in sodium of light, lightbetween the dark bands, Fig.539, B. An instructive experiment with the wedge should also be tried with sodium light illumination but with the planes of vibration of the polarito each other instead of crossed as in the previous cases. parallel scope If light traverses such a thickness of quartz that, on emerging, one ray half of a wave-length over has gained one the other the conditions up to the analyzer will be the same in the time the vibrations enter the as The now vibrations,however, which can previous case. through pass the analyzer result, Fig.542, from the disturbances 0-p' and 0-a',and these in oppositedirections but with unequal force would actingon an ether particle produce a disturbance in the direction 0-p' and, therefore, give rise to the sensation of light. A wedge with the direction of the vertical crystal axis about parallel to C-C' will appear yellow throughout its entire length. This will not be the case, however, if the wedge is turned so that the vertical axis ,

542

makes forces

angle of actingupon an

543

45 an

with the plane of polarization, Fig. 543, for then the ether particle at 0 are 0-p' and 0-a, which,being equal

CHARACTERS

and

DEPENDING

UPON

LIGHT

235

in

will neutralize each other and therefore will not oppositedirections, sensation of light. A wedge in the 45" positionwill therefore of dark bands,the first, show a series from the thin end of the wedge, starting where one being the second where it has gained ray has gained J wave-length, the second ray. over In Fig.539, B, the positions wave-lengths,etc., of the j bands this experiment are indicated by the crosses in marked the stripof on pasted upon one side of the quartz wedge. The lines and crosses paper on this paper stripindicating gainsof whole and one half wave-lengthsfor yellow as serve lightmay now startingpointsfor further considerations. For the next experimentuse a microscope with crossed nicols, 3 or a number 4 objective, and illuminate with ordinarylight;placethe wedge in the 45"

produce any

focus

that part of it opposite the firstline drawn on the paper at its center a blue color, about at the pointwhere strip it is beginning to merge into red. A moment's consideration will indicate this color reallyis. It is a mixture of all colors of the spectrum except what yellow. That this is the case may be proved by analyzingthe blue by means of a small direct-vision spectroscope. This will show a spectrum through which runs band between the red and green, that is,where the yellow a dark would normally appear. The blue of the wedge at this pointis therefore the complement of yellow,which has been made to disappearby interference. Next focus the microscopeon the wedge oppositethe second line. Here the color will be nearly a sky blue,with perhaps a tingeof green. Upon analysis with the spectroscopeagain a dark band will be found in the yellow,this time due to interferencebrought about by a difference in phase of two wave-lengths for sodium light. Proceeding next to oppositethe third line the color will be found to be a lightgreen, which on analysisshows a band where yellow ting should occur and a perceptible by cutshorteningof the spectrum, especially off the extreme blue and violet. Oppositethe fourth line the color would be a very pale green which upon analysiswith the spectroscopewould show The pale green in the yellow and another in the blue. two dark bands, one color is therefore due to a mixture of red,green, and violet. If,in the original blue light experiment the wedge had been illuminated by a monochromatic it would have been found at the thicker end of the wedge, where the fourth band for yellow lightwas located,there would have been a fifth band for the blue light. Consequently the interference color at this point of the wedge is tracted. equivalentto white lightfrom which both yellow and blue have been subIf a wedge of extra lengthwas available for study it would have been

position and The

on

field will show

oppositethe eighthband for sodium lightthe color showing,when white. This upon wedge is studied in the polarizingmicroscope,was in the bands crossed red,yellow, would show green, and a by spectrum analysis the thickness of the quartz at this point, In other words, in traversing blue. the faster ray has gained for red seven wave-lengthsover the slower ray, for effect The white polarization ten. for blue yellow eight,for green nine, white of the is known as the microscope when lookingat this point with seen the colors of several spectrum, primary higherorder. It is a mixture of the some portionsof all of which are present and combine to givethe effect of white. colors of the quartz the polarization It is important to study carefully wedge under the microscope,usingFig.544 as a guide. It will be noted that order as the thickness of the quartz in generalin the following the colors occur increases : violet, blue,green, yellow,orange, red. This sequence of colors is three times and then as the thicker end of the wedge repeated quitedistinctly noted

the

that

236

MINERALOGY

PHYSICAL

fainter and not so clear. This series of is approached the colors become indicated in Fig.544. It is to be into orders as interference colors is divided 544

Ll I!

i

i "JS (C

A

JJfg

x-f-

*+ "-

s

fa

o

First

Order

-A^

Second

Order

Interference

a Third

Colors

122

"", i-A.

Order

with

a Fourth

Order

A -A-

Higher Ordere-

Quartz Wedge

noted that at the very thin end of the wedge before any interference can have Also the thicker end of the wedge is white taken place the color is white. because here there is an overlappingof the various points of interference of the different colors. The thickness of the wedge at the different points is given in millimeters in Fig.544. scope the accessories of the polarizingmicro344. Sensitive Tint. Among of mounted between two is a thin plateof gypsum plates glass. It is and T. marked either X (o)or Z (c), also with marked S. an arrow commonly faster or slower ray. direction vibration of the the of indicatingrespectively in the 45" is If this positionwith the nicols placed on the microscope stage the same that close the interference color shown is reddish violet, as crossed, It is an interesting to the red of the first order of the quartz wedge. ment experithe redto first put a quartz wedge under the microscope and focus on it with the sensitive violet,justbeyond the red of the firstorder and then cover that its X direction is at rightanglesto the tint arranged in such a way X direction of the quartz wedge. The The resultingcolor will be gray. of the faster this is Whatever had made the over simple. gain explanation ray slower in passing through the quartz has been overcome neutralized or by of oppositeopticalorientation- and of suitable passingthrough a layerof gypsum thickness to produce the same interference as the quartz. The name Sensitive Tint is given to this gypsum plate because a slightincrease of the double refraction which it shows will give a blue color while a corresponding tive of the sensiuses slightdecrease will change the color to yellow. Numerous tint will be given in subsequentarticles. 345. Interference Colors of Mineral Sections. interference colThe ors of mineral sections depend upon three things. 1. On the strengthof the birefringence of the mineral,or in other words of the amount that the mineral shows. double refraction The upon greater the higherthe order of interference color, the birefringence the other influencing factors remaining constant. 2. The thickness of the section. The thicker the section the greater will of double refraction and consequentlythe higher the order of be the amount the interference color. "

"

CHARACTERS

3.

The

DEPENDING

orientation crystallographic

UPON

LIGHT

237

of the section.

This will be explained described are 346. Determination of the Order of the Interference Color of a Mineral Section. It is often important to determine to which order (see last paragraph of Art. 343) the interference color of a given section belongs. If, as is often the case, the section has somewhere a taperingwedge-like edge,the bands of color shown successive there can be counted and the order of the color of the surface of the section determined. In other words the order of the color can be told in the same the as way upon quartz wedge itself. If such an edge cannot be found the quartz wedge is used as described below. Suppose a certain mineral section showed an interference color of orangered and it was desired to ascertain whether this color belonged to the first or second order. Under the microscope with crossed nicols find a positionof extinction of the section and then turn it the stage of the microscope upon through an angle of 45". By doing this the vibration directions of the section are brought into such a positionthat they make angles of 45" with the vibration directions of the polarizer and analyzer. Then insert above the section and below the analyzera quartz wedge, the opticalorientation of which is A slot running through the microscopetube justabove the known. objective and making an angle of 45" to the cross-hairs is provided for this purpose. Under these conditions there are two Either the optical possibilities. orientation of the section and the quartz wedge agree; i.e., the X direction of the section is parallelto the X direction of the wedge, or these two directions at rightanglesto each other. are The effect of the introduction of the wedge above the section will be either to increase or decrease the amount of double refraction of the lightdue to the mineral section. If the double refraction is the optical effect will be as if the mineral section had been thickened increased, and in this case its interference color will rise in its order. On the other hand, if the double refraction of the lightis decreased by the introduction of the quartz wedge the effect will be as if the mineral section had been thinned and the interference color will fall in its order. In the firstcase the red interference color of the section would be changed as the wedge is pushed in,firstto In the second case blue and then to green. it would change to orange, then to yellow and green. the introthat upon duction so Arrange the section, therefore, Then of the quartz wedge the interference color will fall in its order. graduallycontinue to push in the wedge, noting the successive colors that the amount of the double refraction is decreased. occur as Finallythe point will be reached where the thickness of the wedge will give practically the same amount of double refraction as the mineral section. The two having opposite opticalorientations the result will be to eliminate all interference and a this condition arises the quartz color of the firstorder will result. When gray By noting the succession of colors wedge is said to compensate the mineral. color of the until this point is reached the order of the original that occurs later when

the

opticalcharacters

of the different

crystalsystems

"

section

can

347.

be determined. of

Determination

Strength of Birefringence. The "

birefringence,

It is expressed varies with different minerals. refraction, the and least between difference is the that greatest numericallyby a figure of calcite, for instance, In the case indices of refraction of a given mineral. or

amount

of double

The of refraction for one ray is 1'486 and for the other is T658. is than for much This 0'172. of calcite therefore equals higher birefringence 0*0091. of most minerals,the strengthof the birefringence quartz being only

the index

238

MINERALOGY

PHYSICAL

An

accurate

of the

estimation

of strengthof the birefringence

greatestand

the

only by determining approximatedetermination,however, be made

can

a

mineral

is

least indices of refraction. in

often be made

a

to An

thin section under

stated in as section, microscope. its the tion orientathe thickness of with varies crystallographic Art. 345, mineral, and the strengthof its birefringence.If the first two factors are known color of the' be estimated by noting the interference the birefringence can The in thickness of the secdetermination. this will aid tion 545 section. Fig. the is left. The column of in the at is shown the strength birefringence of the side that and a figure. Suppose right-hand expressedalong the top interference in thickness and showed an orange-red givensection was 0*03 mm. zontal the horicolor of the first order. By followingthe diagonalline that crosses in the of middle the orange-red at a pointlying 0*03 mm. line marked be of the mineral must that the birefringence of the firstorder it will be seen of determiningbirefringence is most This method about Q'015. commonly The

the

of the interference

order

color of

a

of minerals observed in rock sections. In the case of the best rock sections the thickness of the section is usuallyabout 0'03 to 0'04 mm. also be judged from the interference color The thickness of the section can known which is to be observed shown mineral,like quartz or feldspar, by some of a mineral varies with in the section. As the strengthof the birefringence orientation it is necessary the rock its crystallographic always to look over section and use in the observations that section of the mineral which shows the of a mineral is always highestorder of interference color. The birefringence used in the

case

545

ill *

I! 11

3

I

,OP^P3O

/*

O

"s,i .2o

"

"o'w ".""="

"

oo

II

,

i^jtf

-i ll .1^3122 |MfS diii "-M SS3 g "S "

o

.2

He"^

o

"A

o^^dtf'S^S

"

I

White

of higher order.

ffl

" o

0.06

0.045

0.05 0.050 0.055

0.04

0.060 0.065

|

0.070

I

0.03

\.1

0.100

0.02

0.120 0.160 0.200

0.01

0.300

0.00

Determination

of the

expressed as the maximum with a uniform

Strengthof Birefringence (afterPirsson differencebetween such thickness,

as

and

Robinson)

the indices of refraction. Consequently, is obtained in a rock section, that

240

PHYSICAL

MINERALOGY

the section it on thicker part of the interference as a thinner part did originally. section is now showing the same If this is In other words, the result is as if the section had been thinned. and must the wedge be opposed so, then the X and Z directions of the section off the section it On the other hand, if the color bands move to each other. interference that a thinner part of the section is showing the same means effect that a thicker portiondid originally.The introduction of the quartz wedge has in effect thickened the section and therefore the similar optical ing useful for determindirections of the two coincide. This test is particularly the X and Z directions of deeply colored minerals,as the natural color of the thicker portion of the section,completely mask the mineral may, over the color bands go off toward the edge. When the effect of that the means quartz wedge is such or

move

that

up

a

color. section shows an interference color of white or gray of the first a mineral order the sensitive tint will give better results than the quartz wedge. If the similar opticaldirections of the section and the sensitive tint coincide the effect will be to raise the color of the sensitive tint (red of the first order)to blue. On the other hand, if the opticalorientations of the two are opposed be made to advantage only when the color will fall to yellow. This test can effect of the section is small enough to justraise or lower the the birefringent to blue or yellow. color of the sensitive tint respectively the interference If

\

Polarized 349. Light. In the preceding Circularlyand Elliptically articles the two interfering after light-rays, emerging from the second nicol, in be the to assumed same were polarized plane; for them the resultingphenomena indicated are as comparatively simple. If, however, two planedirection have their vibration-directions polarized rays propagatedin the same at rightanglesto each other,and if they differ one-quarter of a wave-length then it may be shown that (JX) in phase (assuming monochromatic light), the compositionof these two systems results in a ray of circularly polarized to light. Brieflyexpressed,this is a ray that,looked at end-on,would seem be propagated by ether-vibrations taking place in circles about the line of From transmission. the side,the onward motion would be like that of a and either left-handed. right-handedor screw, meet with a difference of phase as above If,again,two light-rays described, from JX (but not equal to an even differing multipleof |X),then the resulting that is,a light-ray compositiongivesrise to elliptically polarized light, propagated by ether-motions takingplacein ellipses. The above results are obtained most simply by passingplane-polarized medium of the proper thickness (e.g., lightthrough a doubly refracting a mica inclined 45" to that of the plate) which is placed with its vibration-planes polarizer. If the thickness is such as to give a difference in phase of JX or an odd multipleof this,the lightwhich emerges is circularly polarized. If the differsfrom is phase \\ (but not equal to |X or X),the emergent lightis elliptically

polarized. 350.

Rotation

of Plane

of Polarization.

In the case of certain doubly media (asquartz),and also of certain solutions,(as of refracting crystallized sugar),it can be shown that the lightis propagated by two sets of ethervibrations which take place,not in definite transverse in planeas planes that is,each ray is circularly polarizedlight but in circles; one polarized, of these being right-handed,the other left-handed. will one Further, rays, uniformly gain with reference to the other. The result is,that if a ray of "

"

"

CHARACTERS

plane-polarized lightfall upon of

DEPENDING

such

section of quartz cut normal

a

the two

a

medium

UPON

241

LIGHT

(assumingthe simplestcase,

to the vertical

as

it is found that crystalaxis),

circularly polarizedwithin unite on emerging to a plane-polarized but the of has suffered an angularchange or rotaplane polarization ray, tion, which may be either to the right(toone lookingin the direction of the ray),when the substance is said to be right-handed, to the left, or when it is rays

called

left-handed. phenomenon is theoretically possiblewith all crystalsof a given system belonging to any of the classes of lower symmetry than the normal class which show a plagiohedral development of the faces *; or, more simply, those in which the correspondingrightand left (or + and ) typicalforms are enantiomorphous (pp.71,112),as noted in the chapteron crystallography. In mineralogy,this subjectis most important with the common speciesquartz, of the rhombohedral-trapezohedral class,and a further discussion of it is postponed to a later page (Art.394). This

"

OPTICAL

INSTRUMENTS

AND

METHODS

351. Measurement of Refractive Indices. Refractometer. For the determination of the refractive indices of crystallized minerals various methods when suitable material is at hand, are employed. The most accurate results, obtained be the refractometer. This requiresthe observation by ordinary may of the angle of minimum deviation (5)of a light-ray on passingthrough a prism of the givenmaterial, having a known angle(a},and with its edge cut in the proper direction. The measurements of a and 5 can be made with an ordinary refractometer or with the horizontal goniometer described in Art. 231. For the latter instrument,the collimator is made stationary, being with the fastened to a leg of the tripodsupport, but the observingtelescope verniers moves freely. Further,for this objectthe graduatedcircleis clamped, and the screw attachments connected with the axis carryingthe support, and loosened. the vernier circle and observingtelescope chromatic are Light from a monoand slit of this is an image source through an appropriate passes With substance thrown by the collimator upon the prism. a doubly refracting deviation must be measured two images are yieldedand the angleof minimum for each ; the proper direction for the edge of the prism in this case is discussed the formula in Art. 327 is used. and 5 are known later. When a The principle of total reflection (Art.323) 352. Total Refractometer. No prism is reindex. refractive the determine quired, also be of to made use may but only a small fragment having a singlepolishedsurface;this may have a but in other cases must have any direction with an isometric crystal, instruments different of number later. A described definite orientation, as be measured of which indices of refraction may have been devised by means is at present represented by the use of total reflection. A type widely used made by Leiss. It consists of a instrument was in Fig.546. This particular hemisphere of glass(H) having a high refractive index which is mounted upon a glasspost through which lightmay be reflected from the mirror Sp. The "

"

be characterized the following eleven may classes among crystals, Of the thirty-twopossible Class 4, p. 71; 5, p. 72; 11 and 12, p. 89; 17, p. 102; by circular polarization: 22, p. 112; 23 and 24, p. 114; 27, p. 128; 29, p. 138; 32, p. 147. *

242

PHYSICAL

MINERALOGY

tube P contains a nicol prism so that when a thin section of a mineral is placed the plane surface of the hemisphere it is possibleto obtain its optical upon with the polarizing orientation in the same microscope. The manner as face polishedmineral sur546 is placed upon the plane surface of H with film of a ing some high refractoilbetween them. of Then beam a

light source

from of

usually

some

illumination, a

chromatic mono-

light, is reflected by means of the mirror such a way

producea

Bl in as

to

total reflection

shadow down the opposite side of the hemisphere. For further details of the operation see The escope telArt. 327. F is attached to the disk V which in turn carries a scale its edge. The on telescope is moved until the up or down between the light line and dark portionsof the field lies on the Total Refractometer cross-hairs.The angle which is read on the scale under these conditions is the desired critical angle for the combination of the glassof the hemisphere and the mineral plate. Knowing this angle and the index of refraction of the glassof the hemisphere to calculate the index of refraction of the mineral ; see Art. 327. it is possible of which the isfurnished with the total refractometer table Usuallya by means measured desired refractive index is obtained directly the of from the value critical angle. The post carryingthe glasshemisphere may be revolved in This the horizontal plane and the angleof rotation measured the scale K. on tions of indices corresponding to different vibration direcpermitsthe measurement the mineral. L is an eye lens which in combination with the other in lenses of the tube F makes a low power liminary microscope,which is used in the preoperationsin order to center the mineral plate,etc. In the tube A is an iris diaphragm and usuallya small nicol prism that may be pushed in out of the tube. or Fig.547 represents a small total refractometer devised by G. F. H. Smith which depends upon the same principle.The mineral plateis placed upon the glasssurface shown on the top of the instrument. The instrument is so on

CHARACTERS

held that

lightenters

by

of

means

DEPENDING

UPON

LIGHT

243

at the forward end, and the reflected lightis sent totally inclined mirror to the eyepiece. A scale is placedin the instru-

an

647

Smith Total Refractometer ment

(Actual Size)

in such

that the boundary between the lightand dark areas a is way superimposed upon it and so yieldsdirectlythe value of the refractive For rapid and approximate determinations index. this instrument is very seen

useful. 353.

A very simple form Tourmaline of polariscopefor converging Tongs. lightis shown in Fig.548; it is convenient in use, but of limited application. Here the polarizer and analyzerare two tourmaline platessuch as in piecesof cork and held in described in Art. 340. were They are mounted them and to a kind of wire pincers. The be examined is placedbetween object In there the in wire. use supported spring the by they are held close to the in this positionthe crystalsection is viewed in convergingpolarized eye, and ference-fig light,with the result of showing (under proper conditions)the axial inter(Arts..389 and 407) "

.

Tourmaline

Tongs

forms of polariscopes The common Polariscope. Conoscope. in 550.* 549 and Fig.549 represents Figs. employing nicol prisms are shown is called a conoscope. often which the instrument arrangedfor converginglight, the light,which after the mirror S, reflecting The essential parts are It is then rendered the is prism lens by the p. e polarized passingthrough stronglyconverging by the system of lenses nn, before passingthrough the section under examination placedon a plateat k. This plate can be revolved 354.

"

*

These

figuresare

taken from

the catalogueof Fuess.

244

PHYSICAL

MINERALOGY

The upper tube angledesired,measured on its circumference. and the the lens t, contains the converging system oo, analyzingprism q. nor The arrangements for loweringor raisingthe tubes need no explanation,

through any

649

Conoscope

550

Polariscope

indeed the specialdevices for settingthe vibration-planes of the nicols at

rightanglesto each other. The accompanying tube (Fig.550) shows the arrangement for observations in parallel the converginglenses having been removed. light,

CHARACTERS

DEPENDING

UPON

LIGHT

245

Fig.551 represents in cross-section a simple,inexpensive but quiteefficient of polariscope.The polarizing device,P, is in the form of two or three thin glass sheets,the back of the bottom 561 These one being blackened. glass plates set at the appropriateangle to secure are the of polarization amount maximum of the lightreflected from them up through the opening in the stage K. M represents an of which lightis adjustablemirror by means P. reflected upon The analyzer,A, is a small nicol prism which is held over the in the of the ard standopening stage by means form

S.

series of lenses may double be placed upon the stage of the instrument and convert it into a conoscope. so 355. Polarization -Microscope. The form and investigation of the optical propertiesof minerals when in microscopic form has been much facilitated by the * of use microscopes speciallyadapted for this purpose. First arrangedwith reference to the special in study of minerals as seen thin sections of rocks,they have now been so elaborated as largely to take the placeof the older opticalinstruments. They not only allow of the determination of the optical Polariscope(| natural size) of with minerals properties greater facility, in hand are far too small but are where the crystals cases applicableto many for other means. A highly serviceable microscope is the Laboratory Model made by the and Lomb Bausch OpticalCo., and illustrated in Fig. 552. The essential arrangements of this instrument are as follows: The eyepieceat A, which is removable, contains the cross-hairs with an eye lens adjustablefor focusing lens that slides in and out of the tube, with them. At B is a Bertrand upon it. At C isthe analyzer box which slides above iris an diaphragm immediately be revolved through a quarter in and out of the body tube. This prism may D is a slot in the microscope tube with a dust-proofshutter for the turn. At E is such as the quartz wedge, etc. introduction of various accessories, which work at right be centered by the two screws the nosepiecewhich can F is held in placeby a spring angles in the N and E positions.The objective The stage, G, revolves and carries a scale clamp and is quicklydetached. vernier permittingthe readingof angles attached the into graduated degrees, phragm at The to one-tenth substage H carries condensinglenses,irisdiadegree. and downward It moved be and the polarizing upward can prism. A

"

to one screw-head and when at its lowest point can be sprung has both and / is a adjustable side,out of the opticalaxis. The mirror at while at is J, surface. The coarse focusingadjustment plane and concave of which a vertical the milled head at K providesa fine adjustment by means be read. of 0'0005 mm. movement can

by

*

of

means

For

Manual

a

of the detailed descriptions of

PetrographicMethods;

microscope and polarizing Wright,

The

Methods

of

Johannsen, Petrographic Research; etc.

its accessories see

246

PHYSICAL

The

356. in

Research

Fig.

553.

MINERALOGY

trated and Lomb of the Bausch microscope is illusModel described after one instrument is by This patterned 553

552

PetrographicalMicroscope (Research Model, Bausch and

PetrographicalMicroscope (Laboratory Model, Bausch and Lomb, | actual size)

Lomb

j

actual size)

The detailed account. Wright to whose papers reference is made for a more follows : summarized as outstandingfeatures of the instrument may be briefly It has a largebody-tube within which are always contained the analyzerand the Bertrand lens, both when scope. they liein or outside the opticalaxis of the microThe bar be connected the and two nicols may of upright by means the measurement rotated simultaneously 90". This enables through an arc of of extinction angles,etc.,to be made without the necessityof revolvingthe in keepingthe mineral grainunder observation stage and the consequent difficulty exactly centered in the field. This bar carries verniers that lie against the scale engraved upon the stage so that the angle of rotation of the nicols be accurately measured. The can polarizing prism can be entirelyremoved from the opticalaxis. A revolvable carrier for to the irisdiaphragm mount of the substage. GENERAL 357.

There

OPTICAL

CHARACTERS

a

sensitive plate is attached

OF

MINERALS

characteristics belonging to all minerals alike, in their relation to light. These are: non-crystallized, 1. DIAPHANEITY: depending on the relative quantityof lighttransmitted.

and crystallized

are

certain

248

MINERALOGY

PHYSICAL

discussed later. Here belong dichroism or pleochroism, the property exhibitingdifferent colors in different crystallographic directions by transmitted light. This subjectis explainedfurther in Arts. which crystallization,

are

of

396 and 411. The followingeight colors were selected by 302. Varieties of Color. Werner as fundamental, to facilitate the employment of this character in of minerals: the description white, gray, black,blue,green, yellow,red,and brown. "

COLORS recognized are as follows: (a) The varieties of METALLIC 2. Bronze-yellow: pyrrhotite. 3. Brass-yellow: Copper-red: native copper. less distinct chalcopyrite. 4. Gold-yellow:native gold. 5. Silver-while: native silver, in arsenopyrite. 6. Tin-white: mercury; 7. Lead-gray:galena,molybdenite. cobaltite. 8. Steel-gray: nearly the color of fine-grainedsteel on a recent fracture; native platinum, and palladium. COLORS: (6) The followingare the varieties of NON-METALLIC A. WHITE. 1. Snow-white: Carrara marble. 2. Reddish white,3. Yellowish white and 4. Grayish white: all illustrated by some varieties of calcite and quartz. 5. Greenish white: talc. 6. Milk white: white,slightlybluish; some chalcedony. B. GRAY. 1. Bluish gray: 2. Pearl-gray:gray, mixed to dirtyblue. gray, inclining with red and blue; cerargyrite. 3. Smoke-gray: gray, with some brown; flint. 4. Greenish gray: gray, with some varieties of talc. 5. Yellowish cat's-eye;some green; varieties of compact limestone. 6. Ash-gray: the purest gray color; zoisite. gray: some C. BLACK. 1. Grayish black: black, mixed with gray (without green, brown, or blue 2. Velvet-black: pure tints);basalt; Lydian stone. black; obsidian,black tourmaline. black: 3. Greenish black: brown augite. 4. Brownish coal, lignite. 5. Bluish 1.

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

'

"

"

"

black cobalt. 1. Blackish blue: dark varieties of azurite. 2. Azure-blue: a clear shade p. BLUE. of brightblue; pale varieties of azurite, 3. Violet-blue: blue, bright varieties of lazulite. mixed with red; amethyst, fluorite. 4. Lavender-blue: red and much blue,with some 5. Prussian-blue, Berlin blue: pure blue; sapphire,cyanite. or 6. Smalt-blue: gray. varieties of gypsum. 7. Indigo-blue:blue,with black and green; some blue tourmaline. 8. Sky-blue: pale blue, with a littlegreen; it is called mountain-blue by painters. E. GREEN. 1. Verdigris-green: to blue; some feldspar(amazon-stone). green, inclining 2. Celandine-green: varieties of talc and beryl. It is green, with blue and gray; some the color of the leaves of the celandine. 3. Mountain-green: green, with much blue; beryl. 4. Leek-green:green, with some brown; the color of leaves of garlic;distinctly in prase, a variety of quartz. seen 5. Emerald-green: pure deep green; emerald. 6-. Apple-green: light green with some yellow; chrysoprase. 7. Grass-green: bright yellow; green diallage. 8. Pistachio-green: green, with more yellowishgreen, with some brown; epidote. 9. Asparagus-green: pale green, with much yellow; asparagus stone (apatite). 10. Blackish green: serpentine. 11. Olive-green:dark green, with much brown and yellow; chrysolite. 12. Oil-green:the color of olive-oil; beryl,pitchstone. 13. Siskin-green: lightgreen, much incliningto yellow; uranite. F. YELLOW. 1.. Sulphur-yellow: sulphur. 2. Straw-yellow:pale yellow; topaz. 3. Wax-yellow: grayish yellow with some brown; sphalerite,opal. 4. Honey-yellow: red and yellow, with some brown; calcite. 5. Lemon-yellow: sulphur, orpiment. 6. Ocher-yellow:yellow,with brown; yellow pcher. 7. Wine-yellow: topaz and fluorite. 8. Cream-yellow: varieties of kaolinite. some 9. Orange-yellow:orpiment. G. RED. 1. Aurora-red: red, with much yellow; some realgar. 2. Hyacinth-red: black:

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

red,with yellow and

brown; hyacinth garnet.

3.

Brick-red:

some polyhalite,

per. jasdark 5. Blood-red: tinge of yellow; cinnabar. some 6. Flesh-red: feldspar. 7. Carmine-red: yellow; pyrope. red; pure ruby sapphire. 8. Rose-red: rose quartz. 9. Crimson-red: 10. Peachblossomruby. red: red,with white and gray; lepidolite. 11. Columbine-red: deep red,with some blue; 12. Cherry-red: dark red, with some garnet. blue and brown; spinel,some jasper. 13. Brownish-red: jasper,limonite. H. BROWN. 1. Reddish brown: 2. Clove-brown: garnet, zircon. brown, with red and some 3. Hair-brown: blue; axinite. 4. Broccoli-brown: wood-opal. brown, with blue, red, and gray; zircon. 5. Chestnut-brown: brown: brown. 6. Yellowish pure 7. Pinchbeck-brown: jasper. yellowishbrown, with a metallic or metallic-pearly luster; several varieties of talc,bronzite. 8. Wood-brown: color of old wood nearly rotten; some 4. red, with "

some

Scarlet-red: brightred, with

"

a

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

CHARACTERS

DEPENDING

UPON

specimens

of asbestus9. Liver-brown: brown, with Blackish brown: bituminous coal,brown coal.

10.

3.

363.

some

249

LIGHT

gray

and

green;

jasper. -

LUSTER

Nature of Luster. The luster of minerals varies with the nature surfaces- A variation in the quantity of lightreflected produces 5different degreesof intensity of luster;a variation in the nature of the reflecting surface produces different kinds of luster. 364. Kinds of Luster. The kinds of luster recognized are as follows: 1. METALLIC: the luster of the metals, as of gold, copper, iron,tin. In general,a mineral is not said to have metallic luster unless it is opaque the mmeralogical in that it transmits is, no sense, lighton the edges of thin splinters.Some minerals have varieties with metallic and others with nonmetallic luster;this is true of hematite. Imperfect metallic luster is expressed by the term sub-metallic, trated as illusby columbite,wolframite. Other kinds of luster are described briefly "

1*

"

as

NON-METALLIC. 2. NON-METALLIC.

also

A.

Adamantine:

the luster of the diamond.

When

it is termed sub-metallic,

as metallic-adamantine, cerussite, pyrargyrite. Adamantine luster belongs to substances of high refractive index. This be connected with their relatively may with great density(and hardness),as the diamond, also corundum, etc. or because they contain ; heavy molecules, thus most compounds of lead,not metallic in luster, have a high refractive

index and an adamantine luster. B. Vitreous: the luster of broken glass. An imperfectly vitreous luster is termed sub-vitreous. The vitreous and sub-vitreous lusters are the most in the mineral kingdom. Quartz possesses the former in an eminent common often degree; calcite, C.

Resinous:

the latter. luster of the yellow resins, as

yellow varieties opal,and some sphalerite. D. Greasy: luster of oilyglass. This is near resinous luster, but is often quitedistinct, as nephelite. E. Pearly: like pearl,as talc,brucite, etc. When united with stilbite, in hypersthene,the term used. as is sub-metallic, metallic-pearly Pearly luster belongsto the lightreflected from a pileof thin glass-plates; it is exhibited by minerals, similarly be which,having a perfectcleavage, may the basal plane of apophyllite. partially separated into successive plates, as on It is also shown for a like reason by foliated minerals,as talc and brucite. F. Silky: like silk;it is the result of a fibrous structure. Ex. fibrous calcite, of

fibrous gypsum. different degreesand kinds of luster are often exhibited differently by unlike faces of the same crystal,but always similarlyby like faces. For has a pearlyluster wanting in the prisexample,the basal plane of apophyllite matic faces,which have a vitreous luster. The

by Haidinger,only vitreous,adamantine,and metallic luster belongto faces In the first, the refractive index of the mineral is I'S-l'S; and pure. in the second, l'9-2'5;in the third,about 2'5. metallic and The true difference between vitreous luster is due to the effect which the different surfaces have upon the reflected light; in general,the luster is produced by the union of two simultaneous impressionsmade upon the eye. If the lightreflected from a metallic surface be examined by a nicol prism (orthe dichroscopeof Haidinger, Art. 393), it will be found that both rays, that vibratingin the plane of incidence and that whose vibrations are normal to it,are alike,each having the As shown

smooth perfectly

250

MINERALOGY

PHYSICAL

little in brilliancy;on the contrary, of the light a color of the material,only differing vibrations are at rightangles to the reflected by a vitreous substance,those rays whose while those whose vibrations a nd less are colorless, of incidence or are more polarized, plane and suffered some into the medium tion, absorpin this plane,having penetratedsomewhat are will show show the color of the substance itself. A plate of red glassthus examined luster occupiesa positionbetween the others. Adamantine a red image. a colorless and

365. as

1.

Degrees of Luster.

"

The

degreesof intensityof luster

fied classi-

follows:

and givingwell-defined images,as with brilliancy Splendent:reflecting

hematite,cassiterite. but not 2. Shining: producingan image by reflection, celestite. 3.

are

one

as well-defined,

"

Glistening:affordinga generalreflection from

the

surface,but

no

image,as talc,chalcopyrite. and apparentlyfrom points 4. Glimmering: affording imperfectreflection, the surface, as flint, chalcedony. over as A mineral is said to be dull when there is a total absence of luster, chalk, the

ochers,kaolin.

The term play of prismaticcolors in rapid to the property belongsin perfection is observed is to It also in its which it due high dispersive power. diamond, of interference; in this in precious opal,where it is explainedon the principle is most brilliant it case by candle-light. color appears The expression change of colorsis used when each particular than in the play of colors and the succession proto pervade a largerspace duced as by turningthe mineral is less rapid. This is shown in labradorite, explainedunder that species. is a milky or pearlyreflectionfrom the interior of a specimen. Opalescence Observed in some opal,and in cat's-eye. Iridescence means the exhibition of prismaticcolors in the interior or on The phenomena of the play of colors, the surface of a mineral. iridescence, sometimes to be explainedby the presence of minute foreign crystals, etc.,are in parallel more positions; generally, however,they are caused by the presence in the lightreflected from which interference takes of fine cleavage-lamellae, place,analogousto the well-known Newton's rings(seeArt. 336). 366.

Play

of Colors.

Opalescence.

colors is used to describe the appearance This succession on turningthe mineral.

367. Tarnish. from that obtained

Iridescence.

"

of several

metallic surface is tarnished when its color differs is the case with specimensof bornite. A surface possesses the steeltarnish when it presents the superficial blue color of columbite. fixed when The tarnish is it exhibits a s irised tempered steel, is with the hematite of Elba. These tarnish and common prismaticcolors,as iris colors of minerals are owing to a thin surface or film,proceedingfrom different sources, either from a change in the surface of the mineral or from foreignincrustation; hydrated iron oxide is one of the most common sources of it and produces the colors on anthracite and hematite. 368. Asterism. This name is given to the peculiarstar-like rays of minerals. This is seen by reflected lightobserved in certain directions in some lightin the form of a six-rayedstar in sapphire,and is also well shown by transmitted light(asof a small flame)with the phlogopitemica from South In the former case it is explainedby the presence of thin Burgess,Canada. twinning-lamellse symmetricallyarranged. In the other case it is due to the of minute inclosed crystals, also symmetricallyarranged,which are presence probably rutile or tourmaline in most cases. Crystallinefaces which have A

"

as by fracture,

"

CHARACTERS

DEPENDING

UPON

251

LIGHT

been artificially etched also sometimes exhibit asterism. The peculiar lightobserved in reflected lighton the faces of figuressometimes crystals either natural or etched,are of similar nature. 369.

Schillerization. The general term schilleris appliedto the liar pecusometimes luster, observed in definite directions in certain nearlymetallic, minerals,as conspicuouslyin schiller-spar (an altered varietyof bronzite) also in diallage, hypersthene, sunstone, and others. It is explainedby the reflection either from minute inclosed platesin parallelpositionor from the surfaces of minute cavities (negativecrystals) having a common orientation In many it is due to alteration which has cases these bodies (or developed the cavities) in the direction of solution-planes (seeArt. 285). The process by which it has been produced is then called schillerization. "

370. Fluorescence. The emission of lightfrom within a substance while it is being exposed to direct radiation, or in certain cases to an electrical dischargein a vacuum tube, is called fluorescence.It is best exhibited by from which the phenomenon gained its name. fluorite, Thus, if a beam of white lightbe passed through a cube of colorlessfluoritea delicate violet color is called out in its path. This effect is due to the action of the ultrachiefly violet rays, and is connected with a change of refrangibility in the transmitted "

light. The electricaldischargefrom the negativepole of a vacuum tube calls out brilliantfluorescence not only with the diamond, the ruby, and many gems, but also with calcite and other minerals. Such substances may continue to emit light, after the dischargeceases. or phosphoresce, 371. Phosphorescence. The continued emission of lightby a substance a

"

after heating, (notincandescent) produced especially to light exposure to an electricaldischarge, or is called phosphorescence. Fluorite becomes highly phosphorescentafter being heated to about 150" C. Different varieties give off lightof different colors;the chlorophane variety,an emerald-greenlight;others purple,blue,and reddish tints. This phosphorescencemay be observed in a dark placeby subjecting the pulverized mineral to a heat below redness. It may even be produced by a sharp blow with a hammer. Some varieties of white limestone or marble, after slight emit also tremolite, a yellowlight; heating, so danburite,and other species. The X-ray and ultra-violet light will produce phosphorescence in willemite, diamonds. The fact that willemite glows when exposed to kunzite,and some ultra-violet lightis made of in testing the residues from a willemite ore to use certain the separationhas been complete. Radium make emanations cause certain minerals to phosphoresce, as willemite and wurtzite. Exposure to the lightof the sun produces very apparent phosphorescence with many to be destitute of this power. diamonds, but some specimensseem This property is most striking after exposure to the blue rays of the spectrum, while in the red rays it is rapidlylost. A mixture of calcium sulphideand bismuth will phosphorescefor a considerable periodafter being exposed to sunlight.

SPECIAL

CHARACTERS

OPTICAL OF

THE

DIFFERENT

BELONGING

TO

CRYSTALS

SYSTEMS

be grouped into three grand classes, minerals may 372. All crystallized as well as their geometriwhich are distinguished by their physicalproperties, cal form. These three classes are as follows:

252

MINERALOGY

PHYSICAL

class, embracing crystalsof the isometric system, which are equal rectangularaxes. of the tetragonaland hexagonal Isodiametric B. class,embracing crystals and a third,or fourth, horizontal axes systems.,referred to two, or three,equal their them to at rightangles axis unequal to plane. Crystalsof this class have of axis crystallographic a fixed principal symmetry. C. Anisometric class,embracing the crystalsof the orthorhombic,monoand triclinicsystems, referred to three unequal axes. Crystalsof this clinic, class are without a fixed axis of crystallographic symmetry. the ISOMETBIC 373. IsotropicCrystals. Of the three classes, CLASS ing includes all crystals which, with respect to lightand related phenomena involvthe ether,are isotropic equal turning) (from the Greek, signifying ; that is, in alldirections. Their distinguishing those which have like optical properties characteristic is that lighttravels through them with equal velocityin all directions, provided their molecular equilibriumis not disturbed by external internal strain. If it be imagined therefore that lightstarts from or pressure at a given moment medium of time the resulting a point within an isotropic surface will be a sphere. wave It must be emphasized here,however, that such a crystalis not isotropic with reference to those characters which depend directly the molecular upon Art. structure alone,as cohesion and elasticity. (See 275.) Further, amorphous bodies,as glassand opal, which are destitute of any that is, those in which all directions are sensiorientated molecular structure bly and not with the same also reference to are isotropic, only light,but also as regardstheir strictly molecular properties. 374. AnisotropicCrystals; Uniaxial and Biaxal. Crystalsof the ISOand ANISOMETRIC the other hand, are in distinction DIAMETRIC on CLASSES, anisotropic(from the Greek,signifying unequal turning) Their opticalproperties in generalunlike in different directions, are the particularly, or, more velocitywith which lightis propagated varies with the direction. of the isodiametric class that variable property of the Further,in crystals which the velocityof propagationdepends remains constant light-ether upon for all directions which are normal to, or, again,for all those equallyinclined axis. In the direction of this axis there is no to, the vertical crystallographic double refraction; it is hence called the opticaxis, and the crystalsof this Isometric referred to three A.

"

"

"

"

.

class are

said to be uniaxial.

Crystalsof the third or anisometric class have more tions complex opticalrelab ut in it stated be that in requiring them special explanation, general may there are always two directions analogousin character to the singleopticaxis said to be optically spoken of above; hence,these crystals are biaxial. A.

ISOMETRIC

CRYSTALS

375.

It has been stated that crystalsof the isometric system are optically and hence lighttravels with the same isotropic, velocityin every direction in them. s uffer Light can, therefore, only singlerefraction in passinginto an in other isotropicmedium; or, words, there can be but one value of the refractive index for a given wave-length. If this be represented by n, while V is the velocityof lightin air and v that in the given medium, then V n

=

V

"

,

v

or

v

=

"

n

"

CHARACTERS

The

wave-front

UPON

LIGHT

253

for

light-wavespropagated from any point within such an alreadystated,a sphere. The sphere,therefore, is, may taken to represent the opticalpropertiesof an medium. tions Secisotropic of a sphere normal to any diameter will always be circles. These circular

isotropicmedium be

DEPENDING

as

with like radii in all directions correspond to the fact that the character of an isotropic optical substance is the same in all directions normal to the line of lightpropagation. Or, in other words, lightvibrations may take place in any direction normal to the direction of the sections

transmission; i.e.,

lightis

not

polarized. Further

its velocityremains uniform no matter what be the direction of its vibration. may This statement holds true of allthe classes of isometric crystals. In other words, a crystal of maximum and one symmetry, as fluorite, having the restricted symmetry characteristic of the tetrahedral or pyritohedral divisions, have alike the same character. Two of the classes, isotropic however,namely, the plagiohedral and the tetartohedral classes, differ in this particular: that crystalsbelongingto them may exhibit what has alreadybeen defined (Art. 350) as circular polarization. 376. of Sections of Isometric Crystalsin Polarized Light. Behavior "

In

of their

isotropiccharacter,isometric crystalsexhibit no consequence specialphenomena in polarizedlight. As a section of an isotropic substance (isometriccrystalor some amorphous material) has no polarizing or doubly effect upon refracting lightit does not change at all the character of lightthat enters it from the polarizer of a polariscope.Therefore thin sections of isotropic media when examined in a polariscope or polarizingmicroscopewith the nicols crossed will appear dark in all positions.In other words, they are always extinguished. Further, when a colored mineral is examined without the analyzerthere will be no change in its color when the section is revolved with the stage of the microscope. Some anomalies are mentioned on a later page, (Art.429). The singlerefractive index

by

means

of

a

of

substance may be determined an isotropic prism (seeArt. 327) with its edge cut in any direction whatever. B.

UNI

General

AXIAL

CRYSTALS

OpticalRelations

and opticalrelations of crystals The crystallographic belongingto have and of the hexagonal systems already been briefly tetragonal crystals remains their to it summarized now opticalcharacters develop (Art.374); This be done most can more simply by making frequentuse of the fully. to representthe character and motion of the familiar conceptionof a light-ray

377.

light-wave. 378.

Behavior

axial mineral

is in

of Light in Uniaxial Minerals. Light enteringa uniin planes generalbroken up into two rays which are polarized "

travel with different velocities and to each other and which perpendicular therefore have different indices of refraction. One of the two rays derived from a single incident ray always vibrates in the planeof the horizontal crystallographic The other ray vibrates at rightangles to the first and axes. axis. always in a vertical plane that includes the vertical crystallographic all directions is for uniform mineral of The opticalcharacter lying a uniaxial tions in the horizontal crystallographic plane and therefore the ray whose vibrawhat its direction lie in this plane will have uniform velocityno matter

254

MINERALOGY

PHYSICAL

index of This ray will therefore have a singleand constant usual follows the law this Since ray refraction,commonly designatedby co. and tion refracincidence of sines of the ratio between the angles as to the constant it is called the ordinary ray. and in generalbehaves in an ordinary way The ray which vibrates in a plane that includes the vertical crystallographic of transmission.

tion the direction of its vibration constantlychanging as the direcof its path through the crystalchanges and its velocitywill correspondingly direction the index of Its will therefore refraction depend upon vary. This of its propagation and it will not in generalobey the usual sine law. the is therefore called extraordinary ray. ray When light travels in a uniaxial mineral in a direction parallelto the axis will have

vertical crystallographic axis,since all its vibrations must take place in the horizontal plane,it behaves wholly as the ordinaryray with a singlevelocity be no double refraction of light, There can and refractive index. therefore, in the this case mineral will behave like an isotropic along this direction and This direction of no double refraction, coincident with the versubstance. tical tion crystalaxis,isknown as the opticaxis and as there is only one such directhe direcin this opticalgroup As soon tion the latter is called uniaxial. as of transmission becomes inclined to the vertical crystalaxis the lightis doubly refracted and as the inclination increases the direction of vibration of from the lightof the extraordinaryray departs more the plane of and more vibration of the ordinaryray with a correspondingchange in its velocityand refractive index. The difference between the refractive indices of the two when becomes maximum the a lightpasses through the mineral in a rays horizontal direction with the direction of vibration of the extraordinaryray to the vertical crystalaxis words or in other parallel as divergentas possible horizontal from the ordinary plane. The value of the refractive index of the extraat its maximum difference from the constant index of the ray when ordinaryray is the one always quoted and is indicated by"e. These two indices, and e, are called the principalindices of a uniaxial crystal. A principal w section of a uniaxial crystalis a section passingthrough the vertical axis. 379. Positive and Negative Crystals. Uniaxial crystals divided into are two classes, depending upon whether the velocityof the extraordinaryray is greater or less than that of the ordinary ray. Those in which the refractive index of the ordinary ray, co, is less than that of the extraordinaryray, e (co" e),are called positive. This is illustrated by quartz for which (foryellow sodium light) : "

"

co

On the other Calcite is an

1-553.

=

e

hand, if e is less than co (e " co), the crystalis said example for which (forsodium light) co

Other

T544.

=

=

T658.

e

=

to be

negative*

1-486.

examples are given later (Art.383)

.

380.

Determination

of the

Refractive Indices in Uniaxial Crystals. indices of refraction of uniaxial minerals are measured in much the same

The

*

It will assist in

positive and each

case.

remembering

negative agrees

with

"

these relations to note that the firstvowel in the words the symbol used fo* the smaller index of refraction in

256

by

MINERALOGY

PHYSICAL

whose ellipse

an

to the above

proportional (OC, OA, Figs.554, 555) are respectively

axes

values. 555

554

c

00:OA=-

The wave-front of the extraordinaryray is then a spheroid,or an ellipsoid axis, axis coincides with the vertical crystallographic whose revolution of that it obvious is axis vertical of the In direction the axis. that is,the optic coincide. will the wave-fronts of the ordinaryand extraordinary rays waveFigures 556 and 557 represent vertical sections of the combined 557

666

Negative

Positive crystal,ox:

crystal,

e.

surfaces for both "rays. Fig. 556 givesthat for a negativecrystallike calcite surface of the extraordinaryray being outside wave (e " "o),the ellipsoidal the

sphericalsurface

of the

ordinary ray;

Fig. 557

that

of

a

e) with

positivecrystal

the ellipsoidal like quartz (co" surface within that of the is an Fig.558 attempt to show the relations of the two wave-fronts of The constant value crystalin perspectivefor a singleoctant.

velocityof the ordinary ray (

-

\

whatever

its direction in the

sphere. a

tive nega-

of the

plane of Figs.

556 and 557, is expressedby the radius of the circle (= OC). On the other hand, the velocityof the extraordinaryray in the horizontal direction is given

by OA

(-1 while

in any

obliquedirection, as Osr,Fig.556 (Ors,Fig.557),it is

CHARACTERS

DEPENDING

UPON

257

LIGHT

558

expressed by the lengthof this line, becoming (

OC

-

J

as

its direction

and

more

more

nearlyequal to

approaches that of the vertical axis.

382.

Uniaxial Indicatrix. The opticalstructure of a uniaxial crystal be represented by an ellipsoid of revolution,called the Indicatrix* from which can be obtained the directions of vibration and indices of refraction of the ordinary and extraordinaryrays derived from any singleincident ray. for an optically section of such an ellipsoid Fig.559 representsa principal tive negacrystalthe line C-C being its axis of revolution. The axes of this ellipsoid made are inverselyproportionalto the indices of refraction of the two rays, co and e, as follows : "

can

,

OC

:

OA

=

:

-

or

-

6

CO.

6

CO

659

sion figurelet Or be a direction of transmisof light. Let Vr and VR be tangents to the elliptical surface at the pointsr and R and OR be a radius vector parallelto the tangent

In this

known then what are the From geometrical ellipseit follows that the propertiesof an of any area parallelogram with conjugate in Fig. radii forming two sides,such as ORVr of the to is constant and a pararea equal 559, allelogram sides. two OA OC and as having line be perpendicular to the extended Let RN Then the area will be equal to Or. of ORVr OA'OC a constant, RN'Or. It follows since RN'Or k OA'OC J^ Vr.

Or

and

OR

form

conjugate radii.

as

=

=

.

(Jr

_ "

"

T-.IT

RN *

The

London,

Optical Indicatrix and 1892.

T-k-"r

RN'

"

~

k, that

.

also

the Transmission

of Light in Crystals,by L.

Fletcher,

258

MINERALOGY

PHYSICAL

From

the last expression see we in other words, other, or,

that OA

and

OC

are

to inverselyproportional

index, OA will as each representsthe minimum be for maximum will the which of the correspondingvelocity light represent and Or RN In in the are same direction the transmission way crystal. any the velocity to each other,the distance Or representing inverselyproportional RN while will direction that represent of the extraordinaryray traveling along will also give the direction of vibration of The line RN its refractive index. the

OC

extraordinaryray.

direction perpendicOr there will be another possible ular This will be a line from 0 surface. to the ellipsoidal This line will section representedin Fig.559. to the principal perpendicular with its length lie in the horizontal circular section of the indicatrix ellipsoid to the index of the ordinaryray, co. equal to OA which in turn is proportional such as Or, the two lines that So for a given direction of transmission of light, normal it and at time the to the surface of the to same are perpendicular indicatrix yieldboth the indices of refraction of the two rays and the directions of their vibrations. axis of the indicato the principal trix, If,however, the lightis passingparallel be infinite will number there of lines which an are C-C, Fig. 559, i.e., to this direction and at the same time normal to the surface of perpendicular the indicatrix. These will lie in the horizontal circular section of the ellipsoid and consequentlywill be of a uniform length. From this it is evident vibrate in any transverse direction and will that such a transmitted ray may index of refraction and velocity. Along this direction, known possess a single there will consequentlybe no double refraction of the light. as the opticaxis, For the radius vector to it and

also normal

Examples of Positive and Negative Crystals. The followinglists give prominent with the values of the refractive indices, positiveand negative uniaxial crystals, co and light.* The difference between these,o" e, for each,correspondingto yellow sodium or the birefringenceor strengthof the double refraction. e co, is also given; this measures be remarked It may that in some varieties have been observed. speciesboth + and Certain crystalsof apophylliteare positivefor one end of the spectrum and negative for the other, and consequently for some color between the two extremes it has no double refraction. The is true for some other species (e.g., same chabazite)of weak double 383.

"

"

"

"

refraction. NEGATIVE

CRYSTALS CO

Proustite.

2 '979

.

2711 1-486

0-268 0-172

1'620 1-760

0-018 0-008

1-578

0'006

1715

0-005 0-004

1-538 1-631

POSITIVE

*

From

CRYSTALS

tables by E. S. Larsen.

0-003

"

e

CHARACTERS

Examination

DEPENDING

UPON

259

LIGHT

in Polarized Light of Uniaxial Crystals

384.

to the Axis in Parallel Polarized Section Normal pose Light. Supsection of a uniaxial crystalto be cut perpendicularto the vertical axis. It has alreadybeen shown that lightpassingthrough crystallographic in this direction suffers no double refraction; the crystal such a consequently, section examined in parallel polarized lightbehaves as a section of an isotropic If the nicols are crossed it appears dark, or extinguished, substance. and remains when revolved. so 385. A section cut parallel Section Parallel to the Axis. cal to the vertihas two directions of lightvibration,one parallel axis,as alreadyexplained,, to this axis,that of the extraordinary ray, and the other at rightanglesto it, that of the ordinary ray. A ray of lightfalling such a section with upon dinary, perpendicularincidence is divided into the two rays, ordinaryand extraorbut one of them which travel on in the same path through the crystal, in polarto the other. retarded relatively When such a section is examined ized its when lightwith crossed nicols it will appear dark, or be extinguished, vibration directions lie parallelto the vibration directions of the nicols. Assume that the section abed, Fig.560, lieswith the direction of its vertical axis parallel to P-P, which representsthe vibration direction crystallographic of the polarizer.The lightenteringthe section under these conditions will and will therefore pass be vibratingparallel to the vertical axis of the crystal into the mineral wholly as the extraordinaryray, there being no vibration "

a

"

possiblein ray.

of the The

the

tion direc560

ordinary lightwill,

leave the section with the same direction of vibration it entered and as when lost by will be entirely reflection in the analyzer. If the section is turned at an angle of 90",as aWd', Fig. 560, similar conditions

therefore,

although in this case the lightwill vibrate in the section as the prevail, during Therefore in such a section there will be four positions ordinaryray. it when o r the of microscope the polariscope its complete revolution on stage will be extinguished. light abed in Fig. 561, it will appear as If the section stand obliquely, have P-P that to vibrations the for parallel to the eye (and usuallycolored), tion resolution a component in the direchave upon passedthrough the polarizer these of each section. the of Again, of each of the vibration-planes of of the direction vibration-plane the components can be resolved along the both from the analyzer, will emerge A- A. Therefore,two rays upper nicol, reference with retarded less but or having the same vibration-plane, one more and with the birefringence of retardation increasing to the other,the amount will these interfere, therefore, rays the thickness of the section. In general, not too great)it will and if the thickness of the section is sufficient (and colored in white lightand, supposingthe thickness uniform, of the appear same

color

throughout.

260

PHYSICAL

MINERALOGY

the vibration directions of a section When Parallel Extinction. and coincide with those of the polarizer assuming them to be crossed, analyzer, in the be the section appears dark and it is said to positionof extinction. If a axis or axial plane is -parallel to when its crystallographic section extinguishes extinction. of the planesof vibration of the nicols it is said to show parallel one the crystallographic exists between If,on the other hand, no such parallelism directions and the directions of vibration in the mineral the section is said to 386.

"

show

inclined extinction. of uniaxial minerals,since the vibration directions always lie case axial plane,all sections of such minerals will show in some crystallographic e xtinction. parallel In the

387.

Determination

of the

Relative

Character

of the

Extinction

tions Direc-

The relative characters of the exof a Given Uniaxial tinction directions of a section of a uniaxial mineral are to be determined by described in Art. the use of the quartz wedge or the sensitive tint as If the orientation of the section is known that it can be told which of so 348. dinary the directions of vibration belongsto the ordinaryand which to the extraorof the the mineral character be determined. can o r negative positive ray if the ordinaryray is proved to be the faster of the two (i.e., the For instance, X direction)it follows that its index is the smaller,i.e.,co " e, and the mineral is positive. 388. Interference Colors of Uniaxial Minerals. Birefringence. The interference color of any section of a uniaxial mineral depends upon the following: first upon the thickness of the section, second upon the strengthof the double refraction of the mineral,i.e., its birefringence, this beingmeasured tion, by the difference between the indices of refraction of the two rays in the secand third upon the crystallographic orientation of the section. A section to the basal planeshows no double refraction and therefore cannot cut parallel exhibit any interference color. The strengthof the birefringence, the other conditions remaining uniform,increases as the inclination of the section to the basal plane increases. The highestbirefringence of a given mineral is therefore shown by its prismaticsections. The following table * givesthe thickness (inmillimeters) of sections of a few uniaxial crystals which yieldred of the firstorder: Mineral.

"

"

Birefringence (03 e) or (e o") "

Rutile Calcite Zircon Tourmaline

"

Thickness in Millimeters

0-287

0'0019

0172

0'0032

0'062

0*0089

0'023

0'0240

Quartz Nephelite

0'009

0*0612

0*004

01377

Leucite

0*001

0*5510

example, it may be noted that with zircon (e co Again, ness 0*062),a thickof about 0'009 mm. givesred of the firstorder; of 0'017 red of the second order: of 0*026 red of the third order. The methods ordinarilyused to determine the birefringence of a section (not J_ c axis) of a uniaxial crystal, also to fix the relative value of its two vibration-directions, as have already been discussed,see Arts. 347 and 348. as

389.

Minerals. *

another

"

=

Effects of Convergent Polarized Light upon Sections of Uniaxial Uniaxial Interference Figures. When certain sections of uni-

See further,Rosenbusch

"

(Mikr. Phys. Min., 1904,p. 292),from whom

these

are

taken.

CHARACTERS

are

as

UPON

261

LIGHT

in convergent polarizedlightthey show what isobtained interference figures. A symmetricalinterference figure

axial minerals known

DEPENDING

observed

are

in uniaxial minerals

by allowingconvergingpolarizedlightto

pass

through a

section of the crystal. Parallel polarizedlightenteringsuch a section would suffer no double refraction and consequentlygive no interference. To the parallel from the polarizerinto conconvert vergent polarizedlightthat comes lens is the a nd the between section. Under a polarizer light placed these conditions a sharply convergingcone of lightrays enters the section. the section to change these obliquerays back lens is placed above Another postion. Such an instrument is known as a conoscope again into a parallel and and may be obtained by placinga pair of lenses between the polarizer the polarizing microscopeis used,the small analyzerof a polariscope, or, in case is swung into position by a lever converginglens that lies above the polarizer lens is introduced the Bertrand and at the same time a small lens known as basal

into the microscopetube. such conditions Under 562

the

lightenteringthe section is composed of a and convergingsystem of rays polarized in the 562. vibrating plane P-P, Fig. Let B-B (Fig.562, A) be a vertical section section of the mineral along the line B-B, Fig. 562, B. Consider any ray, as a, enteringthe the enters section. Since the ray section obliquely it will be doubly the and refracted into e. o rays cross

a

563

calcite the extraordinaryray (calcite being as mineral being taken negative)will have the greater velocityand be least refracted. As the lightenters the section in the form of a cone the traces of the two rays as they from the section will be circles, Fig.562, B. Now consider in a similar emerge the action of the two rays a and b or a' and V (Fig.563) upon each other. case into the rays e Ray a on enteringthe section is doubly refracted and polarized the the section at r. from e and points considered as emerging and o which are and refracted is polarized.Suppose section doubly Ray b also on enteringthe The

from the section at the same extraordinary ray derived from b emerges Since it travels with a is at r. pointas the ordinary ray derived from a, that this point will have at greater velocitythe extraordinary ray emerging In that case they that of the ordinary ray. in its phase over advanced would be in a condition to interfere with each other except that they are

the

The

two

rays to each other and so vibratingin planesperpendicular other and each maintaining to at in rightangles travel on, vibrating planes cannot.

262

PHYSICAL

MINERALOGY

there they are each this difference in phase until they reach the upper 'nicol; in the resolved into rays vibrating in plane A-A, Fig. 562, B, and are now that the conditions with each other. interfere Let it be assumed condition to from the section justone waveare length rightfor the extraordinary ray to emerge the Their components in the upper ahead of nicol will ordinaryray. have oppositephases and therefore compensate each other,see Art. 335. If the section is viewed in a monochromatic light(forinstance,sodium light) this interference will result in a black point. But as these rays are converging in the form of a cone a circular they will make, when they strike the section, trace upon its surface and their interference will result in a dark ring. Going out from the center of the section there will be a succession of these rings correspondingto the interference of waves 1, 2, 3, 4, 5, etc., wave-lengths the paths apart. As the distance from the center of the section is increased, of the refracted rays in the section are lengthened and the points of interference are brought closer together. This will cause the interference rings to lie nearer togetheras the distance from the center of the figureincreases. Fig.564 is a top view of the section without into consideration taking the effects of the upper nicol. Let the two circles represent the traces of the of the two rays emergence into which e and o one incident conical is ray divided ; e, being the least refracted (forcalcite), will be the inner one. The plane of vibration of e is always parallel to some plane passing through the vertical axis of the crystal, therefore the trace of its plane of vibration upon the surface of the section will always be in a radial direction. The plane of vibration of o is at rightanglesto that of the extraordinary and parallel ray to the horizontal axes of the crystal,therefore the trace of its plane of vibration the surface of the section will always be in a tangentialdirection, upon see Fig.564. Along the line P-P, Fig.564, only lightvibratingin a radial plane or that of the extraordinary since the come through the section, ray can lightenteringthe section cannot be resolved into the vibrations of the ordinary The intensity and direction of vibration of the lightthat emerges ray. from the section alongthe line P-P is representedby the double arrow that line. on Along the line A-A, since the lightenteringthe section is stillvibratingin the plane P-P, all the lightpassingthrough the section must vibrate as the It is evident,therefore, ordinaryray. that along these two directions, P-P and A-A the plane of vibration of the lightis not changed by through passage the section and consequently such lightwill be completelyabsorbed in the

264

MINERALOGY

PHYSICAL

the difference between the or figureobviouslydepends upon the birefringence, for the ordinaryand extraordinaryray, and also upon the refractive indices, thickness of the plate. The stronger the double refraction and the thicker which will give a certain the plate,the smaller the angle of the light-cone

the circleswill be to the words, the nearer section the circleswill be nearer for blue light than for red, because of their shorter wave-length. When the plateis either seen. quitethin or quitethick only the black brushes will be distinctly 390. Determination of the Positive or Negative Character of the Birefringence of a Uniaxial Mineral from Its Interference Figure. Use of the Mica Plate. For the identification of a uniaxial mineral it is naturallyimportant to determine whether the character of its birefringence is positive or negative. This can usuallybe best accomplishedby tests made of making this 'testis ways upon its interference figure. One of the common by the use of a sheet of muscovite mica, cleaved so thin that, of the two rays of lightpassingthrough it,one has gained one quarter of a wave-length in phase over the other. The mica is usuallymounted between long and narrow glassplatesand is known as the one quarter wave-length mica plate. It is commonly marked 1 /4M with an arrow indicatingthe Z opticaldirection. In testing interference an figure by of the mica plate the means latter is inserted somewhere between the polarizerand analyzer (in the microscope commonly through the slot and justabove the objective) is so orientated that the Z direction makes an angle of 45" with the planes of vibration of the nicols. amount

center.

of

retardation,or, in

Further,for the

other

same

"

In

Fig. 566 let P-P represent the tion plane of vibraof the polarizerand A-A the plane of vibration of the analyzer of a conoscope. Let 0 be the point of emergence of the optic axis of a mineral. positive uniaxial Suppose a singleconical ray of lightenters the section. It is broken up in the mineral into two rays, o and e, which from the section along the arcs of emerge the circles shown in Fig.566. The trace of the ordinaryray, o, will be within that of the extraordinary mineral the o ray travels ray, e, because in a positive the and is less refracted. The directions of vibration of these two rays at the 45" pointsR and R' are representedby the double-headed When arrows. these rays reach the analyzerthey will be resolved into components vibrating to A-A There are an infinitenumber parallel of such rays enteringand passing through the mineral section with varying angles of inclination and therefore

faster

.

varying lengthsof path. 0 two

rays

will emerge

on

the

At same

some

certain distance out from the center circle with a difference of phase of one

CHARACTERS

DEPENDING

UPON

LIGHT

265

whole

wave-length and when resolved in the upper nicol into rays vibrating same plane will interfere with each other and produce the firstdark ringof the interference figureas it is viewed in monochromatic light. If the mica plateis introduced above the section a change in the interference The figureis noted. opticalcharacter of the mica cannot be fully explainedat this point. It is sufficient for present purposes to know that it is a doubly refracting mineral which breaks lightup into two rays which in at are polarized planes rightangles to each other and which,traveling with different velocities through the mica, will emerge from it with different phases. As stated above, the mica plateis cleaved to the requisite thickness so that the two from it with a difference of phase of one rays emerge quarter of a wavelength. Consider what takes place when such a plateis introduced above the section represented in Fig.566 in such a positionthat its vibration direction Z is parallel to the direction R-O-R of the figure. Consider what takes place at the points R. There the vibration direction of the e ray coincides with the vibration direction Z of the mica plate. These vibration directions in each case those of the rays traveling with the smaller velocity. On the are other hand, at the same the vibration direction of the o ray in the mineral point coincides with the vibration direction X in the plate,both of these being of the rays with the greater velocity. So at this point the effect of the mica plateis to increase the difference of phase between o and e and to produce the result as if the mineral section had been thickened. same Consequently the interference ringsalong the line R-O-R increased in number are and drawn toward the center of the figure. At the pointsR' the oppositeis true. The vibration direction of e coincides now with that of X in the mica plate;the direction of least velocity in the mineral with that of the greatest in the mica. in the

Also

the vibration

direction of

o

coincides with that of Z\ that of the greater

velocityin the mineral with the less velocityin the mica. So at this point the mica will decrease the difference in phase between o and e and produce the effect of thinningthe section and so spreadingthe interference ringsfarther In quadrants 2 and 4, therefore, the ringswill apart along the line R'-O-R'. in and be drawn 1 3 while the will be spread nearer center, quadrants they farther apart. Another effect caused by the introduction of the mica plate is even more pronounced. In quadrants 1 and 3, in the case illustrated in Fig. 566, black dots will appear near the center of the figure. In the interference there were before the introduction of the mica plate, figure, pointsin quadrants 1 and 3 at short distances from the center, 0, where the two rays, o and e, emerged from the section with a difference of phase of one quarter wave-length. Under these conditions no interference could take placeand these spots were light. The effect of the mica platein these two quadrants is to everywhere due to the mineral reduce the birefringence by one quarter of a wave-length. Therefore at these two pointsthe difference of phase caused by the birefringence of the mineral is annulled by the mica plateand consequentlyat these The mica plateproduces pointsinterference will result and black dots appear. dark in the interference figurebecome brushes which were of the lines the brushes the s ection from along crystal light.Lightcoming and ordinarily is is vibratingonly in the vibration direction of the polarizer the with mica t his But above. the plateintervening wholly cut out by analyzer lightis broken up in the mica into two rays which vibrate in the vibration planes of the mica and as these are inclined to the plane of the analyzera through to the eye. As the lightcoming from portionof the lightwill come stillother effects.

The

266

PHYSICAL

MINERALOGY

along the lines of the brushes had only a singlevelocity(was entirelyeither the ordinary or extraordinaryray) there are only two rays emerging from the mica plate along these directions and their difference of phase is one quarter of a wave-length. Under these conditions there can be no the

section

interference and the interference

white

brushes

figurebecomes

result.

In the

same

way

the dark

center

of

light. 667

of

Determination

Optical Character

with Mica

Plate

of the interference figureof Fig.567, A, is a diagrammatic representation positivemineral as affected by the insertion of the mica plate,the direction the direction of vibration the direction Z of the mica, i.e., of the arrow indicating of the ray having the smaller velocity. In the case of a negativemineral the conditions as described above will be completelyreversed. Fig. 567, B, of an interference figure of a negativemineral when representsthe appearance the mica plateis used. Therefore,to determine the opticalcharacter of a uniaxial mineral from insert a mica plateabove the section with its Z direction its interference figure making 45" with the vibration planesof the nicols. Then, if this direction Z the cenis at rightanglesto a line joiningthe two black dots that appear near ter of the figure(i.e., the two lines form a plussign),the mineral is positive; if,on the other hand, these two directions coincide (form together a minus sign)the mineral is negative. mine Art. 344, is used to deterUse of the Sensitive Tint. The sensitive tint, see the positive its ference interuniaxial mineral from of or a negativecharacter when the the mineral section is so thin,or mineral possesses figure such a low birefringence, without to show in the figureonly a black cross as rings. Under such conditions the mica platewould not give a decisive any test. The sensitive tint is usuallyso mounted cides that its longerdirection coina

"

with the direction of the vibration of the faster ray, i.e., the direction X. sensitive tint is introduced somewhere between the polarizerand analyzer in such a positionthat itsvibration directions are at 45" with the planes of vibration of the nicols. Let it be assumed that we have the interference from such a is figure positivemineral, as representedin Fig. 566. If the sensitive tint is introduced in such a positionthat its X direction is parallel to the line R-O-R the X direction of the sensitive tint will be parallelto the direction of vibration of the e ray in the mineral. Since the mineral is positive the e ray will have the smaller velocityand therefore in quadrants 2 and 4 the The

CHARACTERS

opticalorientation

of the

DEPENDING

mineral

and

UPON

267

LIGHT

the sensitive tint will be

opposed

to

sensitive tint alone

would The other. produce an interference color of if the effect of the birefringence But of the mineral is red of the first order. from the birefringence of the sensitive tint the color will such as to subtract

each

yellow. Consequently

to

change the

near

of the field at the

center

lower

sufficient to

been

in these

quadrants yellow spots will

points where

the interference

color to that extent. slower of the mineral rays

1 and 3, the faster and directions and the effect of the two in their coincide tint sequently Contive one.

quadrants,

In

and

substances

the

has

other

sensitive is an

addi-

568

in these two color

the

quadrants

appear

the effect of the mineral

will rise to blue. In

making

the above

the sensitive tint it is convenient to follow the rule that

test with

direction

if the

sensitive

the the

line

a

crosses

blue

two

of

X

tint

uniting dots

plus sign) the mineral is positive ; (makes

if,on these

a

the two

coincide a

391.

other hand, directions

of

Determination

OpticalCharacter

gether to( make minus sign)the mineral is negative

Interference

Figures

from

Inclined

These

Tint

are

illustrated

of Uniaxial

Minerals.

conditions

Sections

569

Eccentric Uniaxial Interference

with Sensitive

Figures

268

PHYSICAL

MINERALOGY

be interference figureobtained from such an inclined section will of course If is section inclined the field. little to the a eccentric to the microscope only of the optic the pointof emergence basal plane,the center of the figure(i.e., and vision in the field of will circle about the move a axis)will stillbe within the microscope stage. center of the field wtien the section is revolved upon of such an interference figure during Fig.569, A, shows the successive positions If the section is more ference revolution. sharply inclined the center of the interthe As outside field. the section is be the turned on quite figuremay will traverse interference the fieldin succession. of the four cross the arms stage bars and, provided the section has the field as straight across They will move the field across been cut not too highlyinclined to the opticaxis,will move This of is the fact of cross-hairs to the microscope. importance in parallel interference from uniaxial s uch certain biaxial a order to distinguish figure bars similar often show which, however, will always figures. The latter will as curve they cross- the field of the microscope. If the first of these bars in left to rightacross from the field, the second will the uniaxial figuremoves from the top to the bottom, the third from rightto left and the last move from the bottom to the top, etc. Fig. 569, B, shows the different positionof of a revolution. such a figureduring one quarter mined The positiveor negative character of the mineral can usuallybe deterfrom an eccentric figureif care is taken 570 to make certain which quadrant is visible when the test is made. For instance, in Fig. 570 is shown how the test is made with the sensitive tint upon the eccentric interference figureof a positivemineral. In examining unorientated sections of a mineral,such as the random section found in rock section or the small a fragments of a mineral placed upon it is advisable a glassslide, hunt to for that section that always gives the lowest interference color. The amount of birefringenceshown in various sections of a uniaxial mineral decreases as the section approaches the orientation of the basal plane. Sensitive Tint with Consequently that section showing the Eccentric Interference Figure lowest interference color will yieldthe most nearlysymmetrical interference figure. 392. Interference Figure from Prismatic Section a of a Uniaxial Mineral. When a prismatic section of a uniaxial mineral is examined for an interference figure indefiniteresult is obtained. an The figure is analogous to one obtained in the case of biaxial crystals.The reasons for this resemblance will be pointed out in a later article. The two types of figures cannot be in this case easily differentiated. Two dark and usuallyindefinite hyperbolas approach each other as the section is turned on the microscope stage,form an indistinctcross, and rapidlyseparate. These bars differ from those obtained in a biaxial interference figurein that they rapidlyfade out as they move from the crossed position. This type of interference figure away be obtained easily can from the quartz wedge. AbsorPtion Phenomena of Uniaxial Crystals. Dichroism. When lightenters colored minerals as rays of white light, i.e., containingvibraAn

.

"

wu393:

"

CHARACTERS

DEPENDING

UPON

269

LIGHT

tions of allwave-lengthsfrom that of violet lightat one end of the spectrum to that of red lightat the other,certain wave-lengthswill be absorbed during the passage of the lightthrough the mineral,so that the it emerges, as light, has a definite color. It happens in certain deeply colored minerals that the and character of this absorptiondepends amount the direction of the upon vibration. For instance in the case of uniaxial minerals, light the ordinary and extraordinary from the section with distinctly rays may emerge different colors. Take, for instance, a prismatic section of a brown colored tourmaline and observe it in planepolarized lightwithout the use of the upper nicol. As the section is revolved upon the stage of the polariscope the color may change from a dark brown to a lightyellow-brown. The greatest difference in the color occurs at positions 90" apart and when the crystallographic directions of the section, i.e.,the vertical crystallographic axis and the trace of the planeof the horizontal or axes, are either parallel perpendicularto the vibration plane of the polarizer. In other words, these extremes of color occur when the directions of the vibration of the ordinaryand P 1 extraordinary parallelor rays in the section are perpendicularto the vibration plane of the lightenteringthe section. In Fig.571,A, let P-P represent the vibration direction of the lightenteringthe section. The mineral section is so placed that the direction of the vertical

crystal axis is perpendicularto P-P.

The

Vertical Axis

^

light on

entering the section will therefore vibrate in the plane of the horizontal axes or the ordinary ray, o. In this positionthe as tourmaline

section is dark colored and consequently it is seen that lightvibratingin the mineral as the ordinaryray is largely absorbed. Now turn the section through a 90" angle to the position shown in In Fig. 571, B. this position the light must in the vibrate the section wholly as fore extraordinary ray, e, and the color is a light yellow-brown. Therethe extraordinaryray is only slightlyabsorbed. This difference in dichroism. Either the absorptionor the color of the two rays is known as and two the ordinaryor the extraordinary absorbed the be most the may ray cases are expressed as either o " e (o"" e) or e " o (e " co). In uniaxial sections where it attains minerals dichroism is to be best observed in prismatic itsfullintensity.Basal sections show no dichroism, since lightpassingthrough the section parallelto the opticaxis must all vibrate in the horizontal axial

plane and belongwholly to the ordinaryray. used for An instrument contrived by Haidinger, is sometimes called a dichroscope, of Iceland spar is placed examining this property of crystals. An oblong rhombohedron in a metallic cylindricalcase, having a convex lens at one end, and a square hole at the other. image belongs to the On looking through it,the square hole appears double; one crystalis examined ordinaryand the other to the extraordinaryray. When a pleochroic lution, with it by transmitted light,on revolvingit the two squares, at intervals of 90" in the revoof the ordinary and to the vibration-planes have different colors,corresponding extraordinaryray in calcite. Since the two images are situated side by side,a very slight difference of color is

microscope.

perceptible.A

similar device is sometimes

used

as

an

ocular in the

270

MINERALOGY

PHYSICAL

Circular

394.

Polarization.

The

"

polarizedlight and circular subject 9f elliptically This phenomenon is most tinctly disto in Art. 350. of crystalsbelonging to the rhombohedralthe case

has already been brieflyalluded polarization observed

among

minerals

in

class,that is,quartz trapezohedral

and

cinnabar.

explained that a section of an ordinary uniaxial crystalcut normal to the dark in parallelpolarizedlight for every position between vertical (optic)axis appears in thickness, be examined crossed nicols. If,however, a similar section of quartz, say 1 mm. dark in monochromatic lightonly, and that not until under these conditions,it appears for sodium lightan angle the analyzer has been rotated so that its vibration-planemakes of 24" with that of the polarizer. In other words, this quartz section has rotated the plane of vibration some 24", and here either to the rightor to the left,looking in the direction of of this rotation increases with the thickness of the section,and, as the light. The amount the wave-length of the lightdiminishes (forred this angle of rotation for a section of 1 mm. denned as is about 19",for blue 32"). The direction of the rotation is to the right or left, right-handedor left-handed (p. 113). above according as the crystalis crystallographically to the axis)be viewed between crossed section of quartz (cut perpendicular If the same differs from that nicols in converging polarizedlight,it is found that the interference-figure has disappeared, of an ordinary uniaxial crystal. The central portion of the black cross colored.* Furthermore, when the and instead the space within the inner ring is brilliantly analyzing nicol is revolved,this color changes from blue to yellow to red, and it is found and in other this change is produced by revolvingthe nicol to the right, that in some cases and the second with left-handed. the first is true with right-handedcrystals, to the left; cases If sections of a right-handed and left-handed crystalare placed together in the polariscope, is occupied with a four-rayedspiralcurve, called,from the center of the interference-figure of quartz crystalsare not the discoverer,Airy's spiral. Twins consistingof uncommon, of right-and left-handed individuals (accordingto the Brazil law) which the combination cinnabar similar phenomena observed. Twins of show these spiralsof Airy. With are this speciesalso not infrequentlyshow Airy'sspiralsin the polariscope. It has

been

"

of Uniaxial Optical Characters Crystals. All show double refraction except those that are cut sections of uniaxial crystals to the basal plane. All doubly refracting sections show parallelextinction. parallel viewed in convergent polarizedlightwith crossed nicols all When sections show a characteristic uniaxial interference figureexcept those that lie in the prism zone of the crystalor that are only slightly inclined to that All doubly refracting sections have two refractive indices correspondzone. ing of these is always co and the other has to the two extinction directions : one a value (c') rangingfrom co to e, dependent on the inclination of the section to the optic axis. Dark colored minerals may show dichroism. Tetragonal and hexagonal substances cannot be distinguished from each other by optical tests. sections of They may be at times told apart by characteristic cross their crystals. 395.

Summary

of the

"

C.

BIAXIAL

General

CRYSTALS

OpticalRelations

The crystals of the remaining systems, i.e., the orthorhombic,monoclinic, and triclinicbelongoptically to what is known as the Biaxial Group. of Light in Biaxial Crystals. 396. The Behavior In biaxial crystals there are three especially important directions at rightangles to each other which are designatedas X, Y, and Z (alsoa, fo,and c). These three directions sometimes in reference are certain to spoken of as axes of elasticity assumed differences in the ether along them. The nature of these three directions is as follows. Light which results from vibrations parallel to X (axisof is propagatedwith the maximum greatest elasticity) velocity;that from vibra"

*

of

an

Very thin sections of quartz, however,show ordinaryuniaxial crystal.

with the microscope)the dark (e.g.,

cross

272

PHYSICAL

ing from vibrations parallelto OF, Likewise

in the

direction OF

there

MINERALOGY

hence

velocity1/0. travelingwith mean from vibrations a resulting ray ing travelto OX, hence parallel

will be

573

maximum

the

with

velocity,I/a.

In

all directions

intermediate between X and F the lightvelocities will be proportionalto the radii of an ellipsehaving

1/0

and

I/a

as respectively and semi-major In the diameters, Fig. 573. and F plane of the X directions,therefore, in a of time light given moment

itssemi-minor

will radiate as

from

ordinaryand

rays,

the

wave

representedby an ellipse.

the

center

extraordinary fronts being a

circlewithin

Consider next the planeof the F and Z directions, Fig. 572. Light will radiate in all intermediate F and directions resulting from 0 toward and Z It will therefore travel with uniform and the to OX. from vibrations parallel maximum I/a. The velocity, distance traveled in a given moment of time be may circle plottedby drawing a the about 0 with radius 574. Likewise I/a, Fig. there in will travel the second direction OF a ray vibrations resulting from

parallel to OZ, with

hence

ing mov-

the

minimum velocity,l/y. Also in the direction OZ there will be a from vibrations ray resulting with the parallel to OF In directions velocity 1/0. intermediate between F and Z the lightvelocities will be proportional to the radii of

ellipsehaving l/y and its semias 1/0 respectively minor and semi-major In diameters, Fig. 574. the plane of the F and Z directions, in a given moment of time,light therefore, will radiate from the center as ordinary and extraordinaryrays, the wave fronts being representedby an ellipse within a circle. an

CHARACTERS

The

DEPENDING

UPON

LIGHT

273

last and most

important plane to be considered is that of the X and Z Light will radiate from 0 toward X and Z and all intermedia directions with vibrations parallelto OF, hence with a traveling

directions,Fig. 572.

intermediate velocity, traveled 1/jS. The distance in a given moment of time is representedin Fig. 575 by the the radius circle with 1/0. There will likewise travel in the direction OZ a resulting ray from vibrations parallel to OX, the hence with imum maxmoving uniform

and

velocity,I/a.

Also

a

will travel in the direction OX with vibrations parallelto OZ, hence having the minimum l/y. In intermediate velocity, positionsthe lightvelocitywill be proportionalto the radii of an ellipsewith I/a and l/y respectivelyas its semi-major and semi-minor diameters,Fig. 575. In the plane of the X and Z directions, therefore,in a given of moment time, light will radiate from the center as ordinary and extraordinaryrays, the wave fronts represented, an ellipse. It is to be by a circle intersecting the two wave four pointswhere noted that in this last plane there are fronts coincide. In other ray

words, lighttraveling along the radial lines connecting these pointswill be moving with uniform velocityand

consequently along

these

directions there will be no These refraction. double directions are known as the the of crystal optic axes and since there are two of them is the opticalgroup spoken of as biaxial. The of these optic character will be more axes fully in later article. a developed In the above paragraphs fronts for light the wave Ellipse in the three principal moving opticalplanes of the fronts in these crystalhave been discussed. Fig. 576 represents the wave The completewave when bounding one octant. three planes as they appear

274

PHYSICAL

MINERALOGY

surfaces for light propagated in all directions consist of warped figures fronts already described in wave to the circular or which conform elliptical the three principal planes and have intermediate positionselsewhere. The to represent these complete surfaces is by means of way only satisfactory a

model.

It is found further that the opticalstructure Biaxial Indicatrix. .known as the indicatrix, be represented biaxial crystal can by an ellipsoid, three lines which at right are having as its axes and in each other to proportional length to angles This is analogousto the similar the indices a, /3,7. described in Art. 382. figurefor uniaxial crystals This ellipsoid, whose axes represent in magnitude refractive the three principal a indices, /3,7 (where " a |8 " 7), (see Fig. 577), not only exhibits the character of the opticalsymmetry, but from it be derived the direction, velocityand plane of may vibration of any lightray traversing the crystal. In generalit may be stated that the character of the two lightrays which result from a single incident, be derived from a study of that elliptical ray may section of the indicatrix which is normal to the If this section happens to be one incident ray. of the three principal sections of the indicatrix, A BAB, or ACAC, BCBC, Fig. 577, its major, and minor diameters give the directions of vibration and their tion semi-lengths the indices of refracof the If the incident two has some Biaxial Indicatrix rays. ray direction different from the directions of the of the indicatrix ellipsoid three axes the derivation of the character of the refracted rays is not as simple. Let Fig.578 represent such an elliptical two section normal to the inclined ray L-L. In this case the major and minor diameters R-O-R and r-0-r of the section liein the vibration elliptical L of the two planes rays but the directions of vibration of the latter will be somewhat inclined to the elliptical section. These directions of vibration may be obtained by erectingnormals to the surface of the indicatrix at the points R and where the r 397.

of

"

a

"

major and minor diameters of the section meet that surf ace. elliptical These normals RN and rn, when extended to the line of the incident L-L, yield the directions of ray vibration and the refractive indices of the two refracted Their directions rays. of transmission (the lines OS and OT) will be perpendicularto these normals and since neither of the latter lie in the elliptical section both rays will be refracted and behave as extraordinaryrays. There are two special sections of the indicatrix that notice. The

require

CHARACTERS

DEPENDING

UPON

LIGHT

275

line B-O-B (Fig.577) is longerthan the line A-O-A but shorter than the line C-O-C. in some Obviously, positionintermediate between A-O-A and C-O-C there will be a diameter of the ellipse AC AC which will be equal in There are two such lines, length to B-O-B. S-O-S and S'-O-S' in Fig. as 577. The major and minor diameters of these sections of the indicatrix, and BS'BS', are equal and the sections therefore become BSBS circles. Consequently lightpassingthrough a section of a crystalcut parallelto either of these circular sections of its indicatrix will have a uniform velocity and may vibrate in any transverse direction. In other words, there will be no double refraction along the lines normal to these two sections. These lines constitute what are known the primary opticaxes as of the crystal;see further in Art. 398. The major and minor diameters of any section of the indicatrix yieldthe traces upon that section of the planesof vibrations of the two rays into which the ray normal to the section is refracted. In other words, the major and minor diameters of the elliptical section of the indicatrix givethe directions of extinction of a crystalsection having this opticalorientation. Further, these extinction directions bisect the angles made by the traces upon the section of two planes,each of which includes the pole of the section and one of the two This be demonstrated of opticaxes. by aid Fig.579 which represents may section of an indicatrix. A- A and B-B a general elliptical the major and are minor diameters of the ellipse and so represent the extinction directions of the mineral section. C-C and C'-C' representthe intersections of the two circular sections of the indicatrix with this elliptical section. As these lines are diameters of equal circlesthey must be equalin lengthand it therefore follows that the anglesAOC of an ellipse from the geometricalnature and AOC' are line P-P intersection section Let with this the the equal. elliptical represent of a plane in which lie the normal of the optic axes. to the section and one Since this plane includes an opticaxis it must 579 be perpendicularto the circular section of the indicatrix of which the line C'-C' is a Also since this plane includes the diameter. eration normal section under considto the elliptical it must be at right angles to the latter plane. Under these conditions it is and C'-C' in Fig. obvious that the lines P-P 579 must be at right angles to each other. In the same it can be proved that the way lines P'-P' and C-C are also at rightangles and to each other. Since the angles AOC AOC' are equal and the angles POC' and P'OC are also equal it follows that the angles A OP* and A OP' are likewise equal. In other words and B-B the lines A-A representing the directions of extinction of the section

by the traces upon two planes which through each opticaxis and

bisect the angles made the section of the

respectively pass

This fact will be the normal to the section. made of later,see Art. 407, in explainingthe characters use interference figure.

of the biaxial

276

MINERALOGY

PHYSICAL

already been stated normal to the circular sections of the indicatrix (SS, S'S', cross Fig. 577) in which all light is propagated in these uniform with velocity. Hence double be no refraction directions there can

Primary and Secondary Optic Axes. namely, (Art.397) that there are two directions, "

580

within

a

It has

those

crystal;nor These

emerges.

two

is there

when

directions bear

the so

ray

close

of a uniaxial analogy to the optic axes also called that are opticaxes, they crystal hence the crystalshere considered are and named biaxial. In Fig.575, which represents an

in the section of the wave-surfaces X Z these optic and directions, plane of the to have the direction SS, S'S' normal axes and the direction the tangent planes tt,t't', is given by the normal of the external wave a

cross

Str

(Fig.580). Properlyspeakingthe directions mentioned

primary opticaxes, for there also two other somewhat PP, P'P', of Fig. 575, are analogous directions, The propertiesof the called for sake of distinction the secondaryopticaxes. are

those of the

latter directions are obvious from the followingconsiderations. in Fig. In the section of the wave-surface shown in Fig.575 (alsoenlarged, 580),correspondingto the axial plane XZ, it is seen that the circlewith radius -

intersects the

whose ellipse

major and minor

axes

are

-

and

-

in the four

pointsP, P, Pf,P'. Correspondingto these directions the velocityof propagation is obviouslythe same* for both rays. Hence within the crystalthese travel together without double refraction. Since, however, there is rays wave-front for these two rays (forthe tangent for one ray is repreno common sented and for the other by nn, Fig.580) they do suffer double refraction by mm on emerging;in fact,two external light-wavesare formed whose directions are given by the normals Pju and Pv. These directions, PP, P'P',therefore, have a relatively minor interest, and whenever, in the pages following, optic axes are spoken of,they are always the primary opticaxes, that is,those having the directions SS, S'S' (Fig.575),or OS, Fig.580. In practice, however, as in the next article, remarked the angular variation between the two sets of is usuallyvery small,perhaps 1" or less. axes 399.

Interior and Exterior Conical Refraction. The tangent plane to the wave-surface normal to the line OS through the point S (Fig.580) may it in a be shown to meet small circle on whose circumference lie the points S and T. This circle is the base .of the interior cone of rays SOT, whose remarkable propertieswill be brieflyhinted at. If a section of a biaxial crystalbe cut with its faces normal to OS, those parallelrays belonging to a cylinderhaving this circle as its base,incident it from without, will be propagated upon within as the cone SOT. Conversely,rays from within corresponding in positionto the surface of this cone will emerge paralleland form a circular cylinder. This phenomenon is called interior conical refraction. On the other hand, if a section be cut with its faces normal to OP, those having rays the direction of the surface of a cone formed by perpendicularsto mm and nn will be propagated within parallel to OP, and emerging on the other surface form without a similar cone the other side. This phenomenon is called exterior conical on refraction. In the various figuresgiven (573-580) the relations much are exaggerated for the sake

drawn

"

CHARACTERS

of a

DEPENDING

small clearness;in practicethe relatively and

7

makes

this

cone

of small

UPON

difference between

angular size,rarelyover

277

LIGHT

the indices of refraction

2".

400.

Optic Axial Angle. Bisectrices. Positive and Negative Biaxial Crystals. The optic axes always lie in the plane of the X and Z optical this plane is called the opticaxial plane (or,briefly, directions; ax. pi.). It is obvious from a consideration of the indicatrix ellipsoid that the positionof its circular sections and consequentlyof the opticaxes normal to them, will "

variation in the relative values of the indices of refraction. As the index 0 is not an arithmetical mean between a and 7 but at times be nearer to a than to 7 or the reverse. As these relations may change,the shape of the indicatrix and the positionof its circular sections and the anglebetween the opticaxes will also change. The mathematical relations between the opticaxial angle and the principle refractive indices are given in the next article. From the above it is obvious that for certain relative values of the refractive indices, the opticanglemust be 90".* Such a case, however, is rarely observed and when it occurs it is true for lightof a certain color (wave-length)only and not for others. The X and Z opticaldirections bisect the anglesbetween the opticaxes and are therefore known bisectrices. The one that bisects the acute axial as the obtuse angle is called the acute bisectrix (orBxa) while the one bisecting bisectrix is the is obtuse If the word bisectrix used alone without angle (orBx0) it is always to be understood as referring to the acute specialqualification bisectrix. Either X or Z may be the acute bisectrix. If X is the acute bisectrix the substance is said to be optically while if Z is the acute bisectrix it is negative, vary

with

a

alreadystated

f

.

positive. optically the opticaxes Roughly expressed,

will lie nearer to Z than to X that is, the value of the intermediate index,/3, is nearer It is obvious (cf Fig.575) that in this case, as to that of a than to that of 7. the angle diminishes and becomes nearlyequal to zero, the form of the ellipsoid then approaches that of the prolatespheroid of the positiveuniaxial of the crystalas its limit (Fig.557, p. 256) ; this shows the appropriateness + signhere used. that is, to X than to Z On the other hand, the opticaxes will lie nearer index 0 is nearer to that of X will be the bisectrix if the value of the mean for which Bxa Such a crystal, X, is called optically 7 than to that of a. the the the In this case the smaller more ellipsoid approaches angle negative. the oblate spheroidof the negativeuniaxial crystal(Fig.556, p. 256). and negativebiaxial crystals: The followingare a few examples of positive Z will be the bisectrix

"

when

"

.

"

"

=

Negative (-).

Positive (+).

Aragonite. Hypersthene.

Sulphur. Enstatite.

Muscovite. Orthoclase.

Topaz. Barite.

*

The

Chrysolite.

Epidpte.

Albite.

Axinite. the indices satisfythe followingequation:

axial angle will equal 90" when

1 _! a2

t

For

danburite

axial angle

=

I

1

-

j82

ft2

89" 14' for green

72' and (thallium)

90" 14' for blue

(CuSO4).

278

MINERALOGY

PHYSICAL

If in a Relation of the Axial Angle to the Refractive Indices. of the interior value the and are known, optic 7 given case the values of a, 0, axial angle known as 2V; see also Art. 408, can be calculated from them by 401.

the

"

followingformulas: 11

11

P

cos2F

72

tan2 V

or

a2

Examination

=

72

of Biaxial Crystalsin Polarized Light

Nicols. Light with Crossed biaxial when examined of sections between Thin Colors. crystals Interference color. This color will interference in crossed nicols depend generalshow some the followingfactors : the thickness of the section, the thicker the section upon the birefringence the higherthe order of color; ofthe substance, the higher the values of a and the greater the difference between the birefringence (i.e., orientation of the section, in gen7) the higherthe order of color; the optical eral, to being parallelto the optic axial plane, the nearer the section comes in which he the vibration directions of the fastest and slowest rays, the higher will be its birefringence and the order of its interference color. A section which,in general, iscolored will show durExtinction Directions. ing the microscopestage four positions at 90" intervals a complete revolution on These are the positions in which it appears dark. of extinction, or are i n the which the of section those positions vibration planes coincide with those 402.

Sections

in Parallel Polarized

"

"

"

of the nicols. at a

the directions of extinction of

When

axis rightangles to a crystallographic axial plane it is said crystallographic extinction 681

or

to the

to show

a

section

directions

are

not

parallelor

parallelto these

crystallographicdirections the said to be inclined. For example, in

are

the

of section, extinction. If the parallel

trace,upon

extinction

Fig.581, let the

two

is

larger

rectangular represent the vibration directions for the two nicols,and between .,6' which suppose section of a biaxial crystal, a ^-P abed, to be placed so that one edge of a known crystallographic tion plane coincides with the direcof one of these lines. The vibration directions of the section are indicated by the dotted arrows and as in this position of the section these directions do not coincide with the vibration directions of the nicols the section will light. The section will have to be turned to the position a'b'c'd' appear in order to achieve this coincidence and so bring about extinction. The in the figure)which it has been angle (indicated to revolve the necessary plateto obtain the effect described, is the angle which one of the vibration directions in the given platemakes with the given crystallographic edge ad', it is called the extinction angle. 403. Measurement of the Extinction Angle. It frequentlybecomes arrows

"

"

importantto

measure

as

accuratelyas possiblethe extinction angle of

a

sec-

280

PHYSICAL

MINERALOGY

to that of the two effect is added positionof extinction its birefringent from that of the remaining subtracted oppositequadrants of the ocular and A very colored. two. Consequentlyadjacentquadrants become differently rotation of the section is sufficientto produce an appreciableeffect. slight Another principleas the Bertrand using the same microscope accessory sists ocular is the so-called bi-quartz wedge platedescribed by Wright. This conof two adjacentplatesof quartz cut normal to the c crystal axis,one from these are left-handed and the other from a right-handedcrystal. Above a the above left-handed two of placed wedges quartz, a right-handedwedge plate,etc. At the point where the wedge is equal in thickness to the plate crossed nicols this beneath there will be zero rotation of the lightand between As the distance increases from this the field. will produce a dark line across in of rotation of the lightincreases equally but opposite point the amount directions on either side of the central dividingline of the plate. Both halves of the platewill be equallyilluminated if the mineral section is in the position of extinction, fringent but if the latter is turned so that it adds or subtracts its bireeffect to that of the quartz platethe two halves become differently illuminated. By moving the plate in or out a positioncan be found where this change in illumination is most marked. This quartz plateis used with in ocular such a positionthat the quartz plate a special providedwith a slot be introduced into the microscopetube at the focal plane of the ocular may and with the medial line of the plateparallel to the plane of vibration of the polarizer.A cap nicol is used above the ocular. 404. Determination of the Birefringencewith the Microscope. The value of the maximum birefringence a) is obviouslygiven at once when (7 the refractive indices are known. It can be approximatelyestimated for a section of proper orientation and of measured ference-col thickness by noting the inter"

"

described in Art. 347. as Determination of the Relative Refractive Power. The relative the refractive power of two vibration-directions in a thin section is readily determined with the microscope(inparallelpolarized light)by the method of to any section, whatever its orientation and compensation. This Is applicable whether uniaxial or biaxial. The methods employed have already been described in Art 348. A crystal-section is said to have positive if its direction of extension elongation approximatelycoincides with the ether-axis Z; if with X the elongation is negative. The same terms are also used, in general, accordingto the relative refractive power of the two directions. 406. Determination of the Indices of Refraction of a Biaxial Mineral. The indices of refraction of a biaxial mineral are determined by the same methods as outlined previously, Art. 327, the only modification introduced see being necessitated by the fact that three principal to indices, a, ftand 7, are be determined. Measurement of the Angles of Refractionby Means Two or of Prisms. three prisms must be used to determine the three indices. If three 405.

"

"

prisms

used

they are

that their edgesare parallelrespectively to the X, F, and Z directions of the mineral. In the case of an orthorhombic mineral,in which these directions are parallelto the directions of the three are

cut

so

crystallo-

graphicaxes, a,

b, and

the proper

c

the

prism edges would have to be respectively parallelto the In crystalsof the monoclinic and triclinic systems crystalaxes.

orientation of the three

prismsis a

matter

of considerable

difficulty.

CHARACTERS

DEPENDING

UPON

281

LIGHT

Each such prism will yieldtwo refracted and polarized rays but only the one whose lighthas its vibrations parallelto the edge of the prism (to be determined In certain cases all three indices by the use of a nicol)is considered. be obtained from two prisms. If one prism is cut so that not only is its may of the directions X, Y, and Z but so that its medial plane to one edge parallel contains not only this direction but one other,then by the use of the method of minimum deviation an index may be determined from each of the two refracted two

when

rays.

Or

with

a

small

of these directions the

the method

of

tains angleprism cut so that one of its faces conindices be two determined corresponding may

perpendicular incidence is used

this face. In making upon it is important to note the crystallographic directions In this way the different rays vibrate. the opticalorientation

these measurements to which parallel

in respect to the crystallographic directions can be determined. Method of Total Reflection.The method of total reflection for determining the indices of refraction of a biaxial mineral has the obvious advantage that

orientated only polishedplatesof the mineral are requiredinstead of carefully prisms. In general,the plane surface of a plate will give with the total refractometer

two boundaries of total reflection. Both of these shadows move Four be taken corresponding the section is rotated. should readings and minimum to the maximum o f each positions boundary. The largestand smallest anglesread will give on calculation the values for the greatestand index of refraction, least indices of refraction, The mean i.e., 0, can j and a. of the other measurements. be derived from one There are certain more or less complicatedmethods by which these two intermediate readingscan be tested in order to prove which is the correct one for the index |8. It is commonly simplerto make use of another platehaving a different crystallographic orientation. It will be found that in the second plateone of the intermediate angles correspondswith one already observed on the first plate while the to second angle shows no such correspondence. The angle that is common the two platesis the one desired. If the plateis orientated so that its plane contains two of the three opticaldirections, X, Y and Z, all three indices can of the boundaries be obtained easilyfrom the singleplate. In this case one of total reflection is stationaryfor different positionsof the plate. This corresponds to the ray whose vibrations are normal to the surface of the plate. The other boundary will vary its positionas the plateis rotated and yieldat its maximum and minimum positionsthe anglescorrespondingto the other when

two

indices of refraction. 407.

Sections

of Biaxial

Crystalsin Convergent Polarized

Light.

"

-

In

general,sections of biaxial crystalswhen examined in convergent polarized lightshow interference figures. The best and most symmetrical figuresare the section has been cut perpendicularto a bisectrix, to be observed when under and preferablyto the acute bisectrix. If such a section is examined Art. 389, figures of uniaxial crystals, the conditions described in the case see the axial plane, When in Fig. 583 will be observed. similar to those shown to the direction of the plane includingthe two opticaxes, lies parallel i.e., the figureis similar to that of Fig. 583, A. When vibration of the polarizer is like that shown in these two directions are inclined at a 45" anglethe figure Fig.583, B. First consider the interference figurein the parallel Fig. 583, A position, bars that of black two It consists and when viewed in monochromatic light. horizonThe uniaxial of a form a cross similar to the cross somewhat figure.

PHYSICAL

282

MINERALOGY

About two points tal bar is thinner and better denned than the vertical one. of dark ellipseries concentric tical be observed a will there the horizontal bar, on and first a eight figure forming coalesce, which, as they enlarge, curves 583

Biaxial Interference

Figures

As the section is rotated on the microscope or polardouble curve. iscopestage, the black bars forming the cross separate at the center and curve Fig. 583, B, the field pivotingon these pointsuntil at the 45" position, across of a hyperbola. they form the two arms the directions of the opticaxes, along A biaxial mineral has two directions, which lighttravels with no double refraction. At these pointsthere would As the paths and consequentlydark spots would result. be no birefringence the light inclined to the directions of the opticaxes of the lightrays become of inclination suffers double refraction and in increasing degreeas the amount from these points becomes greater. Consequently at short distances away be refracted into two rays which have a difference of phase of the lightmust then

a

the yellow of the sodium flame in a certain colored light, result will be extinguishmentat such points. The assemblage of all pointswhere the difference of phase equalsone wave-lengthyields in the figure. the first dark elliptical-like shown called a lemniscate, ire. curve, o" the the Further out will be found curves difference where embracing points

one

this

wave-lengthfor The

case.

i

phase is

two wave-lengths, three wave-lengths, etc. If the interference figureis viewed in daylightinstead of the monochr TOV niatic lightthe black curves Each colored will be replacedby colored ones.

is produced by the elimination from the white lightof some curve particular wave-lengthof lighton account of the interference explainedabove. The convergent bundle of light rays that pass through the section will each have its own particularplane of vibration. The directions of the planes of vibration for lightemerging from the section at any given pointcan be found, as the anglesmade explainedin Art. 397, by bisecting by two lines connecting this pointwith the two pointsof emergence of the opticaxes. Fig.584 shows how the direction of vibration of the two rays emerging from given points be

obtained

in this way.

These directions of vibration vary the over of them must be parallelor very nearly always so to the planes of vibration of the nicol prisms. When this happens the light is extinguished and darkness results. This explains the formation of the black bars of the interferencefigure. Fig.585 shows the bars in the crossed position can

field and

consequentlysome

CHARACTERS

DEPENDING

UPON

283

LIGHT

and Fig. 586 when As the section is separated into the hyperbola arms. turned the vibration directions of new become pointssuccessively parallel to the planesof the nicols and so the dark bars sweep and curve the field. across 584

585

586

With a thick section or one of a mineral of high birefringence, the number of colored curves (when the figureis viewed in daylight)is greater than with with low birefringence.An instructive experiment section or one a thinner be made by notingthe changes in the interference figureobtained from a can section of muscovite as the mineral is cleaved into thinner and thinner sheets. In most rock sections the minerals are ground so thin that their interference but rather only the dark hyperbola figuresdo not show any colored curves bars.

The

biaxial interference figurevaries in appearance with the change in is this Where angle between the opticaxes. angle very small the figure becomes that of a uniaxial crystal. Where the same this as practically of the opticaxes angle becomes greaterthan 60" the pointsof the emergence will commonly lie outside the microscopefield. In the latter case the hyperbola will appear as the section is brought into the parallelposition, form arms out of the field then as the section is further revolved will curve a cross, and again. The largerthe axial angle the more rapidlywill the bars disappear of the axial angles of two from the field. A comparative measurement minerals can be made by notingthe anglethrough which the microscopestage has to be turned in order to cause the bars to leave the field. The system of for the two experiments. Or by experimenting be kept the same lenses must axial anglesa scale could be derived for a with various minerals with known certain microscope and system of lenses so that the axial angle of any other in this way. mineral could be approximatelymeasured A symmetrical interference figure also be obtained from a section cut may perpendicular to the obtuse bisectrix. In general,the obtuse axial angle is considerablylargerthan the acute angleand the interference figurewill differ therefore in this respect from that obtained from the section cut perpendicular

the

to the acute

bisectrix.

recognizethe biaxial interference figures They are chieflycharacterized bars teristic curve as they cross the field. This charachyperbola from uniaxial eccentric in the which the an figure distinguishes figure is the section lines turned. in 587 bars of the cross as Fig. move straight in different positions the appearance shows in the row A a series illustrating It is

which

important

obtained are fact that the the by

to

be

from

able

to

inclined sections.

284

PHYSICAL

MINERALOGY

In inclined to the bisectrix. when the section is slightly of the figure and the axis to an optic the section is cut perpendicular a series where a pivot. In this case the bar bar revolves in the field as upon

B, hyperbola

row

curves

687

Eccentric

Biaxial Interference Figures

90" side toward the acute bisectrix. If the axial angle was with its convex and bisectrices the obtuse and acute there would be no distinction between line. Therefore such a figureindicates bar would then revolve as a straight of the bar the size of the axial angle. The of the curvature by the amount normal to an opticaxis are often of great cut nearly given by planes figures Sections which will furnish them examination of a mineral. in the optical use mineral that remain dark or those sections of the found are easily by noting between nicols. If the singlebar crossed rotation their nearly so during it indicates that the such decided exhibits in curvature shown a a figure inclined to the plane of the direction of the acute bisectrix is not very much section and consequentlyits character, whether X or Z, can be determined by notingthe character of that extinction direction which symmetricallybisects From the curve. this observation the positiveor negative character of the mineral can be determined. In row C, Fig. 587, is shown a series of figures where the section has a stillgreaterinclination. A section cut parallel to the axial plane does not givea decisive interference figure. Often it is difficultto it from the figureobtained from a section cut parallel to the optic distinguish axis of a uniaxial mineral,see Art. 392. It should be pointedout that,while in generalthe interference figures classes are to be clearly of these two optical from each other,cases arise in which such differentiation distinguished may is difficultif not impossible. 408. Measurement of the Axial Angle. The determination of the angle made by the optic axes is most ment accuratelyaccomplishedby use of the instrushown in Fig.588. The section of the crystal, cut at rightangles to the is held in the pincersat p, with the plane of the axes bisectrix, and horizontal, of the nicols. There is a making an angle of 45" with the vibration-plane cross-wire in the focus of the eyepiece, and as the pincersholdingthe section turned by the screw are at the top (here omitted)one of the axes, that is,one black hyperbola, is brought in coincidence with the vertical cross-wire, and "

DEPENDING

CHARACTERS

UPON

LIGHT

285

the second. The angle which the section has a further revolution, axis to the second, as read off at the vernier on the turned from one graduatedcircle above, is the apparent angle for the axes of the given crystal

then, by been

688

Axial

Angle Apparatus

in the air (aca 2E, Fig.589). It is only the apparent angle,for,on or passingfrom the section of the crystalto the air,the true axial angleis more The less increased, accordingto the refractive power of the given crystal. relation between the real interior angleand the measured angleis given below. If the axial angle is large, the axes may suffer total reflection. In this case some oil or liquidwith a high refractive power will no is interposed so that the axes into but be reflected totally emerge longer the liquidand thence into the air. In the small receptacle instrument described a the holding the oil is brought between and the pincers tubes,as seen in the figure, in this holding the section are immersed as

seen

=

anglemeasured majority of axial angle that

and the

as

before. it is

only the practicableto of Axial Angle Measurement when but sometimes, especially measure; also be determined oil (orother liquid)is made use of,the obtuse angle can In the

acute

cases

it is

from a second section normal to the obtuse bisectrix. the apparent semi-acute axial angle in air (Fig.589), If E u " " in oil, Ha =

"

=

Ho

Va

"

"

=

=

the

(realor

angle in oil, semi-acute angle, interior) semi-obtuse

286

MINERALOGY

PHYSICAL

semi-obtuse angle, the (realor interior) oil or other medium, for the index refractive n for the given crystallized index refractive substance, the mean |8 m entioned: the various connect quantities the followingsimplerelations

V0

=

=

=

Bin E

=

0 sin 7"; sin E

n

=

sin Ha; sin Va

=

^sin Ha;

formulas give the true interior angle apparent anglein air (2E) or in oil (2H) when the is known. These

(2F) mean

sin V0

=

^

sin H0.

from

the measured refractive index (0)

of with the Microscope. Approximate measurements Axial Angle Measured 409. with the microscope. In most cases some the axial angle may be made by various methods of this ocular is used which contains an engraved scale. By means sort of a micrometer be determined. of the optic axes can the points of emergence scale the distance between Mallard * showed that the distance of any point from the center of the interference figure the sine of the angle which the as observed in the microscope is very closelythe same as the The Mallard equation of makes axis with the microscope. at this point ray emerging half the measK sin E, in which D equals one ured for the derivation of the axial angle is D which varies with the microscope the optic axes and K a constant distance between be determined K for a given set of lenses may by observing and the system of lenses used. axial angles and then the interference figuresderived from platesof minerals with known substitutingthe values for D and E in the above equation. The angular values of the also be determined scale of the ocular may directlyby the use divisions on the micrometer of an axial angle by means The measurement of an instrument known as the apertometer. of of the microscope is naturallymost easilyaccomplished when the points of emergence both opticaxes are visible in the field. It is possible, however, by various ingeniousmethods its value when plicated only one optic axis is in view. These methods are too comto determine and too seldom used to be explained here and the reader is referred to the text for their details,f of petrographicinvestigationbooks on the methods "

=

Mineral of a Biaxial Optical Character If the section of the Quartz Wedge. and then the quartz is in the 45" position is turned until its interference figure the above 45" section in the the slot inserted through microscopetube wedge the vibration directions of the section along a line that joinsthe opticalaxes and a line at rightanglesto this through the center of the figure will be parallel to the vibration directions of the quartz-wedge. Under these circumstances the effect of the introduction of the quartz wedge will be to gradually increase or diminish alongthese lines the birefringence due to the section alone. 410.

from

Determination

Its Interference

of

the

Figure.

Use

"

If the directions of vibration of the faster and slower rays in the quartz coincide with the vibration directions of the similar rays in the section, the total

will be increased and the effect upon the interference figurewill birefringence be as ifthe section had been thickened. Complete interference will take place and the colored curves with rays of less obliquity will be drawn closer together. They will move, as the quartz wedge is pushed in over the section, as indicated shown in Fig.590. On the other hand, ifthe quartz wedge is so by the arrows placed that its opticalorientation is opposed to that of the section, the effect will be the same if the section was as The thinned. colored being gradually the of about the will until rings points opticaxes ter expand they meet in the cenas a figure The eight and then grow outwards as a continuous curve. directions of their movements shown by the arrows are in Fig. 591. fore, Thereby knowing the opticalorientation of the quartz-wedge and noting the *

Bull. Soc. Min., 6, 7787, 1882. t See especiallyWright, The Methods of Petrographic Microscopic Research, and Johannsen,Manual of Petrographic Methods.

288

PHYSICAL

MINERALOGY

of Biaxial Crystals. Pleochroism. Absorption Phenomena show different degrees uniaxial similar like crystals may Colored biaxial crystals them depending the upon kinds of absorptionof lightpassingthrough or there may be three the direction of vibration of the light. In biaxial crystals different degreesof absorptioncorrespondingto three different directions of In general, these directions coincide vibration lyingat rightanglesto each other. Z. Variations from this parallelism with the opticaldirections X, F, and be observed, however, in crystalsof the monoclinic and triclinic may served systems. It is customary, however, to describe the absorption as it is obIf Z. to and parallel directions the vibrating light t o X, Y, parallel to Z is the least absorbed X is the most absorbed and lightvibratingparallel There are various other possibilities, " Y " Z. these facts are expressedasX the kind to X etc. Z " " such as X " Y F, Further,according Z, for d ifferent colors show t he distinctly of selective absorption, crystalmay in show the different or general pleochr9ism. directions, lightvibratingin of the pleochroismis stated by giving the colors corresponding The character For instance, in the case of to X, F, and Z. to the vibrations parallel Z to X yellow-green. In order lightblue, deep blue, F riebeckite, of a biaxial crystalat (least two sections the absorptionproperties investigate Z. These secbe obtained in which will lie the directions X, F, and tions must or examined the stage of the polariscope on microscope without the are nicol. They will show as they are rotated upon the stage,variations upper to in absorptionand in color as the lightpassingthrough them vibrates parallel 411.

"

=

'

=

=

=

firstone and then the other of their vibration directions. Art. 393. of dichroism in uniaxial minerals,

See the discussion

When to an optic axis of a crystalcharacterized by a high degree a section cut normal of color-absorption is examined verging by the eye alone (or with the microscope) in strongly conor light,it often shows the so-called epopticfigures,polarization-brushes, houppes This is true of andalusite, somewhat resemblingthe ordinary axial interference-figures. held close to the also tourmaline,etc. A cleavagesection of epidote ||c(001) epidote,iolite, here brown on a eye and looked through to a bright sky shows the polarization-brushes, absorbed as it passes ground. These figuresare caused by the lightbeing differently green through the section with different degrees of inclination. In certain minerals small circular or elliptical spots may be observed in which the pleochroism is stronger than in the surrounding mineral. These are commonly spoken of as other mineral. pleochroichalos. They are found to surround minute inclusions of some There have been many diverse theories to account for these ''halos" but recently it has been shown that they are probably due to some radioactive property of the inclosed crystal. Pleochroic halos have been observed in biotite,iolite, andalusite,pyroxene, hornblende, tourmaline,etc.,while the included crystalsbelong to allanite, rutile, titanite, zircon,apatite, etc.

SpecialOpticalCharacters of Orthorhombic

Crystals

412. Position of the Ether-axis. In the ORTHORHOMBIC in SYSTEM, accordance with the symmetry of the crystallization, the three axes of the that is,the directions X, F, and Z, coincide with the three crystalindicatrix, lographic axial planes of symmetry correspond axes, and the three crystallographic to the planesof symmetry of the ellipsoid.Further than this, there is no immediate relation between the two sets of axes in respect to magnitude, for the reason that, as has been stated,the choice of the crystallographic is arbitrary axes so far as relative lengthand positionare concerned,and hence made, in most cases, without reference to the opticalcharacter. Sections of an orthorhombic crystalparallelto a pinacoidplane (a(100), 6(010),or c(001))appear dark between crossed nicols, when the axial directions "

CHARACTERS

DEPENDING

UPON

289

LIGHT

coincide with the vibration-planes of the nicols;in other words, such sections parallelextinction. The same is true of all sections that are parallelto one of the three

show

crys-

sections lyingin the prism,macrodome tallographic axes, i.e., and brachydome zones. Sections,however, that are inclined to all three crystallographic will show inclined extinction. pyramidal sections, axes, i.e., 413. Determination of the Plane of the Optic Axes. The plane of the optic axes, that is,the plane includingthe directions X and Z, must be to one of the three pinacoids. Further,the acute bisectrix must parallel be normal to one of the two pinacoidsthat are at rightanglesto the opticaxial plane while the obtuse bisectrix is normal to the other such pinacoid. The the relation between the principal opticalorientation, i.e., opticaland crystallographic be easilydetermined can directions, by the examination of sections of a crystalwhich are cut parallelto the three pinacoids. To illustrate by an example, let it be assumed that such sections of the mineral aragoniteare available. These are representedin Fig. 592, A, B, and C. If the relative "

6 axis

Optical

Orientation

of

Aragonite

it will be characters of the vibration directions of each section are determined to the c axis in sections parallelto (100) found that lightvibratingparallel that lightvibrating and (010)is in both cases moving with the greatervelocity, is in both in 6 and axis the slower to the cases (001) (100) parallel ray, and that lightvibratingparallel to the a axis is the faster ray in (001)but the slower that the a axis must coincide with the directhis it is seen tion ray in (010). From be the same of vibration of the ray having the intermediate velocity, or X and b axis Z. Also it follows that c axis the opticaldirection Y. as since it must include X and Z, lies parallel The opticaxial plane,therefore, to and examined in t o sections If the (010)are convergent parallel (001) (100). lightboth will show biaxial interference figureswith the pointsof emergence The axial angle of the opticaxes lyingas illustrated in B and C, Fig. 592. than that obtained is smaller much to observed with the section parallel (001) bisectrix is normal to the base (001) from (010). Consequently the acute facts X the mineral is These and since it is the direction negative. optically in summarized the be statements: of opticalorientation may optically , =

=

"

Bxa.1 Ax.pl. ||a(100),

c(001).

MINERALOGY

PHYSICAL

290

in Orthorhombic Crystals. In the Optic Axes the of means refraction of prism method a crystal by determining the indices of the refracted ray white is of incident the light ray it is to be noted that when its into primary colors. The will in generalshow this white lightdispersed substances in certain but becomes is usuallysmall of this dispersion amount varies in this way considerable. Obviously since the angle of refraction of refraction will also vary. the indices of light different wave-lengths the with is dependent In biaxial minerals,as alreadystated,the opticaxial angle directly and y. three indices of refraction, the 0, of values relative a, the upon the considerable differences, depending show upon indices As these may it refracted the follows of wave-length ray, that the opticaxial anglewill also vary with In other words, the color of the lightused.

414.

Dispersionof

"

the

optic axes

may

be

dispersed. Fig. 593

in which the angle represents such a case for red light is between the optic axes The blue. opposite greater than that for condition may hold,in which the angle for From this it blue is greater than for red. follows that the interference figure when observed in blue lightwill not exactly coincide with that produced by rod light. The bisectrices of both figureswill be the but the positionof the pointswhere same will be different and the opticaxes emerge the positionsof the hyperconsequently bolas will also be and lemniscate curves Ditpemoo orthorhombic of orthorhombic different. In the case crystalsthe dispersionwill always be symmetrical to the two symmetry the directions i.e., planesof the indicatrix that pass through the acute bisectrix, and N-N M-M 594 595 in Figs. 594 and 595. A A This particular type of dispersionis said to be Orthorhombic sion, Disperin order to distinguish served it from that obin biaxial crystals of other systems. The two possiblecases N of orthorhombic sion dispershown in Figs. are 594 and 595. In expressing Orthorhombic Dispersion these two cases the Greek letters p (forred) and v (forviolet) for red used. When the axes are lightare more dispersedthan those for blue that fact is expressed as p " v in the reverse it is p " v. or case In the majorityof cases the effect produced upon the interference figure the is o f the be noted. In exceptional too dispersion by opticaxes slightto the where of amount i s effects The cases dispersion largethe seen. are clearly which are black throughout,will, when the figure hyperbolabars, ordinarily

CHARACTERS

DEPENDING

UPON

291

LIGHT

be seen, near the center,to be bordered on one side is observed in white light, and the other red blue on a The firstone one. fringe by by a two of the or colored lemniscates will also be broadened out along the line joining the two As already stated these changes in the of the figure opticaxes. appearance will always be symmetricalin respectto the traces of the two symmetry planes 596

597

'Blue

Orthorhombic

-Red

Dispersion

lyingat rightanglesto each other. In the case, Fig.594, where the axes for red lightare farther apart than those for blue (p " v),the hyperbolasin the interference figurefor the two different wave-lengthsof lightwill not coincide and the ones where the red lightis extinguished will be farther out than those for blue light. When red lightis taken out of the white light, blue remains, and

conversely when

blue is subtracted the resultant color is red. quently Consethe hyperbola bars will be bordered on their concave sides sides by red,Fig.596. In the other case, where by blue and on their convex their concave sides by red and on on p " v, the hyperbolas will be bordered their convex sides by blue,Fig.597. In other words, if blue lightshows at the that red lighthas been eliminated from these positions largerangle it means and the opticaxes for red are more dispersedthan those for blue,etc. in this

case

SpecialOpticalCharacters of Monoclinic 415.

Crystals

of Monoclinic Crystals. In monoclinic crysaxis of symmetry, the b crystallographic axis,and one plane of symmetry, the plane of the a and c crystallographic These are the axes. in elements that fixed are only crystallographic position. One of definitely the three chief opticaldirections, coincident with the 6 crystalX, Y, or Z, is lographic axis,while the other two lie in the symmetry plane,(010),but not parallelto any crystaldirection. There are obviouslythree possiblecases. If Y coincides with the axis b (and this is apparentlythe most common case) the directions X and Z will liein the crystal symmetry plane,which therefore becomes the opticaxial plane. If X or Z coincides with the" 6 axis the optic axial planewill be at rightanglesto (010)and either the acute or obtuse bisectrix -willbe normal of a monoclinic crystal to that plane. This clino-pinacoid is usuallythe best plane upon which to study its opticalorientation. Fig. 598 represents such a section cleaved from an ordinarycrystalof gypsum. The cleavagesparallelto (100) and (111) will serve to give its crystallographic orientation. Examination of the section in convergent lightfails to show a distinct interference figure, that the consequentlyit is to be assumed section itselfis parallelto the opticaxial plane and that the direction Y is

OpticalOrientation

stals there is one

"

PHYSICAL

292

MINERALOGY

the section is rotated on the microscope stage directions are seen to be inclined to the extinction crossed nicols its between of inclination the being measured axis, angle direction of the c crystallographic extinction the directions two be of can as 52J". The relative character of the the use quartz wedge easilydetermined by 598 of X and Z established. In and so the position the orientation of the X, Y and Z this way It is also posbe determined. directions can sible this section to determine from whether to (111) or the mineral is opticallypositive negative. If the section is viewed in convergent lighta somewhat is interference observed. figure vague its positionof the section is turned from When that faint dark extinction it will be noted of the field. out hyperbolas rapidly move Careful observation will show that they disappear (100) more slowly into one set of -quadrantsthan into The line bisecting the the other. opposite the into which bars hyperbola quadrants of is direction the the more slowly disappear bisectrix. The X or Z character of this acute and from this the direction can be determined In positiveor negativecharacter of the mineral. section of similar the a clino-pinacoid crystals way Optical Orientation of Gypsum belongingto the two other possibleclasses would yielddata concerningtheir opticalorientations. 416. Extinction in Monoclinic Crystals. Since only one of the three or Z, of a monoclinic crystalcoincides with opticaldirections, principal X, F, the a crystallographic tions axis,namely symmetry axis 6, it follows that only secthat are sections to this axis,i.e., 599 parallel in the orthodome will show parallel zone, All extinction. other sections will exhibit inclined extinction. 417. Dispersionin Monoclinic Crystals. As previouslystated there are three possible opticalorientations of a monoclinic crystal. In the first case the vibration direction Y coincides with that of the symmetry axis 6 and the optic axial plane coincides with the symmetry plane (010). In the other cases either the vibration direction X Z coincides with the crystalor lographic axis b and the optic axial plane is at right angles to "the crystallographic symmetry these conditions either the acute plane. Under obtuse bisectrix may or coincide with the axis b. Each of these three possibilities produce a may different kind of dispersion.It should be emphasized that the phenomenon of dispersion is seldom to be clearlyobserved and then commonly Inclined Dispersion only in unusually thick mineral sections. Case 1. Inclined Dispersion. Inclined dispersion is observed in the case

normal

to the

section. When

"

-

CHARACTERS

DEPENDING

UPON

293

LIGHT

where the direction Y coincides with the axis 6. This is illustrated in Fig.599. not In this case the axial angles vary for lightof different only may bisectrices of these anglesmay lie along different lines. wave-lengthsbut -the 600

601

f

Red

Inclined

Dispersion, p=*v

and the bisectrices may be dispersed.In Fig. for red lightis greater than 599 with p " v the anglebetween the opticaxes because of the that But for blue. 602 dispersionof the bisectrices it follows that on one side the pointof emergence of the opticaxis for red lightliesbeyond the other side that for blue, while on reversed. Also the the conditions are blue will be for red and optic axes side of the interference farther apart on one figurethan on the other side. ence the interferWith this sort of dispersion figurewill be symmetrical only in all Colon respect to the line which is the trace the section of the opticaxial plane, upon N-N, Fig.600, but is unsymmetricalto J the line at rightanglesto it,M-M. in the Inclined dispersionis shown fact that the the interference figureby colored borders to the hyperbola bars if blue reversed in the two cases, i.e., are side of one, red will is on the concave side of the other. be on the concave Dispersion Horizontal shown Further,tho amount of dispersion bar than with the other. is much Fig.601 representsa greater with one

So, here,both the opticalaxes

r

of inclined dispersion. axis b the crystallographic Case 2. Horizontal Dispersion. In this case be either the X or Z direction, coincides with the obtuse bisectrix which may is optically ter. or negativein characpositive depending upon whether the crystal In this case the direction of the obtuse bisectrix is fixed for lightof all wave-lengths. The angle between the opticaxes may vary and further the of the acute bisectrix may vary as long as itliesin the crystallographic position symmetry plane. In other words, the axial planes may be dispersed,see Fig.602. The pointsof emergence of the opticaxes, when p " v, for blue and red light, might therefore be like that shown in Fig.603. It will be noted that from a section approxin this case the interference figure(obtainedof course case

294

MINERALOGY

PHYSICAL

to the imatelyperpendicular

unsymmetricalin

but

is symmetrical to the line M-M bisectrix)

Fig. 604 shows figure.

respect to the line N-N.

dispersion upon

horizontal

acute

the interference

the effect of

604

603

Axis for Red

"p

for Blue

Axis

"P

Horizontal

Case

3.

Crossed

ion.

In

605,

Dispersion.p"v

the crystallographic axis b this case the acute coincides with bisectrix, be either the X or Z direcwhich may tion acter depending upon the opticalcharof the crystal. In this case the direction of the acute bisectrix is fixed for light of all wave-lengths. The

anglebetween

Red

the

r

all Colors

Blue

Crossed

the

Dispersion

effect of crossed

dispersionupon 606

607

Crossed

opticaxes

may

vary

further the positionof the axial planes for different wave-lengthsmay ular vary as long as they remain perpendicto the crystallographic symmetry of this sort is shown plane. A case in Fig. 605. The gence points of emerof the opticaxes when p " v for blue and red lightmight therefore be like that shown in Fig.606. It will be that in this the figureis symseen case metrical to neither the line M-M nor N-N but only to the central point of the figure, the point of emergence i.e., of the acute bisectrix. Fig.607 shows the interference figure. and

Dispersion p"v

296

PHYSICAL

MINERALOGY

the relative character of the two vibration directions of d. Determine to which as responds corthe two extinction directions), the section (i.e., Test slower be to the to which faster and to the ray. 348. Art. sensitive see tint, made with quartz wedge or Find the grainshowing the highestorder of interference color and e. fringence. so approximately determine the strengthof the mineral's birerefractive indices determine as indices refractive shown of the accurately range be possiblein connection with tests It may by the mineral. the values for certain of the prinunder 3 to determine made indices. refractive cipal 3. Observations in convergent polarized lightwith crossed nicols. and if so interference figure, the mineral shows an Note whether a.

/. By

in oils of known

immersion

as

possiblethe

.

biaxial. or is uniaxial determine the positionof the optic axis in determine respectto the plane of the given section and if possible the positive or negativecharacter of the mineral. If the mineral is biaxial determine the positionof the axial plane in the positiveor respect to the section. Determine, if possible, if of mineral. character the an Obtain, possible, imate approxnegative idea as to the size of the axial angle. Note any evidences

whether 6. If mineral

c.

it is uniaxial

of

dispersion. making the above tests it is helpfulto keep,as far as possible, a graphicrecord of the results, something like that illustrated in Fig.592. The general effects of 422. Effect of Heat OpticalCharacters. upon heat upon venient, as regards expansion,etc.,are spoken of later. It is concrystals the changes produced by this however, to consider here, briefly, in the special that no alteration of means opticalcharacters. It is assumed the chemical compositiontakes place and no abnormal change in molecular In general, structure. the effect of a temperature change causes a change in the refractive indices. In the majority of cases the indices decrease in Note.

"

In

"

value with rise of temperature but in certain cases is consequentlyimportant in any exact statement

the of

a

is true. It refractive index to particularfacts for

reverse

determined. The give the temperature at which it was the different opticalclasses are as follows : at all temperatures. however, (1) Isotropic crystalsremain isotropic Crystals, which, like sodium chlorate (NaClO3 of Class 5, p. 72),show circular polarizationmay have their rotatory power creased altered;in this substance it is inby rise of temperature. remain uniaxial with rise or fall of tempera(2) Uniaxial crystalssimilarly ture; the only change noted is a variation in the relative values of co and e, that is,in the strength of the double refraction. This increases, for example, with calcite and grows weaker with beryland quartz. It is,further, to interesting note that the rotatory power of quartz increases with rise of temperature, but the relation for all parts of the spectrum remains sensiblythe same. the effect of change of temperature varies with (3) With Biaxial crystals, the system to which they belong.

use on

The axial angle of biaxial crystalsmay be measured at any required temperature by the of a metal air-bath. This is placed at P (Fig.588) and extends beyond the instrument either side,so as to allow of its being heated with gas-burners; inserted a thermometer

CHARACTERS

DEPENDING

UPON

297

LIGHT

in the bath makes it possibleto regulatethe temperature as may be desired. This bath has two openings, closed with glassplates,corresponding to the two tubes carrying the lenses, held as usual in the pincers,is seen and the crystal-section, through these glasswindows. Suitable accessories to the refractometer also allow of the measurement of the refractive indices at different temperatures.

In the ether-axes

of orthorhombic crystals, the positionof the three rectangular since must alter, they always coincide with the crystalloThe values of the refractive axes. graphic indices, however, may change,and hence with them also the opticaxial angle; indeed a change of axial plane or of the opticalcharacter is thus possible. With monodinic ether-axis must coincide at all temperatures one crystals, with the axis of symmetry, but the positionof the other two in the plane of and this,with the possiblechange in the value of the symmetry may alter, "refractive indices, cause a variation in the degree(orkind) of dispersion as may well as in the axial angle. With tricliniccrystals, both the positions of the ether-axes and the values of the refractive indices may The observed change. opticalcharacters may therefore vary widely. case

cannot

A

strikingexample of the change of optical characters with change of temperature is At ordinary temperatures, the as by gypsum, investigatedby Des Cloizeaux. the optic axial plane is ||6(010)and 2Er 95". As the temperature dispersionis inclined, rises this anglediminishes;thus,at 47",2Er 0. 76"; at 95",2Er 39"; and at 116",2Er At this last temperature the axes for blue rays have alreadyseparated in a plane _1_6(010); for red rays also separate in this plane (_L 6) and the dispersionbecomes at 120" the axes horizontal. red axis is more The motion toward the center of one rapid than that of the 33" 55' while the other moves other,namely, between 20" and 95",one axis moves only 22" 38'; thus Bxr moves 5" 38'. Another interesting is that of glauberite. Its opticalcharacters under normal concase ditions described as follows: Optically Ax. pi.J_ 6(010),Bxa.r A c axis are "31" 3', -30" 46',Bxa.bi A c axis -30" 10'. The optical character (-) and Bxa.y A c axis of elasticity the positionof the axes remain sensiblyconstant between 0" and 100". The ax. pi.,however, at first _l_ 6(010) with horizontal dispersionand v " p becomes on rise of The axial angle accordingly diminishes temperature 116 with inclined dispersionand v " p. to 0" at a temperature depending upon the wave-length and then increases in the new the interference-figures abnormal and change with plane. In white light,therefore, are furnished

=

=

=

=

=

"

.

=

=

rise in temperature. Des Cloizeaux found that the feldspars,when heated up to a certain point, suffer a change in the positionof the axes, and if the heat becomes greater and is long continued they do not return again to their originalposition,but remain altered.

In addition to the typical cases of temperature is connected

referred to, itis to be noted that when elevation with change of chemical compositionwide changes in opticalcharacters are possible. This is illustrated by the zeolites and related species, where the effect of loss of water has been particularly

investigated. Further,with

ular bringabout a change of moleccharacters. For ple, examoptical the greenish-yellow orthorhombic (artificial) crystalsof antimony iodide (SbI3)on heating (toabout 114")change to red uniaxial hexagonal crystals. Note also the remarks made later in regard to the effect of heat upon leucite and boracite (Art.429). structure

423.

Some

some

heat crystals,

and with that

Peculiarities

a

in Axial

total

to change of serves

Interference-figures.* "

the characteristic interference-figure varies but

* Variations in the axial figuresembraced of later (Art.429).

under

littlefrom

In the one

case

of uniaxial crystals,

speciesto another, such

the head .ofopticalanomalies

are

spoken

298

PHYSICAL

MINERALOGY

fringence. being usuallydue 19 the thickness of the section and the birethe interferenceFor noted. example, are In some cases, however, peculiarities is somewhat peculiar,since its birefringenceis very weak, and it may figureof apophyllite the spectrum and negative for the other. of for one be optically part positive The followingare some common. more are of biaxial crystals, In the case peculiarities variation

is observed

as

typicalexamples: ever, Brookite is optically+ and the acute bisectrix is always normal to a (100). While, howit monly com2ET with is 30", for and 55", 2EV red is axial yellow, the plane ||c(001) Hence 34". 1a(100) in the conoa section 1 ||6(010)for green and blue,with 2Egr resembling that of a uniaxial crystalbut with four sets of shows a figuresomewhat scope =

=

=

hyperbolicbands. of with colored hyperbolas because also gives a peculiarinterference-figure 2E for red and between lightbeing green high color-dispersion, p " v, the variation approximately 10"; the dispersionof the bisectrices is,however, very small. of peculiar axial figuresare afforded by twin crystals(Art.425). The most strikingcases

Titanite

the

of OpticalPropertiesto Chemical Composition. the opticalcharacters has effect of varying chemical compositionupon series of isomorphous salts,and minutely studied in the case of many important results. It is,indeed,only a part of the generalsubjectof the Relation

424.

"

form and molecular structure on crystalline the other,one on part of which has composition

between

chemical

It was shown there that the refractive index calculated from the chemical composition.

Art. 322.

can

the

one

hand

The been with tion relaand

discussed in often be approximately

been

Among minerals,the most important examples of the relation between composition and optical characters are afforded by the triclinic feldspars of the albite-anorthite series. Here, as explained in detail in the descriptivepart of this work, the relation is so close be preof this isomorphous group can that the composition of any intermediate member dicted from the positionof its ether-axes, or more simply from the vibration directions on the fundamental cleavage-directions, ||c(001) and ||6(010). of the The effect of varying amounts of iron protoxide (FeO) is illustrated in the case monoclinic pyroxenes, where, for example, the angle Bxa A c axis is 38" in diopside (2'9 This is also shown in the closelyrelated p. c. FeO) and 47" in hedenbergite (26 p. c. FeO). orthorhombic speciesof the same MgSiOs with littleiron,and hypersthene, group, enstatite, (Mg,Fe)SiO3 with iron to nearly 30 p. c. With both of these speciesthe axial plane is parallelto 6(010),but the former is optically+ (Bxa Z) and the dispersionp " v, the latteris optically (Bxa A^) and dispersionp " v. In other words,the optic axial angle In the case 10 p. c. changes rapidly with the FeO percentage, being about 90" for FeO of the chrysolites, and others,analogous the epidotes,the speciestriphylite and lithiophilite, =

=

"

=

relations have

425.

been

made

out.-

of sections Optical Propertiesof Twin Crystals. The examination of any other than the isometric system in polarized crystals light to establish the compound character at once a'nd also to show the "

of twin serves

relative orientation of the several parts. This is most distinct in the case of but is also well shown with penetration-twins, here the contact-twins, though parts are usually not separated by a sharp line. Thus the examination of a section parallelto 6(010)of a twin crystalof of the of type gypsum, Fig.608, makes it easy not only to establish the fact of the twinning but also to fix the relative positions of the ether-axes in the two parts. The measurement in such cases be made between the extinction-directi can in the two halves,instead of between of these and some one definite crystallographic line,as the vertical axis. The

polysynthetic twinning

of certain

with species,as the triclinic feldspars, appears of a section of albite, case parallel to the basal cleavage, the alternate bands extinguishtogether and assume the same tint when the quartz section is inserted. Hence these directions is easily the angle between measured, and this is obviously double the extinction-anglemade with the edge 6(010) A c(001). A basal section of microcline in the same shows its compound twinning way

great distinctness in polarizedlight. For example, in the

CHAEACTERS

DEPENDING.

UPON

299

LIGHT

according to both the albite and periclinelaws,the characteristicgrating structure being clearlyrevealed in polarizedlight. Fig.609 of a section of chondrodite (from Des Cloizeaux) shows how the compound structure is shown by opticalexamination; the positionof the 609

001

lamellae. The complex plane is indicated in the case of the successive polysynthetic of right-and left-handed crystalsof quartz (seethe descriptionof that penetration-twins revealed in polarizedlight. species)also have their character strikingly axial

610

612

Witherite

Bromlite

(Des Cloizeaux)

Still again, the true structure of complex multipletwins, exhibitingpseudo-symmetry in their external form, can This is illustrated by Fig. only be fullymade out in this way. 610, a basal section of an apparent hexagonal pyramid of witherite. The analogous six613

614

Stilbite

615

(Lasaulx)

sided pyramid of bromlite (Fig.611) has a stillmore complex structure, as shown in Fig. Fig. 613 shows a simple crystalof stilbite;Fig. 614 is the common type of twinand Fig.615 illustrates how the complex structure crystal, (||6010)is revealed in polarized

612.

MINERALOGY

PHYSICAL

300

that the axial It will be understood illustrations are given in Art. 429. show often the superposed, many are where parts of twin crystals, interference-figures illustration. will serve an as 270) o f (p. quartz the spirals Airy peculiarities;

light. Other

in the interesting case, related to the subjectdiscussed particularly of cleavageof superposed that the is properties special precedingarticle, of these,say of rectangular form, be superIf three or more posed sections of mica. of make the axial of lines angles equal planes and so placed that the has which is the that passed effect light polarized 60" (45", etc.)with each other with a rotation to right or through the center suffers circular polarization, The ference-fig interbuilt up. in which the sections are left accordingto the way 426.

A

resembles that of a section of quartz cut normal to the axis. and very thin the imitation of the phenomena If the sections are numerous ular lightupon the ultimate molecof quartz is closer. These facts throw much ther, Furcircular medium of polarization. showing a structure crystallized in sections to have how it is understand to from this possible is it easy of clinochlore) portionswhich are biaxial and others of certain crystals (e.g., intimate twinning after this to an due latter being that are uniaxial,the method

of biaxial

portions.

The specialopticalphenomena of 427. OpticalPropertiesof CrystallineAggregates. the different kinds of crystalline aggregates described on pp. 182, 183, and the extent to in the the distinctness be determined, depend upon which their opticalcharacters can of The orientation. individuals relative and their case ordinary of the lar, granudevelopment Where, however, the aggregates needs no specialdiscussion. fibrous,or columnar to do more doubly refractinggrainsare extremely small,the microscope may hardly serve than to show the aggregate polarization present. that is,aggregates sphericalin form and A case of specialinterest is that of spherulites, various chlorites, with calcite, radiated or concentric in structure; such aggregates occur of a doubly refractingcrystallinemineral, or of an feldspars,etc. If they are formed monly amorphous substance which has birefringentcharacters due to internal tension,they comin the microscope between crossed nicols;further,this cross, as exhibit a dark cross backward. to rotate the section is revolved on the stage, though actuallystationary,seems A distinct and more specialcase is that of sphericalaggregates of a mineral optically Sections of these (not central)in parallel uniaxial (orbiaxial with a small angle) polarized of a uniaxial crystal. The less distinctly the interference-figure or lightshow more tive objecbe focussed on a point a littleremoved from the section itself, must say on the surface of the sphere of which it is a part. In such cases the + or character of the double usual. refraction can be determined as 428. Induced As the difference between Change of Optical Character by Pressure. the opticalphenomena exhibited by an isometric crystalon the one hand and a uniaxial or biaxial crystalon the other is referred to a difference in molecular structure modifying the propertiesof the ether,it would be inferred that if an amorphous substance were subjected to conditions tending to develop an it would analogous difference in its molecular structure also show doubly refractingproperties. This is found to be the case. Glass which has been suddenly cooled from a state of fusion,and which is therefore characterized by strong internal tension,usually shows marked double refraction. Further,glassplatessubjected to great mechanical in pressure direction show in polarizedlightmore one less distinct interference-curves. Gelatine or exhibit like phenomena. sections,also,under pressure Even the strain in a glass block developed under the influence of unlike charges of electricity of great difference of potential its opposite sides is sufficient to make on it doubly refracting. In an analogous manner the double refraction of a crystalmay be changed by the application of mechanical force. Pressure exerted normal to the vertical axis of a section of a tetragonalor hexagonal crystalwhich has been cut _L c axis,changes the uniaxial interference-figur into a biaxial, and with substances opticallypositive, the plane of the optic and with negative substances normal, to the direction of is parallel, axes pressure. The o.uartz crystalsin rocks, which have been subjected to great often are pressure, found to be in an abnormal state of tension, showing an undulatory extinction in polarized "

.

"

"

light.

DEPENDING

CHARACTERS

UPON

301

LIGHT

Since the earlyinvestigations of Brewster, others (1815 et seq.)it has been recognizedthat many crystals in harmony with the apparent which not exhibit opticalphenomena are of their external form. isometric species, Crystalsof many symmetry as less pronounced or analcite,alum, boracite,garnet, etc., often show more and sometimes double refraction, uniaxial or biaxial. A they are distinctly in parallel section examined less sharply or polarizedlightmay show more denned doubly refractingareas, or parallelbands or lamellae with varying extinction. Occasionally,as noted by Klein in the case of garnet,while most others show opticalcharacters which seem are normally isotropic, to crystals be determined by the external bounding faces and edges;thus,a dodecahedron to be made whose apices pyramids (biaxial) up of twelve rhombic appear may the hexoctahedron to made be at seem are similarly center; a may up of forty429.

OpticalAn6malies.

"

Herschel,and

pyramids, etc. eighttriangular common tetragonalor hexagonal species, Similarly, crystalsof many as ence-figures vesuvianite, zircon,beryl,apatite,corundum, chabazite,etc.,give interferdictions resembling those of biaxial crystals. Also, analogous contrabetween form and optical characters are noted with crystalsof and monoclinic orthorhombic species, etc. e.g., topaz, natrolite, orthoclase, such as those a nomalies. optical

All

cases

mentioned

are

embraced

under

the

common

term

of

in recent investigators subjecthas been minutely studied by many have to been made it additions both the and on practicaland important years is The result doubtful side. theoretical stillremain, the that, though cases have found of the typicalones a satisfactory explanation. No single many applied. theory,however, can be universally the anomalies The chief question involved has been whether to be are whether considered as secondary and non-essential, or they belong to the in question. On the one of the crystals inherent molecular structure hand, it has been urged that internal tension suffices (Art.428) to call out double substance or to give a uniaxial crystalthe typical refraction in an isotropic biaxial of structure a crystal. On the other hand, it is equallyclear optical that twinning often produces pseudo-symmetry in external form, and at the the simplest characters. From time conceals or changes the optical same case, witherite that of aragonite, we as complex cases, as (Fig.610), pass to more bromlite (Figs.611, 612),phillipsite times (Figs.400, 452-454), which last is somein form though opticalstudy shows the monoclinic pseudo-isometric character of the individuals.* Reasoning from the analogy of these last cases, anomalies could in most Mallard was led (1876)to the theory that the optical intimate be explainedby the assumption of a similar but stillmore cases unite this without would to themselves form which of molecules tals crysgrouping of a lower grade of symmetry than that which their complex twinned This

crystalsactuallysimulate. In regard to the two probable that points of view mentioned, it seems of sudden or internal tension (due to pressure, rapidity growth, etc.) cooling, be safelyappealed to to explainthe anomalous opticalcharacter of many can as beryl,quartz,etc. Again,it has been fullyproved diamond, halite, species, that the later growth of isomorphous layers of varying composition may *

by

Crystalsshowing pseudo-symmetry of highlycomplex type

Tschermak.

are

called mimetic

crystals

302

PHYSICAL

MINERALOGY

produce opticalanomalies, probably here also to be referred to tension. Alum of this species were earlyinvestigated is a striking example. The peculiarities of lamellar of his the basis polarization," him theory by Biot and made by 616 the true one. doubtless Brauns) is Fig. (from but the present explanation in from section a of || 0(111) in a crystal the appearance polarizedlight shows to Further, have different according composition. which the successive layers be referred to this other speciesmay of many Brauns, the opticalpeculiarities with those some cases garnets) (as He includes here,particularly, cause. same the external to form, as depend upon in which the opticalcharacters seem (from Golden, a section of which Here belongs also apophyllite, noted above. The section has been cut ||c(001) Col.,by Klein) is shown in Fig. 617. "

616

617

Alum, ||111

||001 Apophyllite,

618

Leucite, ||100

through the center of the crystaland is representedas it appears in parallel polarizedlight. Another quite distinct but most important class is that includingspecies which are such as boracite and leucite, dimorphous; that is,those species which at a certain elevation of temperature (300"for boracite and 500" to 600" these species for leucite) become strictly isotropic.Under ordinaryconditions, their but the fact stated makes it probable that originally are anisotropic, form and opticalcharacters were in harmony. The relations for crystalline leucite deserve to be more minutely stated. feeble double refraction: to 1'509. This Leucite usually shows 1'508, e very double refraction, anomalous early noted (Brewster,Biot),was variouslyexplained. In 1873, Rath, on the basis of careful measurements, referred the seemingly isometric crystals to the tetragonalsystem, the trapezohedralface 112 being taken as 111 and 211, 121 as Later Weisbach 421, 241; respectively;also 101, Oil as 201, 021. (1880), on the same ground, made them orthorhombic; Mallard, however, referred them (1876),chieflyon opticalgrounds, to the monoclinic system, and Fouque and Levy (1879) to the triclinic. tend The true symmetry, corresponding to the molecular structure which they possess or to possess at ordinary temperatures, is in doubt, but it has been shown (Klein,Penfield) that at 500" to 600" sections become isotropic;and further (Rosenbusch) that the twinning striations disappear on heating,to reappear again in new positionon cooling. Sections show twinning-lamellae ordinarily |jd(110); in some cases a bisectrix (+) is normal to what correspondsto a cubic face,the axial anglebeing very small. The structure correspondsin general (Klein) to the interpenetrationof three crystals,in twinning position||d, which be equallyor unequally developed; or there may individual with be one fundamental may inclosed twinning-lamellse.Fig. 618 shows a section of a crystal(||a, 100) which is apparently made up by the twinning of three individuals. =

=

Still again,in a limited number of cases, it can be shown that -the interdifferent crystallographic growth of lamellae having slightly orientation is the of the opticalpeculiarities. cause Prehnite is a conspicuous example of this class.

304

PHYSICAL

MINERALOGY

ters structure; change in opticalcharacin their relation to crystalline especially the also or diathermancy, heat; of power with change temperature; specific and other related these discussion of The full radiation. heat of transmitting A few brief subjectslies outside of the range of the present text-book. be made reference must these to and made beyond remarks are them, upon of mentioned which are some to text-books on Physics and specialmemoirs, in the literature (p.305). 431. Fusibility. The

erals of different minapproximate relative fusibility from different in one species distinguishing is an important character is scale For this a conveniently another by means of the blowpipe. purpose used for comparison,as explainedin the articleslater devoted to the blowpipe. and though of little of the fusibility are Accurate determinations difficult, point. from a theoretical standimportancefor the above object,they are interesting They have been attempted by various authors by the use of a number The of different methods. followingare the approximate melting-point 525" : KobelPs scale (Art.491): Stibnite, values for the minerals used in von 1296"; orthoclase,1200"; natrolite,965"; almandite, 1200"; actinolite, bronzite,1380"; also for quartz, about 1600". of different crystallized 432. Conductivity. The conducting power stance He the faces of the subcovered Senarmont. media was early investigated by the and form of under observed the w ith wax figure investigation with the surface at its middle point. melted by a hot wire placed in contact Later investigations have been made by Rontgen (who modified the method of In generalitIs found that, as regards and others. Senarmont),by Jannettaz, their thermal conductivity, crystalsare to be divided into the three classes noted on p. 252. In other words, the conductivityfor heat seems to follow the same the of It generallaws as propagation light. is to be stated,however, that experimentsby S. P. Thompson and 0. J. Lodge have shown a different in tourmaline rate of conductivity in the oppositedirections of the vertical "

"

axis. 433.

Expansion. Expansion, that is,increase in volume upon rise of temperature, is a nearly universal property for all solids. The increment of volume for the unit volume in passingfrom 0" to 1" C. is called the coefficient of expansion. This quantity has been determined for a number of species. Further, the relative expansion in different directions is found to obey the laws as the light-propagation. same as are Crystals, regardsheat-expansion, thus

"

divided into the same three classes mentioned on p. 252 and referred to precedingarticle. The amount of expansion varies widely,and, as shown by Jannettaz,is influenced particularly the Mitscherlich found that in calcite by cleavage. there was of 8' 37" in the angleof the rhombohedron a diminution on passing from 0" to 100" C., the form thus approachingthat of a cube as the temperature increased. The rhombohedron of dolomite,for the same perature, range of temdiminishes 4' 46"; and in aragonite, for a rise in temperature from 21" to 100",the angleof the prism diminishes 2' 46". In some rhombohedrons, of calcite, the vertical axis is lengthened (and the horizontal shortened), as while in others, like quartz, the reverse is true. The variation is such in both that the birefringence cases is diminished with the increase of temperature, for calcite possesses and quartz, positive. negativedouble refraction, It is to be noted that in general the expansion by heat,while it may serve to alter the anglesof crystals, other than those of the isometric system, does

in the

CHARACTERS

DEPENDING

UPON

HEAT

305

alter the zone-relations and the crystalline In certain cases, symmetry. however, the effect of heat may be to give rise to twinning-lamellse (as in not

anhydrite)or to cause their disappearance(asin calcite).Rarely heat serves develop a new molecular structure;thus,as explainedin Art. 429, boracite and leucite, which are anisotropic at ordinarytemperatures, become isotropic when heated,the former to 300" the latter to 500" or 600". The change in the opticalproperties of crystals produced by heat has already been noticed 422). (Art. 434. Determinations of the specificheat of many SpecificHeat. minerals have been made by Joly,by Oeberg,and others. Some of the results to

"

reached

are

follows:

as

Joly 0'0541

Galena, cryst. Chalcopyrite Pyrite

01271 01306

Hematite

Garnet, red cryst.01780 Epidote

"

01683 01793

G'1877

435. Besides the slow molecular propagation of heat Diathermancy. in a body, measured there is also to be considered its thermal by conductivity, the rapid propagationof what is called radiant heat through it by the wavemotion of the ether which surrounds its molecules. This is merely a part of the generalsubjectof light-propagation since heatwaves, alreadyfullydiscussed, in the restricted sense, differ from light-waves only in their relatively greater length The degreeof absorptionexerted by the body is measured by its diathermancy, which correspondsto transparency in light. In this sense and fluorite are highly diathermanous, since they absorb but halite, sylvite, littleof the heat-waves passingthrough them; on the other hand, gypsum and, stillmore, alum are comparativelyathermanous, since while transparent to the short light-wavesthey absorb the long heat-waves, transformingthe of the diathermancy were Measurements energy into that of sensible heat. made early by Melloni,later by Tyndall,Langley,and others. "

*

LITERATURE Heat Mitscherlich.

Pogg. Ann., 1, 125, 1824; 10, 137, 1827. Pogg. Ann., 27, 240, 1833. Gypsum. Ch. Phys., 21, 457, 1847; 22, 179, 1848; also in Pogg. Ann., 73, 50, 482.

F. E. Neumann. Ann. Senarmont.

191; 74, 190; 75.

Pogg. Ann., 86, 206,

Angstrom. Grailich Fizeau.

335, 1866;

1852.

and von Lang. Ber. Ak. Wien, 33, 369, 1858. Ann. Thermal expansion. C. R., 58, 923, 1864. also C. R., 1864-1867.

Ch. Phys., 2, 143, 1864; 8,

C. Neumann. Pogg. Ann., 114, 492, 1868. Pape. Thermic axes of blue vitriol. Wied. Ann., 1, 126, 1877. Rontgen. Pogg. Ann., 151, 603, 1874; Zs. Kr., 3, 17, 1878. Jannettaz. Conductivity of crystals. Bull. Soc. Geol., (3) 1, 117, 252; 2, 264; 3, 499; 4, 116, 554; 9, 196. Bull. Soc. Min., 1, 19, 1879. C. R., 1848, 114, 1352, 1892. O. J. Lodge. Thermal conductivity. Phil. Mag., 5, 110, 1878. Phil. Mag., 8, 18, S. P. Thompson and O. J. Lodge. Conductivity of tourmaline. 1879. Arzruni.

Effect of heat

Beckenkamp. H.

Dufet.

191, 1881.

on

Zs. Kr., 1, 165, 1877. refractive indices of barite,etc. and tricliniccrystals.Zs. Kr., 5,436, 1881. Bull. Soc. Min., 4, 113, refractive indices of gypsum. on

Expansion'ofmonoclinic Effect of heat

306

MINERALOGY

PHYSICAL

Zs. Kr., 12, 321, 1887; TiO2, ibid.,9, 433, 1884. Expansion of crystals. Zs. Kr., 4, 337, 1880. Ch. News, 65, 1, 16, 1892, and Proc. Roy. Irish Joly. Meldometer. Proc. heat. Roy. Soc.,41, 250, 352, 1887. 1891. Specific

Sulphur.

A. Schrauf. L. Fletcher.

kJfJV/V-'ll.lV-'AXV/C*V"

X.

f^.

-1.

"

Ct

C.

J.W.

""

Oeberg.

Specific Specifn heat.

Doelter.

For

1

chemie, 1, 628

"

methods m

e

f^

Acad., 2, 38,

F

Ctj._-l_t_

TVT_

O

/IO

1OOC

Oefv. Ak. Stockh., No. 8, 43, 1885. see and results in fusing silicates, A

1

Handbuch

der

Mineral-

et seq.

DEPENDING

CHARACTERS

V.

.

-*.vv^

ELECTRICITY

MAGNETISM

AND 1.

UPON

ELECTRICITY

The subject of the relative conducting Electrical Conductivity. erals, minor interest.* In generalmost minof is one power and luster the metallic oxides,are sulphides among except those having a show non-conductors can non-conductors. pyro-electrical ena, phenomOnly the and only the conductors can give a thermo-electric current. electrical charge Frictional Electricity. The development of an 437. electric is a familiar subject. All minerals become bodies by friction on many although the degree to which this is manifested differs widely. by friction, There is no line of distinction among minerals,dividingthem into positively be presentedby electric; for both electrical states may electric and negatively and by the same different varieties of the same varietyin different species,

436.

"

of different minerals

"

electric only when polished;the generalpositively It is polishedor not. observed friction was a familiar fact that the electrificationof amber early upon rise to the later gave (600 B. C.),and indeed the Greek name (^Xe/crpo*/) word electricity. 438. Pyro-electricity.The simultaneous development of positiveand different parts of the same on crystalwhen its negativechargesof electricity Crystalsexhibiting temperature is suitablychanged is called pyro-electricity. such first This phenomenon was phenomena are said to be pyro-electric. of tourmaline, which is rhombohedral-hemimorphic in observed in the case and it is particularly marked with crystals crystallization, belongingto groups of relatively low symmetry, especially those of the hemimorphic type. It is of course, only with non-conductors. This subjectwas tigated possible, earlyinvesRiess and Rose later also C. K undt. by (1843), by Hankel, by Friedel, and others (seeliterature). In all cases it is true that directions of like crystallographic symmetry show chargesof like sign, while unlike directions exhibit opposite charges. may Substances not crystallized cannot A few of the many show pyro-electricity. essential points. to bring out the most possible examples will serve Boracite (isometric-tetrahedral, on p. 66) on heatingexhibits + electricity set of tetrahedral faces and one the other. Cf. Fig. 619. on electricity Tourmaline (rhombohedral-hemimorphic, p. 109)shows oppositechargesat the oppositeextremities of the vertical axis correspondingto its hemimorphic In this and in other similar cases, the extremity which crystallization. states.

The

gem"

are

in

whether electricity diamond, however, exhibits positive

"

"

*

On

the

of minerals, Jb. Min., Beil.-Bd., conductivity see Beijerinck, 11,403, 1898.

CHARACTERS

DEPENDING

UPON

ELECTRICITY

AND

MAGNETISM

307

becomes positive on heatinghas been called the analogouspole,and that which becomes negativehas been called the antilogous pole. Calamine and struvite (orthorhombic-hemimorphic, p. 126)exhibit phenomena analogousto those of tourmaline.

Quartz (rhombohedral-trapezohedral, p. 112) shows + electricity on heating at the three alternate

prismaticedges and at the three remaining electricity edges; the distribution for right-handedcrystalsis opposite to that of lefthanded. Twins may exhibit a high degreeof complexity. Cf. Figs.620, 621. Axinite (triclinic, heated to 120" or 130",has an p. 144),when "

analogous

619

pole (Riess" Rose) near plane n.

620

at the solid

621

anglerxM'; the antilogouspole at the angle

mr'M'

convenient and simple method for investigating the phenomena is to w hich is due Kundt: First heat the fully following, crystalor section careit several times in an air-bath;pass through the flame of an alcohol lamp and then place it on a littleupright cylinderof brass to cool. While cooling,a mixture of red lead and sulphur finelypulverizedand previously agitatedis dusted over it through a fine cloth from a suitable bellows. The electrifiedred lead collects on the parts having a negativecharge, positively and the negativelyelectrifiedsulphuron those with a positive charge. This is illustrated by Figs. 619-621, and still better by the illustrations given by Kundt and others. (Cf.Plate III of Groth, Phys. Kryst.,1905.) has been given to 439. Piezoelectricity. The name piezo-electricity This the development of electricalchargeson a crystallized body by pressure. of calcite, also by topaz. This phenomenon is is shown by a cleavage mass be established between the electrical where a relation can most interesting molecular is excitement and the conspicuouslytrue with quartz, structure,as other species. tourmaline, and some This subject has been investigatedby Hankel, Curie, and others, and discussed theoretically by Lord Kelvin (see literature).Hankel has also for the phenomenon employed the term actino-electricity ',or, better,photo-electricity, electrical condition by the influence of direct of producing an A

very

the

"

radiation;fluorite is a conspicuousexample. 440. Thermo-electricity. The contact of two unlike metals in general of them positively and the other negatively. If, results in electrifying one further,the point of contact be heated while the other parts,connected with a wire,are kept cool,a continuous current of electricity shown, for example, of the heat-energysupis set up at the expense suitable galvanometer by a plied. is of the the other hand, point junction cooled,a current is set If,on direction. This phenomenon is called thermo-electricity up in the reverse "

"

"

,

308

PHYSICAL

MINERALOGY

metals so connected constitute a thermo-electric couple. Further it be arranged in order in a table that different conductors can a series so-called thermo-electric according to the direction of the current set of this current. Among up on heating and according to the electromotiveforce at the oppositeends of the the metals, bismuth (+) and antimony (") stand series;the current passes through the connectingwire from antimony to and two

is found

"

"

bismuth. shown by Bunsen This subjectis so far importantfor mineralogy,as it was stand farther off in the series than bismuth that the natural metallic sulphides and antimony, and consequentlyby them a higher electromotive force is of minerals were produced. The thermo-electrical relations of a largenumber determined by Flight. It was minerals have varieties which are both -fearlyobserved that some Rose establish relation between to and the positiveand a attempted forms and and of the positiveor negapyrite cobaltite, negativepyritohedral tive Later investigations thermo-electrical character. by Schrauf and Dana have shown, however, that the same peculiarity belongs also to glaucodot, tetradymite, skutterudite, danaite,and other minerals,and it is demonstrated by them that it cannot be dependent upon crystalline form, but rather upon chemical composition. "

.

LITERATURE

*

etc. Pyro-electricity,

Tourmaline. Pogg. Ann., 39, 285, 1836. and Rose. Pogg. Ann., 59, 353, 1843: 61. 659, 1844.

Rose. Riess Kobell. Hankel.

in Abhandl.

Pogg. Ann., 118, 594, 1863. Pogg. Ann., 49, 493; 50, 237, 1840; 61, 281, 1844. Many important papers K. Sachs. Ges., 1865 and later; also Wied. Ann., 2, 66, 1877; 11, 269, 1880,

etc.

J. and P. Curie. C. R., 91, 294, 383, 1880; 92, 186, 350, 1881; 93, 204, 1882. Kundt. Ber. Ak. Berlin,421, 1883; Wied. Ann., 20, 592, 1893. Kolenko. Quartz. Zs. Kr., 9, 1, 1884. C. Friedel. Bull. Soc. Min., 2, 31, 1879. etc. Sphalerite, C. Friedel and Curie. boracite. Bull. Soc. Min., 6. 191, 1883. Sphalerite, Mack. Boracite. Zs. Kr., 8, 503, 1883. Voigt. Abhandl. Ges. Gottingen,36, 99, 1890. Kelvin. Phil. Mag., 36, 331, 453, 1893. G. S. Schmidt. of fluorite. Wied. Ann., 62, 407, 1897. Photo-electricity

Thermo-electricity Marbach. Bunsen.

C. R., 45, 705, 1857. Pogg. Ann., 123, 505, 1864. Friedel. Ann. Ch. Phys., 17, 79, 1869; C. R., 78, 508, 1874. Rose. Pyrite and cobaltite. Pogg. Ann., 142, 1, 1871. Schrauf and E. S. Dana. Ber. Ak. Wien, 69 (1),142, 1874; Am.

2.

J.

Sc.,8, 255, 1874.

MAGNETISM

441.

Magnetic Minerals. Natural Magnets. A few minerals in their are capableof being attracted by a strong steel magnet; they said to be magnetic. This is are true of magnetite,the magnetic conspicuously oxide of iron; also of pyrrhotiteor and of some varieties of magnetic pyrites, native platinum (especially the varietycalled iron-platinum). A number of other minerals,as hematite,franklinite, etc.,are in some "

natural

*

touched

state

See Liebisch Phys. Krystallographie, 1891, for a full discussion of the topicsbriefly in the preceding upon pages, also for references to originalarticles.

DEPENDING

CHARACTERS

attracted

cases

by

a

UPON

steel magnet,

but

ELECTRICITY

probably in

MAGNETISM

309

if not all cases

because

AND

most

of admixed magnetite (but see Art. 443). Occasional varieties of the three minerals mentioned selves above,as the lodestone varietyof magnetite,exhibit themthe attracting and polarityof a true magnet. power They are then In such cases the magnetic polarity has probably been called natural magnets. derived from the inductive action of the earth,which is itselfa huge magnet. In a very Diamagnetism. strong magnetic all minerals, polesof a very powerful electromagnet, influenced by the magnetic force. Accordindeed all other substances, ing are as divided into two classes, the paramagnetic and to their behavior they are diamagnetic;those of the former appear to be attracted,those of the latter to of experiment the substance in question,in the be repelled. For purposes 442.

as field,

Paramagnetism.

that between

"

the

of a rod,is suspended on a horizontal axis between the polesof the magnet. to the magnetic axis; if diamagnetic, paramagnetic,it takes a positionparallel to it. Iron,cobalt, it sets transversely nickel, platinum are manganese, paramagnetic; silver,copper, bismuth are diamagnetic. Among minerals also diopside; compounds of iron are paramagnetic,as siderite, further, beryl, etc. zircon,wulfenite, dioptase. Diamagnetic speciesinclude calcite, of By the use of a sphere it is possibleto determine the relative amount the in of directions substance. induction different same Experiment magnetic has shown that in isometric crystalsthe magnetic induction is alike in all there is a direction of maximum that in those optically uniaxial, directions; minimum to of it,one and, normal magnetic induction;that in biaxial be there are three unequal magnetic axes, the positionof which may crystals, In other words, the magnetic relations of the three classes of determined. crystalsare analogousto their opticalrelations. 443. Corresponding to the facts juststated,that all compounds of iron are powerful electromagnet paramagnetic, it is found that a sufficiently attracts all minerals containingiron,though, except in the cases given in Art. hence the bar sensible influence has no efficiency 441, a them; upon magnet of separatingores. method of the electromagnetic the magnetic attraction of a number of substances Plucker * determined for magnetitehe obtained compared with iron taken as 100,000. For example,

form If

71; pyrite,150. 533, massive,134; limonite, 40,227; for hematite,crystallized, LITERATURE

Magnetism Pogg. Ann., 72, 315, 1847; 76, 576, 1849; 77, 447, 1849; 78, 427, 1849; 86,

Plucker.

1, 1852. Plucker

and Beer. Pogg. Ann., 81, 115, 1850; 82, 42, 1852. Phil. Trans., 1849-1857, and Experimental Researches, Series

Faraday. XXVI, XXX.

XXII,

Brit. Assoc.,1850, pt. 2, Thomson (Lord Kelvin). Theory of Magnetic Induction. and Magnetism, Electrostatics of etc. Phil. on Reprint Papers Mag., 177, 1, 1851, 23; 1872. Tyndall. Phil. Mag., 2, 165, 1851; 10, 153, 257, 1855; 11, 125, 1856; Phil. Trans., on 1855, 1. Researches diamagnetism and magne-crystallicaction. London, 1870. Knoblauch and Tyndall. Pogg. Ann., 79, 233; 81, 481, 1850 (Phil.Mag., 36, 37, W.

1850).

Jacques. Bismuth, Calcite. Am. J. Sc.,18, 360, 1879. Quartz. Wied. Ann., 27, 133, 1886. Koenig. Wied. Ann., 31, 273, 1887. Stenger. Calcite. Wied. Ann., 20, 304, 1883; 35, 331, 1888. Rowland Tumlirz.

and

*

Pogg. Ann., 74, 343, 1848.

310

action

their

In

under

1.

Astringent:

2.

Sweetish

3.

Saline: Alkaline:

5.

Cooling: Bitter:

7.

Sour:

are

sometimes

it

odor;

when

the

Friction

from

arsenical

odor

of of

elicits

ingredient

designated

thus

are

garlic.

ores

friction

volatile

of

this

minerals

heat

with

acids,

or

:

by

elicits of

means

horse-radish.

This

this

heat. odor

is

heated.

are

from

odor

by

arsenopyrite

compounds

decaying

selenium

species,

friction, moistening

By

odor.

some

which of

the

odor:

Sulphurous:

3.

of

odor

off

soluble

and

gaseous

give

not

obtained

be

perceived

strongly

few

a

do

obtained

also

may

acid.

elimination

Horse-radish

2.

salts.

Epsom

the

Alliaceous:

1.

:

soda.

state

the

and

of

saltpeter.

Excepting

"

kinds

alum.

of

sulphuric

of

unchanged

dry

breath,

odors

of

taste taste

different

salt.

common

of

taste

others

vitriol.

of taste

of

taste

follows

as

The

minerals.

soluble

to

are

taste

of

taste

Odor.

445.

the

the

the

astringent:

4.

6.

reference

for

adopted

and

taste,

possess

odor.

off

only

belongs

Taste

minerals

few

a

senses

give

circumstances

some

444. taste

the

upon

ODOR

AND

TASTE

VI.

in

MINERALOGY

PHYSICAL

pyrite,

and

heat

from

many

sulphides.

by

4.

Bituminous:

5.

Fetid:

friction

from

and

pyrargillite, 446.

Feel.

importance; etc.

the

the

Some

tongue

"

it when

The

when

to

in

brought

of

of

be

moistened

rotten

or

eggs.

is elicited

It

limestone.

and

clay.

It

them

moistening

is obtained with

the

from

tine serpen-

others,

breath;

heated.

smooth

consequence

in

hydrogen

quartz

after

is

FEEL

it is said

minerals,

odor

minerals,

afford

bitumen.

sulphureted

varieties

some

allied

some

of

odor of

odor

Argillaceous:

6.

as

the

the

contact

a

character

which

(sepiolite), of with

their

it.

greasy

is

hygroscopic

of

occasionally

(talc), harsh, character,

or

some

meager,

adhere

to

312

MINERALOGY

CHEMICAL

The Formula. symbol of an element is the initial Latin its often of by which it is represented when or letters, name, letter, into the compoconstitution of substances in notation the chemical sition expressing H is of of hydrogen, Cl the Thus O enters. of which it symbol oxygen, etc. ther, Furof chlorine,Fe (fromferrum) of iron,Ag (from argentum) of silver, that definite to indicate of the understood amount this symbol is always in other it words, represents one givenelement expressedby itsatomic weight; If twice this quantityis involved,that is,two atoms, this is indicated atom. written immediately after the symbol. Thus, by a small subscriptnumber of antimony and three of of two atoms a Sb2S3 means compound consisting 451.

Symbol.

"

sulphur,or of 2 X 120 parts by weight of antimony and 3 X 32 of sulphur. This expression, Sb2S3,is called the formula of the given compound, since it expresses in briefest form its composition. Similarlythe formula of the mineral

albite is NaAlSisOg.

formulas,since they speaking,such formulas are merely empirical Strictly of the result the actual relative number as of analysis, giving only express of each element present,and make no attempt to represent the actual constitution. A formula developed with the latter objectin view is called a constitutional formula (seeArt. 469). or structural, rational, The followingtable gives a list of all 452. Table of the Elements. established elements with their acceptedsymbols and also their the definitely atomic weights.* than eightyin all Of the elements given in this list more only a very small number, say twelve, playan important part in making up the crust of the earth and the water and air surroundingit. The common elements concerned in the compositionof minerals are: minium, aluOxygen, sulphur,silicon, iron,calcium,magnesium, sodium,potassium. Besides these,hydrogen is present in water, nitrogenin the air,and carbon in all animal and vegetablesubstances. Only a very few of the elements occur as such in nature, native gold,native silver, native sulphur,etc. as Of the elements, oxygen, hydrogen, nitrogen,chlorine,and fluorine are is a volatile liquid;mercury is also a liquid, but the others gases; bromine solids under ordinaryconditions. are atoms

"

"

"

* These correspond in value to those decimal place.

commonly accepted,and

are

given accurate

to

one

GENERAL

PRINCIPLES

OF

CHEMISTRY

AS

APPLIED

TO

MINERALS

313

The elements be divided into and Non-metals. may the metals and the non-metals. less distinct classes, Between the two of elements sometimes called the semi-metals. lie a number The those elements are iron, sodium, which, physically metals,as gold, silver, less perfectdegreethe fundamental characters or described, possess to a more metallic luster (and opacity to light), of the ideal metal, viz.: malleability, chemicallydescribed,they moreover, conductivityfor heat and electricity; in a simplecompound, or basic element commonly play the part of the positive as later denned (Arts.462-465). The non-metals, as sulphur,carbon,silicon, of the physicalcharacters etc.,have none etc.,also the gases, as oxygen, chlorine, often transparent to light-radiation, alluded to: they are, if solids, brittle, for heat and electricity. conductors are Chemically expressed,they poor in acid a or the compound. simple part negative usuallyplay The so-called semi-metals,or metalloids,include certain elements, as tellurium,arsenic, antimony, bismuth, which have the physicalcharacters of less brittle); or to a less perfectdegree(e.g., they are more a metal and, more 4 the of the acidic element in the part important han this,they often play compound into which they enter. These pointsare illustrated later. the classes of the It is to be understood that the distinctions between be very sharplyapplied. Thus the typicalmetallic cannot elements named to a very unequal degreeby the different characters mentioned are possessed substances classed as metals; for example,by silver and tin. Corresponding to this a number play the part of an of the true metals, as tin and manganese, 453.

two

more

Metals

"

or

U

acid in numerous described as an

iron both acid and base. the of play part 454. Positive and Negative Elements.

between

in

Further, the mineral magnetite,FeFe2O4, is often element would ferrate;so that in this compound the same

salts.

the

It is common to make tinction disa hi element and a compound. electro-negative electro-positive "

314

CHEMICAL

passage of in many

The

at

one

element

the

pound strong electrical current through a chemical comsufficiently into its ments elein its (or results electrolysis) decomposition cases

that for each compound the atoms negativepole (thecathode) and those of the other (the anode). The former is called the electro-positive

parts. In such

or

of

a

MINERALOGY

cases

it is found

collect at the

positivepole

Thus in the electrolysis element. and the latter the electro-negative is and hence at cathode called posithe tive, of water (H20) the hydrogen collects in hydrois and called at the anode and the oxygen negative. Similarly, chloric to be positive, the chlorine acid (HC1) the hydrogen is thus shown negative. This distinction is also carried to complex compounds, as copper is broken into Cu, which is found to be sulphate(CuSO4),which by electrolysis and SO4 (thelast separatesinto SO3, forming H2SC"4 and free electro-positive, element

oxygen). is said to the positiveelement which will be explainedlater, The in acidic. the as the alreadystated, metals, negative part, the the while to t he non-metals to the former most latter, cases class, belong semi-metals may play both parts. basic element in writingthe formula to put the positive It is common or

For

reasons

play the basic

Here thus H2O, H2S, HC1, H2SO4, Sb2S3,As2O3,AsH3, NiSb, FeAs2. first, of it will be noted that antimony (Sb) and arsenic (As) are positivein some but negativein the others. the compounds named 455.

Periodic

Law.

chief classes of chemical

"

In

order

to

understand

compounds representedamong

relations of the minerals,as stillmore

the

down their further subdivision, to the many isomorphous groups finally of specieshaving analogous compositionand closely similar form, as groups the fundamental ments relations and grouping of the eleexplainedin Art. 471 be understood,especially must as developedof recent years and shown in the so-called Periodic Law. touched upon, it will be useful to Although the subjectcan be onlybriefly as give here the general distribution of the elements into Groups and Series, of Chemistry (Engl.Ed., 1891) of D. Mendeleeff, presentedin the Principles is due more than any one else the development of the Periodic Law. to whom the elements are arrangedaccordingto the values of their atomic weights When it is seen that they fall more less into groups consisting of eightelements or double sixteen or elements. The each, containing corresponding groups members of each group show similar chemical characters. The table given below will illustrate these relationships. For the thorough explanationof this subject, relation more as particularly regardsthe periodicor progressive between the atomic weightsand various properties of the elements,the reader is referred to the work above mentioned of the many other excellent to one or modern text-books of chemistry. The relations of some of the elements of the first group exhibited by are the isomorphism (seeArt. 471, also the description and of the various groups specieshere referred to, which are given in Part IV of this work) of NaCl, KC1, AgCl; or againof LiMnP04 and NaMnPO4, etc. In the second group, reference may be made to the isomorphism of the carbonates and sulphates (p.322) of calcium,barium, and strontium; while among the sulphides, ZnS, CaS, and HgS are doubly related. In the third group, we find boron and aluminium often replacing another among one silicates. In the fourth group, the relations of silicon and titanium are shown in the titano-silicates, while the compounds Ti02,SnO2, Pb02 (and MnO2), also ZrSiO4 and ThSi04, have "

"

GENERAL

PRINCIPLES

OF

CHEMISTRY

AS

APPLIED

TO

II

5 3

6

"

II

O

II 02

"

"

43

II ^

23 ii

H

J

" 8

8 u

ffl

MINERALS

315

316

MINERALOGY

CHEMICAL

In the fifth group,

closelysimilar form. and

bismuth

are

isomorphous

many

among

mony, compounds of arsenic,anticompounds, while the

metallic

relations of phosphorous,vanadium, arsenic,also antimony, are shown among the phosphates,vanadates, arsenates, and antimonates; again the mutual relations of the niobates and tantalates are to be noted. the strongly acidic elements, sulphur, selenium, In the sixth group, telluall closely sulphides,selenides, related,as seen in many are tellurium, and of similarly both rides; further,the relations of sulphur and chromium, artificialsulphates, of these to molybdenum and tungsten, are shown among many

chromates, molybdates,and tungstates. In the seventh

group

specialremark. meteoric iron,and their to need

halogensare too well understood eighthgroup, we have Fe, Co, Ni alloyedin phosphates and sulphatesare in several cases closely the relations of the In the

isomorphous; further,the relation of the iron series to that of the platinum series is exhibited in the isomorphism of FeS2,FeAsS, FeAs2, etc.,with PtAs2 and probably RuS2. that the Chemical 456. investigationproves Combining Weight. into is a of a given element entering compound always proportional mass either to its atomic weight or to some simple multipleof this; the atomic weight is hence also called the combining weight. Thus in rock salt,sodium and chlorine present are found involved of sodium by chloride,the masses in are analysisto be equal to 39'4 and 60'6 in 100 parts, and these numbers proportionto 23 : 35*4,the atomic weightsof sodium and chlorine;hence it is The formula is, of each is present in the compound. concluded that one atom the In the method calcium NaCl. same masses chloride, therefore, by ent presfound to be proportionalto 39'9 : 70*8, that is,to 39'9 : 2 X 35'4; are "

hence the formula

is CaCl2.

Stillagain,a series of compounds of nitrogen with oxygen is known in which the ratios of the two elements are as follows: (1)28 : 16, (2) 14 : 16,(3)28 : 48, (4)14 : 32, of the masses (5)28 : 80. It is seen at once that these must have the formulas (1)N2O; (2)NO, (3)N2O3, (4) NO2, (5) N2O6. On the contrary, atmospheric air which contains these elements in about be a chemical compound of these elements, since the ratio of 76 '8 to 23 '2 cannot in the ratio of n X 14 : m not are X 16 (asidefrom other considerations)these numbers where n and m are simple whole numbers.

457.

Molecular

The

of the of the hydroof the mass gen atom The molecular weight of hydrogen is 2 because the moleas unit. cule be shown The molecular to consist of two can atoms. of weight chloric hydroacid (HC1) is 36*4, of water (H2O) 18, of hydrogen sulphide vapor

molecule

of the

Weight.

"

molecular

given substance,expressedin

weight is the weight

terms

(H2S) 34. Since,accordingto the law of Avagadro, like volumes

of different gases under like conditions as to temperature and pressure contain the same number of molecules, it is obvious that the molecular weight of substances in the form of gas can be derived directly from the relative density or specific gravity. If the densityis referred to hydrogen, whose molecular weight is 2, it will be always true that the molecular weight is twice the densityin the state of a Thus the observed densityof carbon dioxide (CO2) is 22, gas and vice versa. hence its molecular weight must It is this principle be 44. it that makes possiblein the case of a gas to fix the constitution of the molecule when the ratio in number of the atoms enteringinto it has been determined by analysis. In the case of solids, where the constitution of the molecule in generalcannot

OF

PRINCIPLES

GENERAL

be fixed,it is best, as

simplestform,

as

AS

APPLIED

already stated,to write

NaAlSi3Os

present is then taken

CHEMISTRY

as

for albite.

the molecular valence of

The

the

TO

molecular

of the

sum

317

MINERALS

formula

weightsof the

in its atoms

weight.

element is given by a number an to combine of some with the atoms representingthe capacityof its atoms like hydrogen or chlorine. unit element Thus, using the examples of Art. atom of sodium unites with one of chlorine, its 456, in NaCl, since one valence is one; or, in other words, it is said to be univalent. Further, is trivacalcium (as in CaCl2),also barium, etc., are bivalent; aluminium The valence etc. be is silicon tetravalent, expressed by the lent; may is united to another, element in a compound of bonds by which one number 458.

Valence.

The

"

thus: Ba

Na-Cl,

=

SniiCU,

Au=Cl3,

Cl2,

etc.

different valence in different also FeO and Fe2p3; These CuCl and CuCl2. possiblevariations are indicated in the following elements. table which givesthe valences for the common Univalent: H, Cl, Br, I, F; Li, Na, K, Rb, Cs, Ag, Hg, Cu, Au. A considerable number

of the elements show

Sb203 and

Sb2O5

are

a

known;

O, S, Se,Te; Be, Mg, Ca, Sr,Ba, Pb, Hg, Cu, Zn, Co, Ni, Fe,

Bivalent:

Mn, Cr, C,

both

Thus

compounds.

Sn.

B, Au, Al, Fe, Mn, Cr, Co, Ni, N, P, As, Sb, Bi. C, Si,Ti, Zr, Sn, Mn, Pb. Pentavalent: N, P, As, Sb, V, Bi,Nb, Ta. Trivalent:

Tetravalent:

chemical substances with other each upon brought the result of forming new nomenon compounds out of the elements present; this phebe substances may One of the original is called a chemical reaction. and from obtained a a results in similar and are solid, liquid cases a gas, many 459.

Reactions.

Chemical

or

"

less often from

For example, (AgNO3) react on nitrate (NaNO3).

solutions

When

together,in many

are

cases

of

two

they react

solids. chloride (NaCl) and silver nitrate solutions of sodium each other and yield silver chloride (AgCl) and sodium This is expressedin chemical language as follows: NaCl AgCl + NaN03. + AgNO3

two

=

This is a chemical signof equalitymeaning that equal weights after the reaction. involved both before and are Again, hydrochloricacid (HC1) and calcium carbonate (CaCO3) yield calcium chloride (CaCl2) and carbonic acid (H2CO3) ; which last breaks up into water (H2O) and carbon dioxide (CO2),the last going off as a gas with

equation,the

effervescence.

Hence

CaCO3

2HC1

+

=

CaCl2 +

H2O

+

C02.

elements according to of two or more A compound Radicals. 460. rated. is said to be satusatisfied their relative valence in which all their bonds are O"H. H" be If,however, written, This is true of H2O, or, as it may combination of elements is the resulting bonds is left unsatisfied, more one or "

radical, hydroxyl,is a common O radical. Thus H, called briefly is againa univalent NH4 univalent other in words, of ; valence a having one, or, pound radical;so, too, (CaF), (MgF) or (A10). Radicals often enter into a comchloride,NH4C1, the like a simple element; for example,in ammonium part as the univalent element Na in univalent radical NH4 plays the same radical the commonest In the chemical compositionof mineral species, NaCl. called

a

"

"

318

MINERALOGY

CHEMICAL

H) alreadydefined. Other examples are (CaF) in apatite basic silicates, etc. 471),(MgF) in wagnerite,(A1O) in many is combination chemical A a 461. Chemical compound Compound. It is elements united by the force of chemical attraction. of two or more the that elements stated before of (Art. 456), present are it,as always true in the proportionof their atomic weights or some combined simplemultiples this condition is not a compound, of these. A substance which does not satisfy but only a mechanical mixture. Examples of the simplerclass of compounds are afforded by the oxides,or minerals we have Thus, among compounds of oxygen with another element. A1203, alumina Cu2O, cuprous oxide (cuprite);ZnO, zinc oxide (zincite); (corundum); SnO2, tin dioxide (cassiterite) ; SiO2,silicon dioxide (quartz); As2O3,arsenic trioxide.(arsenolite). Another simple class of compounds are the sulphides(with the selenides, compounds in which sulphur (selenantimonides,etc.), ium, arsenides, tellurides, tellurium, arsenic, antimony, etc.)playsthe same part as oxygen in the oxides. Here belongCu2S, cuprous sulphide(chalcocite) ; ZnS, zinc sulphide (sphalerite); PbTe, lead telluride (altaite); FeS2, iron disulphide(pyrite); Sb2S3,antimony trisulphide (stibnite). The more 462. Acids. complex chemical compounds, an understanding of which is needed in a study of minerals,are classed as acids,bases,and salts;the distinctions between them are important. An acid is a compound of hydrogen, or hydroxyl, with a non-metallic element (as chlorine, sulphur,nitrogen,phosphorus,etc.),or a radical containing these elements. When dissolved in water they all give the positive hydrogen ion and a negative ionic substance such as Cl, SO4, etc. The of an acid may be replacedby metallic atoms; the result hydrogen atoms then of salt the formation a being (seeArt. 464). Acids in generalturn blue litmus paper red and have a sharp, sour taste. The followingare familiar examples: HC1, hydrochloricacid, HNO3, nitric acid. H2CO3, carbonic acid. H2S04, sulphuricacid. H2Si03,metasilicic acid. H3PO4, phosphoricacid. H4Si04,orthosilicic acid. is hydroxyl ( "

0

"

(seeArt.

"

"

It is to be noted that with a given acid element several acids are possible. Thus normal, or orthosilicic, acid is H4SiO4,in which the bonds of the element silicon are all satisfied by the hydroxyl (HO). But the removal of one molecule of water, H2O, from this gives the formula H2SiO3, or metasilicic acid. Acids which, like HN03, contain one of hydrogen that atom be may

replacedby

metallic atom in KNO3) are called monobasic. (e.g., If,as in H2CO3 and H2SO4, there are two atoms or a in singlebivalent atom, (e.g., CaC03, BaSO4) the acids are dibasic. Similarly, H3PO4 is tribasic, etc. Most acids are liquids(or gases),and hence acids are represented a

very

sparinglyamong

minerals;B(OH)3, boric acid (sassolite), is an illustration. 463. Bases. The bases,or hydroxides, as they are also called,are compounds which may be regardedas formed of a metallic element (orradical) "

320

MINERALOGY

CHEMICAL

be written * as if the compound consisted of a normal salt and an acid; thus, for the example given,K2SO4 H2SO4. in which- the acid part of the compound is not sufficient A basic salt is one Thus malachite is a basic salt basic all the bonds of the base. to satisfy the formula its composition being expressed by carbonate of copper such

cases

may

.

"

"

_

Cu2(OH)2C03.

This may

be written CuCO3

.

Cu(OH)2,

or

(Cu2) =

f^r\

^g^

as those noted above, but majorityof minerals consist not of simplesalts, several in which metallic elements salts double are less or more complex orthosilicate is both an Thus containing grossulargarnet common present. is Ca3Al2(SiO4)3. calcium and aluminium as bases; its formula far thus salts The 467. spoken of are all oxygen salts. Sulpho-salts. in which sulphur takes the also others,of analogous constitution, There are Thus normal sulphhence called sulpha-salts. they are placeof the oxygen; arsenious acid has the formula H3AsS3, and the correspondingsilver salt is AgsAsS3, the mineral proustite.Similarlythe silver salt of the analogous antimony acid is Ag3SbS3,the mineral pyrargyrite. From the normal acids acids may be derived,as HAsS2, H4As2S5, named, a series of other hypothetical but their salts are important minerals. to exist, etc. ; these acids are not known Thus zinkenite, PbSb2S4,is a salt of the acid H2Sb2S4,and jamesonite,Pb2Sb2S5,

The

of

"

of the acid H4Sb2S5, etc.

Crystallization. As stated in Art. 463, the hydroxides, or bases,and further basic salts-in general,yieldwater when ignited. Thus calcium hydroxide Ca(OH)2 breaks up on heating into CaO and H2O, as expressedin the chemical equation 468.

Water

of

"

2Ca(OH)2

=

2CaO

+

H20.

So also the basic cupriccarbonate,malachite,Cu2(OH)2C03, yieldswater on is true of the complex basic orthosilicates, like zoisite, ignition;and the same whose formula is (HO)Ca2Al3(Si04)3.It is not to be understood,however, in these or similar cases, that water as such is present in the substance. On the other hand, there is a large number of mineral compounds which yieldwater readilywhen heated,and in which the water molecules are regarded as Thus, the formula of gypsum present as so-called water of crystallization. is written

CaSO4

+

2H2O,

and the molecules of water (2H2O) are considered as water of crystallization. So,too, in potashalum, KA1(S04)2 + 12H2O, the water is believed to play the

part.

same

Formulas

of Minerals. The strictly empiricalformula expresses and numbers of atoms of the elements present in the given compound, without attempting to show the way in which it is believed that the atoms combined. are Thus, in the case of zoisite the empiricalformula is HCa2Al3Si3Oi3. While not attempting to represent the structural formula (which will not be discussed here),it is convenient in certain cases to indicate the atoms which there is reason to believe play a peculiarrelation to each other. Thus the same formula written (HO)Ca2Al3(SiO4)3 shows that it is regardedas in other words, a basic salt of orthosilicic acid,H4SiO4. a basic orthosilicate, 469.

"

the kinds

*

This earlyform of writingthe composition explainsthe namely, in this case, "bisulphateof potash."

name

often given to the

pound, com-

CHEMISTRY

OF

PRINCIPLES

GENERAL

AS

APPLIED

TO

MINERALS

321

apatiteis Ca5FP3Oi2 ; but if this Again, the empiricalformula of common is shows that it is written (CaF)Ca4(PO4)3,it regarded as a phosphate of the acid H3PO4, that is,H^PO^s, in which the nine hydrogen atoms are replaced by four Ca atoms togetherwith the univalent radical (CaF). In another kind of apatitethe radical (CaCl) enters in the same Similarlyto this the way. of vanadinite (PbCl)Pb4(VO4)3. formula of pyromorphite is (PbCl)Pb4(PO4)3, ulas Further,it is often convenient to employ the method of writingthe formin vogue under the old dualistic system. For example, 3CaO

.

for CaCO3, CaO.CO2 A12O3 3SiO2 for Ca3Al2Si3Oi2, 3Ag2S Sb2S3 for Ag3SbS3,etc. .

.

however, that the molecular groups CaO, A1203,etc., longerbelieved, But in part because these actuallyexist in the molecule of the substance. and in part because affords what of substance the are directly, analysis groups of writingis stilloften used. this method so easilyretained in the memory, from 470. Calculation of a Formula an Analysis. The result of an hundred of the mineral,of either the the i n a parts proportions, analysisgives elements themselves,or of their oxides or other compounds obtained in the of the elements : chemical analysis. In order lo obtain the atomic proportions Divide the percentages of the elements by the respective ATOMIC WEIGHTS; the the amounts oxides: Divide for those of of each by their percentage or, then find the simplestratio in whole numbers MOLECULAR for the WEIGHTS; It is no

"

numbers

thus obtained. .

An analysisof bournonite from Wolfsberg gave C. Bromeis the results under Example. These percentages divided by the respectiveatomic weights,as indicated,give (1) below. under the numbers gives very nearly 1 : 3 : 1 : 1. (2). Finally the ratio of these numbers The theoretical values called for by the formula Hence the formula derived is CuPbSbS3. added under are (4). (3) (4) (2) (1) "

Sb S Pb Cu

24'34

-r-

=

0'203

1

247

1976

"*"

32

=

0'617

42-88

-5-

206-4

=

0'208

3 1

42'5

13-06

-r-

0-207

1

120

63-2

=

19'8 13'0 lOO'O

100-04

analysesof a garnet from Alaska gave Kountze the of the several molecular usual,the percentage amounts These amounts (SiO2,A12O3, etc.) are given instead of those of the elements. groups under (2). In this case the divided by the respectiveniolecular weights give the numbers of the protoxidesare taken together and the ratio thus obtained is 3 '09 : 1 : 2 "92, amounts or which corresponds approximatelyto the formula 3FeO.Al2O3.3SiO2, Fe3Al2(SiO4)3.The magnesium in this garnet would ordinarilybe explained by the presence of the pyrope molecule (Mg3Al2[SiO4]3) together with the simple almandite molecule whose composition is given above. (2) (3) (1) Second Example. The mean results under (1) below. Here,

of two

"

as

SiO2 A12O3 Fe203

39-29 21-70

FeO MnO

30-82

-5-

60

-5-

102

H-

71 -9 70-8

=

=

0'655

3'09

0-212

1

tr.

MgO CaO

1-51

-f-

5-26

-^40

1-99

-J-

55-9

=

0'429

=

0'022

=

0-132

=

0'036

L.A1Q l

9.Q9

100-57 It is necessary,

above)

are

when

very

small quantitiesonly of certain elements (asMnO, MgO, CaO in the final formula,reckoning them in with the elements

present, to neglectthem

322

CHEMICAL

which

MINERALOGY

spondence quantivalence. The degree of corresame if the latter is correctly assumed, formula the deduced, a nd analysis of the former. the accuracy

that is,with those of the they replace, between

the

depends entirelyupon

Chemical compounds which have an analogous Isomorphism. form are said to be isomorphous. compositionand a closelyrelated crystalline first was clearlybrought out by MitThis phenomenon, called ISOMORPHISM,

i

! 471.

"

scherlich.

isomorphous compounds will be found among Some examples are mentioned followingpages. here in order to elucidate the subject. ments In the brief discussion of the periodicclassification of the chemical eleof Art. 455, attention has been called to the prominent groups among calcium, barium, and the elements which form analogous compounds. Thus series of form the two also analogouscompounds, and lead, strontium, Many

examples of

groups the minerals described in the

of

Barite Group

Aragonite Group

CaCO3, BaC03, SrCO3, PbCO3,

aragonite. witherite. strontianite.

cerussite,

Also

CaSO4, anhydrite.

BaS04, barite. SrS04, celestite. PbSO4, anglesite.

similar forms. The in closely of each series crystallize Further, the members carbonates are orthorhombic,with axial ratios not far from one another; thus the prismaticangleapproximatesto 60" and 120",and correspondingto this they all exhibit pseudo-hexagonalforms due to twinning. The sulphatesalso and though anhydritedeviates somewhat form a similar orthorhombic series, widely,the others are close togetherin angle and in cleavage. form a series of carbonates Again,calcium,magnesium, iron,zinc,and manganese in the list of the speciesof with analogous composition as shown This table brings out clearlythe close the Calcite Group given on p. 437. relation in form between the speciesnamed. true with an isomorphous series that the various Further it is also generally of the enter in greater or less degreeinto the constitution of one molecules may the in members of the series without causing any marked crystal change For instance, in the Calcite Group, calcite itself may contain characters. small percentages of MgCO3, FeCO3 and MnCO3. These different molecules the the in functions as the of mineral structure the assume same crystal may of amounts which have CaC03 corresponding they replaced. The molecules of magnesiteand siderite, and MgCO3 FeCO3, may replaceeach other in any is and the with siderite and rhodochrosite, true same MnC03. proportion intermediate Various mixtures of these latter molecules have been described and givendistinctive names to which definite formulas have been assigned. It is doubtful,however, if these compounds have any real existence but merely represent certain pointsin the complete isomorphous series that lies between the end members. Dolomite,CaMg(CO3)2, on the other hand, is a definite It may, compound and not an isomorphous mixture of CaCO3 and MgCO3. of FeCO3, MnCO3 and also an of however, contain varying amounts excess CaCO3 or MgCO3, all of which enter the regularmolecule in the form of

isomorphousreplacements. The ApatiteGroup forms another valuable illustration since in it are representedthe analogouscompounds, apatiteand pyromorphite,both phosphates, but respectively phosphatesof calcium and lead; also the analogous

GENERAL

PRINCIPLES

OF

CHEMISTRY

AS

APPLIED

TO

MINERALS

323

lead compounds pyromorphite,mimetite, and vanadinite respectively and lead lead vanadate. in arsenate, phosphate, Further, allthese compounds the radical (RC1) or (RF) enters in the same (seeArt. 469). Thus the way formulas for the two kinds of apatiteand that for pyromorphite are as follows : lead

(CaF)Ca4(P04)3, of the

Some

(CaCl)Ca4(PO4)3,

(PbCl)Pb4(PO4)3.

important isomorphous

mentioned For a discusbelow. are sion groups that might be mentioned here, reference must be to the descriptivepart of this work. made The Isometric System. Spinel group, includingspinel,MgAl2O4; also magnetite, gahnite, etc. The Galena group, as galena,PbS; argentite,Ag-"S, chromite, franklinite, The Garnet group, as grossularite, etc. etc. CasAiiSiiOn, Rutile group, including rutile, SnC"2. The TiO2,' cassiterite, Tetragonal System. Scheelite group, includingscheelite, PbW04; wulfenite,PbMoO4. CaWO4; stolzite, of

them,

as

more

well

of many

as

others

"

"

Apatite group, already mentioned, including apatite,pyromorHexagonal System. phite, Corundum mimetite, and vanadinite. corundum, A12O3; hematite,FesOs. group, Phenacite group, Calcite group, already mentioned. etc. Orthorhombic above. Aragonite group, and Barite group, both mentioned System. Chrysolitegroup, (Mg,Fe)2SiO4; Topaz group, etc. Monodinic System. Copperas group, includingmelanterite,FeSO4 + THizO; bieberite, CoSO4 + 7H2O, etc. Pyroxene and Amphibole groups, and the Mica group. Monodinic and Triclinic Systems. Feldspar group. "

"

"

"

It is important to note that the intermediate Isomorphous Mixtures. in such as those spoken the case of an isomorphous series, compounds often show a distinct gradationin crystalline of in the precedingarticle, form, in physicalcharacters (e.g., and more specific gravity,optical particularly etc.). This is illustrated by the speciesof the calcite group already properties, referred to; also stillmore as strikingly by the group of the triclinicfeldspars See further Art. 424. of that group. fullydiscussed under the description The feldsparsalso illustrate two other important points in the subject, alluded to here. The triclinicfeldsparshave been shown which must be briefly to Tschermak be isomorphous mixtures of the end compounds in varying by : proportions Anorthite,CaAl2Si2O8. Albite,NaAlSi3O8. 472.

"

compounds have not an analogouscompositionin the and yet they are isomorphous and form an narrow sense previouslyillustrated, the pyroxenes, isomorphous series. Other examples of this are found among the scapolites, etc. includes several other Further,the Feldspar group in the broader sense KAlSi3Os, which, though species,conspicuouslythe monoclinic orthoclase, belonging to a different system, still approximates closelyin form to the triclinicspecies. Variation in Composition of Minerals. 473. Isomorphous Replacement in its and The idea that a mineral must Solid Solution. rigidlyconform derived from its formula chemical compositionto a theoretical composition It is true that the majorityof minerals do show held. can no longerbe strictly within the limits of possible a close correspondence to that theory,commonly minerals show slightand in the analyses. On the other hand, many errors Here

it is seen

that these

"

certain

ones

considerable

variations

from

their

theoretical

compositions.

of isomorphism. explainedby the principle of sphalerite.Note in the analysesquoted An instructive example is the case below how the percentages of zinc diminish and those of iron correspondingly smaller increase. It is evident from these analysesthat iron,and in a much These

can variations.

usuallybe

324

MINERALOGY

CHEMICAL

ing enter into the chemical compound and while replacof the structure the in crystalline function as it, the zinc perform the same with the zinc of isomorphous as being The iron is therefore spoken mineral. molecule. zinc the with sulphide molecule as isomorphous the iron degree other metals,may

sulphide

or

and zinc that may of the iron the amounts definite ratio between the of the atoms sum be present but there is a constant ratio (1 : 1) between the composition of sulphur. That is,although of the metals and the atoms In constant. structure remain the ratios and atomic crystalline the vary, may be complete, elements or radicals may this interchangebetween cases some be distinct limitations to the amount by which any in other cases there may For instance in sphalerite be replacedby another. radical may element or iron to be about 16 to seems the isomorphous the maximum percentage of

There

is no

18 per cent. Colorless Sphalerite

S Zn Fe

32.93 66.69 0.42

moi

Brown

S Zn Fe

Black

Sphalerite 33.36 63.36 3.60 100.32

Sphalerite

S

33.25

Zn

50.02

Fe

15.44

Cd

0.30

100.02

Further,we have cases where a compound may, in a certain sense, dissolve solid solution. and form what is known as a another unrelated substance artificialsalts and has This kind of phenomenon is well recognizedamong proved with certain minerals. For instance,it has recentlybeen definitely been shown ing experimentallythat the artificialiron sulphide,FeS, correspondof sulphur up to about 6 per cent. dissove an excess to pyrrhotite, can that requiredby of sulphurover Natural pyrrhotite always contains an excess the formula, FeS, and various formulas such as Fe7S8,FenSn+i, etc.,have been assignedto the mineral. This extra sulphurin the mineral varies in amount In view of the experimental about 6 per cent. but also has as its maximum data there is no doubt but that pyrrhotite should be considered as the monoof excess sulphur in the sulphideof iron containingvarying small amounts form of a solid solution. Another of solid solution is undoubtedly shown case by nephelitewhich It contains small is of SiO2. a excess commonly probable that further very show minerals have this power will that many of holding in investigation solid solution small amounts of foreignsubstances and that many hitherto be explained in this way. discrepanciesin their analysesmay inexplicable Such an assumption should not be made, however, without convincingproof of its probability, since many are undoubtedly due to analytical discrepancies either faulty analyses or to impure material. 474. Colloidal Minerals Gels.* Mineral It has been recognized or recentlythat our amorphous hydrated minerals frequentlydo not conform in their analysesto the usuallyaccepted formulas and cannot be regardedin the strict sense definite chemical as compounds. They show rather the properties of solid colloids or as they are commonly called mineral gels. A colloidal solution may be conceived as being intermediate in its characters between a true solution and the case where the mineral material is definitely in suspen"

*

made

For

of the subject of gel minerals and a complete bibliography a resume reference is to articles by Marc and Himmelbauer, Fortschritte Min. Krist. Pet.,3, 11, 33, 1913.

GENERAL

PRINCIPLES

OF

CHEMISTRY

AS

APPLIED

TO

325

MINERALS

liquid. It is probablethat all gradationsbetween these two extremes The mineral gels,or hydrogels,as they are sometimes may called, since water is the liquidinvolved,are apparentlyformed from such colloidal of coagulation. They are considered therefore to solutions by some process mixture of excessively consist of a micro-heterogeneous minute particles of sion in

a

occur.

material and water. mineral gelsare formed at low temperatures and pressures and are found among the products of rock weathering and in the characteristically of ore deposits. Some of them also occur oxidized zone in hot springdeposits. These minerals ordinarily r eniform stalactitic shapes, assume or botryoidal, conditions of when the formation do not permit free growth, they although, be dendritic. mineral colloidal may Frequently a earthy or originally may less character become in more or crystalline through a molecular rearrangement and develop a fibrous" or foliated structure. These have been designated meta-colloids. as One important character of the gelminerals is their power to adsorb foreign If through some materials. change in condition one of these hydrogelsshould lose a part of its water content the remaining material would have a finely of divided and porous structure exactlyadapted to exert a strong power in the main of the cases mass adsorption. Consequently,although many definite crystallized mineral may have a compositioncloselysimilar to some show considerable in it will mineral, a commonly compositiondue both range and of to this secondary water the contained relations to the non-molecular mineral gelsor substances derived from them are opal, adsorption. Common of the phosphate and arsenate various members bauxite,psilomelane, groups, also in crystalAs suggestedabove, gel varieties of minerals that occur etc. line authors speak of bauxite forms are thought to exist. For example some mineral

These

of goethite, the gel form as stilpnosiderite gel form of hydrargillite, such and further as of new gelvariscite, give names, chrysocolla dioptase, minerals. crystalline etc.,to the gelphasesof the corresponding gelpyrophyllite, A chemical 475. Dimorphism. compound, which Isodimorphism. to said be i s in distinct, dimorphous; if in crystallizes two forms genetically This phenomenon is called three,trimorphous,or in generalpleomorphous. as

the

"

DIMORPHISM

Or

PLEOMORPHISM.

example is given by the compound calcium carbonate (CaCO3), which is dimorphous : appearingas calcite and as aragonite. As calciteit crystallizes class of the^hexagonal system, and, unlike as its many in the rhombohedral fundamental be all referred to the same forms axes, they crystalline may are, and the same all the what have same specific is cleavage and, they more, cium opticalcharacters. As aragonite,calgravity(27) and, of course, the same characters w hose in orthorhombic carbonate optical crystals, appears the specific gravityof are entirelydifferent from those of calcite;moreover, aragonite(2'9)is higherthan that of calcite (27). morphous, Many other examples might be given: Titanium dioxide (TiO2) is triG. 4*25; the speciesbeing called rutile, tetragonal(c 0'6442), 3 '9; and brookite,orthorhombic, 1778), G. octahedrite, tetragonal(c and graphite. Other G. 4'15. Carbon appears in two forms, in diamond and wurtzite familiar examples are pyriteand marcasite (FeS2),sphalerite etc. (ZnS), time isomorphous When two or more analogouscompounds are at the same the and be phenomenon is said to and dimorphous, they are isodimbrphous, An

=

=

=

=

=

326

CHEMICAL

MINERALOGY

An example of this is given in the Pyriteand Marcalled ISODIMORPHISM. have in the isometric PyriteGroup, we casite groups described later. Thus Marcasite Group, marcasorthorhombic in the smaltite, CoAs2; FeS2, pyrite,

CoAs2, ite,FeS2, safflorite,

etc.

erals Microchemical Analysis. The analysis of minis a subjecttreated of in chemical works, and need not be touched upon methods, here except so far as to note the convenient use of certain qualitative of this later in the described chapter. as part Of more importance are the microchemical methods applicableto sections under the microscope and often yieldingdecisive results with little labor. Chemical

476.

and

"

developedby Boricky,Haushofer,Behrens, particularly is made to the discussion by Rosenbusch. Reference Streng, Johannsen t o 435 et (Manual of Pet. Methods, seq.), (Mikr. Phys., 1904, p. Microchemical methods used upon 559, et seq., including a bibliography). Murdock described of minerals surfaces are (Micro. by polished opaque of the Deter. Opaque Min., 1916) and by Davy-Farnham (Micro. Exam, Ore Min., 1920). of certain mineral 477. Mineral pounds comSynthesis. The occurrence the furnaces the products of metallurgical (e.g., chrysolites) among But it has only been in recent years that the formation has long been noted. the subjectof minute systematicexperiof artificialminerals has been made mental direction the French chemists have been particularly In this study. be stated that the majorityof common minerals and now it may successful, the mica. etc. have been obtained in crystalamphibole, lized feldspars, quartz, diamond in Even the has been formed minute form. crystals by Moissan. These studies are as obviouslyof great importance particularly of formation of minerals in nature. method The throwing lightupon the chief results of the work thus far done are given in the volumes mentioned in the Introduction, p. 4. 478. Alteration of Minerals. The chemical tion alteraPseudomorphs. of mineral speciesunder the action of natural agenciesis a subjectof when it results in the change of the great importanceand interest, particularly other equallydefinite compound. A crystaloriginal compositioninto some lized mineral which has thus suffered change so that its form no longerbelongs to its chemical compositionhas already been defined (Art.273, p. 183) as a pseudomorph. It remains to describe more fullythe different kinds of pseudomorphs. Pseudomorphs are classed under several heads : 1. Pseudomorphs by substitution. 2. Pseudomorphs by simpledeposition, and either by (a) incrustation or (b)infiltration. 3. Pseudomorphs by alteration; and these may be altered (a)without a change of composition,by paramorphism; (b)by the loss of an ingredient; (c)by the assumption of a foreignsubstance; (d)by a partialexchange of constituents. This

subjecthas and

been

others.

"

"

"

"

1. The

firstclass of pseudomorphs, by substitution, embraces those cases there has been a gradual removal of the original material and a corresponding and simultaneous replacementof it by another,without,however, the two. any chemical reaction between A common example of this is a piece of fossilizedwood, where the original fiber has been replacedentirelyby where

CHEMICAL

328 of the will be

blowpipe,or of both methods given applyingto both cases. EXAMINATION

combined.

IN

THE

Some

WET

instructions practical

WAY

agents most The commonly employed chemical reetc. a nd acids. nitric, mineral sulphuric hydrochloric, acids, three the are ride, be added ammonium hydroxide,also solutions of barium chlothese may ammonium tilled disammonium oxalate;finally, molybdate, silver nitrate,

480. To

MINERALOGY

Reagents,

water

in

a

"

wash-bottle.

dish a porcelain test-tubes are needed for the trials and sometimes and funnel a filter-paper. with a handle called a casserole;further, glass of heat, though an alcohol The Bunsen gas-burner(p.330) is the best source to remark that the use of acids lamp may take its place. It is unnecessary much care to avoid injuryto person or clothing. and the other reagentsrequires the importantpointsto be the powdered mineral with the acids, In testing and (2)the phenomena attendingentire noted are: (1)the degree of solubility, without or partial solution;that is,whether (a)a solution is obtained quietly, its color is if what or a (6) is; evolved,producing and, gas effervescence, so, or (c)an insoluble constituent is separated out. effervescence; 481. Solubility. In testingthe degree of solubility hydrochloricacid in of the metallic case is most commonly used, though minerals,as the many n itric is and acid of lead required. Less silver, sulphidesand compounds acid and aqua regia(nitro-hydrochloric often sulphuric acid)are resorted to. "and in general the fragment of in a test-tube, The trial is usuallymade should be first carefullypulverizedin an mineral to be examined agate the heat of the Bunsen burner must be employed. In most mortar. cases (a) Many minerals are completely soluble without effervescence; among phates, sulof the oxides,as hematite,limonite, these are some gothite,etc.; some and and Gold etc. soluble are arsenates, phosphates platinum many acid. only in aqua regiaor nitro-hydrochloric A yellow solution is usuallyobtained if much iron is present; a blue or blue blue solution (turningdeep the addition of ammonium on greenish droxide hyin excess)from compounds of copper; pink or pale rose from cobalt,etc. takes with effervescence (b)Solubility place when the mineral loses a when is generatedby the mutual reaction of acid one or ingredient, gaseous and mineral. Most conspicuoushere are the carbonates, all of which dissolve A

few

"

with

effervescence, givingoff the odorless gas carbon dioxide (C02),though of them only when In the addition of heat. pulverized, or, again,on acid is employed. applyingthis test dilute hydrochloric Hydrogen sulphide(H2S) is evolved by some sulphideswhen dissolved in is a cid: this of true etc. This gas is readily hydrochloric sphalerite, stibnite, recognizedby its offensive odor. Chlorine is evolved by oxides of manganese and also chromic and vanadic acid salts when dissolved in hydrochloric acid. Nitrogendioxide (NO2) is given off,in the form of red suffocating fumes, by many metallic minerals,and also some of the lower oxides (cuprite, etc.), some

when

treated with nitric acid.

(c) The separation of an insoluble ingredienttakes place: With many the silicaseparating silicates, sometimes as a fine powder, and again as a jelly; in the latter case the mineral is said to gelatinize (sodalite, analcite). In order to test this pointthe finely silicateis pulverized digestedwith strong hydro-

CHEMICAL

OF

EXAMINATION

MINERALS

329

chloric acid,and the solution afterward slowlyevaporated nearlyto dryness. of silicatesthe gelatinization With a considerable number takes place only after the mineral has been previouslyfused; while some narily others,which ordiinsoluble rendered are gelatinize, by ignition. With many sulphides(aspyrite)a separationof sulphurtakes placewhen they are treated with nitric acid. Some compounds of titanium and tungsten are decomposed by hydrochloric acid with the separationof the oxides of the elements named (TiO2, The same is true of salts of molybdic and vanadic acids, WO3) only that here the oxides are soluble in an excess of the acid. .

Compounds containingsilver, give with hydrochloric lead,and mercury acid insoluble residues of the chlorides. These compounds are, however, soluble in nitric acid. When compounds containingtin are treated with nitric acid, the tin dioxide (SnO2) separates as a white powder. A corresponding reaction takes circumstances with under similar minerals place containing arsenic and

antimony. Insoluble Minerals. of the acids. any

A

largenumber

of minerals are not be named the may

attacked sensibly Among by followingoxides: corundum, spinel,chromite,diaspore,rutile, cassiterite, quartz; also cerarof the suland niobates;some phates, gyrite;many silicates, titanates, tantalates, as barite, celestite; phosphates,as xenotime,lazulite, childrenite, many amblygonite; also the borate,boracite. 482. Examination of the Solution. If the mineral is difficultly, or the questionas to solubility is not always or insolubility onlypartially, soluble, settled at once. Partial solution is often shown by the color given to the for example,on the addition or more liquid, yielded, generallyby the precipitate of ammonium hydroxide to the liquidfiltered off from the remaining whether from parpowder. The further examination of the solution yielded, tial a fter of any insoluble the filtration or separation by complete solution, residue,requiresthe systematiclaboratorymethods of qualitative analysis. It may be noted,however, that in the case of sulphatesthe presence of is the of white shown of barium a precipitation heavy sulphur by powder The presence of silver in sulphate(BaSOO when barium chloride is added. solution is shown of silver by the separation of a white curdy precipitate chloride (AgCl) upon the addition of any chlorine compound; conversely, the of chlorine when silver nitrate is added shows the presence same precipitate "

these

"

to the solution.

in small quantity, be detected if present, even nitricacid solution of a mineral by the fine yellow powder which separates, ammonium sometimes after standing,when molybdate has been added.

Again, phosphorus may

in

a

EXAMINATION

BY

MEANS

OF

THE

BLOWPIPE*

of 483. The use of the blowpipe,in skilled hands, gives a quick method compositionof a mineral. obtaininga partialknowledge of the qualitative The apparatus needed includes the followingarticles: * The subject of the student who wishes to be

blowpipe and its use is treated very brieflyin this place. The ments, fullyinformed not only in regard to the use of the various instruuseful in the identification of but also as to all the valuable reactions practically minative minerals,should consult a manual on the subject. The Brush-Penfield Manual of DeterMineralogy, with an introduction on Blowpipe Analysis,is particularlyto be recommended.

MINERALOGY

CHEMICAL

330

Blowpipe, lamp, forceps,preferablywith platinum points,platinum wire, with sharp edges,a steel anvil an charcoal,glasstubes; also a small hammer small a horseshoe agate mortar, a pair of cutting magnet, inch or two long,a a three-cornered file. pliers,

little pure a Further, test-paper, both turmeric and blue litmus paper; fluxes: the borax boxes (sodium tetraborate) also in small wooden tin-foil; ,

salt of phosphorus or microcosmic salt (anhydrous sodium carbonate), acid also a potassium sulphate (HKS04); (sodium-ammonium phosphate), the three acids solution of cobalt nitrate in a dropping bulb or bottle;further,

soda

mentioned 484. The

622.

the

in Art. 480. Blowpipe and

Lamp. air-chamber, at a,

which breath,the tip(6), which may mouthpiece

A

"

good

form

blowpipe is shown

of

in

Fig.

the

condensed moisture of is removable, is usuallyof brass,(c)is a removable

or

is essential to

may

not

stop

be used

as

preferred.

lamp is that furnished by an ordinaryBunsen * gas-burner (Fig.623),providedwith a tube,6, which when inserted cuts off The

most

convenient

form of

a; the gas then burns at the flame. This flame should be one yellow

the air 622

supply at

top with the

to one and of The inches the is held near half a tip blow-pipe high. (orjust within the flame,see beyond), and the air blown in the flame to take the shape shown through it causes usual

Fig.625. to learn to blow continuously, that is,to blast of air from the compressed reservoir in the mouth-cavity while respiration is maintained through the nose. To accomplish this successfully and at the same time to produce a clear flame without unnecessary fatiguing effort calls for some practice. When the tube,6,is removed, the gas burns with a colorless flame and is used for heatingglass tubes,test-

It is necessary

keep

up

a

tubes, etc. 485.

The forceps Forceps. Wire. made of steel, (Fig.624) are and should have a spring nickel-plated, strong enough to support firmlythe small fragment of mineral between the platinum pointsat d. The steel points at the other end are used to pick up small piecesof minerals, but must not be inserted in the flame. Care must be taken not to injurethe platinumby allowing it to come in contact with the fused mineral,especially if this contains of steel wire,etc.,while made antimony, arsenic, lead,etc. Cheaper forceps, not so convenient, will also serve well. reasonably A short lengthof fairly stout platinum wire to be used in the making of bead tests should be available. A similar length of finer wire for making "

flame tests is also desirable.

*

Instead of this, a good stearin candle will answer,

or

an

oil flame with flat wick.

OF

EXAMINATION

CHEMICAL

331

MINERALS

The charcoal employed should not snap and should 486. Charcoal. yieldbut littleash; the kinds made from basswood, pine or willow are best. It is most convenientlyemployed in rectangularpieces,say four inches long, The surface must inch wide, and three-quartersof an inch in thickness. an before trial. each clean be perfectly always Tubes. The 487. Glass glass tubes should be preferably of two about 5 mm. interior diameter to be cut in with hard glasstubing grades; a and used tube tests and in a soft glass inch five tubingwith about open lengths inch in about six be diameter to interior 3 mm. lengths,each length 624 "

"

yieldingtwo closed 488. Blowpipe

tubes. The

blowpipe flame,shown in Fig.625, inner of a blue color, : an consists of three cones pale violet c, a second The invisible consists of a. cone outer c and an cone, b, cone, the blowpipe. There from air is with mixed no unburned gas combustion in this cone and 625 therefore no heat. The cone b is the one in which combustion is takingplace.This cone carbon contains monoxide which is a strong reducing Cone a is merely a agent, see below. envelope composed of the final gas products of combustion, C02 and Blowpipe Flame R^ The ^ ^ mogt intense near the tip of the cone 6, and the mineral is held at this point when its fusibility is to be tested. ized The pointo, Fig.625, is called the OXIDIZING FLAME (O.F.); it is characterthe the and of air of has hence effect an oxygen oxidizing by the excess This flame is best produced when the jet of the blowpipe the assay. upon little in the gas flame; it should be entirelynon-luminous. is inserted a very Flame.

"

6 is called the REDUCING FLAME (R.F.); it is characterized by of carbon the perature the or at the high temof hydrocarbons gas, which excess combine with to of the tend the mineral brought into oxygen present it (atr),or, in other words, to reduce it. The best reducingflame is produced the blowpipe is held a littledistance from the gas flame; it should retain when the yellow color of the latter on its upper edge. of Examination. The blowpipe investigationof minerals Methods 489. includes their examination,(1)in the forceps,(2)in the closed and the tubes, (3) on charcoal or other support, and (4) with the fluxes on the open The

cone

the

"

platinum wire. 1. 490.

Use

of the mineral of

a

of the

while

EXAMINATION

Forceps. a

"

test is made

which volatile ingredient

may

IN

Forceps

THE

are

FORCEPS

employedto

hold the

fragment

also when the presence to its fusibility; the flame characteristic color is tested a give as

for,etc. those The followingpractical points must be regarded: (1) Metallic minerals,especially containingarsenic or antimony, which when fused might injurethe platinum of the forceps,

332

CHEMICAL

MINERALOGY

on charcoal;* (2) the fragment taken should be thin,and as should first be examined well beyond the points; (3)when small as can convenientlybe held,with its edge projecting heat be slowly, must the applied or, if this does not prevent it, takes place, decrepitation made with and be water, thick enough to be held in the a paste the mineral may powdered end in view, be heated on forcepsor on the platinumwire; or the paste may, with the same be held in the hottest part is to be tested must charcoal; (4) the fragment whose fusibility of the flame,just beyond the extremity of the blue cone.

exist among minerals,from 491. Fusibility. All grades of fusibility see those which fuse in largefragments in the flame of the candle (stibnite, in the hottest thinnest the fuse which on blowpipe those to edges only below) which number a considerable are flame (bronzite) ; and stillagain there are "

infusible (e.g., corundum). entirely of the temperature of fusion is not easilyaccomplished exact determination of speciesit is of determination 431 (cfArt. p. 304),and for purposes is readilyfixed by The approximate relative degree of fusibility unnecessary. The

to the

the mineral referring

1. Stibnite. 2. Natrolite 3. Almandite

followingscale,suggestedby

von

Kobell:

Actinolite. 5. Orthoclase. 6. Bronzite. 4.

(orChalcopyrite). Garnet.

the followingphenomena with the trial of fusibility, Art. 493); (b)swelling flame of the coloration (see (a) up may of the mineral (vermiculite) or (stilbite), exfoliation ; or (c)glowingwithout and (d) intumescence,or a spirtingout of the mass fusion (calcite); it as fuses (scapolite). is to be noted; and the nature The color of the mineral after ignition of the fused mass is also to be observed,whether clear or blebby glassis a obtained,or a black slag; also whether the bead or residue is magnetic or not etc. (due to iron,less often nickel,cobalt), The ignitedfragment,if nearly or quiteinfusible, be moistened with may the cobalt solution and again ignited,in which case, if it turns blue,this of aluminium indicates the presence (aswith cyanite,topaz, etc.) ; but note that zinc silicate (calamine)also assumes blue color. If it becomes a pink, this indicates a compound of magnesium (asbrucite). it may, after treatment in the forceps,be placed Also, if not too fusible, turmeric paper, in which case an alkaline reaction a stripof moistened upon of an the presence alkali, proves sodium, potassium; or an alkaline earth, calcium,barium, strontium. 493. Flame Coloration. The color often imparted to the outer blowpipe flame,while the mineral held in the forcepsis being heated,makes possible In connection

492.

be observed:

"

the identification of The

they are

colors which

due, are

as

of the elements. number be produced, and the substances may follows: a

Color

Orange-red

Lithium. Strontium. Calcium.

Yellow.

Sodium.

Yellowish green

Barium. Boron.

Purple-red

Siskine-green Arsenic,antimony, and

less fusible

presence

Substance

Carmine-red

*

to whose

easilyreducible metals like lead,also

alloyswith platinum.

copper,

form

more

or

CHEMICAL

EXAMINATION

OF

333

MINERALS

Emerald-green

Oxide

Bluish

green Greenish blue

Phosphoric acid (phosphates). Antimony.

Whitish blue Azure-blue

Arsenic. Chloride of copper; Potassium.

Violet

of copper.

also selenium.

yellowishgreen flame is also given by the oxide or sulphideof molybdenum; a bluish flame (instreaks)by zinc; a pale bluish flame by tellurium;a blue flame by lead. in small quantities, 494. Notes. The presence of soda,even produces a yellow flame, less completely masks the coloration of the which (except in the spectroscope)more or flame due to other substances,e.g., potassium. A filterof blue glassheld in front of the flame will shut out the monochromatic flame and allow the characteristic yellow of the sodium often so difficultly Silicates are violet color of the potassium to be observed. when the substance is present; in such decomposed that no distinct color is obtained even cases potash feldspar)the powdered mineral may be fused on the platinum wire with (e.g., when the flame can be seen an equal volume of gypsum, (at least through blue glass). phate Again, a silicate like tourmaline fused with a mixture of fluorite and acid potassium sulPhosphates and borates give the yields the characteristic green flame of boron. flame in general best when they have been pulverizedand moistened with sulphuric green acid. cases Moistening with hydrochloricacid makes the coloration in many (as with the distinct. carbonates of calcium,barium, strontium) more A

green

"

2.

HEATING

IN

THE

CLOSED

AND

OPEN

TUBES

useful chieflyfor examining minerals containing tubes are 495. The volatile ingredients, given off at the temperature of the gas flame. In the case uninfluenced of the closed tube,the heatinggoes on practically the driven this is of the tube in since out the air early by present, stages of In the open tube,on the other hand, a continual stream of hot the process. the oxidation that of hot to over produce air, is, assay, tending oxygen, passes and hence often materially changing the result. A small fragment is inserted, 496. Closed Tube. amount or a small with care in this case not to soil the sides of the of the powdered mineral of the ordinary Bunsen flame. The tube and heat is appliedby means is s hown the volatile mate, subliof or a ordinarily by deposit, ingredient presence distance above the assay where the tube is relatively the tube at some upon cool. tion, Independent of this,other phenomena may be noted,namely: decrepitashown calcite, as etc.; glowing,as exhibited by gadoliriite; by fluorite, of which fluorite is an example; change of color (limonite), phosphorescence, and here the color of the mineral should be noted both when hot,and again after cooling;fusion; givingoff oxygen, as mercuric oxide; yieldingacid or alkaline vapors, which should be tested by insertinga stripof moistened litmus or turmeric paper in the tube. those with Of the sublimates which form in the tube, the followingare which it is most important to be familiar: "

"

"

Sublimate

Substance Water

(H20)

Sulphur (S)

;

Tellurium dioxide (TeO2) Arsenic sulphide (As2S3)

Antimony oxysulphide (Sb2S2O) Arsenic (As) Mercury sulphide (HgS) Mercury (Hg) In addition to the above:

in the Closed

Tube

Colorless liquiddrops. Red to deep yellow,liquid ; pale yellow,solid. Pale yellow to colorless, liquid; colorless or white,solid. Dark red,liquid;reddish yellow,solid. solid. Black to reddish brown on cooling, solid Black, brilliant metallic to gray crystalline, Deep black,red when rubbed very fine. Gray metallic globules.

Tellurium

givesblack fusible globules;selenium the

same,

but

CHEMICAL

334

MINERALOGY

chloride of lead and oxides part dark red when very small; the sublimates. solid white give in

of arsenic and

antimony

The small fragment is placed in the tube about inclined (say20"),but not inch from the lower end, the tube being slightly an beneath. The curheat rent and applied enough to cause the mineral to slipout, has the an the tube heating during process of air passingupward through the of formation be observed are to phenomena oxidizingeffect. The special The acid alkaline character or the odor of the escapinggases. a sublimate and The with the closed tube. as is tested for in the same way of the vapors is sulphur dioxide,S02, when in this way most common gas to be obtained be is to This recognizedby its irritating, oxidized. gas sulphidesare being blue litmus paper. moistened reaction its acid and odor upon 497.

Open Tube.

"

pungent The

more

important sublimates

as

are

follows:

Sublimate

Substance

in the

Open

Tube

volatile. White, crystalline, Arsenic trioxide (AsaOa) Antimony antimonate (Sb2O4) Straw-yellow,hot; white, cold.

Antimony trioxide (Sb2O3) .

.

.

Tellurium dioxide (TeO2) Selenium dioxide (SeO2) Molybdenum trioxide (MoO3)

Mercury (Hg)

Infusible,non-volatile, of tube. Obtained amorphous, settlingalong bottom also the from compounds containingsulphur as stibnite, bournonite)as dense white fumes. (e.g., sulphantimonites Usually accompanied by the following: forming as a ring on slowly volatile, White, crystalline, walls of tube. White to pale yellow globules. volatile. White, crystalline, Pale yellow,hot; white, cold. Gray metallic globules,easilyunited by rubbing.

mates, It is also to be noted that if the heating process is too rapid for full oxidation,sublibe formed, especially with sulphur (yellow), like those of the closed tubes, may arsenic sulphide (orange), sulphide (black), antimony oxysulphide arsenic (black), mercury (blackto reddish brown).

3.

HEATING

ON

CHARCOAL

498. The fragment (orpowder) to be examined the piece and this so held that the flame passes be powdered, mixed mineral decrepitates, it may

is placed near end of one along its length. If the with

water, and

then

the

material

employed as a paste. reducing flame is employed if it is desired to reduce a metal (e.g.., eral case. silver, copper)from its ores : this is the common If,however, the minis to be roasted, that is, heated in contact with the air so as to oxidize and for example,the sulphur,arsenic, volatilize, antimony present, the oxidizing flame is needed and the mineral should be in powder and spread out. The

The

points to be noted are as follows : (a) The odor given off after short heating. In this

way

the

presence

of

alliaceous odor),and selenium (odor of decayed sulphur,arsenic (garlic or be horseradish) recognized. may In the case (b) Fusion. of the salts of the alkalies the fused mass is absorbed into the charcoal;this is also true, after long heating,of the carbonates and sulphatesof barium and strontium. (Art.501.) (c) The Sublimate. the presence of many of the metals By this means be determined. The color of the sublimate, both near may the assay (N) and at a distance (D) as also when hot and when cold,is to be noted. The important sublimates are the following: "

"

,

336

MINERALOGY

CHEMICAL

of soda on coal charBy means 500. Detection of Sulphur in Sulphates. be in the in the shown, of following sulphates may the presence sulphur The Fuse the powdered mineral with soda and charcoal dust. manner. the to sulphate a sulphide latter acting as a strong reducing agent changes is placed with the fused mass with the formation of sodium sulphide. When silver surface a black or yellow stain of silver a clean a drop of water upon be obtained from A similar reaction would of course sulphidewill be formed. "

a

sulphide.

the open

tube

latter

The or

upon

4.

however

can

charcoal and TREATMENT

be readily distinguished by roastingin notingthe formation of SO2.

PLATINUM

THE

ON

WIRE

fluxes are The three common of the Fluxes. borax, salt of phosphorus,and carbonate of soda (p.330). They are generallyused with the platinum wire, less often on charcoal (see p. 335) If the wire is employed it must have a small loop at the end; this is heated to redness and dipped into fused to a bead; this operation the powdered flux,and the adheringparticles in the use of soda the wire may is repeateduntil the loop is filled. Sometimes adhere. little it to to be first moistened cause a at the bead is ready,it is,while hot,brought in contact with the powWhen dered the to will adhere and then which of it, mineral, some heating process be continued. Very littleof the mineral is in generalrequired,and the may with a minute quantity and more added if experimentshould be commenced The be heated successively bead must firstin the oxidizing flame necessary. (O.F.)and then in the reducingflame (R.F.),and in each case the color noted cold. The phenomena connected with fusion,if it takes when hot and when be must also observed. place,

501.

Use

"

.

Minerals containingsulphur or arsenic,or both, must be first roasted (see p. 334) till have been volatilized. If too much of the mineral has been added and the these substances bead is hence too opaque to show the color,it may, while hot, be flattened out with the and the remainder diluted hammer, or d'rawn out into a wire,or part of it may be removed with more of the flux With salt of phosphorus, the wire should be held above the flame so that the escaping support the bead ; this is continued tillquiet fusion is attained. gases may It is to be noted that the colors vary much of material present ; they with the amount also modified by the presence of other metals. are .

502. Borax. The followinglistenumerates the different colored beads obtained with borax, both in the oxidizing (O.F.)and reducingflames (R.F.), and also the metals to the presence of whose oxides the colors are due. pare Comfurther the reactions given in the listof elements (Art.504). -

Color in Borax

-

Bead

Substance 1. OXIDIZING

or Colorless,

opaque

white. .

.

calcium,aluminium; Silica,

also silver, zinc,etc. (paleyellow,hot, if in small amount). Chromium (CrO3),hot (yellowishgreen, cold). Manganese (Mn2O3), amethystine-red (violet, hot). Iron (Fe2O3),hot if saturated. (yellow,cold) Nickel (NiO) red-brown to brown, cold" (violet, hot). Uranium (UO3), hot cold). (yellow, Copper (CuO), hot (blue,cold,or bluish green if highly

Iron, cold

Ked, red-brown

to brown

FLAME

"

"

"

"

"

"

Green

"

saturated). Chromium

(CrO3),yellowishgreen,

cold

"

(red,hot).

CHEMICAL

EXAMINATION

Yellow

OF

(Fe2O3),hot

Iron

337

MINERALS

but (paleyellow to colorless, cold) yellow if saturated. Uranium (UOs), hot, if in small amount; paler on cooling. Chromium (CrO3),hot and in small amount (yellowish cold). green, Cobalt (CoO), hot and cold. Copper (CuO), cold if highly saturated (green,hot). Nickel (NiO), hot (red-brown, cold). Manganese (Mn2O3), hot (amethystine-red,cold). red-brown

"

"

and

"

Blue

"

Violet

"

,.

.

"

2.

Colorless

REDUCING

FLAME

(R.F.)

Manganese (MnO), or a faint rose color. Copper (Cu2O, with Cu), opaque red. Iron (FeO), bottle-green. Chromium (CrjOs),emerald-green. Uranium (U^Os),yellowishgreen if saturated.

Red Green

Blue

Cobalt Nickel

Gray, turbid

(CoO), hot

and

cold.

(Ni).

503. Salt of Phosphorus. This flux gives for the most part reactions The only cases similar to those obtained with borax. enumerated here are and hence those where the flux is a good test. those which are distinct, With silicates this flux forms a glassin 'which the bases of the silicate are but the silicaitselfis left insoluble. It appears as a skeleton readily dissolved, in a bout the melted bead. seen floating The colors of the beads,and the metals to whose oxides these are due, are : "

Color Red Green

Substance :

Chromium Chromium

in

(finegreen when cold). R.F., when cold (red in O.F., hot). in R.F., dirtygreen, hot; fine green, cold (yellow-green O.F., hot

in O.F.

Molybdenum in O.F.).

"

and

"

"

hot. in R.F., cold; yellow-green, Vanadium, chrome-green in R.F., cold (brownishred,hot). In O.F., dark yellow,hot, paleron cooling. Molybdenum, yellowishgreen in O.F.,hot,paleron cooling (inR.F., dirty green, hot; fine green, cold). Uranium in O.F. hot; yellowishgreen, cold (inR.F. yellowish green, hot; green, cold). Vanadium in O.F., dark yellow,hot, paler on cooling (in R.F., brownish red, hot; chrome-green, cold). Titanium (TiO2) in R.F., yellow,hot. (Alsoin O.F.,yellow,hot; colorcold.) Uranium

"

Yellow

"

"

,

,

"

Violet

CHARACTERISTIC

REACTIONS

OF OF

THE

THEIR

IMPORTANT

ELEMENTS

AND

OF

SOME

COMPOUNDS

504. The followinglistcontains the most characteristic reactions, chiefly before the blowpipe and in some also in the wet way, 'of the different cases elements and their oxides. It is desirable for every student to gain familiarity with them by trial with as many minerals as possible.Many of them have For a thoroughlyfull in the precedingpages. mentioned alreadybeen briefly of these and other characteristic tests (blowpipe and otherwise) description reference should be made to the volume by Brush and Penfield referred to on p. 329.

be

It is to be remembered that while the reaction of a singlesubstance may if distinct or perfectly alone,the presence of other substances may more

338

CHEMICAL

MINERALOGY

consequentlyobvious that in the have to be taken, and special precautions actual examination from this the cause. arising to difficulty have to be devised, overcome methods in characters" nection (Pyr.)given conThese will be gatheredfrom the "pyrognostic of Part this Fourth work. in the of each species with the description less

entirelyobscure

these

reactions; it

is

of minerals

infusible minerals,containinga conin most siderable of aluminium presence when, after being be detected by the blue color which they assume cyanite,andalusite, heated,they are moistened with cobalt solution and again ignited(e.g., etc.). Very hard minerals (as corundum) must be first finelypulverized. The test is not be formed. conclusive with fusible minerals since a glasscolored blue by cobalt oxide may Aluminium,

"

amount,

The

may

also assumes a blue color when (zincsilicate) It is to be noted that the infusible calamine will be precipitated as a flocculent solutions aluminium treated with cobalt nitrate. From hydroxide in excess. white or colorless precipitateon the addition of ammonium minerals roasted on charcoal give dense white odorless fumes; Antimonial Antimony. tube a white sublimate of metallic antimony and its sulphur compounds give in the open also many sulpharitimonites, oxide of antimony (seep. 334). Antimony sulphide (stibnite), give in a strong heat in the closed tube a sublimate of antimony oxysulphide, black when "

hot, brown-red when cold. See also p. 333. In nitric acid,compounds containing antimony deposit white

insoluble metantimonic

acid. roasted on when Arsenic. charcoal, etc., give off fumes Arsenides, sulpharsenites, In the open tube they give a white, usuallyeasilyrecognizedby their peculiargarlicodor. volatile,crystallinesublimate of arsenic trioxide. In the closed tube arsenic sulphide gives a sublimate dark brown-red when hot, and red or reddish yellow when cold; arsenic In arsenates arsenides yielda black mirror of metallic arsenic in the closed tube. and some be detected by the garlicodor yielded when mixture of the powdered the arsenic can a carbonate mineral with charcoal dust and sodium is heated (R.F.) on charcoal. Barium. A yellowish coloration of the flame is given by all barium salts,except green alkaline reaction is usually obtained the silicates; after intense ignition. an In solution the presence is proved by the heavy white precipitate(BaSO4) of barium the addition of dilute sulphuricacid. formed upon Bismuth. On charcoal alone,or better with soda, bismuth gives a very characteristic orange-yellow sublimate; brittle globules of the reduced metal are also obtained (with treated with 3 or 4 times the volume of a mixture in equal parts of soda). Also when iodide and sulphur,and fused on charcoal,a beautiful red sublimate of bismuth potassium iodide is obtained; near the mineral the coating is yellow. Boron. danMany compounds containing boron (borates,also the silicates, datolite, burite,etc.)tinge the flame intense yellowishgreen, especiallyif moistened with sulphuric acid. For some .silicates(as tourmaline) the best method is to mix the powdered mineral with one part powdered fluorite and two parts potassium bisulphate. The mixture is moistened and placed on platinum wire. of fusion the green At the moment color appears, "

"

"

"

but lasts but an instant. A clilute hydrochloric acid

solution containing boron gives a reddish brown color to turmeric paper which has been moistened with it and then dried at 100"; the color changes to black when ammonia is poured on the paper. Cakium. Many calcium minerals (carbonates, sulphates,etc.)give an alkaline reaction turmeric paper after being ignited. A yellowishred color is given to the flame by some on calcite after moisteningwith HG1) ; the strontium flame is a much compounds (e.g., deeper "

red. In

weakly

acid or alkaline solutions calcium is precipitatedas oxalate by the addition of oxalate. Cadmium. On charcoal with soda, compounds of cadmium limate give a characteristic subof the reddish brown oxide. Carbonates. All carbonates effervesce with dilute less hydrochloricacid,yieldingthe odorgas CO2 (e.g., calcite); and some requireto be pulverized, need the addition of many heat (dolomite,sidente). Carbonates of lead should be tested with nitric acid. LMprides. If a small portion of a mineral containing chlorine (a chloride,also pyromorphite,etc.)is added to the bead of salt of phosphorus,saturated with copper oxide,the bead when heated is instantlysurrounded with an intense purplishflame of copper chloride. In solution chlorine gives with silver nitrate a white curdy precipitateof silver chloride which darkens color on exposure in to the light;it is insoluble in nitric acid, but entirely soluble m ammonia. ammonium

"

"

"

CHEMICAL

OF

EXAMINATION

339

MINERALS

Chromium. Chromium giveswith borax a bead which (O.F.)is yellow to red (hot)and yellowish green (cold)and R.F. a fine emerald-green. With salt of phosphorus in O.F. the bead is dirty green Cf. Vanadium (hot) and clear green (cold); in R.F. the same. beyond (alsopp. 336, 337). "

Cobalt.

beautiful blue

A

"

bead

is obtained

with

borax

in both

flames

from

minerals

containing cobalt. Where sulphur or arsenic is present the mineral should first be thoroughly roasted on charcoal. On charcoal,at least with soda, metallic copper be reduced from most of Copper. can its compounds. In the case of sulphides the powdered mineral should be roasted firstin order to eliminate the major part of the sulphur before fusion with soda. With borax it gives (O.F.)a green bead when hot,becoming blue when cold; also (R.F.),if saturated,an red bead containingCu2O and often Cu is obtained. Copper chloride,obtained by opaque moistening the mineral with hydrochloricacid (inthe case of sulphidesthe mineral should be previouslyroasted)yieldsa vivid azure-blue flame; copper oxide gives a green flame. Most metallic compounds are soluble in nitric acid. Ammonia in excess produces an "

intense blue color in the solution. in the closed tube with potassium bisulphate and powdered glass Heated Fluorine. acid present produces a white sublimate of SiO2. This sublimate and the hydrofluosilicic But ifthe lower end of the tube isbroken off and the open tube form a volatile combination. then dipped in a test tube of water that the acid is removed, the depositof SiO2 which so will appear when the tube is dried will be found to be no longer volatile. Heated gently in a platinum crucible with sulphuric acid, many compounds (e.g., fluorite) give off hydrofluoricacid,which corrodes the exposed parts of a glassplate placed and then scratched. it which has been coated with wax over Iron. Minerals which contain of iron yield a magnetic mass small amount even a when heated in the reducing flame. With borax iron gives a bead (O.F.) which is yellow red (according to quantity) while hot, but is colorless to yellow on cooling; to brownish R.F. becomes bottle-green(seepp. 336', 337). Lead. With soda on charcoal a malleable globuleof metallic lead is obtained from lead compounds; the coating has a yellow color near the as"ay; the sulphide gives also a white ing coating (PbSO3) farther off (p.335). On being touched with the reducing flame the coatdisappears,tingeingthe flame azure-blue. In solutions dilute sulphuric acid gives a white precipitateof lead sulphate;when of the acid is added, the solution evaporated to dryness,and delicacyis required an excess water added; the lead sulphate,if present, will then be left as a residue. Lithium. Lithium givesan intense carmine-red to the outer flame,the color somewhat resembling that of the strontium flame but is deeper; in very small quantitiesit is evident in the spectroscope. Magnesium. Moistened, after heating,with cobalt nitrate and again ignited, a pink color is obtained from some infusible compounds of magnesium (e.g., brucite). In solution the addition of ammonium and a littlehydrogen sodium hydroxide in large excess phate phosElements produces a white granular precipitateof NH4MgPO4. precipitatedby ammonium oxalate should be removed first. hydroxide or ammonium With borax manganese Manganese. givesa bead violet-red (O.F.),and colorless (R.F.). With soda (O.F.) it gives a bluish green bead; this reaction is very delicate and may be relied upon, even in presence of almost any other metal. In the closed tube sublimate of metallic mercury is yielded when a the Mercury. mineral is heated with dry sodium carbonate. In the open tube the sulphidegivesa mirror of metallic mercury; in the closed tube a black lusterless sublimate of HgS, red when rubbed, is obtained. On charcoal molybdenum the assay a copper-red Molybdenum. sulphide gives near stain (O.F.),and beyond a white coating of the oxide; the former becomes azure-blue when for a moment touched with the R.F. The salt of phosphorus bead (O.F.) is yellowish (hot) and nearlycolorless (cold); also (R.F.) a fine green. green Nickel. With borax, nickel oxide gives a bead which (O.F.) is violet when hot and red-brown on cooling; (R.F.) the glass becomes gray and turbid from the separation of metallic nickel. Niobium An acid solution boiled with metallic tin gives a blue color. (Columbium). The reactions with the fluxes are not very satisfactory. Nitrates. These detonate when heated on charcoal. Heated in a tube with sulphuric acid they give off red fumes of nitrogen dioxide (NO2). Most Phosphorus. after having phosphates impart a green color to the flarne, especially beenn moistened with sulphuricacid,though this test may be rendered unsatisfactory by "

"

"

"

"

"

"

"

"

"

"

"

340

CHEMICAL

MINERALOGY

used in the closed tube with a fragment are with water, phosphureted moistened afterward and magnesium or sodium, odor. by its disagreeable hydrogen is given off,recognizable tion A few drops of a nitric acid solution,containing phosphoricacid,produce in a soluof ammonium phosphoof ammonium molybdate a pulverulentyellowprecipitate

of other coloring agents. If they

the presence of

metallic

molybdate. The flame is best Potash imparts a violet color to the flame when alone. Potassium. observed through a blue glassfilterwhich will eliminate the sodium flame color which will soda or almost invariablybe present. It is best detected in small quantities,or when lithia is present, by the aid of the spectroscope. See also p. 333. On charcoal selenium fuses easily, giving off brown fumes with a peculiar Selenium. and when heated (R.F.) disagreeableorganic odor; the sublimate on charcoal is volatile, givesa fine azure-blue flame. A small fragment of a silicatein the salt of phosphorusbead leaves a skeleton Silicon. the bases being dissolved. of silica, then dissolved If a silicatein a fine powder is fused with sodium carbonate and the mass and acid and evaporated to dryness,the silicaseparates as a gelatinousmass in hydrochloric acid is added and on evaporationto dryness is made insoluble. When strong hydrochloric dissolved and the silica left then water to the dry residue in the test tube, the bases are behind. those which are hydrous, are decomposed by strong hydrochloric especially Many silicates, acid,the silicaseparatingas a powder or, after evaporation,as a jelly(seep. 328). On charcoal in O.F. silver givesa brown Silver. coating. A globuleof metallic silver if soda is added. generallybe obtained by heating on charcoal in O.F., especially may circumstances it is desirable to have recourse to cupellation. Under some down solution containing any salt of silver, the insoluble chloride is thrown From a acid is added. is insoluble in acid or water, but entirely when hydrochloric This precipitate It changes color on in ammonia. to the light. so exposure Strontium. Compounds of strontium are usuallyrecognized by the fine crimson-red which they give to the blowpipe flame; many yield an alkaline reaction after ignition. "

"

"

"

"

(Cf.barium.) Compounds containingsodium in large amount give a strong yellow flame. Sulphur,Sulphides,Sulphates. In the closed tube some sulphidesgive off sulphur; in the open tube they yieldsulphur dioxide,which has a characteristic odor and reddens a In small quantities,or in sulphates, strip of moistened litmus paper. sulphur is best detected by fusion on charcoal with soda and charcoal dust. The fused mass, when sodium sulphidehas thus been formed, is placed on a -clean silver coin and moistened; a distinct black stain on the silver is thus obtained (the precaution mentioned be on p. 336 must exercised). A solution of a sulphatein hydrochloricacid giveswith barium chloride a white insoluble of barium sulphate. precipitate Tellurium. Tellurides heated in the open tube give a white or grayish sublimate, fusible to colorless drops (p. 334). On charcoal they give a white coating and color the Sodium.

"

"

"

R.F.

green. Tin. Minerals

when heated on charcoal with soda or containingtin (e.g., cassiterite), potassium cyanide,yield metallic tin in minute globules; these are malleable, but harder than silver. Dissolved in nitric acid,white insoluble stannic oxide separates out. Titanium. Titanium gives in the R.F. with salt of phosphorus a bead which is violet when cold. Fused with sodium carbonate and dissolved with hydrochloric acid, and heated with a piece of metallic tin,the liquidtakes a violet color,especiallyafter partial evaporation. Tungsten. Tungsten oxide gives a blue color to the salt of phosphorus bead (R.F.). Fused and treated as titanium (see above) with the addition of zinc instead of tin,gives a "

"

"

fine blue color. Uranium. Uranium compounds give to the salt of phosphorus bead (O.F.) a greenish yellow bead when cool; also (R.F.) a fine green on cooling (p. 337). Vanadium. With borax (O.F.)vanadates give a bead yellow (hot)changing to yellowish green and nearly colorless (cold) ; also (R.F.) dirtygreen (hot),fine green (cold). With "r"i PhosPhorus (O.F.) a yellow to amber color (thus differingfrom chromium); also (R.F.) fine green (cold). Zinc. On charcoal in the reducingflame compounds of zinc give a coating which is yellow while hot and white on cooling, and moistened by the cobalt solution and again "

"

"

heated when

becomes heated

a

fine green.

after

Note, however,that the zinc silicate (calamine) becomes moistening with cobalt solution.

blue

CHEMICAL

Zirconium.

"

A

orange-yellow color

dilute

EXAMINATION

OF

341

MINERALS

hydrochloricacid solution, containing zirconium, imparts

to turmeric

paper,

moistened

DETERMINATIVE

an

by the solution. MINERALOGY

505. Determinative be properly considered under the Mineralogy may general head of Chemical Mineralogy, since the determination of minerals and all the physidepends mostly upon chemical tests. But crystallographic cal observed. characters have also to be carefully in which There is but one exhaustive way the identityof an unknown mineral may in all cases be fixed beyond question,and that is by the use of a of such tables the mineral in set of determinative tables. By means is referred successively from a generalgroup into a more specialone, until at last all other species have been eliminated, and the identity of the one given is beyond doubt. A careful preliminaryexamination of the unknown mineral should,however, is had to the tables. This examination always be made before final recourse will often suffice to show what the mineral in hand is,and in it is not it should be since in this that a case omitted, only any way with the appearance and characters of minerals can be practicalfamiliarity

complete

hand

gained. The student will naturallytake note firstof those characters which are at obvious to the senses, that is: crystalline ture, once form, if distinct;generalstruccolor (and streak), cleavage, fracture, luster, feel;also,if the specimen is not too small,the apparent weight will suggest something as to the specific of very unequal importance. Structure, are gravity. The characters named if crystals not present, and fracture are are generallyunessential except in distinguishing varieties;color and luster are essential with metallic,but tance generallyvery unimportant with nonmetallic,minerals. Streak is of imporand metallic with those colored minerals of luster (p.247) Crystalonly line form and cleavageare of the highestimportance,but may requirecareful .

study. firsttrial should be the determination of the hardness (forwhich end the pocket-knife is often sufficient in experiencedhands). The second trial of the specific of the powshould be the determination gravity. Treatment dered mineral with acids may come (seepp. 328,329) a next; by this means is readilyidentified, Then should carbonate and also other results obtained. the color given to the flame, to ascertain the fusibility; follow blowpipe trials, if any; the character of the sublimate given off in the tubes and on charcoal; and other points the metal reduced on the latter;the reactions with the fluxes, The

as

explainedin the precedingpages.

learns in the above way, in regard to the nature his knowledge of the characters of minerals in of his mineral,depends upon with the chemical behavior of the various general,and upon his familiarity elementarysubstances with reagents and before the blowpipe (pp.338 to 341). definite to If the results of such a preliminaryexamination are sufficiently of of reference in is the hand small number that mineral one a species, suggest for the final this work i n of be Part. IV their full to made. description may How

much

the observer

decision. included are arrangedaccording added in the Appendix. They and physicalcharacters, to their crystalline are A number

of

tables,in which

the minerals

342

will

MINERALOGY

CHEMICAL

In

The

of

first

these

principle

their

to

the

reaching

in

observer

conclusion

a

in

regard

to

a

hand.

in

specimen

aid

cases

many

tables

gives

basic

elements

lists

arranged

minerals

of

secondarily

and

primarily

according

ing accordtheir

to

acid

radicals. second

The

according

grouped under

each

added

in

by

of

the

each

type

in

the

in

some

cubes, species

of

relative

to

of

specimens,

of

learning

minerals.

are

frequent

use

but

minor

the of

rather

prominent

of

tables

tables,

because characters

hardness

Other

not

of

tables

The

simply

the

is, those give of

structure

etc.

will

also

species

that

cleavage;

they

is

is shown

enumerating forms;

colors,

arranged

species

etc.

their

various these

the

individual

the

species, and

belong

gravities;

crystalline

because

luster;

the

of

well-defined

they

rhombohedrons,

prominent

identification task

this

octahedrons,

make

specific

prominent

the

of

all

which

to

importance

Following one

recommended

difficult

their

include

to

system

of

order

hardness;

types;

intended

is

crystalline

employed. by

names

tables

the

The

case.

crystallizing

different

to

system

characterized

the

these

for

help more

student aid him

is in

in

important

the the

MINERALOGY

DESCRIPTIVE

344

be stated that, in general, regardto the various classes of salts it may and basic hydrous sections;the into acid, anhydrous, they are separated the different in cases. called for,however, vary specialsubdivisions In

For

the abbreviations

explanationof

an

descriptionof species,see

p. 5.

ELEMENTS.

I. NATIVE

SULPHARSENITES,

Sulpho-salts. "

ARSENIDES,

TELLURIDES,

SELENIDES,

II. SULPHIDES, III.

in the

CLASSIFICATION

OF

SCHEME

used

ANTIMONIDES.

SULPHANTIMONITES,

SULPHO-

BISMUTHITES.

IV. V.

VI.

Haloids.

"

BROMIDES,

CHLORIDES,

J FLUORIDES.

IODIDES

OXIDES.

Oxygen

Salts.

1.

CARBONATES.

2.

SILICATES, TITANATES.

3.

NIOBATES,

4.

PHOSPHATES,

6.

BORATES.

6.

SULPHATES,

TANTALATES.

ARSENATES,

ANTIMONATES.

VANADATES;

NITRATES.

7.

VII. VIII.

Salts

URANATES.

CHROMATES,

TUNGSTATES,

HYDROCARBON

Oxalates,Mellates,etc.

Acids:

of Organic

TELLURATES.

MOLYBDATES.

COMPOUNDS. I. NATIVE

ELEMENTS

divided into the two distinct sections of the The NATIVE ELEMENTS are Metals and the Non-metals,and these are connected by the transition class of The distinction between them as regardsphysicalcharacters the Semi-metals. and chemical relations has alreadybeen given (Art.453) The minerals are only non-metals present among carbon, sulphur,and in of its the is one last, allotropic selenium; closelyrelated to the forms, semi-metal tellurium. The native semi-metals form a distinct group by themselves,since all in the rhombohedral mental class of the hexagonal system with a fundacrystallize anglediffering only a few degreesfrom 90", as shown in the following list: 93" 3'. 94" 54'. Tellurium,rrr Arsenic,rr' 92" 53'. 92" 20'. Antimony, rr' Bismuth, rr' .

=

=

=

An

=

artificialform

of selenium is known with metallic luster and rhombohedral rr' with 93". Zinc dral crystallization, (alsoonly artif.)is rhombohe(rr' 93" 46')and connects the semi-metals to the true metals. Metallic tantalum has been described in cubic crystals. is prominent,includinggold, Among the metals the isometric GOLD GROUP in

=

=

silver,copper, mercury,

amalgam (AgHg), and lead.

NATIVE

345

ELEMENTS

includes the metals platinum,iridium, related isometric group An allot iron. and ropic form of palladium and also iridosmine palladium, rhombohedral. both (IrOs)are Another

DIAMOND.

but with the + and forms usuallyequallydeveloped tetrahedral, Isometric, from each other. and not to be distinguished dral, octaheCommonly showing and other forms ; faces frequently rounded or striated and hexoctahedral, Twins with tw. pi.0(111). with triangular common depressions(on o(lll)). In distorted. massive. sphericalforms; Crystalsoften "

627

628

Cleavage: o(111)highlyperfect. Fracture conchoidal. G.

Brittle.

H.

=

10.

3-516-3-525

to greasy. Color white or crystals. Luster adamantine various pale shades of yellow,red, orange, green, blue, occasionally colorless; brown; rarelydeeply colored;sometimes black. Usually transparent; also Refractive and dispersive 2-4195. translucent, opaque. power high; index n =

=

(SeeArt. 328.) 1 Ordinary. In crystalsusuallywith rounded faces and varying from those colorless and free from flaws (first faint shades of color, water) through many often full of flaws and hence of value only for cuttingpuryellowbeing the most common; poses. Var.

which

2.

--

.

are

Bort

Boort; rounded

or

forms

with rough exterior and

radiated

or

confused

line crystal-

structure. 3. Carbonado

without Brazil.

or Carbon; black diamond. granular to compact, Massive, crystalline, from Bahia, cleavage. Color black or grayish black. Opaque. Obtained chiefly

Comp.

Pure

carbon; the varietycarbonado

yieldson combustion a slight ash. Unaffected by heat except at very high temperatures, when Pyr.,etc. (inan oxygen atmosphere) it burns to carbon dioxide (CO2) ; out of contact with the air transformed into of coke. Not acted upon a kind by acids or alkalies. Diff. from quartz crystal)by its extreme hardness and brilliant Distinguished (e.g., adamantine ters; luster;the form, cleavage,and high specific gravity are also distinctive characit is opticallyisotropic ; transparent to X-rays. Artif. Minute diamonds have been formed in several ways. Moissan artificially firstproduced them by dissolvingcarbon in molten iron and then coolingthe mass suddenly under they have been formed by dissolving pressure; graphitein fused olivine or artificial magnesium silicate melts; they have been formed when an electric current was passed in carbon while under high pressure in an atmosphere of through an iron spiralembedded hydrogen. Obs. The diamond occurs chieflyin alluvial depositsof gravel,sand, or clay,associated with quartz, gold,platinum, zircon,octahedrite, brookite,hematite,ilmenite, rutile, and also andalusite, chrysoberyl,topaz, corundum, tourmaline,garnet, etc.; the associated minerals being those common in graniticrocks or graniticveins. Also found in quartzose "

"

"

"

"

346

MINERALOGY

DESCRIPTIVE

with the laminated granular quartz rock or less flexible. This or in thin slabs is more lina, at the mines of Brazil and the Ural Mts.; and also in Georgia and North Carorock occurs have been found. where a few diamonds It has been reported as occurring in situ in a pegmatite vein in gneiss at Bellaryin in South Africa and in a further in connection with an eruptiveperidotite It occurs India. It has been noted as grayishparticles forming one similar formation in Pike County, Ark. the meteorite which fellat Novo-Urei, Russia, Sept. 22, 1886; also in the form per cent of 9) in the meteorite of Carcote, Chile; in the meteoric iron of of black diamond (H.

conglomerates, and

further

in

connection

which quartzose hydromica schist,itacolumite,

=

Canon Diablo, Ariz. down from very early times to the discovery of of diamonds the chief source India was in that southern the small. Of the is mines localities, India,in the now Brazilian yield the ; The diamond mines." "Golconda deposits of Madras presidency, included the famous since the early part of the 18th century, and have yielded very Brazil have been worked The most important obtained is small. largely,although at the present time the amount in the province of Minas Geraes; also from Bahia, etc. region was that near Diamantina firstfound in in South Africa dates from 1867. They were The discovery of diamonds from Potchefstroom down to the junction with the Vaal the of occur river;they the gravel More recentlythey have been Orange river,and along the latter as far as Hope Town. South found in gravelsin the Somabula Forest,Rhodesia and at Liideritzbucht,German of much less importance than the dry diggings, river diggingsare now Africa. These West discovered in 1871. The latter are chieflyin Griqualand-West, south of the Vaal river,on the border of the of limited areas Kimberley a number mately approxiOrange Free State. There are here near 200 to 300 yards, of oval in form, with an average diameter of some or spherical mines are the most important. which the Kimberley,De Beer's,Dutoitspan and Bultfpntein The general structure is A circle 3" miles in diameter encloses these four principalmines. shale with upturned edges enclosing similar: a wall of nearly horizontal black carbonaceous The upper portion of the deposit consists of a friable mass of the diamantiferous area. the reach of littlecoherence of a pale yellow color,called the "yellow ground." Below firm and of a bluish green or greenishcolor; it is the rock is more atmospheric influences, of a serpentinous This consists essentially called the "blue ground" or simply "the blue." breccia: a base of hydrated magnesian silicatepenetrated by calcite and opaline silica and enclosingfragments of bronzite,diallage,also garnet, magnetite, and ilmenite,and less rather abundantly disseminated are commonly smaragdite,pyrite,zircon,etc. The diamonds claims to the amount of 4 to 6 carats per cubic yard. The through the mass, in some to have been a peculiartype of peridotite. These areas believed originalrock seems are to be volcanic pipes,and the occurrence of the diamonds is obviouslyconnected with the eruptiveoutflow,they having probably been brought up from underlyingrocks. Other important mines, similar in character to those near Kimberley, are the Jagersfonteinmine in Orange Free State and the Premier, near Pretoria,Transvaal. The South African mines up to the beginningof 1914 are estimated to have yielded about 120 million carats valued at nearly 900 million dollars. (26 tons) of diamonds Diamonds also obtained in Borneo, associated with platinum, etc.; in Australia, are and the Ural Mts. In the United States a few stones have been found in gravelsin N. C., Ga., Va,, Col., Cal. and Wis. Reported from Idaho and from Oregon with platinum. In 1906 diamonds found in Pike County, Ark., both loose in the soil and enclosed in a peridotiterock. were Considerable explorationwork has been done at this locality and probably between two and three thousand stones found. The stones have been of good color but usually small. Some of the famous diamonds of the world with their weights are as follows: the Kohiwhich weighed when brought to England 186 carats, and as recut as a brilliant, noor, 106 carats; the Orloff,194 carats; the Regent or Pitt, 137 carats; the Florentine or Grand of Tuscany, 133 carats. Duke The "Star of the South" found in Brazil weighed before and after cutting respectively 254 and 125 carats. Also famous because of the rarity of their color are the green diamond of Dresden, 40 carats,and the deep blue Hope diamond from

at

India,weighing 44

the Premier

Assembly li Ibs.

to

mine.

carats.

It

It has

since

named

the Cullinan When

and was presented by the Transvaal found it weighed 3,025 carats or over been cut into 105 separate stones,the two largest weighing516 and 309

King Edward

was

VII

of

England.

347

ELEMENTS

NATIVE

carats, respectively, being the largestcut stones

in existence.

The

historyof

the above

of others is given in many works on gems. In addition to its use as a gem, the diamond is extensivelyused as an abrasive. Use. Crystal fragments are used to cut glass. The fine powder is employed in grinding and The noncrystalline, polishinggem stones. varieties, especiallythe carbonado, are opaque drills. The used in the bits of diamond is also used in wire drawing and in the diamond stones

and "

of tungsten filaments for electric lights. in minute CLIFTONITE. Carbon cubic and cubo-octahedral crystals. H. G. Color and streak black; from the Youndegin, West Australia,meteoric 2' 12. found in 1884, and other meteoric irons.

making

"

=

GRAPHITE.

Black

Plumbago.

=

2'5.

iron,

Lead.

In six-sided tabular crystals.Commonly Rhombohedral. embedded in foliated masses, also columnar or radiated;scalyor slaty;granular to con"

pact; earthy. inelastic. Feel greasy. Cleavage: basal,perfect. Thin laminae flexible, H. 1-2. 2'09-2'23. Luster metallic, G sometimes dull,earthy. Color iron-black to dark steel-gray.Opaque. A conductor of electricity. Comp. Carbon, like the diamond; often impure from the presence of ferric oxide,clay,etc. =

=

"

Pyr., etc. At a high temperature some graphite burns more easily than diamond, B.B. infusible. Unaltered other varieties less so. by acids. Diff. softness (soapy feel);iron-black color; metallic Characterized by its extreme luster;low specific gravity; also by infusibility.Cf. molybdenite,p. 360. Artif. It is a common furnace product being formed from the fuel. It is produced extensivelyby heating coke in the electric furnace. Obs. ceous Graphite is most commonly formed through the metamorphism of carbonadepositsand is most frequently found in metamorphic rocks, contact metamorphic converted into graphiteby intense metamorphism deposits,etc. Coal beds may be largely It is not always of organic origin,however, as is shown in meteorites,in by its occurrence pegmatite depositsand as a magmatic separationin various igneous rocks. Frequentlyits Found laminae or scales in granite, beds and embedded originis obscure. as as masses, limestone. The depositsof crystalline gneiss,mica schist,quartzite,crystalline graphite which are of the greatest commercial importance have formed as veins along rock fractures. Island of Ceylon from which the largestpart of the world's Important localities are: Passau district in Bavaria; southern supply comes; Bohemia; Korea; Madagascar; Sonora in Mexico ; eastern Ontario and adjacent portionsof Quebec in Canada. The most productive localityin the United States is in the eastern and southeastern Adirondack It occurs here in region in Essex, Warren, Saratoga and Washington Counties, N. Y. graphiticquartzites,with quartz in small veins running through gneissand in pegmatite veins. Also found in metamorphosed Carboniferous rocks near Providence and Tiverton, R. I.; in granite and schists in Clay, Chilton and Coqsa Counties, Ala.; as amorphous graphite near Raton, N. M.; in irregularveins near Dillon,Mon.; near Turret, Chaff ee Co., Col. for making crucibles and other refractoryproducts,in lubriUse. Its chief uses cants, are paint,"tove polish,"lead" pencilsand for foundry facings. black lead,applied to this species,is inappropriate, The name it contains no lead. as The name graphite,of Werner, is derived from ypa"t"cu",to write, alluding to its use for "

"

"

"

pencils. QUISQUEITE. the vanadium

"

ores

A black lustrous material composed of Minasragra, Peru.

of chiefly

carbon

and

sulphur from

SULPHUR.

Orthorhombic.

Axes

a

:

b

: c

=

0'8131

:

1

:

1-9034.

pyramidal; sometimes thick tabular ||c(001). Also massive,in reniform shapes,incrusting, stalactitic and stalagmitic; in powder. conchoidal to Cleavage: c(001), m(110), 'p(lll)imperfect. Fracture 1/5-2 -5. G. 2 '05Rather brittle to imperfectlysectile. H. uneven. Crystals commonly See also Fig.79, p. 47.

acute

=

=

MINERALOGY

DESCRIPTIVE

348 Luster

2-09.

Color

resinous.

630

629

and strawhoney-yellow, sulphur-yellow, reddish to greenish, brown, yellowish Streak white. parent Transyellowish gray. A ductor non-conto translucent. friction of electricity; by atively negelectrified. A poor conductor Double refraction of heat. Optically+ .

Bx 2 a

c(001).

_L V =

=

69"5'.

2 -245. 2-038, 7 1-958, j8 Pure Comp. sulphur; often -

-

with

clay, bitumen,

impurities.

ofher

also be obtained in the

Sulphurmay form

=

=

contaminated and

plane ||6(010). Dispersion p " v. Refractive indices,

Ax.

strong.

laboratoryin

other allotropic forms;

a

monoclinic

is common.

Melts at 108" C., and at 270" burns with a bluish flame yieldingsulphur Insoluble in water, and not acted on by the acids,but soluble in carbon disulphide. and combustibility. by the color,fusibility Diff. Readily distinguished of sulphur are either beds of gypsum and the associate The great repositories Obs. rocks, or the regions of active and extinct volcanoes. Sulphur may have several different modes of origin. At times it is a volcanic sublimate quently freIt occurs sulphur dioxide and hydrogen sulphide gases. formed by reactions between around mineral springswhere it has been formed by the incomplete oxidation of and sulphur hydrogen sulphide. Where such waters act upon limestone rocks both gypsum in small elsewhere it is formed coal and In be formed. a deposits by way many may the slow decomposition of pyriteand other sulphides. the Island of Sicily, often in fine crystalsand associated in large amounts Found on and barite. with celestite, aragonite,gypsum, calcite, Important deposits are found in In the South America. the volcanic districts of Japan, Hawaii, Mexico, and western In Calcasieu United States the most productive deposits are in Louisiana and Texas. 300 Parish,Louisiana,a bed of sulphur 100 ft. in thickness is found at a depth of between and salt. A similar deposit occurs and 400 ft. It is underlain by beds of gypsum near It is found in numerous other Western localities; Utah, Freeport in Brazoria Co., Texas. at Sulphurdale,Beaver Co., in a rhyolitictuff;Wy., in limestones near Cody and TherCo. near mopolis and about the fumeroles of the Yellowstone Park; Nev., in Esmeralda and at Eureka, Rosebud, Humbolt Luning and Cuprite, near Co., sometimes in crystals Eureka Co.; Cal.,in Colusa, Lake, San Bernadino and other Counties, at the geysers of Co., on Lassen Peak, Tehema Napa Valley,Sonoma Co.; Col.,at Vulcan, Gunnison Co., and in Mineral Co. Use. In manufacture of sulphuric acid, in the process of making paper from wood for vulcanizingrubber, for pulp, in making matches, gun powder, fireworks,insecticides, medicinal purposes, etc. Sulphuric acid is now largelyderived from the oxidation of

Pyr., etc.

"

dioxide.

"

"

"

pyrite. Selensulphur.

Contains

the islands Vulcano

and

"

sulphur and Lipari.

selenium,orange-red or

reddish

brown;

from

ARSENIC.

Rhombohedral. sometimes Generally granular massive; reticulated, reniform,stalactitic. Cleavage: c(0001) highly perfect. Fracture uneven and fine granular. Brittle. H. 3'5. G. 5'63-573. Luster Color and metallic. nearly streak tin-white, to dark gray. tarnishing Comp. Arsenic,often with some antimony, and traces of iron,silver, =

=

"

gold, or bismuth. cnarcoal Pyf'and*:i'B"".on affords ~~

"

tnoxide, flame

blue.

volatilizes without fusing,coats the coal with white arsenic garlicodor; the coating treated in R.F. volatilizes, tingeing the closed tube givesa volatile sublimate of arsenic. a

In the

NATIVE

349

ELEMENTS

white color similar to galena. Smooth In polishedsection shows surface. with Feds. Changes color in same turning dark. slowly effervesces, way Unaffected and HC1. by KCN Obs. rocks and the older schists, often accompanied by Occurs in veins in crystalline and other metallic minerals. of antimony, the ruby silvers, Thus sphalerite, ores realgar, of Saxony; also Andreasberg, Harz in the silver mines Mts., Germany; Joachimstal and Pfibram, Bohemia; in Hungary; Norway; Zmeov, Siberia; Prov. Echizen, Japan, etc. In the United States sparinglyat Haverhill and Jackson, Abundant at Chanarcjllo,Chile. N. H.; near at Leadville,Col.; Washington Camp, Santa Cruz Co., Ariz. In Canada Watson Creek, British Columbia; Montreal, Quebec. Micro. With HNOs

"

"

Use.

An

"

of arsenic.

ore

Allemontite.

In reniform masses. 6'203. Arsenical Antimony, SbAs3. G. Luster From tin-white or reddish gray. Allemont, France; Pfibram, Bohemia, =

"

Color

metallic. etc.

In prismatic crystals; Rhombohedral. Tellurium. commonly columnar to fine-granular 2-2'5. 6'2. Perfect prismatic cleavage. H. G. massive. Luster metallic. B.B. wholly volatile. In warm Color and streak tin-white. concentrated sulphuric acid From of places in Australia,and a number Transylvania, West gives red solution. Colorado. =

=

ANTIMONY.

Rhombohedral. Generally also radiated;granular.

massive, lamellar and

distinctlycleavable;

Cleavage: c(0001)highlyperfect;also other cleavages. Fracture brittle. H tin-white.

Comp.

3-3'5.

=

G.

=

6'65-672.

Luster

Antimony, containingsometimes

"

metallic.

Color

uneven;

and

streak

iron,or arsenic. silver,

charcoal fuses very easily and is wholly volatile giving a white coating. on Pyr. The white coating tingesthe R.F. bluish green. Crystallizes readilyfrom fusion. Obs. Sala in Sweden; Andreasberg in the Harz mont, Occurs near Mts., Germany; AlleIn the United Dauphine, France; Pfibram, Bohemia; Mexico; Chile; Borneo. States,at Warren, N. J.,rare; in Kern Co., and at South Riverside,Cal. At South Ham, Quebec; Prince William parish,York Co., New Brunswick. An ore of antimony. Use. B.B.

"

"

"

BISMUTH.

Usuallyreticulated, arborescent;foliated or granular. but when heated somewhat Cleavage: c(0001)perfect. Sectile. Brittle,

Rhombohedral. H.

malleable. color

=

2-2*5.

with silver-white,

Comp.

Bismuth,

"

970-9-83. Luster metallic. Streak G. reddish hue; subjectto tarnish. Opaque. with traces of arsenic, sulphur,tellurium,etc. =

and

a

B.B. on charcoal fuses very easilyand entirelyvolatilizes, giving a coating Pyr., etc. orange-yellow while hot, lemon-yellow on cooling. With potassium iodide and sulphur B.B. on charcoal gives a brilliant red coating. Dissolves in nitric acid; subsequent dilution causes a white precipitate. Crystallizes readilyfrom fusion. Micro. In polished section shows creamy and white color with pink tinge. Smooth metallic surface. HC1 vescence With slowly darkens and dissolves. Rapidly darkens with efferand aqua with HNO3 regia. Obs. rocks and clay slate,accomOccurs in veins in gneiss and other crystalline panying various ores of silver, cobalt,lead and zinc. Thus at the mines of Saxony and Also at Modum, Bohemia, etc.; Meymac, Correze, France. Norway; at Falun,Sweden. In Cornwall and Devonshire; near Copiapo,Chile; Bolivia. Cummins S. C.; near Occurs at Monroe, Conn.; Brewer's mine, Chesterfield district, with silver ores at Cobalt, Ontario. City, and elsewhere in Col. Abundant "

"

"

Use.

An

"

ore

of bismuth.

In the laboratoryit is obtained in the native state. Probably does not occur in hexagonal prisms with tapering pyramids; also in complex crystalline aggregates. It in the isometric system, at least in various alloys. also appears to crystallize In cubic crystals and Tantalum. fine grains. Color Isometric. grayish yellow. Zinc.

"

MINERALOGY

DESCRIPTIVE

350 Found

containingsmall amounts

of niobium

in the

gold washings

of the Ural

and

Altai

Mis.

Gold

Group

GOLD.

d(110) and axis,giving ra(311);crystalsoften elongatedin direction of an also in plates arborescent and shapes; to'rhombohedral-like forms, rise either to the edges or diagonals o(lll),and branching at 60" parallel flattened || Skeleton Twins: o. tw. crystals plane face 173). of an o (seepp. 172, Isometric.

Distinct crystals rare, 0(111)most

also

common,

octahedral

634

633

dendritic shapes. in filiform, reticulated, in flattened often or in thin Also massive and grains scales. laminae; malleable and ductile. Fracture none. hackly. Very Cleavage metallic. Color Luster 2*5-3. G. H. 15-6-19-3, 19'33 when pure. sometimes and streak gold-yellow, incliningto silver-white and rarelyto

edges salient or rounded;

common;

=

=

orange-red. Opaque. Comp. Gold, but usuallyalloyedwith silver in varying amounts sometimes containingalso traces of copper or iron. "

Var. 1. Ordinary. Containing up to 16 p. c. of silver. from deep gold-yellow to pale yellow,and specific gravity from gold to silver of 3 : 1 corresponds to 15'1 p. c. silver. For "

Color

and

varying accordingly

The ratio of 9 p. c.; G. 17'6,Ag 38'4. The purest gold which has been described G. 13'2; G. 16'9,Ag 14'6,Ag is that from Mount Morgan, in Queensland, which has yielded 99'7 to 99'8 of gold, the with a littleiron; silver is present only as a minute trace. remainder being copper Color pale yellow to yellowishwhite; G 15'5-12'5. 2. Argentiferous;Electrum. Ratio for the gold and silver of 1 : 1 corresponds to 36 p. c. of silver;1| : 1, to 26 p. c.; 2 : 1, to 21 p. c.; 1\ : 1, to 18 p. c. The word in Greek means also amber; and its use for from the pale yellow color it has as compared with gold. this alloyprobably arose Varieties have also been described containing copper up to 20 p. c. from the Ural Mts.; from Porpez, Brazil;bismuth, includingthe black gold of palladium to 10 p c. (porpezite), Australia (maldonite); also rhodium (?). B.B. fuses easily (at 1100" C.). Not acted on Pyr.,etc. by fluxes. Insoluble in than 20 p. c. any singleacid; soluble in aqua regia,the separationnot complete if more =

=

=

19'3 to 15'5.

=

=

=

=

.

"

Ag

is present. Diff. Readily

from other metallic minerals,also from scales of yelrecognized (e.g., low and high specific mica) by its malleability gravity,which last makes it possibleto separate it from the gangue by washing ; distinguishedfrom chalcopyriteand pyrite since both sulphidesare brittle and soluble in nitric acid. Micro. In polishedsection shows a golden yellow color with a smooth, metallic surface. Unaffected by reagents except KCN, with which it quicklydarkens and its surface becomes rough. Obs. Gold is widely distributed in the earth's crust. It has been found in various rocks, more igneous commonly in the acid types, and sometimes in visible particles. It occurs in sedimentaryrocks and quite frequentlyin connection with metamorphic rocks. "

"

"

352

DESCRIPTIVE

MINERALOGY

Some isfound in Egypt in the section between the Nile and the Red Sea. worked in very earlydays. Gold has been produced for a long time Important deposits are found in district on the Gulf of Guinea. The most Rhodesia. in Southern important gold district and Mashonaland Matabeleland The mines occur in an east in the Transvaal. in the world is that of the Witwatersrand and west belt,some sixtymiles in length,near Johannesburg. The gold is found scattered Gold

Africa.

of these depositswere the Gold Coast from

in small amounts through a series of steeplydipping quartz conglomerate rocks. of gold. The chief Colonlbiahas in the past produced largeamounts South America. Comparatively small amounts districts today are in the states of Antioquia and Cauca. are produced at the present time in the other northern countries. The important deposits Geraes along the Sierra do of Brazil lie 200 miles to the north of Rio de Janeiro in Minas in the northern and in the coast in Chile lie The chiefly ranges deposits gold Espinhaco. central parts of the country. siderable While Mexico is chieflynoteworthy for its silver output it produces also conMexico. gold. Important districtsare as follows: Altar,Magdalena and Arizpe in Sonora; about Parral,and the Dolores mine on the western various placesin Chihuahua, especially in the state of Mexico; the Pachuca district in border of the state; the El pro mines Hidalgo; also various places in Guanajuato and Zacatecas. in Yukon the Klondike The three important placer districts of Canada are Canada. The most productive vein Territory and the Atlin and Cariboo in British Columbia. depositsare found in British Columbia in the West Kootenay and Yale districts. Gold is Scotia. also found in Ontario and Nova in the United States chieflyalong the mountain in Gold occurs United States. ranges Smaller amounts have been found along the Appalachians in the the western states. North and South Carolina and Georgia. The more states of Virginia, important localities in the western states are given below, the states being arranged approximately in the order put of their importance. California. At the present time about two thirds of the state's outfrom the lode mines and one third from placerdeposits. The quartz veins are comes belt that lies on the western chieflyfound in what is known as the Mother-Lode slope of the Sierra Nevada and stretches from Mariposa County for more than 100 miles toward the north. The veins occur chieflyin a belt of slates. The lode mines are found chiefly in Amador, Calaveras,Kern, Nevada, Counties. The Shasta, Sierra and Tuolumne About and Yuba Counties. 90 important placermines are located in Butte, Sacramento in Gold is mined per cent of the placergold is obtained by the use of dredges. Colorado. various districts in Gilpin County, from the Leadville district and others in Lake County, in the region of the San Juan mountains in the Sneffels, Silverton and Telluride districts, CrippleCreek district (telluride ores)in Teller County, placerdepositsin the Breckenridge district in Summit The most important lode mines are in the Juneau County. Alaska. while the chief placerdepositsare those of Fairbanks and Iditarod in the Yukon district, basin and the Nome district on the Seward Peninsula. Nevada. The most important districtsare those of Goldfield in Esmeralda County and Tonapah in Nye County. South Dakota. The output is chieflyfrom the Homestake mine at Lead in Lawrence County. Montana. There are various producing districts, the more important being in Madison Deer Lodge and Silver Bow Counties. placers), (largely Arizona. The important counties Mohave are and Cochise. Utah. Gold is produced chieflyfrom the Bingham and Tintic districts in Salt Lake County and from Juab County. Use. The chief ore of gold. -

,

"

SILVER.

Isometric. Crystalscommonly distorted, in acicular forms,reticulated or arborescent shapes; coarse to fine filiform; also massive,in platesor flattened scales. Ductile and malleable. Cleavage none. 2'5-3. Fracture hackly. H. G. 10-1-11 -1,pure 10*5. Luster metallic. Color and streak silver-white, often gray to black by tarnish. with some Comp. Silver, and sometimes gold (up to 10 p. c.), =

=

"

copper,

platinum, antimony, bismuth, mercury. a

r

~B-B?y5'?iet,C*

faint dark

red

on

charcoal fuses easilyto

a

silver-white globule,which

in O.F.

coating of silver oxide; crystallizes about on cooling;fusibility

gives

1050" C. Soluble in nitric acid, and deposited again by a plate of Precipitatedfrom its copper. solutions by hydrochloricacid in white curdy forms of silver chloride.

NATIVE

Diff.

353

ELEMENTS

color (on the fresh surface),and Distinguished by its malleability,

"

specific

gravity. In polished section shows white color with a metallic,smooth Micro. a creamy With surface. regia and FeCl3 tarnishes quickly with bright iridescent color-s aqua Blackens with HNO?. in arborescent and filiform shapes,in veins in masses, Obs. Native silver occurs or Also occurs but usually traversinggneiss,schist,porphyry, and other rocks. disseminated, invisibly,in native copper, galena, chalcocite,etc. It is commonly of secondaryorigin having been derived from the reduction of sulphidesand other compounds of silver. of the most Native silver is found at a great many some famous of which localities, follow: Kongsberg, Norway, in magnificentspecimens and in very largemasses; Freiberg Schneeberg, etc., in Saxony; Pribram and Joachimstal in Bohemia; Andreasberg in the Harz Mts., Germany; Allemont in Dauphine, France; at various points in Cornwall at England. At Chanarcillo and other localities in Chile; in large masses In many Peru. places in Mexico, especiallyat Batopilas in Chihuahua; in Zacatecas and in Guanajuato. A very important district is at Cobalt,Ontario,where native silver occurs there associated with various cobalt and to 1000 masses pounds in weight; it occurs up nickel minerals. in the Lake Superior copper In the United States it has been found with native copper district;at Silver Islet,Lake Superior; at Butte and the Elkhorn mine in Mon.; at the Poor Man's Lode in Idaho; in Col.,with various sulphide deposits, at Aspen. especially An ore of silver. Use. "

"

Huantaya'

"

COPPER.

form (Fig. The tetrahexahedron a common hedral 635); also in octaDistinct rare. crystals Frequently plates. irregularlydistorted and passing into twisted and wirelike forms; filiform and arborescent. Massive; Twins: tw. sand. as pi. o (111), very common, often flattened or elongated to spear-shapedforms. Isometric.

Cf. p. 173. Fracture hackly. Highly ductile Luster 8'8-8'9. H. G. 2-5-3. malleable. metallic. Color copper-red. Streak metallic shining. for heat and An excellent conductor Opaque.

Cleavage none.

and

=

=

electricity. Pure Comp. "

copper,

often

containingsome

(410).

bismuth, mercury, silver,

etc. B.B. fuses readily; on cooling becomes covered with a coating of black Pyr., etc. Dissolves readilyin nitric acid,giving off red nitrous fumes, and produces a deep oxide. of ammonia. azure-blue solution with excess Fusibility780" C. In polished section shows Micro. pink color with smooth, metallic surface. With cone. HNp3 dissolves and shows iridescent tarnish. With FeCl3 blackens and shows a "

"

solution pit. Obs. Copper is usually,if not always,secondary in its origin. It has either been reducing agent which is commonly a compound of iron deposited from solution by some solid compound. prite, Pseudomorphs of copper after cuor by the gradual reduction of some It is associated with other copper ores, azurite,chalcocite,etc., are well known. of copper veins; also with the especiallycuprite,malachite and azurite in the upper zone in the vicinityof dikes of igneous etc.; often abundant chalcocite, sulphides,chalcopyrite, rocks; also in clay slate and sandstone. In Occurs in crystalsat Bogoslovsk, Nijni Tagilsk and elsewhere in the Ural Mts. in Cornwall, England. Occurs in Brazil,Chile,and Peru. Nassau, Germany. Common in pseudomorphs after the pseudo-hexagonal twins of aragoniteat Corocoro,Bolivia. Found South Wales. Occurs Hill,New Abundant at Wallaroo, South Australia and at Broken at various places in Mexico. Occurs native throughout the red sandstone region of the eastern United States, ingly sparin Mass., Conn., and more Haven, Conn., a mass abundantly in N. J. Near New have also been found in the drift weighing nearly 200 pounds; smaller isolated masses was in minor amounts at Bisbee,Ariz, (inbranching crystalgroups); at Georgefound. Found "

354

DESCRIPTIVE

MINERALOGY

lin M (pseudomorphs after azurite); Ducktown, Tenn.; Cornwall,Pa.; and Franknative copper is the Lake Superior J. The most important region in the world for The rocks of this district consist northern Mich. peninsula, district on the Keweenaw copper and conglomerates which dip steeply of a series of interbedded lava flows,sandst9nes all in the native m state, sometimes is obtained practically The to the northwest. copper the sandstone and the interstices in filling It occurs as (1) a cement immense masses. and pebbles themselves, (2) filling conglomerate, sometimes replacingin largepart the grains all kinds of rock. that traverse the amygdaloidalcavities in the diabase and (3)in veins The was probably brought into the district by the igneous rocks. It is associated N

town

N

copper

with native silver, prehnite,datolite,analcite,etc. calcite, Use.

An

"

ore

of copper.

Quicksilver.

MERCURY.

In small fluid

globulesscattered through its gangue.

metallic,brilliant. Color tin-white. Opaque. Pure mercury (Hg) ; with sometimes Comp. "

B.B. entirelyvolatile, vaporizing at 350" C. Pyr.,etc. with cubic cleavage; G. in regularoctahedrons crystallizing "

G

=

Luster

13 '6.

littlesilver.

a

Becomes =

14 '4.

solid at Dissolves

40" C.,

"

in nitric

Obs. Mercury in the metallic state is a rare mineral, and is usually associated with is obtained. The rocks affording the sulphidecinnabar,from which the supply of commerce Also the metal and its ores are chieflyclay shales or schists of different geologicalages. found in connection with hot springs. See cinnabar. "

LEAD.

Usually in thin plates and small globular Crystals rare. 11*4. G. ductile. H 1-5. masses. Very malleable, and somewhat Luster metallic. Color lead-gray. Opaque. contains a little silver,also Nearly pure lead; sometimes Comp. antimony. Isometric.

=

=

"

bility fuses easily, coating the charcoal with a yellow to white oxide. Fusiin dilute nitric acid. Dissolves easily Found at Pajsberg, Harstig, and rare occurrence. Langban in Sweden; similarlyat Nordmark; also in the gold washings of the Ural Mts.; reported elsewhere, In the United States,occurs but localitiesoften doubtful. at Breckinridge and Gunnison, Col.; Wood River district, Idaho; Franklin,N. J.

Pyr.

B.B.

"

330" C. Obs. Of "

AMALGAM.

Isometric. Common habit dodecahedral. Crystalsoften highlymodified. Also massive in plates, a nd embedded coatings, grains. Cleavage: dodecahedral in traces. Fracture conchoidal, Rather uneven. brittle to malleable. H. 3-3'5. G, 1375-14-1. Luster liant. metallic,bril^Colorand streak silver-white. Opaque. Comp. (Ag,Hg), silver and mercury, varying from Ag2Hg3 to Ag36Hg. =

=

"

Var. Ordinary amalgam, Ag2Hg3 (silver26'4 p. c.) or AgHg (silver35-0); also Ag5Hg3, etc. Arquerite, 86 "6); G. Agi2Hg (silver 10'8; malleable and soft. Kongsbergite,AgasHg or Ag36Hg. B.B. on charcoal the mercury Pvr.,etc. volatilizes and a globule of silver is left. In "

=

"

the closed tube the mercury

sublimes

globules. Dissolves in nitric acid. Obs.

"

From

Germany

Nassau; Jriednchssegen,

in

the

and condenses on Rubbed on copper

the cold part of the tube in minute it gives a silveryluster. Rhine-Palatinate at Moschel-Landsberg and at

from

Sala, Sweden; Kongsberg,Norwav; Allemont, Dauphine", France; Almaden, Spain; Chile; Vitalle Creek, British Columbia (arquerite).

Tm'~

Native doubt

tin

has been reported from several localities. The only occurrence is that from the washings at the headwaters of the Clarence river,near bouth "ban, New Wales. It has been found here in grayish white rounded grains,with platinum,mdosmine, gold, cassiterite, and corundum .

.

fairlyabove

NATIVE

355

ELEMENTS

Platinum-Iron Group PLATINUM.

Crystalsrare; usuallyin grainsand scales. Fracture 4-4-5. Cleavage hackly. Malleable and ductile. H. G. Luster metallic. 14-19 native; 21-22 chem. pure. Color and streak whitish steel-gray; shining. Sometimes magnetic and occasionallyshows polarity. Platinum alloyed with iron, iridium, rhodium, palladium, Comp. Isometric.

none.

=

=

"

osmium, and other metals. platinum yieldsfrom

Most 1 to 3 p. of copper. Var.

c.

each of rhodium

8 to 15

and

or

iridium,a

18 per cent trace of osmium

even

of iron,0*5 to 2 p. and

finally0'5

c.

to 2 p.

palladium, c.

or

more

1. Ordinary. 16'5-18'0 mostly. Non-magnetic or only slightlymagnetic. G. Magnetic. G. about 14. Much platinum is magnetic, and occasionallyit has polarity. The magnetic property seems to be connected with high percentage of iron (iron-platinum), although this distinction does not hold without exception. B.B. infusible. Not affected by borax or salt of phosphorus,except in the Pyr.,etc. reactions for iron and copper may state of fine dust, when be obtained. Soluble only in heated aqua regia. Diff. and Distinguished by its color,malleability, high specificgravity,infusibility in ordinary acids. insolubility The platinum of commerce Obs. almost exclusivelyfrom placerdeposits. Its comes originalsource, however, is in the basic igneous rocks,usually peridotites. The associated Platinum minerals are firstfound in was commonly chrysolite, serpentineand chromite. posits pebbles and small grains,associated with iridium,gold,chromite, etc.,in the alluvial deof the river Pinto,in the district of El Choco, Colombia ; South America, where it received its name platina (platinadel Pinto) from plala,silver. The greater part of the in alluvial material world's supply comes from Russia (discoveredin 1822) where it occurs in the Ural Mts. at Nijni Tagilsk, and with chromite in a serpentineprobably derived from a peridotite;also in the Goroblagodat and Bisersk districts. Also found in Borneo; in New rock with serpentine; in New Zealand, from a region characterized by a chrysolite South Wales, at the Broken Hill district, and in gold washings at various points. In Cal. in small amounts in the gold placers,chieflyin Trinity Co.; at Port Orfqrdin At various points in Canada, the most Ore. District in important being the Tulameen British Columbia Use. Practicallythe only ore of platinum. Iridium. Platin-iridium. Iridium alloyed with platinum and other allied metals. Occurs 6-7. G. 22 '6-22 '8. usually in angular grains of a silver-white color. H. With the platinum of the Ural Mts. and Brazil. =

"

2.

"

"

"

"

=

=

IRIDOSMINE.

Osmiridium.

Rhombohedral.

flattened grains. Usually in irregular Cleavage: c(0001)perfect. Slightlymalleable to nearly brittle. H. 6-7. G. 19-3-21 -12. Luster metallic. Color tin-white to light steelOpaque. gray. in different proportions. Some Iridium and osmium rhodium, Comp. platinum,ruthenium, and other metals are usuallypresent. =

=

"

Var.

Over

1.

"

40 p.

c.

Nevyanskite. of iridium.

steel-gray.G.

=

2.

20-21'2.

In flat scales; color tin-white. 18'8-19'5. 7; G. color grayishwhite, Siserskite. In flat scales, often six-sided, than the lightLess common 30 p. c. of iridium. .Not over H.

=

=

colored variety. Diff.

Obs. in New

"

"

Distinguishedfrom platinum by greater hardness and by its lightercolor. Occurs with platinum in South America; in the Ural Mts.; in auriferous drift

South Wales. and Oregon.

Palladium.

"

Rather

Isometric.

abundant

in the auriferous

Palladium, alloyed with

a

beach-sands little

of northern

platinum

and

fornia Cali-

iridium.

356

MINERALOGY

DESCRIPTIVE

with

11 '3-11 '8. Color whitish steel-gray.Occurs G. 4'5-5. Mostly in grains. H. platinum in Brazil; also from the Ural Mts. under the hexagonal-rhombohedralclass (?). From Allopalladium. Palladium kerode in the Harz Mts. in small hexagonaltables with gold. =

=

Til-

"

IRON.

Usually massive, rarelyin crystals. a( 100),perfect;also a lamellar structure Cleavage: Isometric.

hackly. Malleable. Color steel-grayto iron-black. Fracture

H.

4-5.

=

G.

||0(111)and ||d(110).

7-3-7-8.

=

Luster

metallic.

Stronglymagnetic.

in masses, Found occasionallyof great size,as well as Terrestrial Iron. in basalt at Blaafjeld,Oyifak(or Uifak), Disko Island,West particles, This iron contains 1 to 2 p. c. of Ni. In coast. Greenland; also elsewhere on the same In Kassel, Hesse Nassau, Germany. small grains with pyrrhotite in basalt from near Some minute Township, Nipissing Dist.,Ontario. spherules in feldspar from Cameron be in fact terrestrial. other occurrences, usually classed as meteoric,may in the drift of the Gorge A nickeliferous metallic iron (FeNi2)called awaruite occurs land; ZeaBay on the west coast of the south island of New river,which empties into Awarua associated with gold, platinum, cassiterite, chromite; probably derived from a ring partiallyserpentinizedperidotite. Josephiniteis a nickel-iron (FeNia) from Oregon, occurin stream lumbia, gravel. Similar material from near Lillooet on the Fraser river,British Coin some Native iron also occurs has been called soucsite. basalts;reported sparingly from gold or platinum washings at various points. in most meteorites,forming in some 2. Meteoric Iron. Native iron also occurs cases cellular matrix in which are (a) the entire mass (ironmeteorites) ; also (6) as a spongy, embedded nated grainsof chrysoliteor other silicates (siderolites)} (c)in grainsor scales dissemiless freelythroughout a stony matrix more or 636 (meteoric stones). Rarely a meteorite consists of a singlecrystallineindividual with numerous twinning lamellse !(o(lll).Cubic cleavage sometimes observed: also an octahedral, less often dodecahedral, lamellar structure. Etching with dilute nitric acid (or iodine) Var.

1.

"

"

in small embedded

"

commonly

r"i

"

4. loneta

distinct

iv/r"u AT Mt., New

develops

a

crystallinestructure

(called

Widmanstdtten figures)(Fig. 636); usually consisting of lines or bands crossing at various angles according the direction of the section,at 60" if ||0(111), to 90" |!a(100),etc. They are formed by the edges of crystalline usually 11o, of the nickeliferous iron plates, of different composition (kamacite,tcenite, as plessite), shown by the fact that they are differently attacked and with by the acid. Irons with cubic structure twinning lamellse have a series of fine lines correspondto those developed by etching (Neumann m" lines) A damascene luster is also produced in some cases, due to quadrilateraldepressions. Some irons show no .

TV/T

Mexico

crystallinestructure

The exterior of

masses

etching. upon of meteoric iron is usually more

or

less deeplypittedwith rounded

thumblike and the surface at the time of fallis covered with depressions, a film of iron oxide in fane ridgesshowing lines of flow due to the melting caused by the heat developed by the resistance of the air; this film disappears when the iron is to the Meteoric rom

rare.

5 to

iron

is

weather. exposed is usuallypresent in amounts varying of other metals, as cobalt,manamounts

always alloyedwith nickel, which

10 p. c., sometimes

sometimes Cohenite,

much

more;

small

is (Fe,Ni,Co)3Cin identified,

tin-white crystals.

Moissanite. CSi. This material,originally produced artificially as carborundum, has found occurring naturally as small green hexagonal plates in the meteoric iron of Canon Diablo,Ariz "

been

SULPHIDES,

II.

SELENIDES,

SULPHIDES,

TELLURIDES,

SELENIDES,

ARSENIDES,

357

ANTIMONIDES

TELLURIDES,

ARSENIDES,

ANTIMONIDES The

sulphides, etc.,fallinto element. positive I. II.

Groups accordingto the character

two

Sulphides, Selenides, Tellurides of the Semi-metals. Sulphides, Selenides, Tellurides, Arsenides, Antimonides

of the

of

the

Metals.

I. This

Sulphides,etc., of

the

Semi-Metals

section includes one distinct group, the Stibnite included stand alone. ; the other species

Group,

to which

orpiment is related

637

REALGAR.

Monoclinic. mm'",

Axes

110

HO

A

a

:

b

: c

1-4403

=

105" 34'.'

=

:1

rr',012

:

A

0*9729; 0 012

=

=

66" 5'.

47" 57'.

Crystals short prismatic; striated vertically.Also or coarse fine;compact; as an incrustation. small Cleavage: 6(010) rather perfect. Fracture

ular, gran-

con-

Sectile. H. 1-5-2. G. Luster choidal. resinous. 3 '56. Color aurora-red or orange-yellow. Streak varying from translucent. orange-red to aurora-red. Transparent Arsenic monosulphide,AsS Sulphur 29*9,arsenic 70*1 Comp. =

=

"

=

"

=

100.

In the closed tube melts and gives a dark red liquidwhen hot and a reddish Pyr., etc. yellow solid when cold; in the open tube (ifheated very slowly)sulphurous fumes, and sublimate of arsenic trioxide. B.B. on charcoal burns with a blue flame, a white crystalline Soluble in caustic alkalies. emitting arsenical and sulphurous odors. Artif Realgar is frequently noted as a sublimation product from furnaces roasting of arsenic. arsenic sulphide is heated in a sealed tube ores Crystals are produced when "

"

.

with

a

solution of sodium

bicarbonate.

It has usually in veins associated with silver and lead ores. regionsas a sublimation product. It has also been noted as a deposit It is often associated from hot spring waters. at Felsobdnya, with orpiment. It occurs in dolomite. Binnental,Switzerland, Kapnik and Nagy^g, Hungary; Allchar,Macedonia. In the United States,at Mercur, Utah; in the Norris Geyser Basin, Yellowstone Park, as a Cristo mining district, Found at the Monte Snohomish depositionfrom the hot waters. Co., Washington; the name realgar is from the Arabic, Rahj al ghar,powder of the Obs. been found "

Realgar

occurs

in volcanic

mine. Was used in fireworks to give a brilliant white lightwhen Use. used for this purpose. and ignited. The artificialmaterial is now "

mixed

with saltpeter

ORPIMENT.

90"41'. :b :c 0'596 : 1 : 0;665, 0 columnar distinct. in foliated or Usually Crystalssmall, rarely masses; sometimes with reniform surface. striated;a(100) Cleavage: 6(010)highlyperfect,cleavageface vertically in traces; gliding-plane inelastic. c (001). Sectile. Cleavage laminae flexible, Luster b H. elsewhere 3'4-3'5. T5-2. G. (cleavage); pearly on but paler. resinous. Color lemon-yellowof several shades; streak the same, sub translucent. Subtransparent Arsenic trisulphide, 100. A^Sa Sulphur 39*0,arsenic 61*0 Comp. Monoclinic.

Axes

=

a

=

=

=

"

"

=

=

358

MINERALOGY

DESCRIPTIVE

Pyr.,etc.

"

Same

as

for realgar,p. 357. its fine yellow

bility color,pearly luster,easy cleavage,and flexiplates. nium Artif Orpiment has been synthesizedby heating solutions of arsenic with ammounder pressure of arsenic acid sulphocyanate in a sealed tube; also by the treatment with hydrogen sulphide. associated. conditions as realgarwith which it is commonly Occurs under same ObSc in foliated and fibrous masses at MolIt is found in Hungary at Tajowa in small crystals, dowa, in metalliferous veins at Kapnik and Felsob"nya; with realgarat Allchar,Macedonia. in Kurdistan. Occurs in fine crystalsat Mercur, Julamerk A largedeposit occurred near Utah. Springs, Nevada; also with realgar in the Among the 'depositsof the Steamboat Diff. when "

Distinguishedby in

"

.

"

Yellowstone

Park.

orpiment is a corruption of its Latin name auripigmentum, "golden paint," given in allusion to the color,and also because the substance was supposed to contain gold. For a pigment, in dyeing and in a preparation for the removal of hair from skins. Use. The artificialmaterial is largelyused as a substitute for the mineral. The

name

"

Stibnite

Group a

Stibnite Bismuthinite

Guanajuatite

:

b

: c

Sb2S3

0*9926

:

1

:

1-0179

Bi2S3 Bi2Se3

0-9679

:

1

:

0'9850

1

1 approx.

:

The speciesof the Stibnite Group crystallize in the orthorhombic system and have perfectbrachypinacoidal cleavage,yieldingflexible-laminae. The

speciesorpiment is in physical properties somewhat

in crystallization. Groth mpnoclinic

notes

that in

related to stibnite, but is the oxide,As2O3, is monoSb2O3 (valentinite), is orthorhombic.

similar way,

a

clinic in claudetite, while the correspondingcompound, STIBNITE.

Antimonite,Antimony

Orthorhombic. mm'", ppf, ss', ss'",

Axes

110

A

110

111 113

A

111

=

A

113

=

113

A

113

=

=

a

:

b

: c

Glance. =

0'9926

1

89" 34'. 71"

:

1-0179.

bv, 010 br,,010 br, 010 bp, 010

24|'.

35" 52"'. 35" 36'.

A

121

A

353

=

=

A

343

=

A

111

=

35

40" 46" 33' 54" 36'

Crystalsprismatic;striated or furrowed vertically; often curved or twisted in confused aggregates or radiating (cf.p. 188). Common groups of acicular fine crystals;massive, coarse or 640 columnar, commonly bladed,less often granular to impalpable. Cleavage : b (010) highly perfect. Slightlysectile. Fracture =

2.

-

small G.

sub-conchoidal. =

4-52^-62.

H. Luster

metallic,highly splendent on cleavageor fresh crystallinesurfaces. Color gray,

to blackish iridescent.

California

antimony p~

fc

Hungary 71'4

=

100.

Ife^^

Sometimes

Japan

and

streak

lead-

to steel-gray: inclining subject

Comp.

~

sometimes tarnish,

Antimony

auriferou^also

trisul-

MINERALOGY

DESCRIPTIVE

360

the Santa

From Color bluish gray. from Salmon, Idaho.

Catarina

mine,

Guanajuato, Mexico.

near

Noted

YMITE.

TETRAD

Crystalssmall,indistinct.

Rhombohedral.

Commonly

in bladed

forms

granularmassive. not very sectile. H. 1-5-2; Cleavage: basal,perfect. Laminse flexible; 7-2-7-6. Luster metallic,splendent. Color palesteel-gray. G. soilspaper. and tellurium, with sometimes Consists of bismuth sulphur Comp. most afford the the for the part general of trace and a analyses selenium; formula Bi2(Te,S)8. foliated to

=

=

"

Var. from

51*9. G. 48' 1, bismuth Tellurium 7'642 from sulphur. Bi2Te3 Tellurium 36 '4, sulphur 4 '6, 2. Sulphurous. 2Bi2Te3 Bi2S3 common This is the more variety and includes the tetradymitein 100.

1. Free

"

Dahlonega.

bismuth

59'0

=

=

=

Var.

=

.

crystalsfrom Schubkau. B.B. fuses to In the open tube a white sublimate of tellurium dioxide,which Pyr. tingesthe colorless drops. On charcoal fuses,gives white fumes, and entirelyvolatilizes; coats the coal at firstwhite (TeO2), and finallyorange-yellow (Bi2O3); R.F. bluish green; varieties give sulphurous and selenous odors. some Schemnitz at Rezbanya and Orawitza; Obs. near Occurs in Hungary at Schubkau at Carrock Fells,Cumberland, England. Occurs on Liddell Creek, Kaslo river,West In the United States,in Va., at the Whitehall gold mines, Kootenay, British Columbia. and SpottsylvaniaCo.; in Davidson Co., N. C., and in the gold washings of Burke At the Montgomery mine McDowell Dahlonega, Ga.; in Mon. counties,etc.; near and near from TeTp'dvuos, fourfold,in allusion to complex twin Bradshaw, Ariz. Named crystalssometimes observed. 7'321. One distinct cleavage. Color,gray. G. Griinlingite. Bi4TeS3. Massive. From Cumberland, England. Oruetite is a similar mineral,Bi8TeS4,from Serrania de Ronda, Spain. 7'9. San Jose, Joseite. A bismuth telluride (Te 80 p. c., also S and Se). G. "

"

=

"

=

"

Brazil. Wehrlite.

"

A

foliated bismuth

telluride (Te 30 p. c.)of doubtful

formula.

G.

=

8'4.

Deutsch-Pilsen,Hungary. MOLYBDENITE.

Crystalshexagonalin form, tabular,or short prisms slightly taperingand s triated. m assive in horizontally or Commonly foliated, scales; also fine granular. Laminse very flexible, but not elastic. Sectile. Cleavage: basal eminent. H. 1-1-5. G. 4-7-4-8. Luster metallic. Color lead-gray; a pure bluish gray trace on paper. Opaque. Feel greasy. Comp. Molybdenum disulphide,MoS2 Sulphur 40 -0, molybdenum =

=

"

=

60-0

100.

=

In the open tube sulphurous fumes and a pale yellow crystalline Pyr.,etc. sublimate molybdenum trioxide (MoOg). B.B. in the forcepsinfusible, imparts a yellowish green color to the flame; on charcoal the pulverizedmineral gives in O.F. a strong odor of sulphur dioxide and coats the coal with crystalsof molybdic oxide,yellow while hot, white on cooling; near the assay the coating is copper-red,and if the white coating be touched with an intermittent R.F., it assumes a beautiful azure-blue color. Decomposed by nitric acid, leaving a white or grayishresidue. Diff. Much resembles graphite in softness and structure (see p. 347), but has a bluer trace on paper and readilyyieldssulphur fumes on charcoal. Artif. Molybdenite has been made artificially by adding molybdic oxide to a fused of potassium carbonate and mixture sulphur;also by heating a mixture of molybdates and lime in an atmosphere of hydrochloricacid and hydrogen sulphide. Micro. In polished section shows surface. affected Ungrayish white color with smooth by reagents. "

of

"

"

"

SULPHIDES,

TELLURIDES,

SELENIDES,

ARSENIDES,

361

ANTIMONIDES

Obs. embedded Generally occurs in,or disseminated through,granite,gneiss,zirconrocks. and At Arendal Laurvik syenite,granular limestone, and other crystalline in Norway; Altenberg, Saxony; Zinnwald and Schlaggenwald,Bohemia; near Miask, Ural Mts.; Chessy in France; in Italy,on island of Sardinia;Carrock Fells,in Cumberland; at In largecrystals at Kingsgate, Glen Innes,N. S. W. several of the Cornish mines. in gneiss; in Ver., at Newport; in In Me. at Blue Hill Bay; in Conn., at Haddam, N. H., at Westmoreland; in N. Y., two miles southeast of Warwick; in N. J.,at Franklin; in Pa., in Chester,near Reading and at Frankford; near Concord,Cabarrus Co., N. C.; in Molybdenite has been mined in various places in Point, Wash. quartz vein at Crown Ariz.,Col.,Nev., Mon., Tex., Utah. etc. In Canada, at St. Jer6me,Quebec; in largecrystals in Renfrew county, Ontario; also in Aldfield township,Pontiac Co.,Quebec. Named from tSoXvpdos,lead; the name, first given to some substances containing lead, later included graphite and molybdenite, and even some compounds of antimony. The distinction between graphite and molybdenite was established by Scheele in 1778-79. Use. An important ore of molybdenum. Tungstenite. Probably WS2. Earthy or foliated. Color and streak, dark leadH. 2'5. 7'4. G. Found at Emma mine, Salt Lake Co., Utah. gray. Patronite. of a Rizopatronite. Complex composition, containing large amounts vanadium Color black. Occurs in a complex mixture sulphide,perhaps "84. Amorphous. of mineral substances among which are quisqueite and bravoite, at Minasragra, Peru. "

"

"

=

=

"

II.

Sulphides, Selenides, Tellurides, Arsenides, Antimonides

of the

Metals The sulphidesof this second section fall into four divisions depending the proportionof the negativeelement present. These divisions with upon the groups belongingto them are as follows : A.

Basic

Division ii

B. 1. 2. 3. 4.

Monosulphides, Monotellurides,etc., RjjS,RS,

etc.

Galena Isometric-normal. Group. Orthorhombic. Chalcocite Group. Isometric-tetrahedral. Sphalerite Group. Cinnabar hedral.

"

Wurtzite

Millerite

"

Group.

Intermediate

C.

Hexagonal and

rhombo-

Division

Melonite, Te2S3; Bornite,5Cu2S.Fe2S3;Linnaeite,"08.00283; Chalcopyrite,Cu2S.Fe2S3;etc. Embraces

[D. Disulphides,Diarsenides, etc., RS2, RAs2, etc. 1. 2.

Isometric-pyritohedral. Pyrite Group. Orthorhombic. Group.

Marcasite

A.

Basic

Division

The basic division embraces several rare basic compounds of silver, copper of nickel chiefly with antimony and arsenic. Of these the crystallization or and maucherite dyscrasite only is known. DYSCRASITE.

Orthorhombic.

Axes

a

:

b

:

dohexagonal in angles (mm'", massive.

Fracture

uneven.

c

110

0-5J75 :

=

A

Sectile.

110

=

H.

=

1 : (V6718. 60" 1')and G. 3'5-4.

Crystalsrare, pseuby twinning. Also =

9 '44-9 '85.

Luster

362

MINERALOGY

DESCRIPTIVE

and streak silver-white, incliningto tin-white;sometimes blackish. Opaque. yellowor Antimony 27' 1, silver A silver antimonide, includingAg3Sb Comp. 84 -3 silver 100, and perhaps other Antimony 157, 72 '9 100,and AgeSb Color

metallic. tarnished

=

"

=

=

=

compounds. Analyses

vary

widely, S9me

conforming also

Agj"Sb,Ag4(Sb,As)3,etc.

to

By

some

authors classed with chalcocite. mony Pyr., etc. B.B. on charcoal fuses (1'5)to a globule,coating the coal with white antitrioxide and finallygiving a globuleof almost pure silver. Soluble in nitric acid, leavingantimony trioxide. Obs. Occurs near Wolfach, Baden; Andreasberg in the Harz Mts., Germany; AlleNamed Also from Mexico arid Chile. Noted at Cobalt, Ontario,Canada. mont, France. "

a bad alloy. dvffKpacrts,

from

Lake Superior,apparently contain The ores from Silver Islet, ANIMIKITE. Ag9Sb?), (animikite, silverarsenide (huntilite, Ag3As?) and perhaps also a silverantimonide the latter probablya mixture.

HENTILITE,

a

G.

A silver-white, Horsfordite. massive Asia Minor, near 8'8. Mytilene.

copper

antimonide, probablyCu6Sb (Sb

24 p.

c.).

=

inated. also massive, dissemReniform and botryoidal; Copper arsenide,Cu3As. Luster metallic. Color tin-white to steel-gray, G. 7'2-775. readilytarnished. In North From several Chilian mines; also Zwickau, Saxony. America, with niccolite at MichipicotenIsland,Lake Superior. Microscopic examination shows this mineral to be intimate mixture of two unknown constituents. an Usually identical with algodonite.

Domeykite.

"

=

Co. Mohawkite. Like domeykite, Cu3As, with Ni and Massive, fine granular to Brittle. 3'5. Color gray with faint yellowtinge; tarnishes to dull purple. H. G. From 8 '07. Microscopic examination, shows it to be a mixture. mine, Mohawk Keweenaw mine"said to be Cu4As has been shown Ledouxite from the Mohawk Co., Mich. to be a mixture. "

compact.

=

=

Resembles 7'62. Algodonite. Copper arsenide,Cu6As (As 16'5 p. c.);G. domeykite. From Chile;also Lake Superior. Microscopic examination shows this mineral to be of two constituents. a mixture =

dish Color pale red8'4-8'6. Whitneyite. Copper arsenide,Cu9As (As 11'6 p. e). G. white. From Houghton Co., Mich.; Sonora, Lower California. Chilenite. Perhaps Ag6Bi. Copiapo,Chile. COCINERITE. Color silver-gray, ing tarnishCopper, silver sulphide,Ci^AgS. Massive. 2'5. From G. black,H 6*1. Cocinera mine, Ramos, San Luis Potosi,Mexico. Stiitzite. A rare silver telluride (Ag4Te?). Probably from Nagyag, Transylvania. Rickardite. H. Cu4Te3. Massive. 3'5. G. 7'5. Color deep purple, dullingon Fusible. at Vulcan, Col. Found exposure. Maucherite. Ni3As2. Tetragonal. Habit, square tabular. H. =5. G. 7'83. Color reddish silver-white tarnishingto Easily fusible. gray copper-red. Streak blackish gray. From Eisleben,Thuringia. The furnace product, placodine,is identical wfth maucherite. =

=

=

=

=

=

B.

Monosulphides,Monotellurides,* etc.,R2S, RS, 1.

Galena

Group.

PbS

Also,

(Pb,Cu2)S,(Cu2,Pb)S

Altaite

Clausthalite Naumannite The

Galena

known following,

Berzelianite Lehrbachite Eucairite

PbTe PbSe

ETC.

Isometric.

Argentite Jalpaite Hessite

Aguilarite

Ag2S (Ag,Cu)2S Ag2Te Ag2Se

(Ag2,Pb)Se only in massive form, probably also belong here: Cu2Se Zorgite (Pb,Cu2,Ag2)Se? t Crookesite (Pb,Hg2)Se (Cu,Tl,Ag)2Se Cu2Se.Ag2Se

SULPHIDES,

SELENIDES,

TELLURIDES,

ARSENIDES,

363

ANTIMONIDES

The GALENA GROUP embraces number a of monosulphides,etc.,of the related metals, silver, and lead, These crystallize in the copper, mercury. normal class of the isometric system, and several show perfectcubic cleavage. These characters are most distinctly exhibited in the type species, galena. GALENITE.

GALENA.

Lead

glance. in

Isometric. Commonly less often octacubes, or cubo-octahedrons, hedral. Also in skeleton crystals,reticulated, tabular. Twins: tw. pi. o(lll),both contact- and penetration-twins (Figs.401,404, p. 165),sometimes often tabular ||o. Also other tw. planes givingpolyrepeated; twin crystals synthetic tw. lamellae. Massive cleavable, fine granular,to impalcoarse or pable; fibrous or plumose. occasionally 641

642

643

644

!

! !

a

p(221),w Fracture flatsubCleavage: cubic,highlyperfect;less often octahedral. H. conchoidal or even. 2-5-275. G. 7*4-7 '6. Luster metallic. Color and streak pure lead-gray. Opaque. Lead sulphide,PbS 100. Often Comp. Sulphur 13'4,lead 86'6 contains silver, and occasionally selenium,zinc,cadmium, antimony, bismuth, silver and gold. also,sometimes nativ,e copper, as sulphides;besides, =

"

=

=

=

1. Ordinary, (a) Crystallized; fibrous and plumose; (c) cleavable, (6) somewhat or fine; (d) crypto -crystalline.The granular coarse varietywith octahedral cleavage is rare; in it the usual cubic cleavage is obtained readilyafter heating to 200" or 300"; the peculiarcleavagemay be connected with the bismuth usuallypresent. One varietyshowing octahedral cleavage contained a small amount of tellurium. 2. less argentiferous, and no external characters or Argentiferous. All galena is more from much those that are not. The silver is to distinguishthe kinds that are serve so of one detected by cupellation, from a few thousandths and may amount per cent to one Var.

"

when mined for silver it ranks as a silver ore. per cent or more; of these metals,as 3. Containing arsenic, or a compound or antimony , from belong bleischweif Claustal,Harz'Mts.,with 0'22 Sb, and steinmannite

impurity. from

Here

PHbram,

Bohemia, with both arsenic and antimony. B.B. on charcoal fuses,emits sulphurous In the open tube gives sulphurous fumes. Pyr. fumes, coats the coal yellow near the assay (PbO) and white with a bluish border and yields at a distance (PbSO3, chiefly), a globuleof metallic lead. Decomposed by strong nitric acid with the separationof some sulphur and the formation of lead sulphate. Diff. by its cubic cleavage;the Distinguished,except in very fine granular varieties, also the blowpipe reactions. color and the high specific gravity are characteristic; surface usually showing white color with smooth In polished section shows Micro. triangularpits. With HNO3 blackens; with FeCl3 becomes bright,iridescent. In nature it is apparArtif. Crystallizedgalena has been formed in numerous ways. ently laboratory commonly formed by hydrochemicalreactions perhaps similar to the following bonate methods : galena was produced by allowing a mixture of lead chloride,sodium bicarand a solution of hydrogen sulphide to remain in a sealed tube for several months. "

"

"

"

MINERALOGY

DESCRIPTIVE

364

Pyriteor marcasite heated with a solution of lead chloride will produce galena; a solution of quently sulphydratewill yield galena. Galena is frelead nitrate when heated with ammonium observed in furnace slags. One of the most widely distributed of the metallic sulphides. Occurs in beds Obs. rocks. Very commonly found togetherwith and uncrystalline and veins,both in crystalline It is often associated with pyrite,marcasite, zinc ores in connection with limestone rocks. barite or fluorite, of quartz, calcite, in a a rsenopyrite, e tc., gangue chalcopyrite, sphalerite, and other salts of lead,which are frequent results of its anglesite, etc.; also with cerussite, with gold,and in veins of silver ores. alteration. It is also common A few of the notable localitiesat which galena has been found are as follows: At Freibergin Saxony in veins in gneiss;at Claustal and Neudorf, etc.,in the Harz Mts., in Styria; in limestone and at Pribram in Bohemia, it forms veins in clay slate;similarly near Laasphe, Westphalia; at Prussia;at Gonderbach at Bleiberg,Carinthia;in Silesia, Schemnitz, Kapnik, etc.,Hungary; Joachimstal,Bohemia; at Poullaouen and Huelgoet, in district in Belgium; in province of Cagliari,Sardinia; Brittany,France; in Moresnet Spain,in graniteat Linares,also in Catalonia,Grenada, and elsewhere; in veins through the cavities in Scotland,and the contact hornstones of Cornwall; filling graywacke of Leadhill, the limestone of Derbyshire,Cumberland, and the northern districts of England, associated in many calamine and sphalerite; with calcite, placesin barite,witherite, dolomite,fluorite, "

Chile,Bolivia,Peru, etc. Australia, Extensive depositsof this ore in the United States exist in Missouri, Illinois, Iowa, The ore occurs cavities or chambers"in stratified limestone, and Wisconsin. usuallyfilling from Silurian to Carboniferous. It isassociated with sphalerite, of different periods, smithpyrite,etc. The Missouri mines are situated in three districtsin the southern sonite,calcite, in St. Francis,Washington and Madison counties, part of the state,(1) Southeastern,chiefly the latter producing chieflyzinc. Other (2) Central,(3) Southwestern or Joplindistrict, districts in the upper Mississippi Valley are found in southwestern Wis., eastern Iowa and in N. Y., at Rossie,St. Lawrence northwestern 111. Also occurs Co., in crystalswith calcite and elsewhere. In Col.,at Leadville and Aspen, and chalcopyrite;in Pa., at Phcenixyille there are productivemines of argentiferous trict galena,also at Georgetown, the San Juan disand elsewhere. Mined for silver in the Cceur d'Alene region in Idaho; at the Park City and Tintic districtsin Utah. The name galena is from the Latin galena (ya\i)t"rj), a name 'givento lead ore or the melted lead. The most important

dross from Use.

"

of lead and

ore

frequentlya

valuable

ore

of silver.

A massive mineral,from Chile,varying in characters from galena to CUPROPLUMBITE. those of chalcocite and covellite; composition,Cu2S.2PbS(?). Material classed here from Alisonite is massive, deep indigo-bluequickly Butte, Mon., gave formula, 5Cu2S.PbS. Mina tarnishing;correspondsto 3(?u2S.PbS. From these and Grande, Chile. Whether similar minerals represent definite homogeneous compounds, or only ill-definedalterationproducts,is uncertain,and if so it is not clear whether they should be classed with isometric galena or with orthorhombic chalcocite. Altaite.

with

cubic

Lead

PbTe. telluride,

cleavage. G.

bronze-yellow.From

Rarely in cubic

Color the Altai Mts., with =

8 '16.

or

octahedral

crystals, usuallymassive

with yellowish tinge tarnishingto tin-white, hessite;Coquimbo, Chile; Cal.,Col.,British

Columbia.

(

Clausthalite.

Lead selenide, PbSe. Commonly in fine granular masses resembling 7 '6-8 -8. galena. Cleavage: cubic. G. Color lead-gray, somewhat From bluish. Claustal, Harz Mts., Germany; Cacheuta mine, Mendoza River, Argentina. Tilkerodite is a cobaltiferous variety. =

Naumannite. Silver-lead telluride (Ag2,Pb)Se. In granular,in thin plates. Cleavage: cubic. G. 8'0. "

=

From

Tilkerode

in

the Harz

Mts ,

ARGENTITE.

cubic Color

crystals;also massive, and

streak

iron-black.

Germany.

Silver Glance.

Isometric.

Crystals often octahedral, also cubic; often distorted, frequently arborescent forms; also filiform. Massive; or embedded; as a coating. Cleavage: a(100),d(110)in traces. Fracture small subconchoidal. fectly Pergrouped in reticulated

sectile. H.

=

2-2-5.

G.

7'20-7'36.

=

Luster

metallic.

Color

streak blackish

Comp.

"

lead-gray;streak shining. Opaque. Silver sulphide, AgaS Sulphur 12-9,silver 871 =

=

100.

and

Diff.

"

365

ANTIMONIDES

ARSENIDES,

B.B. on charcoal fuses with tube gives off sulphurous fumes. O.F., emitting sulphurous fumes, and yieldinga globuleof silver. from other sulphidesby being readilycut with a knife; also by Distinguished In the open

Pyr., etc. intumescence

TELLURIDES,

SELENIDES,

SULPHIDES,

in

yieldingmetallic

silver

charcoal.

on

shows surface which is grayish white color with a smooth and FeCl3; with cone. HC1 brown with HNO3,KCN Turns tarnished easily scratched. iridescent by fumes and blackened by acid. and in numerous Artif. Argentite is very easilyprepared artificially ways. Sulphur, sulphur dioxide or hydrogen sulphide will act upon metallic silver or any of its common to.produce silver sulphide. compounds, either in solution or as solids, Found at Freiberg,etc.,Saxony; Andreasberg, Harz Mts., Germany; Schemnitz, Obs. ver Hungary: Joachimstal,Bohemia; Kongsberg, Norway; Sardinia. In South America at silin the states of Chihuahua, Guanajuato, In Mexico mines in Chile,Peru and Bolivia. etc. Lode, Tonapah, etc., Nev.; Aspen, Leadville,etc. Col. Important ore at Comstock Found at Port Arthur on north shore of Lake Superior. An important ore of silver. Use. JALPAITE is a cupriferousargentitefrom Jalpa, Mexico. Silver telluride,Ag2Te. Isometric. grained. Hessite. Usually massive, compact or finesectile. H. G. 2*5-3. Color 8 '31-8 '45. Cleavage indistinct. Somewhat between lead-grayand steel-gray. From the Altai Mts.; at Nagyag, Botes and Rezbdnya In Mexico at San Sebastian, Jalisco. in Transylvania; Chile near Arqueros, Coquimbo. This speciesalso In the United States,Calaveras Co., Cal.; Boulder Co., Col.; Utah. often contains gold and thus graduates toward petzite. 3 : 1. Petzite. Massive; granularto compact. Slightly (Ag,Au)2Te with Ag : Au Color steel-gray to iron-black ; tarnishing. G. 2*5-3. 8 '7-9 '02. sectile to brittle H. British Columbia; From Nagyag, Transylvania; Kalgoorlie,West Australia;Yale District, Co., and elsewhere,Cal. Col.; Poverty Hill,Tuolumne crystals. Aguilarite. Silver selenide,Ag2S and Ag2(S,Se). In skeleton dodecahedral From 7'586. Color iron-black. Sectile. G. Guanajuato, Mexico. Berzelianite. Copper selenide,Cu2Se. In thin dendritic crusts and disseminated. 671. Color silver-white, G. Skrikerum, Sweden; Lehrbach, in the tarnishing. From Harz Mts., Germany. PbSe with HgSe. Selenide of lead amd Lehrbachite. Massive, granular. mercury, From Color lead-grayto iron-black. 7'8. G. Lehrbach, in the Harz Mts., Germany. silverColor between 7-50. Eucairite. granular. G. Cu2Se.Ag2Se. Massive, the Skirkerum white and lead-gray. From mine, Sweden; also Chile. copper sive, MasPerhaps a mixture. Zorgite. Selenide of lead and copper in varying amounts. the Harz Mts.,Germany; 7-7 '5. Color dark or lightlead-gray. From granular G. Cacheuta, Argentina. and thallium, also silver (1-5 p. c.),(Cu,Tl,Ag)2Se. Selenide of copper Crookesite. of the mine Color lead-gray. From metallic. Luster G. 6*9. Massive, compact. Skirkerum, Sweden. G. 5-620. H. =3. to compact. Massive, fine-granular Umangite. CuSe.Cu2Se. La Rioja,Argentina. Color dark cherry-red. From Micro.

In

"

polished section

"

"

"

"

=

=

=

"

=

=

=

=

=

=

"

=

=

=

2.

Chalcocite

Group a

Chalcocite

Stromeyerite Sternbergite

Cu2S

Ag2S.Cu2S Ag2S.Fe4S5

Frieseite Acanthite

Ag2S

:b

: c

0'9701

0'5822

:

1

0'5822

:

1

0.9668

0-5832

:

1

0.8391

0-5970

:

1

0-7352

0-6886

:

1

0-9944

in the orthorhombic GROUP crystallize speciesof the CHALCOCITE hence pseudoto are they 60"; a prismaticangle approximating to the is The twinned. w hen in parallel form, especially group hexagonal and in in form isometric Ag2S cuproplumbite since Galena Group, Cu2S appears h ere include authors Some (see 361). in also dyscrasite p. argentite.

The

system with

366

MINERALOGY

DESCRIPTIVE

Axes

Orthorhombic. 110

A

dd'f(021) A

Redruthite.

Glance.

Copper

CHALC0CITE.

a

110

=

021

=

:

b

: c

=

0'5822

60" 25'. 125" 28'.

:

1

0-9701.

"

p, 001

A

111

pp"r, 111

A

111

62" 35*'. =53"-

=

646

645

647

in angle,also by twinning (tw. pi.w(110)). Crystalspseudo-hexagonal granularto compact and impalpable. ages developscleavetchingof orientated crystals Cleavage: m(110) indistinct; Rather sectile. conchoidal. to the three pinacoids. Fracture parallel

Often massive, structure

H.

=

2-5-3.

G.

Comp.

Luster metallic. Color and blue or green, dull. Opaque.

5-5-5-8.

=

often tarnished lead-gray,

Cuprous sulphide,Cu2S

"

iron in small amount

Sometimes

Sulphur 20*2,

=

streak

copper

blackish

79'8

=

100.

is present,also,silver.

charcoal melts to a B.B. In the open tube gives sulphurous fumes. on Pyr.,etc. which boils with spirting;the fine powder roasted at a low temperature on charcoal, globule, Soluble in'nitricacid. then heated in R.F.,yieldsa globuleof metallic copper. Resembles Diff. argentitebut much more brittle;bornite has a different color on the fresh fracture and becomes magnetic B.B. In polishedsection shows grayish or bluish white color with smooth surface. Micro. tions; With HNO3 effervesces and etches,turning more less blue,and develops cleavage direcor "

"

"

wibh KCN blackens and etches. Chalcocite has been prepared artificially by heating the vapors of cuprous chloride and hydrogen sulphideor by the treatment of cupricoxide with hydrogen sulphide; also by the heating of cupric solutions with ammonium sulphocyanate in a sealed tube. Obs. Chalcocite is an important ore of copper. It is usuallysecondary in its origin, being found in the upper, enriched portionsof copper veins. It is commonly associated with Artif

"

.

"

chalcopyrite, bornite,pyrite,cuprite, malachite,azurite,etc. Cornwall affords splendidcrystals, the districts of Saint Just,Camborne, and especially Redruth Occurs at Joachimstal,Bohemia; Tellemarken, Norway; compact (redruthite). and massive varieties in Siberia;Saxony; Mte. Catini mines in Tuscany; Mexico; South America. In the United States, Bristol, Conn., has afforded largeand brilliant crystals ; also found at Simsbury and Cheshire;at Schuyler'smines, *N. J.; in Nev., in Washoe, Humboldt, Churchill and Nye counties;at Clifton, Ariz.;in Mon., massive at Butte in great amounts. Notable deposit at Kennecott, Copper River District,Alaska. in Canada, with Found and bornite at the Acton mines and elsewhere in the province of Quebec. chalcopyrite An important ore of Use. copper. "

Stromeyerite. (Ag,Cu)?S, or

Ag2S.Cu2S. Rarely in orthorhombic crystals,often H. 2 '5-3. 6'15-6'3. massive, compact. G. Luster metallic. also Chile, steel-gray.From the Zmeinogorsk mine, Siberia;Silesia; Zacatecas, Mexico; Cobalt,Ontario;the Heintzelman mine in Ariz.; Col. Chalmersite. Cu2S.Fe4S5. Orthorhombic. Axial ratio near that of chalcocite. In thin elongated prisms vertically striated. Twins with ra(110) as tw. pi.resemcdmmon bling twinned. Commonly Color and streak dark

chalcocite. H. From the Morro

=

=

3'5. G. 47. Color Velho gold mine, Minas =

=

brass- to bronze-yellow.Stronglymagnetic. Geraes,Brazil.

368 and may

DESCRIPTIVE

MINERALOGY

contains traces auriferous.

tin. Also sometimes and be argentiferous

of

indium, gallium and thallium;

iron; from colorless white to yellowish Var. 1. Ordinary. Containing little or no transparent crystallizec 4-0-4 '1. The red or reddish brown brown, sometimes green; G. The massive cleavable forms are the called ruby blende or ruby zinc. kinds are sometimes Schalenblende to fine granular;also cryptocrystalline. most common, vary ing from coarse is a closelycompact variety,of a pale liver-brown color,in concentric layerswith reniform surface; galena and marcasite are often interstratified. The fibrous forms are chiefly in Cherokee Co., Kan. A soft white amorphous form of zinc sulphideoccurs wurtzite. of iron; dark-brown to black; Marmatite. 2. Ferriferous: Containing 10 p. c. or more The proportionof FeS to ZnS varies from 1 : 5 to 1 : 2, and the last ratio is S'9-4'05. G. from St. Christophe mine, of Breithaupt,a brilliant black sphalerite that of the christophitc 3 '91-3 '923. at Breitenbrunn, having G. of cadmium The amount present in any 3. Cadmiferous: Pribramite,Przibramite. thus far analyzed is less than 5 per cent. sphalerite tube sulphurous fumes, and generally fusible. In the open Difficultly Pyr., etc. changes color. B.B. on charcoal,in R.F.,givesa coatingof zinc oxide,which is yellow while is present a reddish brown hot and white after cooling. If cadmium coating of cadmium oxide will form first. With cobalt solution the zinc oxide coatinggives a green color when after roasting, Most heated in O.F. givewith borax a reaction for iron. Dissolves varieties, in hydrochloricacid with evolution of hydrogen sulphide. but distinguishedby the resinous luster Diff. Varies widely in color and appearance, in all but deep black varieties;usually exhibits distinct cleavage; nearly infusible B.B.; yieldsa zinc oxide coatingon charcoal. In polished section shows Micro. a grav'colorwith smooth surface. Transparent, becomes with oblique illumination. /HiVith HNOs slowly brown, often yellow to brown showing crystalstructure; with aqua regiaeffervesces and blackens. Arttf formed by heating zinc solutions in hydrogen Sphaleritehas been artificially heated zinc sulphide inclosed in a sealed tube; also by passing hydrogen sulphide over "

=

=

=

"

"

"

"

.

chloride. Obs. Sphaleriteis the most important sedimentary rocks,being especiallycommon

in both crystalline It occurs and as limestones,where it often occurs beds of considerable size. It is frequently associated with galena,also with chalcopyrite, Of the two forms etc. pyrite,barite. fluorite, siderite, Commonly found with silver ores. of zinc sulphide,sphaleriteis the form which below 1020" while wurtzite is crystallizes depositedat higher temperatures. Zinc sulphide is deposited from alkaline solutions as sphalerite;from acid solutions both forms are deposited,the amount of sphaleriteincreasing with the temperature while that of wurtzite increases with the acidityof the solution. Some of the chief localitiesfor crystallized in Cumberland Alston Moor sphaleriteare: and at St. Agnes and elsewhere in Cornwall, England; Andreasberg and Neudorf in the Harz in BoheMts., Freiberg,and other localitiesin Saxony; Pfibram, and Schlackenwald mia; Kapnik, Schemnitz and Felsobanya,in Hungary; Nagyag and Rodna in Transylvania; the Binnental in Switzerland, isolated crystalsof great beauty, yellow to brown, in cavities of dolomite. A beautiful transparent variety yieldinglarge cleavage masses is brought from Picos de Europa, Santander,Spain,where it occurs in a brown limestone. A similar varietywith golden brown to green colors from Chivera mine, Cannanea, Mexico. Large crystalsfrom Ani copper mines,Ugo, Japan. Fibrous varieties (seewurtzite)are obtained at Pribram; Geroldseck in The original Baden; Raibl,Carinthia; also in Cornwall. is from Marmato marmatite near Popayan, Italy. The important zinc ore districts of the United States in which sphaleriteis the chief mineral zinc found in Missouri,Colorado,Montana, Wisconsin, Idaho and Kansas, are borne localities noteworthy for the specimens they have produced are as follows: In Conn., N* J-'a white variety In Pa., at the at Franklin Furance. (cleiophane) ?in, y'j lead mines,in crystals;near Wheatley and Perkiomen Friedensville, Lehigh Co., a grayish variety. In 111., waxy near with galena and calcite;at Marsden' Rosiclare, diggings,near Galena, m stalacites, with crystallized In Wis., at marcasite,and galena; at Warsaw. Mineral Point,in fine crystals. In with Ohio, at Tiffin. In Mo., in beautiful crystallizations and calcite at Joplinand other galena, marcasite pointsin the southwestern part of the state; deposits here occur in limestone and are of great extent and value; also in adjoining In Col.,at parts of Kan. places. many "

ore

of zinc.

in the

.

i

Named

blende

German use.

meaning "

ine

because,while blind

most

or

often resembling galena, it yielded no lead, the word deceiving.Sphaleriteis from cr0aXepds, treacherous.

important

ore

of zinc.

in

SULPHIDES,

SELENIDES,

TELLURIDES,

Metacinnabarite. in black tetrahedral

369

ANTIMONIDES

Mercuric sulphide,HgS. In composition like cinnabar,but occurs G. 77. In Cal., from the Reddington crystals;also massive. county, with cinnabar, quartz and marcasite; and from San Joaquin, Orange

mine, Lake Co.

ARSENIDES,

=

also at Idria in Austria.

Found

Guadalcazarite. Near Probably cazar, Mexico.

metacinnabarite,but contains zinc (up a

to 4 p.

c.). Guadal-

mixture.

Mercuric

Tiemannite.

selenide,HgSe. Isometric-tetrahedral. Commonly massive' Claustal. Luster metallic. Color steel-gray Utah; 8'30-8'47 to blackish lead-gray. Streak nearly black. Occurs at Claustal in the Harz Mts.; Cal.,in the vicinity of Clear lake; MarysVale, Piute Co., Utah. Onofrite. 4'5 to 6'5 p. c. San Onofre,Mexico; Marysvale,Utah. Hg(S,Se) with Se Coloradoite. Mercuric Massive. Conchoidal telluride, fracture. H. HgTe. 2'5. G. 8'07 (Kalgoorlie). Color iron-black. Originallyfound sparingly in Colorado. Rather abundant at the Kalgoorlie district, West Australia. Material called kalgoorlite is a mixture of coloradoite and petzite. Alabandite. sulphide, MnS. Manganese Isometric-tetrahedral; usually granular 3 '95-4 '04. massive. Luster submetallic. Cleavage: cubic, perfect. G. Color ironblack. Streak Occurs at Nagyag, Transylvania; Kapnik, Hungary; Mexico; green. and massive on Snake River, Summit Peru; crystallized county, Col.; Tombstone, Ariz. In pale brown Oldhamite. Calcium sulphide,CaS. spheruleswith cubic cleavagein the Busti meteorite. Also noted in Allegan meteorite. compact.

G.

8'19

=

=

=

=

*

=

PENTLANDITE.

Isometric. Fracture uneven. Massive,granular. Cleavage:octahedral. H. 5-0. Brittle. 3*5^. G. Luster metallic. Color light bronzeyellow. Streak lightbronze-brown. Opaque. Not magnetic. A sulphide of iron and nickel,(Fe,Ni)S. In part, 2FeS.NiS Comp. 100. Sulphur 36-0,iron 42-0,nickel 22-0 =

=

"

=

=

Occurs with chalcopyrite near Also from Lillehammer, Norway. Ontario, where it is intimately associated with nickeliferous pyrrhotite. It can from the latter by its cleavage. Obs.

4.

"

Cinnabar-Wurtzite-Millerite

Group.

Rhombohedral

or

Sudbury,

be distinguished

Hexagonal

c

Cinnabar

HgS

Covellite

CuS

Greenockite

CdS ZnS

Rhombohedral-Trapezohedral

1*1453 1-1466 c

Wurtzite Millerite

Niccolite

Breithauptite Arite

Pyrrhotite Troilite

Hexagonal-Hemimorphic

NiS NiAs NiSb

Ni(Sb,As) FenSw, etc.

"

0*8109 0*8175

Rhombohedral "

Hexagonal

c or

0*9364 0*9440

0*9883 0*8194

0*9462

0'8586

0*9915

0*8701

1*0047

FeS

the monosulphides includes several subdivisions, This fourth group among in the scheme shown above, and the relations of the speciesare not in all as of mercury and zinc, clear. It is to be noted that the sulphides cases perfectly here again. group, appear already representedin the sphalerite If,as suggested by Groth, the prominent pyramids of wurtzite,greenockite,etc.,be x 1122, instead of 1011), then the values of c pyramids of the second series (e.g., in the second column are obtained,which correspond to millerite. The form of several of form for greenockite A rhombohedral known. these species,however, is only imperfectly has been suggested. made

=

MINERALOGY

DESCRIPTIVE

370 CINNABAR.

Axis Rhombohedral-trapezohedral. rr'

1011

1011 4045

A A A

u', 4045 cr, 0001

1C11

c

=

=

=

=

11453. 87" 23'. 78" 0"'. 52" 54'.

thick tabular in

habit,rarelyshowing also acicular prismatic. faces; trapezohedral as an granular,massive; sometimes incrustations, In crystalline earthy coating. what Somesubconchoidal, uneven. Cleavage: ra(1010) perfect. Fracture to Luster 8-0-8-2. adamantine, inclining G..= sectile. H. 2-2;5. Crystalsusuallyrhombohedral

or

in rhombohedral

twins; penetration

=

metallic when dark-colored,and to dull in friable varieties. red and lead-gray. Streak to brownish red, often inclining 2 -82,er Indices: o"r Optically+ to opaque. =

=

Color cochinealparent scarlet. Trans3 '14. See Art.

.

394. or pact; com(b) massive,granular embedded 1. Ordinary: either (a) crystallized; brightred to reddish brown in color; (c) earthyand bright red. 2. Hepatic. Of a fiver-brown color,with sometimes a brownish streak,occasionallyslatyin structure, though commonly granularor compact.

Var.

"

Mercuric sulphide,HgS Sulphur 13'8,mercury Comp. Usually impure from the admixture of clay,iron oxide,bitumen. =

"

86'2

=

100.

In the closed tube alone a black sublimate of mercuric sulphide,but with sodium Pyr. Carefully heated in the open tube gives sulphurous of metallic mercury. carbonate one which condenses in minute globuleson the cold walls of the fumes and metallic mercury, but only when quite free from gangue. B.B. on charcoal wholly volatile, tube. Characterized gravity (reduced, Diff. by its color and vermilion streak,high specific in however, by the gangue usuallypresent),softness;also by the blowpipe characters (e.g., varieties of hematite and cuprite. Resembles some the closed tube) which are, however, has been produced artificially Artif. by several methods Cinnabar the black mercury phide sulin generalmodifications of the two followingtypes: (1) When and sulphur is sublimed,cinnabar is the prodformed byjthe direct union of mercury uct; (2) the black sulphidewhen treated with solutions of alkaline sulphides is converted In generalcinnabar is formed under alkaline conditions and metacinnabarite into cinnabar. under acidic conditions. mineral of mercury and with rare is the only common Obs. Cinnabar exceptions in veins filling fissures and cavities in rocks which It occurs constitutes the ore of the metal. shales,sandstones or limestones. are commonly sedimentary in character,being often slates, While infrequentlyoccurring in igneous rocks such rocks are commonly near by and are of the metal. Cinnabar is deposited from hot alkaline thought to have been the source solutions or as the result of solfataric action. Pyrite and marcasite,sulphidesof copper, realgar,gold, etc.,are associated minerals; calcite, stibnite, quartz or opal, also barite, are fluorite, minerals; a bituminous mineral is common. gangue in Spain, and at Idria in CarThe most important European depositsare at Almaden southern Russia. niola,where it is usuallymassive; also at Bakmut.in Crystallizedat Moschellandsberg and Wolf stein in the Palatinate and at the mines of Mt. Avala, near chinsk Belgrade,Servia; at Ripa in Tuscany; at Als6sajo, Hungary; in the Ural Mts., the Nerfrom Province of Kweiregion in Transbaikalia;in large twinned rhombohedrons chow, China; Japan; Mexico; Huancavelica,Peru; Chile. In the United States forms extensive mines in Cal.,the most important at New Almaden in Santa Clara Co.; also at Altoona, Trinity Co.; it is now and the vicinity, forming by solfataric action at Sulphur Bank, Cal.,and Steamboat Springs,Nev.; has been found in southern Utah; important depositsoccur in Brewster Co., Texas; also mined in Nev. and "

"

.

"

"

Ariz.

The name cinnabar is supposed to come from India,where itis applied to the red resin, dragon's blood. The native cinnabar of Theophrastus is true cinnabar; he speaks of its of cinnabar,minium, is now affordingquicksilver. The Latin name given to red lead,a substance which was early used for adulterating cinnabar,and so got at last the name. Only comparativelyfew localitieshave furnished the mineral in quantity. Use.

"

The

most

importantore

of mercury.

TELLURIDES,

SELENIDES,

SULPHIDES,

ARSENIDES,

ANTIMONIDES

371

COVELLITE.

Monoclinic ? Pseudohexagonal through twinning. Crystalsusuallythin hexagonal plates. Often massive. T5-2. G. 4'6. Luster submetallic to CleaVage: basal,perfect. H. Often shows fine purple color when darker. resinous. Color indigo-blue or Streak lead-grayto black. moistened with water. Opaque. 100. Sulphur 33'6,copper 66'4 Cupric sulphide,CuS Comp. =

=

=

"

=

Fusible at 2'5 yieldingsulphurous fumes. After roasting and moistening Pyr., etc. Much acid givesazure-blue flame. with hydrochloric sulphur in C.T. In polished section shows blue color with smooth surface. With KCN Macro. comes beinstantlydeep violet which rubs off,leavinga yellowcoating and rough surface. Covellite has been prepared artificially Artif. by heating in sealed tubes a cupric solution with ammonium sulphocyanate and by heating sphaleritein a solution of copper "

"

"

sulphate. Covellite is a mineral of secondary originfound in the enriched portionsof copper Obs. in small amounts Found in many bornite,etc. sulphide veins,associated with chalcocite, places. Noteworthy localities are as follows: various places in Germany; in exceptional crystalsat Bor in Timoker Kreis,Servia; on the lavas of Vesuvius; in Chile; Province of Rikuchu, Japan. In the United States at the Butte district, Mon.; Summitville,Col.; La Sal district, Utah; Kennecott, Alaska, etc. "

GREENOCKITE.

Hexagonal-hemimorphic. Rarely in hemimorphic crystals;also as a coating. Cleavage: a(1120) distinct,c(0001) imperfect. Fracture conchoidal. Brittle.

H.

=

3-3'5.

G.

4'9-5*0.

=

Luster

adamantine

to resinous.

Color

honey-, citron-,or orange-yellow. Streak between Nearly transparent. orange-yellow and brick-red. 2*529. co 2-506,e Optically+ Cadmium Sulphur 22'3, sulphide,CdS Comp. =

=

.

=

"

cadmium

77-7

=

100.

carmine-red color In the closed tube assumes a Pyr., etc. hot, fading to the originalyellow on cooling. In the B.B. on charcoal, either open*tube gives sulphurous fumes. alone or with soda, gives in R.F. a reddish brown coating. Soluble in hydrochloricacid,affordinghydrogen sulphide. in sevhas been prepared artificially Artif. Greenockite eral fused with sulphide when Precipitated cadmium ways. cadmium potassium carbonate and sulphur produced greenockite crystals; also when fused together. Greenockite is sulphide were sulphate,calcium fluoride and barium oxide is heated in sulphur vapor. formed when cadmium Obs. Occurs with prehnite at Bishopton, Renfrewshire, and elsewhere in Scotland. At Pfibram in Bohemia, as a coating on sphalerite;similarlyat other points; so too in the United States near Mo.; in Friedensville, Pa., and in the zinc region of southwestern common Marion Co., Ark., it colors smithsonite bright yellow; noted at Franklin, N. J. Not unas a furnace product. "

white

"

"

Use.

"

An

ore

of cadmium.

but in hemimorphic hexagonal crystals; Wurtzite. Zinc sulphide, ZnS, like sphalerite, See under sphalerite, Color brownish black. also fibrous and massive. 3 '98. G. p. 368, Oruro in Bolivia; Portugal; for the conditions of its formation. From a silver-mine near with sphaleriteand quartz at the "Original Butte" at Mies, Bohemia; Peru. In crystals In crystalsfrom Joplin,Mo.; from near Frisco,Beaver Co.,Utah. mine, Butte, Mon. at Pfibram, Bohemia; Liskeard, The massive fibrous forms of "Schalenblende" occur Cornwall,etc. Other forms, from Stolberg,Wiesloch, Altenberg, Germany, are in part =

wurtzite,in part sphalerite.

372

MINERALOGY

DESCRIPTIVE

CapillaryPyrites. Rhombohedral. Usually in very

MILLERITE.

often in capillarycrystals, hair. like wad of Also in a delicate radiatinggroups; The rhomboheradiated. a nd columnar tufted coatings, partlysemi-globular be formed. twins may dron (0112)is a gliding plane and artificial slender to

interwoven

sometimes

to (1011)and (0112). Fracture Cleavage perfectparallel H.

3-3 '5.

G.

5 '3-5 '65.

capillarycrystalselastic. with often to bronze-yellow, Color brass-yellow, .inclining tarnish. Streak greenishblack. Nickel sulphide,NiS Sulphur 35'3, nickel Comp. =

=

=

"

Brittle;

uneven.

Luster a

gray

64-7

=

metallic. iridescent 100.

charcoal fuses to a globule. bead in O.F., becoming nickel. On charcoal in R.F. the roasted mineral gives metallic from reduced R.F. in gray Most varieties also show traces of attractable by the magnet. metallic mass, a coherent copper, cobalt,and iron with the fluxes. Artif by treatingunder pressure a Crystalsof millerite have been formed artificially solution of nickel sulphate with hydrogen sulphide. in Bohemia; in Germany and Pfibram at JohannFound Obs. at Joachimstal georgenstadtand Freiberg,Saxony; Wissen, Prussia; in Cornwall, England. In the United States,at Antwerp, N. Y., in cavities in hematite; in Lancaster Co., Pa., With calci'te, at the Gap mine, in thin velvety coatings of a radiated fibrous structure. dolomite and fluorite, forming delicate tangled hair-like tufts,in geodes in limestone,often At at St. Louis, Mo.; similarly near the calcite crystals, Milwaukee, Wis. penetrating

Pyr., etc. In the open roasted,gives with

When

B.B. sulphurous fumes. and salt of phosphorus a

tube

borax

on

violet

"

.

"

Orford,Quebec. Use.

An

"

of nickel.

ore

but with lower specific NiS like millerite, siders gravity(4'7). Laspeyres conin Westerwald, all millerite as formed by paramorphism from beyrichite. Found Rhine-Prussia. BEYRICHITE.

=

6*4.

Ni(Bi,Sb,S). In

Perhaps

HAUCHECORNITE.

G.

Color lightbronze-yellow.From

Copper

NICCOLITE.

Hamm

tabular tetragonal crystals.H. a. d. Sieg,Germany.

=

5.

Nickel.

Usually massive, structure nearly impalpable; Hexagonal. Crystals rare. Fracture also reniform,columnar; reticulated, arborescent. uneven. 7'33-7'67. Luster 5-5'5. G. Brittle. H. metallic. Color pale copper-red. Streak pale brownish black. Opaque. Nickel Arsenic 100. arsenide, NiAs Comp. 56'1, nickel 43*9 contains a littleiron and Usually cobalt,also sulphur; sometimes part of the arsenic is replacedby antimony, and then it graduatestoward breithauptite. =

=

=

"

The

intermediate Pyr., etc.

varieties have

In the closed tube tube a sublimate of

been

=

called write.

intense ignitiongives a faint sublimate of arsenic. In the open arsenictrioxide,with a trace of sulphurous fumes, the On charcoal gives arsenical fumes and fuses to a globule, assay becoming yellowishgreen. which, treated with borax glass,affords, by successive oxidation,reactions for iron,cobalt, and nickel;the antimonial varieties give also reactions for antimony. Soluble in aqua "

on

regia. Obs. Accompanies cobalt,silver and copper ores in Germany in the Saxon mines of Annaberg, Schneeberg, Mansfield,etc.; also in Thuringia,Hesse, and in Styria; at Allemont, Dauphine, at Balen in the Basses Pyrenees, France (arite) ; at the Ko mines in Nordmark, Sweden; occasionallyin Cornwall,Chile: abundant de la Rioja,Oriocha, at Mina Argentina. In the United States, at Franklin Furnace, N. J.,Silver Cliff, Col. sparingly In Canada, at Cobalt,Ontario. "

Use.

"

An

ore

of nickel.

TEMISKAMITE.

Described as ture having composition Ni4As3,has been shown to be a mixmaucherite and a littlecobaltite. niccolite, Breithauptite. Nickel antimonide, NiSb. Rarely in hexagonal crystals; usually disseminated. massive, arborescent, G. 7'54. Color lightcopper-fed. From Andreasberg in the Harz Mts., Germany. of

=

TELLURIDES,

SELENIDES,

SULPHIDES,

ARSENIDES,

Magnetic Pyrites.

PYRRHOTITE.

Hexagonal,

c

0'8701.

=

652

1011

cs, 0001

A

cu, 0001

A

4041

cy, 0001

A

(20-0-20-3)

=

45"

=76"

8'. 0'.

XC~

gg

_

=

with pi.s(10ll), rightangles(Fig.418, p. 167). commonly tabular; also acute striated horizontally. Usually Parting: c(0001),sometimes Twins:

373

ANTIMONIDES

tw.

81" 30*'.

vertical

nearly at \" crystalsrare, pyramidal with faces massive, with granular structure. axes

Distinct

distinct.

Fracture

to subconchoidal. uneven metallic. Color between bronze-yellow and copper-red, and subject to speedy tarnish. Streak dark grayishblack. Magnetic, but varying much in intensity;sometimes possessing

Brittle.

H.

3 -5-4-5.

=

G.

Luster

4-58-4-64.

=

polarity. of dissolved Ferrous sulphide containing variable amounts Comp. variation show from Often also contains to FeieSi?. FesSe sulphur. Analyses iron nickel. 60'4 100. Art. Fe7S8 (Cf. 473, p. 323.) Sulphur 39'6, "

=

=

less of dissolved sulphur, while or Pyrrhotite differs from troilite in containing more form the pure of iron,may troilite, occurringin meteorites where there is always an excess monosulphide. In the open tube gives sulphurousfumes. Pyr., etc. Unchanged in the closed tube. in O.F. is converted On charcoal in R.F. fuses to a black magnetic mass; into red oxide, which with fluxes gives only an iron reaction when but many varieties yield small pure, of nickel and cobalt. amounts Decomposed by hydrochloricacid,with evolution of hydrogen sulphide. Diff. Distinguishedby its peculiar reddish bronze color; also by its magnetic properties. "

"

In polished section shows color with a shiny and pitted surface. Micro. cream a with aqua With hot HC1 tarnishes quickly,giving bright colors, then blackens and dissolves; becomes iridescent in center of drop and brown at the edge. regiaeffervesces, of iron and sulphur and has been synthesized by the direct union Artif. Pyrrhptite also when Pyrrhotite pyrite is heated in an atmosphere of hydrogen sulphide at 550". exists in two crystallinemodifications, hexagonal at ordinary temperatures and orthorhombic-above 138". Obs. Occurs at Kongsberg, Modum, Kristiania,etc., in Norway; Falun, Sweden; Andreasberg in the Harz Mts., Germany; Schneeberg, Saxony; Leoben and Lavantal, wall. Carinthia; Minas Geraes in Brazil,in large tabular crystals; the lavas of Vesuvius; Corn"

"

"

In North America, in Me., at Standish with andalusite; in Ver., at Stafford,etc. In In Pa., at the N. Y., near Diana, Lewis Co.; Orange Co.; at Tilly Foster mine, Brewsters. In In Tenn abundant. Ducktown at mines, Gap mine, Lancaster Co., nickeliferous. ., Ontario; largedeposit mined for nickel Canada, in largeveins at St. Jerome, Elizabethtown , at Sudbury, Ontario. Named Use.

"

from irvpporw, Often becomes

reddish. a

valuable

ore

of nickel.

Troilite. Ferrous sulphide,FeS, occurring in nodular iron meteorites. Color tombac-brown. G. 4 -75-4*82. many member of the pyrrhotite series. See above. =

C.

Intermediate

masses

and in thin veins in Considered to be the end

Division

sulphide, perhaps Ni4S8. In octahedral crystals;frequently From Color gray. Griinau, Westphalia, Germany. Sychnodymite. Essentially (Co,Cu)4S6. Isometric, in small steel-gray octahedrons. From the Siegendistrict, Germany.

Polydymite.

twinned.

G.

=

A nickel 4'54-4'81.

374

MINERALOGY

DESCRIPTIVE

Ore.

Peacock

BORNITE.

Isometric.

regarded as

sometimes

followingspeciesare etc. Sulpho-ferrites, The

PurpleCopper

cubic,faces often rough Crystalsrare. penetration-twins.

Twins:

curved.

or

Usually

Erubescite.

Ore.

VariegatedCopper

Ore.

Habit

o(lll),often granularor compact. Cleavage : o (11 1)

namely, Sulpho-salts,

tw.

pi.

massive,structure

Brittle. small conchoidal, uneven. metallic. Color between copper-red and Streak fresh fracture,speedilyiridescent from tarnish. Fracture

in traces.

,

H.

G.

3.

=

4-9-5-4.

=

on pinchbeck-brown

Luster

palegrayishblack. Opaque. A sulphide of copper Comp. 11-1,sulphur25-6=100.

iron.

and

"

Cu5FeS4.

Copper 63-3,iron

siderable of chalcocite, mineral often contains small amounts etc.,and therefore shows conand variation in its percentage composition,givingfrom 50 to 70 p. c. of copper 15 to 6*5 p. c. of iron. of sulphur. In the open tube In the closed tube gives a faint sublimate Pyr., etc. B.B. on charcoal fuses in R.F. to a brittle magnetic globule. yieldssulphurous fumes. The roasted mineral gives with the fluxes the reactions of iron and copper, and with soda a metallic globule. Soluble in nitric acid with separationof sulphur. from Diff. chalcocite)by the peculiarreddish color on the fresh Distinguished(e.g., fracture and by its brilliant tarnish; B.B. becomes stronglymagnetic. With surface. In polishedsection shows a pinkish brown Micro. color with smooth becomes HNO3 quickly golden-brown with effervescence. Artif. Bornite has been obtained by fusingpyrite,copper and sulphur together; by heating a mixture of cuprous, cupric and ferric oxides in hydrogen sulphide at 100" to 200". Obs. Bornite is often a primary mineral of magmatic origin,being frequentlyfound in igneous rocks. It is also often a secondary mineral,occurring with chalcocite,etc.,in It is usually associated with other copper the enriched portionsof copper sulphideveins. of copper. Crystallinevarieties are found in Cornwall, called by ores, and is a valuable ore the miners "horse-flesh ore." Occurs massive at Ross Island, Killarney,Ireland; Monte Catini,Tuscany; the Mansfeld district, Germany; in Norway, Sweden, Siberia,Silesia, and Hungary. It is the principalcopper ore at some in Peru, Chilian mines; also common Bolivia,and Mexico. In the United States,found at the copper mine in Bristol, Conn.; massive at Mahoopeny, near in Canada, at Wilkesbarre,Pa.; in western Idaho; Butte, Mon., etc. A common ore the Acton and other mines. Named after the mineralogistIgnatiusvon Born (1742-1791).

The

"

"

"

"

"

Use.

"

An

ore

of copper.

Linnaeite. A sulphide of cobalt,Co3S4 analogous to the spinel group. CqS.Co2S3, Also contains nickel (var. siegenite). Commonly in octahedrons; also massive. H. 5 '5. G. 4*8-5. Color pale steel-gray, tarnishing copper-red. Occurs at Bastnaes, etc., Sweden; Mtisen, near in octahedrons. In the Siegen,Prussia; at Siegen (siegenite), United States at Mine la Motte, Mo.; Mineral Hill,Md. =

=

=

Daubreelite. irons.

An iron-chromium Color black. G.

meteoric

sulphide,FeS.Cr2S3, occurring with troilite in =

some

5 '01.

CUBANITE. Described as an CuS.Fe2S3. iron-coppersulphide, perhaps CuFe2S4 of specimens from several localitiesshow it to be a mixture of pyriteor pyrrhoExamination tite with chalcopyrite. =

CARROLITE. A copper-c9balt CuS.Co2S3. sulphide,CuCo2S4 Isometric; rarely in octahedrons. G. 4*85. Usually massive. Color lightsteel-gray, with a faint reddish hue. From Carroll Co.,Md., near Finksburg. Probably linnseitewith intergrown bornite =

=

and

chalcopyrite. Badenite.

Color

Massive (Co,Ni,Fe)2(As,Bi)3. 7'1. Metallic. granular to fibrous. G. From near Badeni-Ungureni,Neguletzul valley,Roumania. =

steel-gray. Fusible.

CHALCOPYRITE.

Copper Pyrites. Yellow Copper Ore. Axis c Tetragpnal-sphenoidal. 0-98525. 108" 40'. ppf, 111 A 111 70" 7i'. PPl, 111 A 111 =

=

=

ce, 001

A

101

=

44"

34|'.

376

MINERALOGY

DESCRIPTIVE

with nickel and cobalt ores in the Kupferschiefer forms a bed in argillaceous schist;occurs at Freiberg affords well-defined crystals; the Kurprinz mine In Germany of Mansfield. elsewhere as at Mte. Catini in Common also Horhausen, Dillenburg,Neudorf, Musen. in South Tin New. Rio Chile; Wales; Japan, etc. Spain; to, Tuscany; In the United States it is found in largecrystalsassociated with quartz at Ellenville, N. Y.; in exceptional crystalsat the French Creek mines, Chester Co., Pa., associated with pyrite,magnetite, etc.; in Mo., with sphaleriteat Joplin; at various localities in Gilpin in many The most important sulphide deposits of copper of and other counties in Col. which chalcopyriteis the chief ore are found in the states of Arizona, Montana, Utah, and Tennessee. Alaska, Nevada, New Mexico, California, In Canada there are important copper depositsin British Columbia,Ontario arid Quebec, The Use. most important ore of copper. Named from XO\KOS, brass,and pyrites, by Henckel (1725). "

D.

Bisulphides,Diarsenides, etc.

distinct groups. two The diarsenides, disulphides, etc., embrace in the included viz. metals cobalt are same and nickel. : both, iron, prominent several cases of isodimorphism, The groups present,therefore, is shown in as These sulphidesare all relatively the listsof speciesbelow. hard,H. 5-6; this has strike firewith a nd hence the familiar a steel, given name they pyrites The color varies between appliedto most of them. pale brass-yellowand The

=

tin-white.

RS^RAs^RSb^

Pyrite Group. FeS2 FeAs2

Pyrite Arsenoferrite

(Co,Ni,Fe)S2 Cobaltnickelpyrite

Isometric-pyritohedral

Gersdorffite

NiS2.NiAs2

Corynite

NiS2.Ni(As,Sb)j

Ullmannite

NiS2.NiSb2 (isometric-

MnS2

Hauerite

[Smaltite |Chloanthite Cobaltite

tetartohedral)

CoAs2,also (Co,Ni)As2 Sperrylite NiAs2,also (Ni,Co)As2 Laurite CoS2.CoAs2

Marcasite

Group.

RS2, RAS2,

FeS2 FeAs2

07662

0-6689 Lollingite Fe3 As4 Leucopyrite Arsenopyrite FeS2.FeAs2 0-6773 Danaite (Fe,Co)S2. (Fe,Co)As2 Safflorite

:

1

:

1

:

c

110 A 110

101AI01

1-2342 1-2331

74" 55' 67" 33'

116" 20' 123" 3'

1-1882

68" 13'

120" 38'

1-1925

69" 32'

119" 35'

CoAs2

Rammelsbergite NiAs2 Glaucodot (Co,Fe)S2. (Co,Fe)As2 Alloclasite (Co,Fe)(As,Bi)S Wolfachite

Orthorhombic

etc.

a

Marcasite

PtAs2 RuS2?

0-6942

:

NiS2.Ni(As,Sb)2

The PYRITE GROUP includes,besides the compounds of Fe, Co, Ni, also others of the related metals Mn and Pt. The crystallization is isometric-

pyntohedral. The speciesof the MARCASITE GROUP system with prismaticanglesof about 70" dome

of about

crystallizein the orthorhombic 110" and a prominent macrofivefold and sixfold repeated twins are and

60" and 120". Hence with several species, in the one case the macrodome named being the twinning-plane. common

prism and in the other the

SELENIDES,

SULPHIDES,

TELLURIDES,

ARSENIDES,

377

ANTIMONIDES

Pyrite Group Pyrites.

Iron

PYRITE.

and pyritohedron e(210) the common often with striations ||edge a(100)/e(210), due to and these forms to of c ombination rounded tending produce oscillatory faces; faces also striated J_ to this edge; octahedron also common. pyritohedral Twins: tw. ax.= See Figs.657-662, also Figs.133-138, pp. 65, 66. a crystal with a xes parallel (Fig.407, p. 166); rarely axis,usuallypenetration-twins subfibrous contact-twins. Frequently massive, fine granular; sometimes stalactitic. radiated; reniform, globular,

Cube Isometric-pyritohedral. of both

forms, the faces

657

658

660

661

Cleavage: a(100), o(lll),indistinct. Brittle.

H.

=

6-6-5.

G.

=

Fracture

conchoidal

to

uneven.

4-95-5-10; 4-967 Traversella,5-027 Elba.

ter Lus-

form. metallic,splendentto glistening.Color a pale brass-yellow, nearly uniStreak greenishblack or brownish black. Opaque. Iron disulphide, FeS2 100. Sulphur 53'4, iron 46*6 Comp. -

=

"

=

sometimes Nickel,cobalt,and thallium,and also copper in small quantities, replacepart of the iron, or else occur Gold is as mixtures; selenium is sometimes present in traces. sometimes distributed invisiblythrough it,auriferous pyritebeing an of important source gold. Arsenic is1rarely present, as in octahedral crystalsfrom French Creek, Pa. (0'2 p. c. As). Easily fusible,(2'5-3). Becomes magnetic on heating and yieldssulphur Pyr.,etc. sublimate of sulphur in the closed tube. dioxide. Gives nn abundant Insoluble in hydrochloric The fine powder is completely soluble in strong nitric acid acid. Diff. Distinguished from chalcopyriteby its greater hardness and paler color; in form and specific gravity different from marcasite,which has also a whiter color. color with a scratched and dull surface. In polished section shows Micro. cream a With effervesces slowly becoming faintlybrown. HNOa Alteration. Pyrite readily changes by oxidation to an iron sulphate or to the hydrated oxide,limonite,with sulphuric acid set free. Crystals of pyrite which have been This change may continue until tho changed on their surfaces to limonite are common. of pyritelying near the surface originalmineral has completely disappeared. Large masses "

.

"

"

"

may

tHe iron gossan of the miners of limonite while the a cellular mass and enters into various important reactions with free travels downward be continued until The alteration of pyriteto limonite may minerals below.

be altered to

sulphuricacid

"

"

set

the unaltered hematite is formed. Gbs. Experiments show "

high temperatures.

that pyriteis formed in neutral or alkaline solutions and at the other hand, is deposited from acid solutions and

Marcasite, on

MINERALOGY

DESCRIPTIVE

378

be formed through the only at temperatures below 450" C. These sulphidescan although the reducingaction of carbonaceous materials may also action of hydrogen sulphide, in rocks of all ages and types, being most common at times be of importance. Pyriteoccurs found as a minor accesit is also frequently sory in the metamorphic and sedimentary rocks,but in disseminated in the rocks it usually occurs constituent of igneous rocks. When in crystals etc.,but in veins it may occur small crystals, cubes,octahedrons,pyritohedrons, At times it is in nodular or tionary concreor radiatingmassive structure. with a is stable

granular

or

forms. sulphide mineral. being the most common Pyrite is very widespreadin its occurrence, is mined for its sulphur content or because and amounts in is it found large At times very It is frequently valuable metal, like copper, gold,etc. of some it contains small amounts for of notable localities its occurrence Some more fine luster. ^the with in a found

crystals

given below. deposits of pyrite are found in Norway, Germany, France, Important commercial Italy,Spain and Portugal. The mines at Rio Tinto, Spain, are especiallynoteworthy. The mineral has been mined in the United States in Louisa and Prince William Cos.,Va.; ally in St: Lawrence Co., N. Y.; at Davis, Mass., etc. The followinglocalitiesfurnish exceptionfine crystallized specimens: Cornwall, England; Traversella and Brosso, Piedmont Italy; Island of Elba; Ardennes, France, in distorted cubes; Minden, Prussia,in interpenetrationtwins; in various localitiesin Bohemia, Hungary, Germany, Sweden, etc.; at Firmeza, Cuba; at French Creek, Pa., in pyramids with apparently tetragonalor orthoat Rossie and Scoharie,N. Y.; Roxbury, Conn.; Franklin, N. J.; rhombic symmetry; Gilpin Co. and at Leadville,Col.; Bin^hamCanyon, Utah. The name pyriteis derived from irvp, fire,and alludes to the sparks formed when the mineral is struck with a hammer; hence the earlyname pyrites, p. 376. of copper Use. or gold and becomes an important Pyrite often carries small amounts It is also mined for its sulphur content which is used in the form of of these metals. ore phuric sulphur dioxide (used in the preparationof wood pulp for manufacture into paper), as sulin the purification of kerosene and in the acid (used for many especially purposes, and as the ferrous sulphate,copperas (used in dyeing, in preparationof mineral fertilizers), and as a disinfectant). inks,as a wood preservative, Bravdite (Fe,Ni)S2. Contains nearly 20 per cent nickel. In small grainsand crystal seminated fragments,apparently octahedral. Pale yellowwith a faint reddish tarnish. Occurs disat Minasragra, Peru. ores through the vanadium Iron cobalt and sulphide with about 20 per cent Cobaltnickelpyrite.l nickel, (Co,Ni,Fe)S2. In minute pyritohedralcrystals. Steel-graycolor. Gray-black streak. H. 4-716. Found. at Musen, Germany. 5. G. Iron arsenide, probably FeAs2. Arsenoferrite. In small Isometric-pyritohedral. Fine splinters crystals. Color dark brown. the transparent with ruby-red color. From Binnental,Switzerland. Hauerite. In octahedral Manganese disulphide,MnS2. or pyritohedral crystals; are

"

=

=

"

also massive.

G.

Color

3'46.

=

reddish

brown

or

brownish

black.

From

Kalinka,

Hungary; Raddusa, Catania,Sicily. SMALTITE-CHLOANTHITE.

Isometric-pyritohedral. Commonly massive; in reticulated and other shapes. Cleavage: o(lll) distinct;a (100) in traces. Fracture granular and

imitative uneven.

Brittle.

H.

=

G.

5'5-6.

=

.

6*4 to

6-6.

Luster

metallic.

Color

when tin-white, inclining, sometimes massive, to steel-gray, or iridescent, grayishfrom tarnish. Streak grayishblack. Opaque. SMALTITE is essentially Comp. cobalt diarsenide,CoAs2 Arsenic "

=

71;8,cobalt 28-2 71-9,nickel 28'1

=

100.

=

100.

Cobalt and nickel

CHLOANTHITE

is nickel diarsenide, NiAs2

=

Arsenic

are usuallyboth present,and thus these two speciesgraduate into each sharp line can be drawn between them. Iron is also present in varying amount ; the variety of chloanthite containingmuch iron has been called chathamite. ther Fursulphuris usuallypresent,but only in small quantities. Many analysesdo not conform even approximately to the formula RAs2, the ratio risingfrom less than 1 : 2 to 1 : 2 '5 and nearly 1 : 3, thus showing a tendency toward skutterudite (RAs3), perhaps due to either molecular or mechanical mixture. Microscopicexamination of polishedspecimens shows

other, and

no

TELLURIDES,

SELENJDES,

SULPHIDES,

ARSENIDES,

379

ANTIMONIDES

of the group. Material known as keweenawite is a probable zoning of different members mixture of smaltite,niccolite and domeykite. by the high specific Much that has been called smaltite is shown gravityto belongto the orthorhombic speciessafRorite. In the closed tube gives a sublimate of metallic arsenic; in the open Pyr., etc. and sometimes traces of sulphur dioxide. tube a white sublimate of arsenic trioxide, B.B. charcoal gives a coating of As2O3, the arsenical odor, and fuses to a globule, on which, affords reactions for iron, treated with successive portionsof borax-glass, cobalt,and nickel. in veins,accompanying ores of cobalt or nickel,and ores Obs. of Usually occurs silver and copper; instances,with niccolite and arsenopyrite. Found at the also,in some Saxon Sparnon, Cornwall; Riechelsdorf, mines; Joachimstal,Bohemia; Wheal Hesse, In the Germany; Tunaberg, Sweden; Allemont, Dauphine, France; Cobalt, Ontario. in mica slate, occurs with arsenopyrite United States,at Chatham, Conn., the chathamite and niccolite;at Franklin Furnace, N. J. "

"

Use.

nickel.

Ores of cobalt and

"

COBALTITE. or Commonly in cubes,or pyritohedrons, Isometric-pyrithohedral. binations comforms of pyrite. Also granular massive to resembling common

compact.

Cleavage: cubic,rather G.

=

6-6 -3.

gray, with

a

Brittle. H. 5-5. perfect. Fracture uneven. inclined to red; also steelColor silver-white, violet tinge, or grayishblack when containingmuch iron. Streak =

metallic.

Luster

grayishblack. Sulpharsenideof cobalt,CoAsS Comp.

or

"

arsenic 45'2,cobalt 35'5

=

CoS2.CoAs2

=

Sulphur 19'3,

100.

is present, and in the varietyferrocobaltite in largeamount. In the open in the closed tube. tube gives sulphurous fumes, Unaltered Pyr., etc. and sublimate of arsenic trioxide. B.B. on charcoal gives off sulphur and a crystalline arsenic oxides,and fuses to a magnetic globule; with borax a cobalt-blue color. Soluble in nitric acid,with the separationof sulphur. warm in Sweden; at the Nordmark Obs. Occurs at Tunaberg and Hakansbo mines; also at Skutterud in Norway; at Schladming, Styria; Siegen in Westphalia;Botallack mine, near St. Just,in Cornwall; Khetri mines, Rajputana, India; Cobalt,Ontario,Canada. Iron

"

"

Use.

"

An

ore

of cobalt.

NiS2.NiAs2. Iron, and sometimes or less of the nickel. Isometric-pyritohedral; usually massive. H. Color silver-white to steel-gray. From 5*5. 5'6-6'2. G. Loos, Sweden; the Harz Mts., and Lobenstein, Reuss-Schleiz,Germany; Schladming, Styria;Sudbury and Ontario; Rossland, British Columbia. Algoma districts,

Sulpharsenide of nickel,NiAsS

Gersdorffite.

cobalt, replace =

more

or

=

is near but contains also antimony. Probably represents a mixture. gersdorffite, Olsa,Carinthia. Cleavage cubic. Color tin-white to steel-gr.ay. Willyamite. CoS2.NiS2.CoSb2.NiSb2. Broken South Wales. Hill mines, New Villamaninite. of Co,Fe. H 4'5. Sulphide of Cu,Ni with smaller amounts In irregulargroups of cubo-octahedral 4-4-4-5. G. Color, iron-black. crystalsand in In dolomite from Carmenes near district, radiating nodular masses. Villamanm, Prov. Leon, Spain. UUmannite. Sulphantimonide of nickel,NiSbS or NiS2.NiSb2; arsenic is usually both pyritohedraland tetrahedral forms Isometric-tetartohedral; present in small amount. 5-5 '5. G. Color steel-grayto 6 '2-6 7. occur. Usually massive, granular. H. silver-white. Occurs in the mines of Siegen, Prussia; Lolling,Carinthia (tetrahedral); Monte Narba, Sarrabus, Sardinia (pyritohedral). From KALLILITE. Ni(Sb,Bi)S or NiS2.Ni(Sb,Bi)2. Massive,color lightbluish gray. the Friedrich mine near Schonstein a. d. Sieg,Germany. with Sperrylite. Platinum diarsenide,PtAs2. In minute cubes, or cubo-octahedrons G. 10*6. 6-7. Luster metallic. at times small pyritohedral or diploid faces. H. Found Color tin-white. Streak black. at the Vermillion mine, 22 miles west of Sudbury, Co., N. C. Found associated with covellite at the Rambler Ontario,Canada; also in Macon This is the only known native compound of platinum. mine, Medicine Bow Mts., Wy.

CORYNITE From

"

=

=

=

=

"

=

=

380

MINERALOGY

DESCRIPTIVE

RuS2. osmium, probably essentially

Laurite. Sulphideof ruthenium and 7 '5. G. in grains. H. octahedrons; From the platinum washings of Borneo.

=

=

Color 6 '99. Luster metallic. Also reported from Oregon.

In minute dark iron-black.

^

Skutterudite.

Cobalt

arsenide,CoAs3.

Also Isometric-pyritohedral.

massive

lar. granu-

between Color tin-white 672-6 '86. G. 6. Cleavage: a(100),distinct. H. and pale lead-gray. From Skutterud,Norway; the Turtmanntal, Switzerland. From near NICKEL-SKUTTERUDITE. (Ni,Co,Fe)As3.Massive, granular. Color gray. Silver City, N. M. Color tinBISMUTO-SMALTITE. Co(As,Bi)3. A skutterudite containing bismuth. 6 '92. G. white. Zschorlau,near Schneeberg,Saxony. =

=

=

Marcasite

Group see For the listof speciesand their relations,

p. 376.

White iron pyrites. Axes a : b : c 07662 Orthorhombic. : 1 : 1*2342. 101" 58'. Oil A Oil 74" 55'. II', mm"', 110 A 110 111 63" 46'. 116" 20'. 001 A ee', 101 A 101 cs, in stellate fivelings Twins: tw. pi.m(110), sometimes (Fig.436, p. 169, cf. Fig. 664); also tw. less common, pi.e(101), the crystals crossingat angles of nearly 60".

MARCASITE.

=

=

=

=

=

Crystals commonly ||c(001), also pyramidal;- the brastriated chydomes ten edge6(010)/c(001).Oftites massive; in stalacren; also globular, tative iform, and other imishapes. Cleavage: m(110) tabular

Folkestone

rather distinct; 6-6*5. Brittle. H. Z(Oll)in traces. Fracture uneven. G 4-85-4-90. Luster metallic. Color pale bronze-yellow,deepening on Streak grayishor brownish black. exposure. Opaque. Iron disulphide, like pyrite,FeS2 Comp. Sulphur 53'4, iron 46'6 100. Arsenic is sometimes present in small amount. =

=

"

=

=

Var-

The

varieties named

depend mainly on state of crystallization.Radiated: Pyrite: Aggregationsof flattened twin crystals in crest-likeforms. with re-enteringangles a littlelike Spear Pyrite: Twin crystals, the head of a spear in form. (Fig.664.) Capillary:In capillarycrystallizations. Like pyrite. Very liable to decomposition, Pyr.,etc. than pyrite. more so Diff. Resembles pyrite,but has a lower specificgravity,and the color when fresh (e. with acid)is paler:when crystallized e.g., after treatment easilydistinguishedby the forms. M ore subjectto tarnish and final decomposition than pyrite. Marcasite can be distinguished from pyriteby the followingmethods. When chemically both minerals are finelypowdered and treated with nitric acid,first a littleconcentrated in the cold and after vigorous action has ceased,by warming, it will be found that in later, the case of pyrite the greater part of the sulphur of the mineral has been oxidized and taken into solution as sulphuric acid,while in the case of marcasite most of the sulphur has separated in a free state. The Stokes method, which can be used quantitatively to determine the amounts of the two minerals in a mixture,depends the difference in their behavior upon when boiled with a standard solution of ferric sulphate. In the case of pyriteabout 52 per cent pjthe sulphur is oxidized to sulphuricacid,while with marcasite only about 12 per cent "

Radiated;also the simplecrystals. Cockscomb

"

"

is

oxidized.

tfr~^ With

HNO3

polished sections shows

slowlyturns

brown

a

cream

color with

to black with effervescence.

a

scratched

and

dull surface.

SULPHIDES,

SELENIDES,

TELLURIDES,

ARSENIDES,

ANTIMONIDES

381

Marcasite Alteration. being relativelyunstable is easilyaltered. Specimens often disintegratewith the formation of ferrous sulphate and sulphuricacid. It also alters to pyrite,limonite,etc. Obs. unstable compound than pyriteand is formed under Marcasite is a much more that it is deposited at temperatures comparatively limited conditions. Experiments have shown below 450" C. and in acid solutions. The higher the temperature the more acid At ordinary temperatures marcasite be deposited from the solution contain. must may while in nearly neutral solutions. Marcasite is formed in general under surface conditions, deep veins where the minerals are depositedfrom ascending hot and usuallyalkaline waters only pyriteis found. Marcasite occurs Found Carlsbad, Bohemia. at several abundantly at Littmitz near In itscockscomb form occurs at Tavistock in Devonlocalitiesin the Harz Mts., Germany. shire Folkestone and Dover, England. In and as Spear Pyritesin the chalk-marl between in stalactites with where it occurs the United States a notable localityis at Galena, 111., concentric layers of sphaleriteand galena. In fine crystalsat Mineral Point, Wis.; in Frequently associated with galena, crystalsaltered to limonite from Richland Co., Wis. Mo. sphaleriteand dolomite from the Joplindistrict, The word marcasite, of Arabic or Moorish origin(and variouslyused by old writers,for of common miners and mineralogists pyrite among bismuth, antimony), was the name crystallized first given to this in later centuries, until near the close of the eighteenth. It was speciesby Haidinger in 1845. Essentiallyiron diarsenide, FeAs2, but passing into FesAs4 (leucopyrite) Lb'llingite. ; also tending toward arsenopyrite (FeAsS) and safflorite (CoAs2). Bismuth and antimony T'0-7'4 sometimes H. G. 5-5*5. are chiefly,also 6*8. present. Usually masswe. Luster Color silver-white and metallic. between steel-gray. Streak grayish black. also sparinglyin a number Found Occurs in the Lolling-Huttenberg district in Carinthia. "

"

=

=

of other districts. GEYERITE

is near

ARSENOPYRITE, Orthorhombic.

but contains sulphur; from Geyer, Saxony. lollingite, or

MISPICKEL.

Axes

a

:

b

: c

mm'", uu', nnf,

=

0'6773

110

A

110

101

A

014

A

101 014

012

A

012

Oil

A

Oil

: =

=

=

=

1

:

1-1882.

68" 120" 33" 61" 99"

13'. 38'. 5'. 26'. 50'.

665

Twins:

pi.ra(110),sometimes repeated like marcasite (Figs.667 and 437, p. 109); e(101) cruciform twins,also trillings (Figs.432, 433, p. 169). tion combinaCrystals prismaticm(110) or flattened vertically by the oscillatory of brachydomes. Also columnar, straight, and divergent;granular,or tw.

compact.

Cleavage: ra(110) rather uneven.

Comp.

faint traces. Fracture metallic. Color silver-white to steel-gray.Streak dark grayishblack. inclining Opaque. Arsenic 46 '0,sulSulpharsenideof iron,FeAsS or FeS2.FeAs2

Brittle.

"

H.

=

5*5-6.

distinct;c(001) G.

=

5'9-6'2.

in

Luster

=

382

MINERALOGY

DESCRIPTIVE

Part of the iron is sometimes 100. phur 197, iron 34 -3 danaite in the variety as (3 to 9 p. c. Co). =

replacedby cobalt,

In the closed tube may give at firsta littleyellowsulphide of arsenic and Pyr.,etc. the then a conspicuoussublimate of metallic arsenic which is of bright gray crystalsnear In the open tube gives heated end and of a brilliantblack amorphous depositfarther away. sulphurousfumes and a white sublimate of arsenic trioxide. B.B. on charcoal givesarsenical fumes and a magnetic globule. Decomposed by nitric acid with the separationof sulphur. of Diff. Characterized by its hardness and "tin-whitecolor; closelyresembles some in most the sulphidesand arsenides of cobalt and nickel,but identified, cases easily,by its blowpipe characters. Lollingitedoes not give a decided sulphur reaction. white color with scratched and dull surface. In polished sections shows Micro. a darkens quickly through iridescent colors to brown, showing rough surface. With HNO3 in crystalline Found Obs. rocks,its usual mineral associates being ores of principally and sphalerite. Abundant at Freiberg,etc., silver,lead,and tin,also pyrite,chalcopyrite, "

"

"

"

in

Saxony;

at

Andreasberg, Harz

Mts., Germany;

Sala,Sweden; Skutterud,Norway;

at

in the Binnental,Switzerland. In crystals several pointsin Cornwall. Crystalsof danaite from Sulitjelma, Finland. In the United States,in N. H., in gneiss,at Franconia (danaite). In Conn., at Mine Hill,Roxbury, with siderite. In crystalsat Canton, Ga.; Leadville,Col. In twin crystals in quartz ore veins at Deloro,Hastings Co., Ontario. The name term of doubtful origin. Danaite is from J. Freeman mispickelis an old German Dana of Boston (1793-1827),who made known the Franconia locality. Use. An ore of arsenic. "

Safflorite. Like

Form CoAs2. that of smaltite,essentiallycobalt diarsenide, near H. 4'5-5. G. Color tin-white, 6'9-7*3. arsenopyrite. Usually massive. nishing. tarsoon From Germany at Schneeberg, Saxony; Bieber, Hesse; Wittichen, Baden; from Tunaberg, Sweden. Rammelsbergite. Essentially nickel diarsenide,NiAs2, like chloanthite. Crystals G. 6'9-7'2. Color tin-white with tinge of red. resemblingarsenopyrite;also massive. Occurs at Schneeberg,Saxony, and at Riechelsdorf, Hesse, Germany. Glaucodot. Sulpharsenide of cobalt and iron, (Co,Fe)AsS. In orthorhombic crystals H. 5. (axes,etc., p. 376). Also massive. G. Luster metallic. $-90-6'01. Color grayish tin-white. Occurs in the province of Huasco, Chile; at Hakansbo, Sweden. Named from yXavnos, blue,because used for making smalt. ALLOCLASITE. Probably glaucodot containing bismuth and other impurities. Commonly in columnar to hemispherical aggregates. H. 4'5. G. =6'6. Color steel-gray. From Orawitza,Hungary. Wolfachite. Probably Ni(As,Sb)S,near corynite. In small crystalsresemblingarsenopyrite; =

=

=

=

=

=

also columnar H. radiated. From Wolfach,Baden, Germany. =

white.

4 '5-5.

G.

=

6 "372.

Color

silver-white to tin-

Melonite. A nickel telluride, In indistinct granular and foliated particles. NiTe2. reddish white,with metallic luster. From the Stanislaus mine, Cal.; probably also Boulder Co.,Col. Found at Worturpa, New South Wales.

Color m

The

following speciesare

SYLVANITE.

tellurides of

etc. gold,silver,

Graphic Tellurium.

Monoclinic.

a : b : c 1-6339 : 1 : M265; 0 89" 35'. Often in branching arborescent forms resemblingwritten characters;also bladed and imperiectly columnar to granular. =

=

_

Cleavage: 6(010) perfect. 7 '9-8 -3.

Fracture

Brittle.

uneven.

H.

1-5-2.

=

Luster

brilliant. Color and streak pure steel-erav metallic, to silver-white, to yellow. inclining Comp. Telluride of gold and silver (Au,Ag)Te2 with Au : 1 : 1: Ag this requires: Tellurium 62-1,gold 24-5,silver 134 100. ~

~'

"

=

=

,Pyr*' ej?-

When a littleof the powdered mineral is heated in concentrated sulphuric violet color is given to the solution. When treated with nitric acid is decom1 leavingresidue of rusty colored gold. A few drops of hydrochloric acid added to this ~

.

da

reddish

384

MINERALOGY

DESCRIPTIVE

H3AsS3, etc.,and the meta-acids,H2AsS2, etc.; but H4As2S5,etc.,and a series The metals present as bases are chiefly included. are copper, silver, in small amount. lead; also zinc,mercury, iron,rarelyothers (asnickel,cobalt} of others

of the acids whose salts are here hypotheticalcharacter of many there is a certain advantage,for the sake of comparison,in writi ig represented, the compositionafter the dualistic method, RS.As2S3,2RS.As2S3,etc. As a largepart of the specieshere included are rare and hence to be mentioned but briefly, the classification can be only partially developed. The divisions under the first and more important section of sulpharsenites, etc., with the prominent speciesunder each,are as follows: In view of the

A.

Acidic

B.

MetaDivision. General formula:

Division.

RS

:

RS

(As,Sb,Bi)2S3 =

.

Miargyrite C.

Intermediate

:

3, 1

:

2, 2

:

(As,Sb,Bi)2S3 1:1. RAs2S4,RSb2S4,RBi2S4. :

3, 3

:

4, 4

:

5.

=

Zinkenite

Zinkenite Sartorite Also

1

;

:

Group

PbS.Sb2S3 PbS.As2S3

Emplectite

CuoS.Bi2S3

Chalcostibite

Cu2S.Sb2S3,etc.

Ag2S.Sb2S3

Lorandite

Tl2S.As2S3

Division.

RS

:

(As,Sb,Bi)2S3 =

5

:

4, 3

:

2, 2

:

1, 5

2

:

Here

belong Plagionite

5PbS.4Sb2S3.

Schirmerite

3(Ag2,Pb)S.2Bi2S3 Jamesonite

Klaprotholite 3Cu2S.2Bi2S3, etc.

Group

Jamesonite Dufrenoysite

2PbS.Sb2S3 2PbS.As2S3

Also Freieslebenite

5(Ag2,Pb)S.2Sb2S3 Boulangerite 5PbS.2Sb2S3

D.

Ortho-

Division.

General

RS

formula:

Cosalite

:

(As,Sb,Bi)2S3 =3:1

R3AsS3,R3SbS3;R3As2S6,R3Sb2S6, etc. Bournonite

Bournonite

Seligmannite Aikmite

2PbS.Bi2S3,etc.

3(Cu2,Pb)S.Sb2S3 3(Cu2,Pb)S.As2S3 3(Pb,Cu2)S.Bi2S3

Group Wittichenite

3Cu2S.Bi2S3

LiUianite

etc. 3PbS.Bi2S3,

Pyrargyrite Group Pyrargyrite E.

Basic

Division.

3Ag2S.Sb2S3 RS

:

(As,Sb,Bi)2S34

Tetrahedrite Tetrahedrite

Proustite

4Cu2S.Sb2S3

=

:

1, 5

Group Tennantite

3Ag2S.As2S3 :

1, 6

:

1, 9

:

1, 12

:

1

385

SULPHO-SALTS

Jordanite

Jordanite

4PbS.As2S3

Also Geocronite Kilbrickenite

Group Meneghinite

4PbS.Sb2S3

5PbS.Sb2S3

Stephanite

5Ag2S.Sb2S3

6PbS.Sb2S3

Beegerite

6PbS.Bi2S3

Polybasite Group Pearceite

Polybasite

9Ag2S.Sb2S3

Polyargyrite

12Ag2S.Sb2S3

A.

Acidic

Division

Color iron-gray. H. " 6. G. Eichbergite. (Cu,Fe)2S.3(Bi,Sb)2S8. 5*36. From Austria. Eichberg, Semmering district, stibnite in form. Color Livingstonite. HgS.2Sb2S3. Resembles lead-gray;streak H. =2. red. From 4'81. G. Huitzuco, Mexico. In radiatinggroups Histrixite. 5CuFeS2.2Sb2S3.7Bi2S3. Orthorhombic. of prismatic Color and streak steel-gray. Found 2. Tasmania. at Ringville, crystals. H. Chiviatite. 2PbS.3Bi2S3. Foliated massive. Color lead-gray. From Chiviato,Peru. bismuthCuprobismutite. Probably 3Cu2S.4Bi2S3,in part argentiferous. Resembles From inite. G. 6*3-67. Hall valley, Park Co., Col. Color lead-gray. G. 6' 1-6*4. Rezbanyite. 4PbS.5Bi2S3. Fine-granular,massive. From Rezbanya, Hungary. =

=

=

=

=

B.

Meta-

Division.

Zinkenite

RS.As2S3,RS.Sb2S3,etc.

Group.

Orthorhombic

Zinckenite.

ZINKENITE.

Axes a : b : c 0'5575 : 1 : 0*6353. Orthorhombic. tinct Crystalsseldom disin nearlyhexagonalforms through twinning. Lateral faces ; sometimes striated. Also columnar, fibrous, massive. longitudinally H. 3-3*5. G. Cleavage not distinct. Fracture slightlyuneven. Luster metallic. 5*30-5*35Color and streak steel-gray.Opaque. PbSb2S4 or PbS.Sb2S3 Sulphur 22*3, antimony 41*8, lead Comp. Arsenic sometimes replaces 35*9 100. part of the antimony. =

=

=

=

"

.

=

mate Decrepitatesand fuses very easily;in the closed tube gives a faint subliPyr., etc. of sulphur, and antimony trisulphide. In the open tube sulphurous fumes and a white sublimate of oxide of antimony; the arsenical varietygivesalso arsenical fumes. On charcoal is almost entirelyvolatilized, giving a coating which on the outer edge is white, and near the assay dark yellow; with soda in R.F. yieldsglobulesof lead. Soluble in hot hydrochloricacid with evolution of hydrogen sulphide and separationof lead chloride on cooling. Obs. Occurs at Wolfsberg in the Harz Mts.; Kinzigtal,Baden; Val Sugana,Tyrol; Oruro, Bolivia; Sevier County, Ark.; San Juan Co., Col. Andorite. 3-3'5. prismatic, Orthorhombic crystals. H. Ag2S.2PbS.3Sb2S3. In From black. to G. 5*5. Color dark gray Felsobanya, Hungary; Oruro, Bolivia. "

"

=

=

Webnerite

and Sundtite

are

identical with andorite.

G. 5'4. Color dark lead-gray. Occurs in the dolomite of the Binnental. Basal and rhombohedral cleavages. H. Platynite. PbS.Bi2Se3. Rhombohedral. 7'98. Color like graphite. Streak shining. In small lamellae in quartz at 2-3. G. Falun,Sweden. Sartorite.

PbS.

As2S3. In slender,striated crystals,probably monoclinic.

=

=

=

386

MINERALOGY

DESCRIPTIVE

6'3-6'5. Color grayishwhite prisms. G. Schwarzenberg and Annaberg, Saxony. In small Chalcostibite. Wolfsbergite. Cu2S.Sb2S3. aggregated prisms; also fine 475-5 '0. Color between G. lead-grayand iron-gray. From Wolfsgranular,massive. Guejaritefrom Spain is the same species. berg in the Harz Mts.; from Huanchaca, Bolivia. to compact. also with Galenobismutite. Ag,Cu. Crystallinecolumnar PbS.Bi2S3; From b'9. Color lead-grayto tin-white. G. Nordmark, Sweden; Poughkeepsie Gulch, Col. (alaskaite, argentiferous) ; material from Falun, Sweden, containingselenium has been weibulliteand given the formula, 2PbS.Bi4S3Se3. named 4'0. Color dark Berthierite. steelFeS.Sb2S3. Fibrous massive, granular. G. From Chazelles and Martouret, Auvergne, France; Charbes, Val de Ville,Alsace; gray. Braunsdorf,Saxony, etc. Matildite. 6-9. Color Ag2S.Bi2S3. In slender, prismatic crystals. G. gray. From Morochoca, Peru; Lake] City, Col. PLENARGYRITE, from Schapbach, Baden, similar in composition,has been shown to be a mixture. In thin striated

Emplectite. Cu2S.Bi2S3. Occurs

to tin-white.

=

in quartz at

=

=

=

=

In complex monoclinic also massive. H. 2-2-5. crystals, metallic-adamantine. Color iron-black to steel-gray, in thin splinters deep blood-red. Streak cherry-red. From Braunsdorf, Saxony; Felsobanya and Nagybanya, Hungary; Pfibram,Bohemia; Zacatecas,Mexico; Bolivia.

Miargyrite. Ag2S.Sb2S3.

G.

=

Luster

5'1-5'30.

=

Smithite.

Ag2S.Sb2S3. Monoclinic. Crystals resemble a flattened hexagonal pyramid. One perfectcleavage. H. 4'9. Color lightred changing to orangeT5^2. G. to light. Streak vermilion. From the Binnental,Switzerland. exposure =

red

on

=

Trechmanite. Ag2S.As2S3. Rhombohedral, tetartohedral. Crystalsminute with prismatic habit. Good rhombohedral T5-2. Color and streak scarletcleavage. H. the Binnental,Switzerland. From vermilion. =

Lorandite.

A sulpharsenideof thallium,TlAsS2. Monoclinic. Allchar,Macedonia; Rambler mine, Encampment, Wy.

From

Color

cochineal-red.

Vrbaite. H. TlAs2SbS5. Orthorhombic. 3'5. G. 5'3. Color dark red in thin splinters.Streak lightred. From Macedonia. Allchar, =

Hutchinsonite.

gray-black

=

to

Orthorhombic. (Tl,Ag,Cu)2S.As2S3+PbS.As2S3(?).

prisms. Cleavage o(100) good. the Binnental,Switzerland.

C.

H.

=

G.

1-5-2.

Intermediate

=

4'6.

In flattened rhombic Color scarlet to red. From

Division

Baumhauerite.

In complex crystalswith varied habit 4PbS.3As2S3. Monoclinic. perfectcleavage. H. 3. G. 3 -3. Metallic. Color lead to steel-gray. From

One the

=

=

Switzerland. Binnental,

Schirmerite. 3(Ag2,Pb)S.2Bi2S3. Massive,granular. Treasurylode,Park Co.,Col.

G.

=

674.

Color

lead-gray.

KLAPROTHOLITE. 3Cu2S.Bi2S3. In furrowed prismatic crystals. G. 4'6. Color steel-gray.Wittichen, Baden. Probably a mixture and not a definite species. Rathite. 3PbS.2As2S3. Orthorhombic, in prismatic crystals. Cleavage, 6(010). H. 3. G. 5'41. From the Binnental, Switzerland. Wiltshireite is the same species. =

=

=

Jamesonite Group.

2RS.As2S3,2RS.Sb2S3,etc.

Monoclinic

JAMESONITE.

Monoclinic.

QAxes:

b

0'8316

1

0-4260.

88" 36'. mm'" 0 in capillary crystals;common forms; also fibrous massive,parallel or divergent; compact massive. Cleavage: basal, perfect. Fracture uneven to conchoidal. Brittle. 2-3G. 5-5-6-0. Luster metallic. Color steel-grayto dark leadStreak grayish black. gray. Opaque. 110

A

110

=

:

: c

=

:

:

=

In acicular

=

-

Comp.

a

79" 28'.

"

Pb2Sb2S5or

2PbS.Sb2S3

=

Sulphur 197, antimony 29'5, lead

387

SULPHO-SALTS

50-8 also

100.

=

Most

silver, copper,

varieties show and

a

littleiron

(1 to

3 p.

c.),and

contain

some

zinc.

It has been suggested that the iron shown by the analysesis an integral part of the mineral and that the formula should be 4PbS.FeS.3Sb2S3 and that the usual jamesoniteformula, 2PbS.Sb2S3,belongs to the material commonly called plumosite. Same as for zinkenite, Pyr. p. 385. in Cornwall; also in Siberia;Hungary; at Valentia d*AlObs. Occurs principally cantara in Spain; at the antimony mines in Sevier Co.,Ark.; from Bolivia. Named after "

"

Prof. Robert

Jameson

of

Edinburgh (1774-1854).

The featherore occurs at Wolfsberg,etc.,in the Harz Mts.; Freiberg,Germany; Schemnitz,Hungary; in Tuscany, near Bottino,Italy. These so-called feather ores may be divided into flexibleand brittle, all the latter being referred to jamesonite and the former to either zinkenite, plumosite,boulangerite,or meneghinite. Warrenite has been shown to probably be a mixture of jamesonite and zinkenite.

Dufrenoysite. 2PbS.As2S3. In highly modified crystals;also massive. Cleavage5'55-5'57. Color blackish lead-gray.From G. 6(010) perfect. H. =3. the Binin dolomite. nental,Switzerland, Cosalite. 2PbS.Bi2S3. Usually massive, fibrous or radiated. G. 6'39-675. Color lead- or steel-gray.Cosala, Province of Sinaloa,Mexico; Bjelke mine (bjelkite), Nordmark, Sweden; Deer Park, Wash.; Col. =

=

Kobellite.

G. 6'3. 2PbS.(Bi,Sb)2S3. Fibrous radiated or granular massive. Color Hvena, Sweden; Ouray, Col. BRONGNIARDITE. in some Lead, silver, antimony sulphide. Shown cases to be a mixture. A doubtful species. Plagionite. Heteromorphite. Semseyite. Lead, antimony sulphides ranging from 5PbS4.Sb2S3 to 9PbS.4Sb2S3. Perhaps a morphotropic series with the vertical crystallographic axis increasingin length with increase in the percentage of lead. Monoclinio. G. 5'4-5'9. Plagionite from Wolfsberg, Harz Mts.; heteromorphitefrom Arnsberg, Westphalia; semseyite from Felsobanya, Hungary and Wolfsberg. Liveingitefrom the Switzerland,is said to have the same composition as plagionite. BismutoBinnental, From Wickes, Jefferson a plagionite, variety containing bismuth instead of antimony. Co., Mon. A lead, SCHAPBACHITE. bismuth sulphide. From Shown silver, to Schapbach,Baden. =

lead-grayto steel-gray. From

=

be

mixture.

a

FREIESLEBENITE.

Monoclinic. 87" 46'. Habit Axes a : b : c 0-5871 : 1 : 0-9277; ft Luster 6-2-6-4. metallic. Color and streak lightsteelprismatic. G. to silver-white, also to blackish lead-gray. gray inclining or Comp. (Pb,Ag2)5Sb4Sii 5(Pb,Ag2)S.2Sb2S3. =

=

=

"

Freiberg,Saxony; Kapnik and Felsobanya, Hungary; Hiendelencina, Spain; also from the Augusta Mt., Gunnison Co., Col. in form. G. 5'9. Diaphorite. Like freieslebenite in composition but orthorhombic From Wash. Pfibram,Bohemia; Lake Chelan district, Obs.

"

From

=

BOULANGERITE.

In prismaticor tabular : 0*7478. H. 2*5-3. compact. granular, masses; G. 6-18. Luster metallic. Color bluish lead-gray; often covered with yellow spots from oxidation. Opaque. Pb5Sb4Sn or 5PbS.2Sh"S3 Sulphur 18'9, antimony 25*7,lead Comp.

Orthorhombic.

Axes

a

:

b

: c

=

0*5527

:

1

plumose crystalsor crystalline

=

=

=

"

55-4

100.

=

Same

as for zinkenite, p. 385. good crystalsfrom Sala,Sweden; Molieres,Depart, du Gard, France; at cany, Nerchinsk, Siberia;Wolfsberg in the Harz Mts. Pfibram,Bohemia; near Bottino,TusUnion county, Nev. Italy. Echo District, Embrithite and plumbostibare from Nerchinsk; they correspond nearlyto 10PbS.3Sb2Sj,

Pyr. Obs.

"

"

In

but the material

analyzedmay

not have

been

quitepure.

MINERALOGY

DESCRIPTIVE

388

(?)prisms. Cleavage, c(001) and

In slender orthorhombic

5PbS.2Sb2S3.

Mullanite.

H. black 6(010). Color, steel-gray. Streak, brownish Mullan, Idaho, and at Iron Mountain Gold Hunter mine, near

3'5.

=

Ortho-

D.

Division.

Wheel

BOURNONITE. mm"'

110

co,

001

Found

at

Superior,Mon.

Prismatic

angle 86"

to 87"

Ore.

Axes:

Orthorhombic.

6'35.

=

near

3RS.As2S3,3RS.Sb2S3,etc.

Orthorhombic.

Group.

Bournonite

G

mine,

a

A

110

=

A

101

=

:

b

: c

=

1

0-9380

:

0-8969.

en, 001 cu, 001

86" 20' 43C 43'

A

Oil

=

A

112

=

41" 53' 33" 15'

Twins: tw. pi. ra(110), often repeated, forming cruciform and wheel shaped crystals.Also massive;

669

granular,compact. fect; Cleavage: 6(010)impera(100), c(001) less Fracture subdistinct. conchoidal to uneven. 2-5-3. Rather brittle. H. Kapnik 5-7-5-9. LustermetalG. leadstreak steel-gray,incliningto blackish =

Harz

=

lie,brilliant. Color Comp. =

and

iron-black.

or

gray

2:1)

Opaque. (Pb,Cu2)3Sb2S6or 3(Pb,Cu2)S.Sb2S3 PbCuSbS3 Sulphur 19'8,antimony 247, lead 42*5, copper 13*0

(ifPb

=

"

=

=

:

Cu2

100.

In the In the closed tube decrepitates, and gives a dark red sublimate. Pyr., etc. B.B. on charcoal tube givessulphurdioxide,and a white sublimate of oxide of antimony. and at firstcoats the coal white; continued blowing givesa yellow coating fuses easily, posed Decomof lead oxide; the residue,treated with soda in R.F., gives a globule of copper. and leavinga residue of sulphur,and a white by nitric acid,affordinga blue solution, powder containingantimony and lead. From Neudorf in the Harz Mts.; also Wolfsberg, Claustal, and Andreasberg; Obs. Pfibram, Bohemia; Kapnik and Nagybanya, Hungary; Horhausen, Prussia; Liskeard, "

open

"

Cornwall. In the United States at the Boggs mine, Yavapai Co., Ariz.; also Montgomery Co.,Ark.; reportedfrom San Juan Co., Col; Austin, Ney. In Canada, in the township of Marmora, Hastings Co., and Darling,Lanark Co., Ontario. Orthorhombic. : b : c a Seligmannite. (Pb,Cu2)3As2S6isomorphous with bournonite. In small complex crystals. Commonly 0*9233 : 1 : 0'8734. twinned with m(110) as H. tw. pi. Color lead-gray. Chocolate streak. 3. Found at Lengenbach quarry, Binnental,Switzerland;reportedfrom Emery, Mon. Aikinite. Acicular crystals; also massive. 2PbS.Cu2S.Bi2S3. G. Color 6'l-6'8. blackish lead-gray. From Berezov near Ekaterinburg,Ural Mts. Wittichenite. 3Cu2S.Bi2S3. Rarely in crystalsresembling bournonite; also massive. Color steel-gray 4*5. G. tin-white. or Wittichen,Baden, etc. in cruciform twins like Stylotypite.3(Cu2,Ag2,Fe)S.Sb2S3. In orthorhombic crystals, bournonite. G. Color iron-black. 47-5'2. Copiapo, Chile; Peru. =

=

=

=

=

Lfflianite. 3PbS.BiSbS3 and Color steel-gray.Gladhammar, Guitermanite.

3PbS.Bi2S3.

Orthorhombic.

Crystallineand

Col. (argentiferous). Sweden; Leadville, Perhaps 3PbS.As2S3. Massive, compact. G. 5-94. =

Zufii

massive.

Color

bluish

Col. mine, Silvertqn, Lengenbachite. 7[Pb,(Ag,Cu)2]S.2As2S3.Probably triclinic. In thin blade-shaped crystals. One 5*8. perfect cleavage. Soft. G. Color black. steel-gray.Streak From the Lengenbach quarry, Binnental, Switzerland. gray.

=

389

SULPHO-SALTS

of bismuth A sulpho-telluride and silver, TAPALPITE. perhaps 3Ag2(S,Te).Bii(S,Te)8. of polishedspecimen shows it to be a mixture of unknown components. Massive, 7 '80. Sierra de Tapalpa, Jalisco, Mexico. granular. G.

Study

=

Rhombohedral-hemimorphic

Pyrargyrite Group. Ruby Silver Ore.

PYRARGYRITE.

Dark

Rhombohedral-hemimorphic. ee',0112 rrf,1011

1012 1101

A A

42"

=

Red

Axis:

c

=

5'

07892; tw',2131

71" 22'

=

Silver Ore.

yyv, 2131

Crystals commonly prismatic. tw. Twins: mon, pi. a(1120), very comthe c axes parallel; also common. Also massive,compact. Cleavage: r(1011)distinct; e(0112) conchoidal to imperfect. Fracture =

A

2311

=

3121

=

1011

42"20J.'

=

74" 25'

35" 12'

670

Brittle. H. 2-5. G. 577Luster metallic5*86; 5-85 if pure. adamantine. Color black to grayish black, by transmitted lightdeep red. Streak purplishred. Nearly opaque, but transparent in very thin splinters. Refractive indices, co Optically 3'084,e uneven.

0001 A A

671

=

'"cd^r=J'

=

-

=

2-881.

.

Comp. 59'9

Ag3SbS3

"

Some

100.

=

or

3Ag2S.Sb?S3 Sulphur =

17'8,antimony 22'3,silver

varieties contain small amounts

of arsenic.

gives a reddish sublimate of antimony oxysultube sulphurous fumes and a white sublimate of oxide of antimony. B.B. on charcoal fuses with spirtingto a globule,coats the coal white, and the assay is into silver sulphide,which, treated in O.F., or with soda in R.F.. gives a globule conyerted of silver. In case arsenic is present it may be detected by fusing the pulverized mineral with soda on charcoal in R.F. Decomposed by nitric acid with the separationof sulphur and of antimony trioxide. Occurs at Andreasberg in the Harz Obs. Mts.; Freiberg, Saxony; Pfibram and and Nagybanya, Hungary; Kongsberg, Norway; Joachimstal, Bohemia; Schemnitz In Mexico it is worked at Guanajuato and elsewhere as Gaudalcanal, Spain; in Cornwall. of silver. In Chile with proustiteat Chanarcillo near an ore Copiapo. thus in Ruby district, Gunnison In Col., not uncommon; Co.; with sphaleritein in Daney Sneffle's district, Mine; about Austin, Ouray Co., etc. In Nev., at Washoe In N. M., Utah, and with cerargyrite. Reese river; at Poorman lode,Idaho, in masses Ariz, with silver ores at various points. At Cobalt, Ontario. in allusion to the color. and apyvpos, Named from wvp, fire, silver, In the closed tube fuses and

Pyr.,etc. phide; in the "

open

"

Ruby

PROUSTITE.

Silver Ore.

Rhombuhedral-hemimorphic. ee',0112 rr',1011

A

1012

A

1101

=

=

Silver Ore.

Light Red Axis

c

=

1011

0001 _A 0'8039;_

42" 46'

w', 2131

72" 12'

Wv, 2131

A A

2311 3121

=

42" 52'.

74" 39'

=

=

35" 18'

Twins: scalenohedral. rhombohedral tw. pi. or Also and massive, compact. r(10HX w(1014) conchoidal Brittle. to uneven. Cleavage: r(1011) distinct. Fracture admantine. Color scarletLuster H. 2-2-5. G. 5-57-5*64;5'57ifpure.

Crystals often

=

acute

=

lucent. vermilion;streak same, also inclined to aurora-red. Transparent to trans3'084. 2-881. e Opticallynegative, co AgsAsSa or 3Ag2S.As2S3 Sulphur 19'4, arsenic 15'2, silver Comp. =

65*4

=

=

=

"

100.

In the closed tube fuses easily,and gives a faint sublimate of arsenic triPyr., etc. sublimate of arsenic sulphide; in the open tube sulphurous fumes and a white crystalline "

390

MINERALOGY

DESCRIPTIVE

charcoal fuses and emits odors of sulphur and arsenic;with soda in on of silver. Decomposed by nitric acid,with separationof sulphur. globule gives mia; BoheOccurs at Freiberg,Johanngeorgenstadt, etc.,in Saxony; Joachimstal, Obs. in Spain; in Dauphine and Markirch, Alsace; Guadalcanal at Chalanches in France Sarrabus,Sardinia; in Mexico; Peru; Chile,at Chanarcillo in magnificentcrystallizations. Girl In Col.,Ruby Co.; Sheridan mine, San Miguel Co.; Yankee distr.,Gunnison at various points. In Ariz.,with silver ores Co. Summit mine, Ouray Co.; Montezuma, lode. In Nev., in the Daney mine, and in Comstock lode,rare; Idaho, at the Poorman after the French chemist, J. L. Proust (1755-1826). Named scales,hexagonal or rhomSanguinite. Near proustitein composition. In glittering From bohedral. Chanarcillo,Chile. tal, FALKENHAYNITE. Perhaps 3Cu2S.Sb2S3. Massive, resembling galena. From JoachimsBohemia. Perhaps identical with stylotypite. Pyrostilpnite.Like pyrargyrite,3Ag2S.Sb2S3. In tufts of slender (monoclinic)crystals. 4'25. Color hyacinth-red. From Andreasberg in the Harz Mts.; Freiberg, G. Saxony; Pribram, Bohemia; Heazlewood, Tasmania. Habit prismatic. Color,steel-black, red Samsonite. 2Ag2S.MnS.Sb2S3. Monoclinic. vein of Andreasberg silver mines, Harz in -transmitted light. Occurs in Samson Mts., Germany. B.B.

trioxide.

R.F.

a

"

=

*

E. Tetrahedrite

Division

Basic

Isometric-tetrahedral

Group.

TETRAHEDRITE.

Fahlerz. Gray Copper Ore. Habit Isometric-tetrahedral. tetrahedral.

with

Twins: tw. pi..0(111);also (Fig.392, p. 163, Fig.408, p. 166). Also massive; granular,

axes parallel

coarse

fine;compact.

or

672

674

673

Cleavage

Fracture subconchoidal none. to uneven. Rather brittle. 4-4-5'L G. Luster metallic,often splendent. Color between and iron-black. Streak like color,sometimes flint-gray incliningto brown and cherry-red. Opaque; sometimes subtranslucent (cherry-red) in very thin H-

3-4.

=

=

splinters. Comp.

EssentiallyCu8Sb2S7

"

24-8,copper Antimony

52'1

and arsenic

are

4Cu2S.Sb2S3

or

=

mony Sulphur 23-1, anti-

100.

=

usuallyboth present

and

thus tetrahedrite graduates into the

allied species tennantite. There are also varieties containingbismuth, chieflyat the arsenical end of the series, rarelyselenium. Further the copper be replaced by iron,zinc, may silver,mercury, lead,manganese, and rarelycobalt and nickel.

\ar. "

.

iron-black.

Ordinary. G.

=

Contains

little or

Argentiferous; Freibergite.Contains ,r.

no

silver.

3 to 30 p.

the ordinaryvarieties; sometimes r.teJ^han

4 oo-o'O. '

Color

steel-grayto dark

gray

and

4 '75-4*9. c.

of silver.

Color usually steel-gray, often reddish. G.

streak iron-black;

=

392

MINERALOGY

DESCRIPTIVE

Brittle Silver Ore.

STEPHANITE.

Axes

Orthorhombic. mm"'

110

c8,

001 001

ck,

a

:

A

110

=

A A

101

=

Oil

=

b

: c

=

0*6292

:

1

:

cd, ch, cP,

64" 21' 47" 26' 34" 25'

0'6851. 001

A

021

=

53" 52'

001

A

112

=

32" 45'

001

A

111

=

52"

9'

Crystalsusuallyshort prismaticor tabular ||c(001).

675

Twins: tw. pi.w(110),often repeated,pseudo-hexagonal. Also massive,compact and disseminated. Cleavage: 6(010),d(021) imperfect. Fracture subBrittle. H. 2-2'5. conchoidal to uneven. G. 6'2 Color and metallic. Luster streak iron-black. -6*3. =

Comp. 68'5

Ag5SbS4

"

Opaque. or 5Ag2S.Sb2S3 =

=

Sulphur 16*3, antimony 15'2, silver

100.

=

.

In the closed tube decrepitates, fuses,and after long heating gives a faint tube fuses,giving off antimonial of antimony oxysulphide. In the open and B.B. on charcoal fuses with projectionof small particles, coats the coal sulphurous fumes. with oxide of antimony, which after long blowing is colored red from oxidized silver, and Soluble in dilute heated nitric acid,sulphur and a globule of metallic silver is obtained. antimony trioxide being deposited. Obs. In veins,with other silver ores, at Freiberg,Schneeberg,etc.,in Saxony; Pribram, Bohemia; Schemnitz, Hungary; Andreasberg in the Harz Mts., Germany; KongsSonora and elsewhere, berg,Norway; Sarrabus,Sardinia; Wheal Newton, Cornwall; Arispe, Mexico; Peru; Chanarcillo,Chile. In Nev., in the Comstock lode,Reese" river,etc. In Idaho,at the silver mines at Yankee Fork, Queen's River district. Named after the Archduke Stephen, Mining Director of Austria.

Pyr.

"

sublimate

"

Geocronite. 5PbS.Sb2S3. Rarely in orthorhombic crystalscloselyresemblingthose of stephanite; usually massive, granular. G. 6 '4. Color lead-gray. From Sala, Kilbrickenite from Kilbricken, Co. Clare,Ireland, is the Sweden; Val Castello, Tuscany. =

species.

same

'

Beegerite. 6PbS.Bi2S3. Massive, indistinctly crystallized. G. Park From Co., Col. gray.

=

7'27.

Color light

to dark

Ultrabasite. HAg2S.28PbS.2Sb2S3.3GeS2 Orthorhombic. black. H. 5. G. 6. From Freiberg,Germany. =

Color

and

streak

gray-

=

Polybasite Group.

9RS2As2S3,9RS.Sb2S3.

Monoclinic, pseudo-

rhombohedral POLYBASITE.

Monoclinic. Axes 17309 a : b : c : 1 : 1'5796,0 90" 0'. Prismatic 60" 2'. In short six-sided tabular angle prisms,with beveled edges; c(001) faces with triangular in part repeated twins,tw. pi.m (110). striations; Cleavage: c(001)imperfect. Fracture uneven. H. 2-3. G. 6'06'2. Luster metallic. Color iron-black, in thin splinters cherry-red. Streak black. Nearly opaque. =

=

=

Comp. 75-6

=

Ag9SbS6

"

100.

Part

or

9Ag2S.Sb2S3

=

=

Sulphur 15'0, antimony 9'4,silver

of the silver is replacedby copper;

also the antimony

by

arsenic. In the open tube fuses, Pry.,etc. givessulphurous and antimonial fumes, the latter forming a white sublimate, sometimes mixed with crystalline arsenic trioxide. B.B. fuses "

393

SULPHO-SALTS

with spirtingto a globule,gives off sulphurous (sometimes arsenical) fumes, and coats the varieties givea faint yellowcoal with antimony trioxide;with long-continuedblowing some ish white coating of zinc oxide,and a metallic globule,which with salt of phosphorus reacts for copper, and cupelledwith lead gives pure silver. Decomposed by nitric acid. Occurs in the mines of Guanajuato, from Las Chipas and Arispe, Sonora, Obs. Mexico; at Tres Puntos, desert of Atacama, Chile; At Freiberg,Saxony; and Pvibram, Lode. Bohemia; at Sarrabus,Sardinia. In Nev., at the Reese mines and at the Comstock In Col, at the Terrible Lode, Clear Creek Co., at Ouray. In Ariz.,at the Silver King "

mine;

Neihart, Mon.

at

from

Named

iro\vs,many,

base,in allusion to the basic character /3e*"ns,

and

of the

compound. 9Ag2S.As2S3. Monoclinic, pseudo-rhombohedral. The arsenical variety Aspen, Col.; Marysville,Lewis and Clarke Co., Mon.

Pearceite.

of polybasite. From

Polyargyrite. 12Ag2S.Sb2S3. In indistinct Wolfach, Baden, Germany.

isometric

crystals. G.

=

6'97.

Color

iron-black.

etc. Sulpharsenates,Sulphantimonates; Sulpho-stannates,

II. Here

included

are

antimony;

arsenic and

of quintivalent few minerals,chieflysulpho-salts a and rare also several sulpho-stannates sulpho-german-

ates. ENARGITE.

Orthorhombic.

Axes:

b

0*8711 : 1 : 0'8248. faces striated. Twins: tw. pi. vertically Crystalsusuallysmall; prismatic in A lso massive,granular,or columnar. star-shapedtrillings. #(320) Cleavage :m(l 10) perfect; a(100), 6(010) distinct;c(001) indistinct. 3. G. 4'43-^'45. Brittle. H. Luster metallic. Color Fracture uneven. iron-black. Streak black. to grayish Opaque. grayishblack Cu3AsS4 or 3Cu2S.As2S5 Sulphur 32'6, arsenic 19*1, copper Comp. 100. 48*3 Antimony is often present, cf. famatinite. a

:

: c

=

=

=

=

"

=

and gives a sublimate of sulphur; at a higher In the closed tube decrepitates, of sulphide of arsenic. In the open tube, heated gently,the powdered mineral givesoff sulphurous and arsenical fumes, the latter condensing antimony oxide. B.B. on charcoal fuses,and gives a to a sublimate containing some faint coating of the oxides of arsenic,antimony, and zinc; the roasted mineral with the Soluble in aqua regia. fluxes gives a globule of metallic copper. In polishedsections shows a white color with a smooth surface. With KCN Micro. with aqua regia. turns black quickly and surface is etched; quickly brown From Obs. Morococha, and Caudalosa, Peru; in Chile and Argentina; Mexico; Matzenkopfl, Brixlegg,Tyrol,Austria; Mancayan, island of Luzon; Kinkwaseki, Formosa. S. C. ; in Col.,at mines In the United States,at Brewer's gold mine, Chesterfield dist., Central City, Gilpi'n Co.; in Park Co., at the Missouri mine; from Red Mountain near district. In southern Utah; also in the Tintic district;Butte, Mon. from the Clara Mine, Schapback, Baden, and luzonite from the island of Luzon, Clarite, identical with enargite. are Philippines, Use. Serves as an ore of copper and arsenic.

Pyr.

"

temperature fuses,and givesa sublimate

"

"

"

4*57. Color gray with 3Cu2S.Sb2S5,isomorphous with enargite. G. the Sierra de Famatina, Argentina; Goldfield,Nev. tinge of copper-red. From H. 3'5. G. 4'0. Color bronze-yellow. Streak Sulvanite. 3Cu2S.V2S5. Massive. nearly black. From near Burra, South Australia. Famatinite.

.=

=

Xanthoconite.

reniform. same

G.

species.

=

"

5.

=

crystals;also massive, 3Ag2S.As2Ss. In thin tabular rhombohedral is the orange-yellow. From Freiberg,Germany. Rittingerite

Color

394

MINERALOGY

DESCRIPTIVE

prismatic needles and granular. G. Altenberg, Saxony, Germany. In short prisms resembling arsenopyrite. Epigenite. Perhaps 4Cu2S.3FeS.As2S5. Wittichen, Baden, Germany. Color steel-gray. From Epiboulangerite. 3PbS.Sb2S3. "

6-31.

dark

Color

bluish gray

In

black.

to

striated

=

From

"

Tin

STANNITE.

Pyrites. Bell-metal

Ore.

isometric-tetrahedral

Pseudo Tetragonal-sphenoidal.

through twinning.

with e(101)as tw. pi.,(2)interpenetrant Twinning, (1) always interpenetrant Also to massive,granular,and disseminated, ^.-i with twin axis J_ p(lll). Brittle. H. =4. Fracture G. uneven. Cleavage: cubic,indistinct. Streak blackish. metallic. Color Luster steel4 -3-4 -522; 4 -506 Zinnwald. sometimes a bluish tarnish; often to iron-black,the former when pure; gray yellowishfrom the presence of chalcopyrite. Opaque. iron and sometimes A zinc, sulpho-stannate of copper, Comp. =

"

Cu2FeSnS4

Cu2S.FeS.SnS2

or

=

Sulphur 29-9, tin 27-5, copper

29'5, iron

131

100.

=

and gives a faint sublimate; in the open In the closed tube decrepitates, Pyr.,etc. charcoal fuses to a globule,which in O.F. gives off sulB.B. on phur sulphurous fumes. dioxide and coats the coal with tin dioxide; the roasted mineral treated with borax Decomposed by nitric acid,affordinga blue solution, gives reactions for iron and copper. with separationof sulphur and tin dioxide. In Cornwall Obs. formerly found at Wheal Rock; and at Carn Brea; more recently in graniteat St. Michael's Mount; also at Stenna Gwynn, etc.; at the Cronebane mine, Co. Wicklow, in Ireland; Zinnwald, in the Erzgebirge, Germany. Crystallizedat Oruro, From Bolivia. the Black Hills,S. D. Argyrodite. A silver sulpho-germanate, Ag8GeS6 or 4Ag2S.GeS2. Isometric,crystals forms with frequent usually indistinct;at times they show octahedral and dodecahedral H. 2'5. G. 6 '085twinning according to the Spinel Law; also massive, compact. 6*266. Luster Color steel-grayon a fresh fracture, metallic. with a tinge of red turning to violet. From the Himmelsfurst mine, Freiberg, Saxony; from Colquechaca and Aullagas,Bolivia. "

tube

"

=

Canfieldite.

=

AggSnSe

or metric, Iso4Ag2S.SnS2,the tin in part replaced by germanium. with d(l10). Twins according to Spinel Law. G. 6 '28. Luster Color black. Colquechaca,Bolivia.

in octahedrons

metallic.

Teallite. H.

=

exact

PbSnS2.

G. 6-4. localityunknown. 1-2.

=

Orthorhombic? Color blackish

Pb5Sn3FeSb2S14

Franckeite.

blackish gray

=

black.

or

In gray.

3PbSnS2

thin flexible folia. Streak black.

+

Luster metallic. Color blackish lead-gray. In into distinct shells or folia. Poopo, Bolivia.

IV.

HALOIDS.

Pb2FeSb2S8.

Massive.

basal from

G.

=

cleavage. Boh' via,

5'55.

Color

Las

Animas, Bolivia. Cylindrite. Pb3Sn4FeSb2S14 or 3PbSnS2 to

Perfect

Probably

"

CHLORIDES,

+

SnFeSb2S8.

H.

=

2'5-3.

G.

forms separating under cylindrical

BROMIDES,

=

5'42.

pressure

IODIDES;

FLUORIDES I.

Anhydrous Chlorides,Bromides, Iodides; Fluorides. Oxy chloride s ; Oxyfluorides. m. Hydrous Chlorides; Hydrous Fluorides. The Fourth Class includes the haloids,that is,the compounds with the halogen elements,chlorine, bromine, iodine,and also the less closelyrelated II.

fluorine.

HALOIDS.

BROMIDES,

CHLORIDES,

"

IODIDES;

395

FLUORIDES

Anhydrous Chlorides, Bromides, Iodides; Fluorides

I.

Horn

CALOMEL.

Quicksilver.

59" 52'. Crystalssometimes c Tetragonal. 17234; 001 A 101 tabular ||c(001); also pyramidal; often highlycomplex. conchoidal. Cleavage: a (100) rather distinct;also r(lll). Fracture 6*482. Luster adamantine. 1-2. G. Sectile. H. Color white,yellowish also and brown. Streak or grayish, yellowish ash-gray, white, pale gray, Translucent subtranslucent. T970. yellowishwhite. Optically+. o" Axis

=

=

=

=

=

"

2-650.

=

e

Comp.

Mercurous

"

chloride, HgCl

=

Chlorine

15

-1,mercury

84 -9

=

100.

In the closed tube volatilizes without

fusion,condensing in the cold part of Pyr.,etc. B.B. on the tube as a white sublimate; with soda gives a sublimate of metallic mercury. Insoluble in water, but dissolved by aqua charcoal volatilizes, coating the coal white. regia; blackens when treated with alkalies. Obs. Thus at Moschellandsberg in the Palatinate, Usually associated with cinnabar. in Spain; at Mt. Avala near Germany; at Idria in Carniola,Austria; Almaden Belgrade In crystalswith many forms from Terlingua,Tex. in Servia. Calomel is an old term of uncertain originand meaning, perhaps from KO\OS, beautiful, and /zeXi, dulcis of early honey, the taste being sweet, and the compound the Mercurius chemistry; or from /caXos and /xeXas,black. "

"

A mercury Mercurammonite. ammonium chloride of uncertain composition. 3*5. G. 8'0. Color Crystals short prismatic. Basal cleavage. H. Volatile. From Terlingua,Tex. yellowto orange, darkening on exposure. Nantokite. H. Granular, massive. Cuprous chloride,CuCl. Cleavage cubic. Kleinite.

Hexagonal.

=

=

=

Luster adamantine. 3*93. G. Chile; Broken Hill,New South Wales. 2-2*5.

=

iodide, Cul. Color oil-brown..

G.=5'59.

2'5.

Halite

n

NaCl KC1

Halite

Sylvite Cerargyrite

Bromyrite lodobromite

Miersite

Nantoko,

dodecahedral. South Wales.

Isometric

Embolite

(NH4)C1 AgCl

Sal Ammoniac

grayish. From

=

RC1, RBr, RI.

Group.

or

Isometric- tetrahedral. Cleavage 2'346. Hill mines, New Broken

Cuprous

Marshite. H.

Colorless to white

=

Ag(Cl,Br) AgBr Ag(Cl,Br,I) Agl

related includes the halogencompounds of the closely GROUP also ammonium and silver, (NH4). They lize crystalpotassium, metals,sodium, common. in the isometric system, the cubic form being the most Sylvite and others. of the true the be same are and sal-ammoniac plagiohedral, may The

HALITE

COMMON

HALITE.

or

SALT.

ROCK

sometimes Isometric. Usuallyin cubes;crystals faces. Also massive, granular 676 to compact; less often columnar. ture Cleavage: cubic,perfect. Frac-

H.

=

conchoidal. G.

2-5.

crystals 2-135. Colorless

or

brittle.

Rather =

2-1-2-6; Luster

white

also

pure

vitreous.

yellowish,

Transparreddish,bluish,purplish.ent to translucent. Soluble; taste saline, n thermanous.

=

1-5442.

Highly dia-

or with distorted,

ous cavern-

396

MINERALOGY

DESCRIPTIVE

39 -4 Chlorine 60 -6, sodium 100. Sodium chloride,NaCl ride, calcium chloride, magnesium chlomixed with calcium sulphate, which render it liable to deliquesce. and sometimes magnesium sulphate, fused on the In the closed tube fuses,often with decrepitation;when Pyr., etc. the residue intense After ignition flame gives an the colors wire yellow. deep platinum Nitric acid solution gives precipitateof moistened test paper. alkaline reaction upon Dissolves readilyin three parts of water. addition of silver nitrate. silver chloride upon perfectcubic cleavage. softness, Diff. (taste), Distinguishedby its solubility in extensive but irregularbeds in rocks of various ages, salt occurs Common Obs. clay, sandstone, and calcite; associated with gypsum, polyhalite,anhydrite,carnallite, of the ocean and salt seas. also in solution forming salt springs' similarlyin the water by the gradual evaporation and ultimate drying up The depositsof salt have been formed Salt beds formed in this way are subsequently covered of enclosed bodies of salt water. and graduallyburied beneath the rock strata thus formed. by other sedimentary deposits

Comp. Commonly

=

=

-

"

"

"

than one hundred feet in thickness and from a few feet up to more salt strata range beneath the earth's surface. feet and more have been found at depths of two thousand The principalsalt mines of Europe are at Stassfurt, near Magdeburg, Saxony; Wieliczka,in Galicia;at Hall,in Tyrol,Austria; and along the range through Reichental in Bavaria, Hallein in Salzburg,Hallstadt,Ischl,and Ebensee, in Upper Austria,and Aussee and elsewhere; Transylvania; Wallachia,Galicia, in Styria; in Hungary, at Marmoros The

Upper Silesia;in southern and southeastern Russia; Vic and Dieuze in France; Valleyof Cardona and elsewhere in Spain; Bex in Switzerland;and Northwich in Cheshire, England. Salt also occurs, forming hills and covering extended plains, Lake Urumia, the near Caspian Sea, etc. In Algeria; in Abyssinia. In India in enormous depositsin the Salt Range of the Punjab. In China and Asiatic Russia; in South America, in Peru, and at Zipaquera and Nemocon, the former a large mine long explored in the Cordilleras of Colombia; clear salt is obtained from the Cerro de Sal,San Domingo. In the United States,salt has been found in largeamount in central and western N. Y. in this region,but rock salt is now Salt wells had long been worked known to exist over a large area from Ithaca at the head of Cayuga Lake, Tompkins Co., and Canandaigua Lake, Ontario Co., through LivingstonCo., also Genesee, Wyoming, and Erie Cos. The salt is found in beds with an average thickness of 75 feet,but sometimes much thicker (in and at varying depths from 1000 to 2000 feet and more; instance 325 feet), one the depth increases southward with the dip of the strata. The rocks belong to the Salina period of the Upper Silurian. Extensive depositsof salt occur in Mich., chiefly in Saginaw, Bay, Counties. Midland, Isabella,Detroit,Wayne, Manistee and Mason Salt has also been found near in Kan.; in La., extensive beds Cleveland,Ohio, associated with gypsum; in the southern portionof the state at and in the neighborhood of Petite Anse island. occur Salt has also been obtained from Nev., Utah, Ariz, and Cal. In Utah and Cal. salt is chieflyobtained by the evaporationof the waters of Great Salt Lake and the ocean. Brine springsare very numerous in the Middle and Western States. Vast lakes of salt and

exist in many The Great Salt Lake in Utah is 2000 square miles parts of the world. L. Gale found in this water 20 '196 per cent of sodium chloride. The Dead and and the waters of the former contain 20 to 26 parts of solid matter in Caspian seas are salt, 100 parts. Sodium chloride is the prominent salt present in the ocean. Use. The chief uses of salt are for culinaryand preservative Soda ash is purposes. also made from it,being employed in the manufacture of glass,soap, bleaching, preparation of other sodium compounds, etc. water

in area;

"

Villiaumite. NaF. Isometric. In small carmine colored grains. Soft. Refractive index 1'33. Found in nepheline-syenite from the Islands of Los.

G.

2'8.

=

=

Wot

Huantajayite. 20NaCl.AgCl. In cubic crystalsand as an sectile. Color white. From Huantajaya,Tarapaca, Chile.

incrustation.

H.

2.

=

SYLVITE.

Also in granular crystalline Isometric-plagiohedral. masses;

Cleavage:cubic,perfect. Fracture

compact.

Brittle. H. 2. G. 1-97-1-99. Luster vitreous. Colorless, bluish red from or white, yellowish inclusions. Soluble; taste resembling that of common salt, but bitter. n 1'490. Potassium Comp. KC1 Chlorine 47-6, potassium 52'4 chloride, 100. Sometimes contains sodium chloride. uneven.

=

=

=

"

=

=

HALOIDS.

CHLORIDES,

"

BROMIDES,

IODIDES;

397

FLUORIDES

B.B. in the platinum loop fuses,and gives a violet color to the outer Pyr.,etc. flame completely in water (salinetaste). After ignitionresidue reacts alkaline upon moistened test paper. Solution in nitric acid givesprecipitateof silver chloride with silver "

Dissolves

nitrate. Obs.

"

Occurs

Stassfurt, Saxony; Use. Sal

"

A

source

Ammoniac.

about

at

Vesuvius, about the fumaroles of the volcano. Also in Germany at Leopoldshall (leopoldite) Anhalt; at Kalusz in Galicia. potash compounds used as fertilizers.

and of

at

,

Ammonium

NH4C1. chloride,

volcanoes,as

at

n

1'642.

=

Observed

as

a

white

crustatio in-

Etna, Vesuvius, etc.

Cerargyrite Group.

Isometric-Normal

An isomorphous series of silver haloids in which silver chloride, bromide mix in varying proportions. The suggestionhas been made iodide may that the name be kept as the group name and that the different cerargyrite named be follows: chlorargyrite, sub-species as AgCl; bromargyrite, AgBr: and

embolite, Ag(Cl,Br); iodembolite, Ag(Cl,Br,I). CERARGYRITE.

Horn

Silver.

Isometric. Habit cubic. Twins: tw. pi.o(lll). Usually massive and resemblingwax; sometimes columnar; often in crusts. Fracture somewhat conchoidal. Cleavage none. Highly sectile. H. 1-1*5. Luster G. 5 -552. resinous to adamantine. Color pearl-gray, grayish green, whitish to colorless,rarelyviolet-blue;on exposure to the 2-0611. lightturns violet-brown. Transparent to translucent, n Silver chloride, 100. Some Comp. AgCl Chlorine,24-7,silver 75-3 =

=

=

=

"

=

varieties contain mercury. In the closed tube fuses without decomposition. B.B. on charcoal gives a Pyr., etc. to a bead of salt of phosphorus,previously saturated globule of metallic silver. Added with oxide of copper and heated in O.F., imparts an intense azure-blue to the flame. Insoluble in nitric acid,but soluble in ammonia. Obs. Cerargyrite and the related minerals are products of secondary action and are commonly found in the upper parts of silver deposits. Descending waters containing chlorine,bromine or iodine act upon the oxidation products of the primary silver minerals and these relatively insoluble compounds. so associated with precipitate' Commonly other silver minerals,with lead,copper and zinc ores and their usual alteration products. The largestmasses are brought from Peru, Chile,Bolivia,and Mexico, where it occurs with native silver. Also once obtained from Johanngeorgenstadt and Freiberg,Saxony; in the Altai Mts.; at Kongsberg in Norway. occurs In the United States,in Col.,near Leadville,Lake Co.; near Breckenridge,Summit Co., and elsewhere. In Nev. near Austin, Lander Co.; at mines of Comstock lode; Tonapah. In Idaho, at the Poorrnan In Utah, in mine, in crystals; also at various other mines. and Salt Lake counties. At Tombstone, Ariz. Beaver, Summit Named from /cepas, horn, and apyvpos, silver. "

"

Use.

"

An

ore

of silver.

Silver chloro-bromide Ag(Br,Cl), the ratio of chlorine to bromine varying Resembles but color grayish green to yellowish widely. Usuallymassive. cerargyrite, Abundant in Chile. and also at Broken 2*15. Found Hill, New yellow, n green Yuma South Wales; Tonapah, Nev.; Leadville, Col.,; County, Ariz.; Georgetown, N. M. 5*8-6. Color bright yellow to amber-yellow; Bromyrite. Silver bromide, AgBr. G. From 2'25. slightlygreenish, n Mexico; Chile. Color sulphur-yellow, Isometric. G. lodobromite. 5713. 2AgCl.2AgBr.AgI. From 2'2. near greenish, n Dernbach, Nassau; Broken Hill,New South Wales. Embolite.

=

=

=

=

=

Miersite. iodide,4AgI.CuI. Isometric; tetrahedral. G. 5'64. In Silver, copper South Wales. Hill Silver Mines, New Cuprobright yellow crystalsfrom the Broken from Huantajaya, Peru, belongs here also. iodargyrite Hexagonal-hemimorphic; usually in thin plates; pale lodyrite. Silver iodide,Agl. =

MINERALOGY

DESCRIPTIVE

398

5'5-57. G. yellow or green. Lake Valley, Sierra Co., N. M. Tonapah, Nev. =

Optically + crystalsfrom .

=

co

2 '182.

Broken

In

ii

ii

Fluorite The

CaCl2.

RF2,RC12

Group.

CaF2Tand the specieshere included are Fluoritel V^ "4 habit cubic. Both are isometric,

FLUORITE

or

Mexico, Chile, etc. South Wales, and

From

Hill,New

rare

Hydrophilite,

SPAR.

FLUOR

Habit cubic; less frequently octahedral or dodecahedral ; also the vicinal form f (321-0?), /(310),e(210) (fluoroids)common; hexoctahedron striations on 2(421)also common a(100)(Fig. 682) producing ; sometimes with the cube (Fig.681). Cubic in parallel grouped crystals Twins: tw. t hus a position, pi. 0(111),comforming pseudo-octahedron. Isometric.

forms

679

678

monly penetration-twins(Fig.682). Also massive; granular,coarse fineor rarelycolumnar; compact. Cleavage: o(lll) perfect. Fracture flat-conchoidal; of compact kinds

splintery. Brittle. 681

G. Luster

682

=

3-01-3-25; vitreous.

H.

4

=

318

cryst.

Color

white,

yellow,green, rose- and crimsonred, violet-blue, sky-blue,and

brown; wine-yellow,greenish blue, violet-blue, most common; red, rare. Transparent Sometimes

A Comp. -"-.is

=

when 1-4339.

test

compared

a bluish fluorescence. varieties phosphoresce

heated

(p. 251)

Calcium fluoride, CaF2 Fluorine 348'9,calcium 511 nuorme sometimes present in minute quantities -

ipitatesand sometimes on

white.

subtranslucent.

-

shows

Some n

Oniorme

Streak -

"ne

Fused

b

with certain treated with sulphuric

a

closed

phosphoresces. B.

=

100.

B. in the

flame i

orange, to an enamel which reacts alkaline "otassmm bisulphategivesreaction

for fluorine. octahedral cleavage, relative softness (as i, also with the feldspars); etchingpower when effervesce with acid like calcite "rm,

400

MINERALOGY

DESCRIPTIVE

black. reddish or brownish to brick-red or even sometimes Transparent to Mean 1-364. translucent. index, Optically+. p_ A fluoride of sodium and aluminium^ Na3AlF6 lor3NaF.AlF3 Comp. !D6"----rAr-nttleiron sesqui32*8 Fluorine 54*4, aluminium 12'8, sodium oxide is sometimes present as impurity. =

"

=

in C. T. with Fusible in small fragments in the flame of a candle. Heated Pyr.,etc. potassium bisulphate gives fluorine reaction. In the forceps fuses very easily,coloring the flame yellow. On charcoal fuses easilyto a clear bead, which on cooling becomes after long blowing, the assay spreads out, the fluoride of sodium is absorbed by opaque; the coal,a suffocatingodor of fluorine is given off,and a crust of alumina remains, which, with cobalt solution in O.F., gives a blue color. Soluble in sulphuric acid, when heated with evolution of hydrofluoricacid. Diff. Distinguishedby its extreme fusibility.Because of its low index of refraction almost invisible when Its planes of partthe powdered mineral becomes placed in water. ing (resemblingcubic cleavage) and softness are characteristic. Obs. Occurs in a bay in Arksukfiord,in West Greenland, at Ivigtut (or Evigtok), about 12 m. from the Danish settlement of Arksuk, where it constitutes a large bed in a graniticvein in a gray gneiss. Cryolite and its alteration products, pachnolite,thomin limited quantity at the southern base of Pike's Peak, prosopite,etc.,also occur senolite, El Paso county, Col.,north and west of Saint Peter's Dome. from Kpvos, frost, Named in allusion to the transX"9os, stone, hence meaning ice-stone, lucency of the white masses. In the manufacture Use. of sodium salts,certain kinds of glass and porcelain,and for the production of aluminum. as a flux in the electrolytic process is a variety of cryolitewith half the sodium replaced by lithium. Cryolithionite G. 278. Refractive index T34. Associated with cryoliteat Ivigtut. In small pyramidal crystals(tetragonal);also massive Chiolite. 5NaF.3AlF3. lar. granu3'5-4. Cleavages, c(001) perfect, p(lll) distinct. H. G. Color 2'84-2'90. snow-white. 1*349.. From Miask Optically in the Ilmen co near Mts., Russia; also with the Greenland cryolite. "

"

"

"

=

=

=

=

"

.

A

Hieratite.

isometric.

From

fluoride of potassium and the fumaroles of the crater

II.

silicon. of

In

grayish stalactitic concretions;

Vulcano, Lipari Islands.

Oxychlorides, Oxyfluorides

ATACAMITE.

Orthorhombic.

Axes " mm", ee',

684

:b

a

: c

=

0-6613

:

1

:

07515.

110

A

110

=

66" 57'.

rr'"t111

A

111

=

Oil

A

Oil

=

73"

mr,

110

A

111

=

51'.

52" 48'. 36" 16*'.

in slender Commonly prismatic crystals,vertically striated. Twins accordingto a complex law. (Paratacamite is twinned atacamite.) In confused crystallineaggregates; also massive,fibrous or granularto as sand.

compact;

Cleavage: 6(010) highly perfect. Fracture

conchoidal. 3-3-5. G. 375-377. Luster adamantine Color of various bright green shades, dark emerald-green to blackish green. Streak apple-green. Transparent to translucent. Optically T831 a Brittle. H. to vitreous.

=

=

=

"

.

0

Comp. cupnc on

=

T861.

Cu2ClH303

"

oxide

55-8,water

7 or

1-880.

=

CuCl2.3Cu(OH)2

12-7

=

=

Chlorine

16'6,copper

14'9,

100.

charcoal _

owmsn

sflv

.

w.u^

Viiv,

UIMI^I

gioijriBii

touched C?aujngs'

^h

wince,

the

uuiiuiiueu

uiowuig

yieias

the R.F.,volatilize, coloring

a

gioouie

flame

oi

met

azure-blue.

In

HALOIDS.

BROMIDES,

CHLORIDES,

"

401

FLUORIDES

IODIDES;

in the northern part of Chile; also found at CollaObs. Originallyfrom Atacama hurasi,Tarapaca and elsewhere in Chile and Bolivia; at Wallaroo and Bimbowrie, in In the United South Australia; at Gloncurry, Queensland; at St. Just in Cornwall. States,with cuprite,etc.,at the United Verde mine, Jerome, Ariz. In sky-blue cubes. Percylite. A lead-copperoxychloride,perhaps PbCl2.CuO.H2O. From Sonora, Mexico; Atacama, Chile; Bolivia,etc. Boleite. to 9PbCl2.8CuO.3AgC1.9H2O. Tetragonal, pseudo-isometric. Twinned form Pseudo-boleite. 5PbCl2.4CuO.6H2O. pseudo cubes. Tetragonal. Cumengite. in parallel 4PbCl2.4CuO.5H2O. Tetragonal. Pseudo-boleite and cumengite occur growth crystalsof boleite. Boleite and pseudo-boleitehave pearlyluster on cleavage,while upon cumengite has not. All three deep blue in color,the firsttwo showing a greenishtinge in powder. Found at Boleo, near Santa Rosalia,Lower California. Matlockite. Lead oxychloride, Pb2OCl2. In tabular tetragonalcrystals. G. 7-21. Luster adamantine to " pearly. Color yellowish or slightlygreenish. Optically =2 '15. From co Cromford, near Matlock, Derbyshire. In fibrous or columnar often radiated. Mendipite. Pb2O2Cl2 or PbCl2.2PbO. masses; H. =2-5-3. 7-7'l. G. Color white. the Mendip Hills,Somersetshire, Index, 1'93. From England; near Brilon,Westphalia. Lorettoite. 6PbO.PbCl2. Tetragonal? Coarse fibers or blades. Perfect basal cleavage. H. 7-6. G. 3. Fusible at 1. Color honey-yellow. Uniaxial, Indices,2'37From 2-40. Loretto,Tenn. Laurionite. PbClOH or PbCl2.Pb(OH)2. In minute prismaticcolorless crystals(ortho2-116. Pararhombic), in ancient lead slags at Laurion, Greece. Optically /3 From Same laurionite. Laurion. composition as laurionite but monoclinic. Rafaelite from Chile is the same mineral. as Suggested that laurionite is the same paralaurionite but owing to submicroscopictwinning has apparentlyorthorhombic Fiedlerite, symmetry. associated with laurionite, is probably also a lead oxychloride; in colorless monoclinic crystals. In white hexagonal crystals. Laurion,Greece. Penfieldite. Pb3OCl2 or PbO.2PbCl2. Daviesite. A lead oxychloride of uncertain composition. In minute colorless prismatic crystals(orthorhombic)from the Mina Beatriz,Sierra Gorda, Atacama, Chile. Schwartzembergite. Probably Pb(I,Cl)2.2PbO. In druses of small crystals;also in crusts. Color honey-yellow. Desert of Atacama, Chile. G. 6"2. Nocerite. In white hexagonal acicular crystals Perhaps 2(Ca,Mg)F2(Ca,Mg)O(?). in the tufa of Nocera, Italy. from bombs An oxychlorideof aluminium Koenenite. Rhombohedral. and magnesium. Perfect 2'0. Color red,due to included hematite. cleavageyieldingflexible folia. Very soft. G. From near Volpriehausenin the Soiling, Germany. An earthy yellowishoxychlorideof bismuth. From Daubreeite. Bolivia. "

=

"

.

=

=

=

-.

=

"

.

=

=

The

from the mercury oxychloridesof mercury depositsat Terlingua, are montroydite,calomel,native mercury and calcite. Eglestonite. Hg4Cl2O. Isometric in minute crystalsof dodecahedral habit. Many

Texas.

forms

followingare Associated

observed.

minerals

H.

=

2-3.

G.

=

8'3.

Luster

to resinous.

adamantine

Color brownish

Volatile. 2*49. yellow darkening on exposure to black, n In Monoclinic. small striated prismaticcrystalselongated Terlinguaite. Hg2ClO. 2-3. 87. G parallelto the 6-axis. Many forms observed. Cleavage perfect. H. Luster adamantine. Color sulphur-yellowchanging to olive-green on exposure. =

=

III.

=

Hydrous Chlorides, Hydrous Fluorides, etc.

CARNALLITE.

Orthorhombic. Crystalsrare. Commonly massive,granular. No distinct cleavage. Fracture conchoidal. 1. G Brittle. H. 1-60. Luster Color milk-white,often reddish. Transparent to shining,greasy. translucent. Stronglyphosphorescent.Optically 2 V 70". a + 1 -466. 1-475. Taste bitter. Deliquescent. 1-494, 0 T Chlorine 38'3, potasor Comp. KMgCl3.6H2O KCl.MgCl2.6H2O sium =

=

"

=

=

=

"

14-1,magnesium

87,

water

39'0

=

100.

=

=

402

in beds,alternatingwith thinner beds of common Occurs at Stassfurt, from Beienrode, near Konigshiitte,Silesia. In large crystals of potash compounds used in fertilizers. Carnallite is a source

Obs. kieserite. "

Use.

"

is said to be 2KCl.FeCl2.2H2O. associated with carnallite, white. to

DOUGLASITE,

colorless MgCl2.6H2O. Crystalline-granular; From Leopoldshalland Stassfurt,Prussia.

Bischofite. /3

1-507.

=

MINERALOGY

DESCRIPTIVE

In

KCl.NH4Cl.FeCl2.H2O.

Kremersite.

From

red octahedrons.

salt and

Optically+.

Vesuvius

and

Mt.

Etna, Sicily. containing chlorine, sulphur trioxide and A mercury-ammonium compound Mosesite. octahedrons. Minute Spinel twins. kleinite in composition. Isometric. Near water. Found Color yellow. Doubly refractingat ordinary temperatures. sparingly H. = 3+ at Terlingua,Texas. .

In 2KCl.FeCl3.H2O. Erythrosiderite. CaCl2.2MgCl2.12H2O. Tachhydrite.

red tabular In

crystals. Vesuvius. honey-yellow masses.

to

wax-

From

furt, Stass-

Germany.

In colorless or white rhombic, pyramids. A1F3.H2O. Index, 1'47. From ' Gwyn, Cornwall. H. 4'5. or granular massive. Prosopite. CaF2.2Al(F,OH)3. In monoclinic crystals, From 1'502. 2-88. Altenberg, Saxony; St. Peter's G. Colorless,white, grayish. 0 Dome Pike's Peak, Col.; Utah. near in Greenland, Col.,and Ural Mts., Pachnolite and Thomsenolite, occurringwith cryolite in monoclinic Both have the same occur composition, NaF.CaF2.AlF3.H2O. prismatic 98" 36', crystaltwins, orthorhombic in aspect. crystals;prismatic angle for pachnolite, For 1-413. thomsenolite, 89" 46', crystalsoften resembling cubes, also prismatic; /3 T414. /3 distinguishedby its basal cleavage; also massive. Gearksutite. Occurs with Earthy, clay-like. CaF2.Al(F,OH)3.H2O. Index, T448. cryolite. In colorless to white,isometric, Ralstonite. hedrons. octa(Na2,Mg)F2.3Al(F,OH)3.2H2O. H. With the Greenland 4-5. G. 2-56-2-62. 1'43. n cryolite. Creedite. Monoclinic. In grains,prismatic crys2CaF2.2Al(F,OH)3.CaSO4.2H2O. tals and radiatingmasses. 3'5. G. 2*71. Perfect Usually colorless, rarelypurple. H. Y b axis. 2 V 64". Fusible with intumescence. cleavage. Indices, 1-46-1-49. Soluble in acids. Found near Wagon Wheel Gap, Creed Quadrangle,Col. Tallingite.A hydrated copper chloride from the Botallack mine, Cornwall; in blue globularcrusts. Yttrocerite. Massive-eleavable to granular and (Y,Er,Ce)F3.5CaF2.H2O. earthy. H. 4-5. G. 3'4. Color From reddish brown. violet-blue,gray, near Falun, Sweden, etc. Fluellite.

Stenna

=

=

=

=

=

=

=

=

=

=

=

=

V. I.

n.

=

=

Oxides Oxides also

of Silicon, of the Semi-Metals

Molybdenum,

III. Oxides

The

of the

OXIDES

: Tellurium,Arsenic, Antimony, Bismuth Tungsten.

;

Metals.

Fifth

Class,that of the OXIDES, is subdivided into three sections, positiveelement present. The oxides of the non-metal placedby themselves,but it will be noted that the compounds of

according to silicon are

the

the related element

titanium are included with those of the metals proper. This last is made necessary by the fact that in one of its forms Ti02 is isomorphous with MnO2 and Pb02. A series of compounds which are properlyto be viewed as salts, oxygen e.g., the speciesof the SpinelGroup and a few others,are for convenience also included in this class.

403

OXIDES

I. Oxides

of Silicon

QUARTZ.

Rhombohedral-trapezohedral. Axis:

685

rrf,1011

A

TlOl

rz,

1011

A

0111

mr,

1010

A

1011

=

85" 46'.

=

46"

16'.

=

38"

13'.

686

c

=

1-09997.

mz,

1010

A

0111

=

66" 52'.

ms,

1010

A

1121

=

37" 58'.

mx,

1010 A. 5161

=

12"

687

1'. 688

Crystals commonly prismauc, with the m(10TO) faces horizontally striated;terminated commonly by the two rhombohedrons, r(1011) and of a hexagonal 2(0111),in nearlyequal development, giving the appearance it is in almost all cases r. pyramid; when one rhombohedron predominates Often in double six-sided pyramids or quartzoidsthrough the equal development of r and 2; when r is relatively largethe form then has a cubic aspect (rrf 85" 46'). Crystalsfrequentlydistorted,when the correct orientation be obscure except as shown by the striations on m. gated Crystalsoften elonmay to acicular 'forms,and taperingthrough the oscillatory of combination successive rhombohedrons with the prism. Occasionallytwisted or bent. with a surface of pyramids,or in druses. Frequentlyin radiated masses =

Simple crystalsare either right-or left-handed. On a right-handedcrystal(Fig.690) the right trigonalpyramid, s(1121),if present, lies to the right of the m face,which is below the predominating positive rhombohedron with this belong the positive r, and right trapezohedrons, as "(5161). On a left-handedcrystal (Fig.691), s lies to the left of the m below r. The right-and left-handed forms occur togetheronly in twins. In the absence of trapezohedral faces the striations on s (|| tinguish to disedge r/m), if distinct,serve the faces r and z, and hence show the right-and left-handed character of the crystals. The right-and left-handed character is also revealed by etching (Art.286) and by pyro-electricity (Art.438). Thermal as study of quartz shows that it exists in two modifications,known aand and is /3-quartz. a-quartz is apparently hexagonal,trapezohedral-tetartohedral formed at temperatures below 575" while /3-quartzis hexagonal,trapezohedral-hemihedral and forms at temperatures ranging from 575" to 800". Above 800" tridymiteis formed. The crystalangles of a-quartz change with increase of temperature up to?575", the inversion In a similar point to /3-quartz,while beyond this point they remain nearly constant.

404

MINERALOGY

DESCRIPTIVE

gence, marked lowering of the refractive indices and birefringeodes and large pegmatiteswhile the /3modification heated is found in graphitegranite,granite pegmatites, and porphyries. Tridymite when into cristobalite. Quartz, tridymite and cristobalite are probto about 1470" passes over ably to be considered as polymers of the fundamental molecule,SiO2. manner

at this point there is a sudden in veins and a-quartz occurs

Twins: (1) tw. axis c, all axes parallel.(2) Tw. pi.a, sometimes called the Brazil law, usuallyas irregular penetration-twins (Fig.692). (3) Tw. pi. 84" of at the axes crossing angles 33'_andwith a prism " (1122),contact-twins, Tw. individuals. face in common to the two (4) pi.r(1011). See further forms and 427^429. Massive and in great variety, 168 common Figs. ing passp. and from the coarse kinds to those which are fine granular or crystalline Sometimes and flint-like or cryptocrystalline. in mammillary, stalactitic, concretionary forms; as sand. Cleavage not Distinctly observed; sometimes fracture surfaces (|| r(1011), 2(0111)and m(1010),developedby sudden coolingafter being heated (seeArt. 279). Fracture conchoidal to subconchoidal in crystallized to forms,uneven massive kinds. Brittle to tough. H. 7. G. 2-653splinteryin some 2-660 in crystals;cryptocrystalline forms somewhat lower (to 2 -60)if pure, but impure massive forms (e.g., Luster vitreous," sometimes jasper)higher. to dull. Colorless when pure; often various shades splendent nearly greasy; of yellow,red, brown, green, blue,black. Streak white,of pure varieties; if but much as the color, impure,often the same paler. Transparent to opaque. Double refraction weak. Polarization Optically+. circular; righthanded the opticalcharacter or left-handed, =

692

=

left-handed corresponding to right- and character of crystals, defined as above; in twins both and left forms (law2), right sometimes then often united, sections showing Airy's spirals in the polariscope (cf.Art. 394, p. 270, and Fig. 692). Rotatory proportionalto thickness of power plate. Refractive indices for the D line, co 1-55328; also rotatory 1-54418, e for section of lmm thickness, 21 71 power a (D line). Pyroelectric; also electric by See Arts. 438, or piezo-electric.pressure 439. On etching-figures, Arts. 286, 287. see silicon Comp. Silica, or dioxide, 100. Oxygen 53'3, silicon 467 =

=

=

Basal section in polarizedlight, mg showof right-and interpenetration left-handed portions. Des Cloi-

"

=

=

In massive varieties often mixed with a littleopal silica. Impure varieties contain- iron oxide, calcium carbonate,clay,sand, and various minerals as inclusions. Artif. Quartz has been produced artificially in numerous Recently crystals ways. have been obtained at temperatures below 760" from melts containing dissolved silica which were composed of (1) a mixture of potassium and lithium chlorides,(2) vanadic acid, (3) sodium tungstate. At higher temperatures tridymite crystalsformed. "

PHENOCRYSTALLINE: Var"~A-,

vitreous Crystallized,

in luster.

B.

LINE: CRYPTOCRYSTAL-

Flint-like, massive. The

firstdivision includes all ordinaryvitreous quartz, whether having crystalline faces 1 he varieties under the second in general acted are somewhat more upon by rition and by chemical agents, as hydrofluoricacid, than those of the first. In all kinds made of as layers, up agate, successive layersare unequallyeroded.

405

OXIDES

A.

PHENOCRYSTALLINE

OR

VITREOUS

VARIETIES

tinct Ordinary Crystallized;Rock Crystal. Colorless quarts, or nearly so, whether in disHere belong the Bristol diamonds, Lake George diamonds, Brazilian not. or crystals Some variations from the common etc. pebbles, type are : (a) cavernous crystals;(6) cap(c) drusy quartz, a crust of small or minute quartz made up of separable layers or caps; quartz crystals;(d) radiated quartz, often separableinto radiated parts, having pyramidal terminations; (e) fibrous,rarely delicately so, as a kind from Griqualand West, South Africa,altered from crocidolite (seecat's-eye below, also crocidolite, p. 493). Asteriated;Star-quartz. Containingwithin the crystalwhitish or colored radiations exhibits distinct asterism. along the diametral planes. Occasionally Clear purple, or bluish violet. Color perhaps due to manganese. Amethystine; Amethyst. "

"

"

Rose. Rose-red or pink, but becoming paler on exposure. Commonly massive. sometimes Color perhaps due to titanium. a littlegreasy. Yellow and pellucid;resembling yellow topaz. Yellow; False Topaz or Citrine. parent; Smoky; Cairngorm Stone. Smoky yellow to dark smoky brown, and often transvarying to brownish black. Color is probably due to some organic compound of Banff, in (Forster). Called cairngorms from the localityat Cairngorm, southwest Scotland. The name is given to nearly black varieties. morion and nearly opaque. Milk-white Luster often greasy. Milky. or Siderite, Sapphire-quartz. Of indigo or Berlin-blue color;a rare variety. Sagenitic. Inclosingacicular crystalsof rutile. Other included minerals in acicular forms are: black tourmaline; gothite;stibnite;asbestus; actinolite; hornblende; epidote. Cat's-eyeexhibits opalescence,but without prismatic colors,especiallywhen cut en cabochon,an effect sometimes due to fibers of asbestus. Also present in the siliceous pseudocalled tiger-eye (see crocidolite).The Oriental morphs, after crocidolite, highly-prized cat's-eyeis a variety of chrysoberyl. Aventurine. Spangled with scales of mica, hematite,or other mineral. Impure from the presence of distinct minerals distributed densely through the mass. The more kinds are those .in which the impuritiesare: common (a)ferruginous,either red kind of from some or yellow, from anhydrous or hydrous iron sesquioxide; (6) chloritic, sand. or chlorite;(c) actinolitic;(d) micaceous; (e) arenaceous, Containing liquidsin cavities. The liquid,usually water (pure, or a mineral solution), or some petroleum-likecompound. smoky quartz, also often contains Quartz, especially inclusions of both liquidand gaseous carbon dioxide. "

Luster

"

"

"

"

"

"

B.

CRYPTOCRYSTALLINE

VARIETIES

Having the luster nearly of wax, and either transparent or translucent. Chalcedony. Also of to dark brown, black. Color white, grayish,blue, pale brown 2'6-2'64. G. Often other shades, and then having other names. mammillary, botryoidal,stalactitic, disseminated opalIt often contains some cavities in rocks. and occurringliningor filling be silica. The thermal study of chalcedony shows that it differs from quartz and may therefore a distinct species. The name taining enhydros is given to nodules of chalcedonyconunder the generalname in large amount. Embraced chalcedony water, sometimes form of silica which forms concretionarymasses with radial-fibrous and is the crystalline unlike true concentric structure, and which, as shown by Rosenbusch, is opticallynegative, Often in spherulites, 2'59-2'64. showing the spheru1*537; G. quartz. It has n liticinterference-figureLussatite of Mallard has a like structure, but is optically+ and has the specific gravity and refractive index of opal. It may be a fibrous form of tridymite. See also quartzine,p. 407. red Carnelian. Sard. A clear red chalcedony, pale to deep in shade; also brownish "

=

=

=

.

"

to brown.

apple-greenchalcedony, the color due to nickel oxide. and dull leek-green. Rather Plasma. bright green to leek-green,and also sometimes nearly emerald-green, stone and subtranslucent or feebly translucent. Heliotrope,or Blood-stone,is the same with small spots of red jasper,looking like drops of blood. essentially, colors are either (a) banded; or (6) irreguA variegated chalcedony. The larly Agate. moss-like clouded ; or (c) due to visible impuritiesas in moss agate, which has brown The bands are dendritic forms, as of manganese or oxide,distributed through the mass. delicate parallellines,of white, pale and dark brown, bluish and other shades; they are often waving or zigzag, and occasionallyconcentric circular. sometimes straight,more Chrysoprase. "

Prase.

"

"

An

Translucent

"

406

MINERALOGY

DESCRIPTIVE

the edges of layersof deposition,the agate having been formed by a deposit supplied,in irregularcavities in rocks,and deriving solutions intermittently of the walls of the cavity. The from the irregularities their concentric waving courses in color by artificial means, be varied and therefore in agates may porosity, layersdiffer There is also with the agates cut for ornament. to a large extent and this is done now w ith clouded wood agate. petrified agatizedwood; white and black,white and of layersof different colors, Like agate in consisting Onyx. and hence its use for in and the straight, banding but the even planes, layers red, etc., bands-

The

are

of silica from

"

cameos.

in structure, but includes layersof carnelian (sard)along with whitish,and brown, and sometimes black colors. Agate-jasper. An agate consistingof jasper with veiningsof chalcedony. taining Siliceous -sinter. Irregularlycellular quartz, formed by depositionfrom waters consilica or soluble silicates in solution. See also under opal, p. 408. and of dull colors, Somewhat Flint. allied to chalcedony, but more usually opaque, The exterior is often whitish,from mixture with black. brownish and smoky, brown, gray, Luster subvitreous. Breaks barely glistening, lime or chalk,in which it is embedded. and a sharp cuttingedge. The flintof the chalk formation with a deeply conchoidal fracture, and other marine productions. consists largelyof the remains of diatoms, sponges, Flint implements kind is mostly carbonaceous matter. of the common The coloringmatter the relics of early man. play an important part among the fracture more Resembles but is more Hornstone. flint, brittle, splintery.Chert is a term often applied to hornstone,and to any impure flintyrock, including the jaspers. A velvet-black siliceous stone or flinty Basanite; Lydian Stone,or Touchstone. jasper, used on account of its hardness and black color for trying the purity of the preciousmetals. The color left on the stone after rubbing the metal across it indicates to the experienced of alloy. It is not splinterylike hornstone. eye the amount Jasper. Impure opaque. colored quartz; commonly red, also yellow, dark green and grayish blue. Stripedor riband jasper has the colors in broad stripes. Porcelain jasper is nothing but .baked clay,and differs from true jasper in being B.B. fusible on the edges.

Sardonyx.

others

Like onyx

"

of white

or

"

"

"

"

"

"

C.

Besides the above

Granular

there

are

also:

or Quartz,Quartz-rock, Quartzite. A rock consistingof quartz grains very firmly compacted; the grains often hardly distinct. Quartzose Sandstone, Quartz-con* The pebbles sometimes glomerate. A rock made of pebbles of quartz with sand. are jasperand chalcedony,and make a beautiful stone when polished. Itacolumite, Flexible or Sandstone. A friable sand-rock,consistingmainly of quartz-sand,but containing a little mica, and possessinga degree of flexibility when in thin laminae. Buhrstone,or Burrstone. A cellular, flintyrock,having the nature in part of coarse chalcedony. also under the forms of many PseudomorphousQuartz. of the mineral Quartz appears which it has taken through either the alteration or replacement of crystalsof those species, species. The most common quartz pseudomorphs are those of calcite, and barite,fluorite, siderite. Silicified wood is quartz pseudomorph after wood (p.326). B.B. unaltered; with borax dissolves slowly to a clear glass; with soda Pyr., etc. dissolves with effervescence; unacted upon by salt of phosphorus. Insoluble in hydrochloric acid,and only slightlyacted upon by solutions of fixed caustic alkalies, the cryptovarieties to the greater extent. crystalline Soluble only in hydrofluoricacid. When fused and cooled it becomes opal-silica 2'2. having G. Diff. Characterized in crystalsby the form, glassyluster, and absence of cleavage; also in generalby hardness and infusibility. Micro. Easilyrecognizedin rock sections by its low refraction (" low relief," p. 212) and low birefringence (e co 0'009); the interference colors in good sections not rising above yellow of the firstorder; also by its limpidity and the positiveuniaxial cross yielded by basal sections (p.270, note),which remain dark when revolved between crossed nicols. Commonly in formless grains (granite), also with crystaloutline (porphyry, etc.). Obs. Quartz is an essential component of certain igneous rocks,as granite,graniteporphyry quartz-porphyry and rhyolitein the granite group; in such rocks it is comnonly in tormless grains or masses the interstices between filling the feldspar, the last as product of crystallization. Further it is an essential constituent in quartz-diorite, quartzdiorite porphyry and dacites in the diorite in the porphyries frequently in distinct group; crystals. It occurs also as an accessory in other feldspathicigneous rocks,such as syenite and trachyte. Among the metamorphic rocks it is an essential component of certain varieties of gneiss, of quartzite, etc. It forms the mass of common sandstone. It occurs as the vein-stone m various rocks,and forms a largepart of mineral veins; as a foreignmin"

"

"

"

"

"

=

"

"

-

"

=

408

MINERALOGY

DESCRIPTIVE

Comp.

Pure

"

SiO2, like quartz. silica,

Tridymite is formed above 800" C. See further under Quartz, p. 403. carbonate. Like quartz, but soluble in boilingsodium Pyr., etc. Obs. Occurs chieflyin acidic volcanic rocks,rhyolite,trachyte,andesite,liparite, often associated with sanidine,also hornblende, less often in dolerite;usually in cavities, augite,hematite; sometimes in opal. First observed in crevices and druses in an augitenear Pachuca, Mexico; later proved to be rather andesite from the Cerro San Cristobal, generallydistributed. Thus in trachyteof the Siebengebirge,Germany; of Euganean In the ejected Hills in northern Italy;Puy Capucin (Mont-Dore) in Central France, etc. In the lavas of Mt. Etna, Sicily, and of sanidine. from Vesuvius consistingchiefly masses Mt. Kibosan, Prov. Higo, Japan. With quartz, feldspar, Pelee, Martinique. From In the andesite of Mt. Rainier, Park. Yellowstone fayalitein lithophysesof Obsidian cliff, Washington. in allusion to the common in trillings. occurrence Named from rpiSu/zos, threefold, in the meteoric iron of Breitenbach,in.very minute A form of silicafound ASMANITE. referred to the orthorhombic grains,probablyidentical with tridymite;by some system. Silica in white octahedrons Christobalite. CRISTOBALITE. (pseudo-isometric?).G. 2'27. 1*486. With tridymitein andesite of the Cerro S. Cristobal,Pachuca, Mexico, n For thermal relations to quartz Also noted in lava at May en, Germany, and in meteorites. and tridymitesee under quartz, p. 403. In minute cubes and sphericalaggregates. Occurring with calcite MELANOPHLOGITE. the sulphur crystalsof and celestite implanted upon an incrustation of opaline silica over Girgenti,Sicily. Consists of SiO2 with 5 to 7 p. c. of S03, perhaps SiO2 with SiS2. The "

"

=

=

mineral

black

turns

when superficially

heated

B.B.

OPAL.

Massive; sometimes

Amorphous. H.

small

or reniform, stalactitic, large

Also earthy.

tuberose.

5-5-6-5.

G.

1-9-2-3; when

2-1-2-2.

Luster vitreous,frequently resinous,and sometimes to pearly. Color white,yellow,red,brown, green, gray, blue,generallypale; dark colors arise from foreignadmixtures; sometimes rich play of colors, different a or colors by refracted and reflected light. Streak white. Transparent to nearly =

=

subvitreous;often

n

opaque,

pure

incliningto

1-44-1-45.

=

Often shows double refraction similar to that observed in colloidal substances due to tension. The cause of the play of color in the preciousopal was investigated by Brewster, who ascribed it to the presence of microscopiccavities. Behrends,however, has given a monograph on the subject (Ber.Ak. Wien, 64 (1),1871),and has shown that this explanation is incorrect;he refers the colors to thin curved lamellae of opal whose refractive power differ by O'l from that of the mass. These are may conceived to have been originally formed in parallel but have been changed, bent, and finally position, cracked and broken in the solidificationof the groundmass.

Comp. The

"

water

like quartz, with a varying amount Silica, is sometimes regarded as non-essential.

of water, Si02.nH20.

The

opal condition is one of lower degrees of hardness and specificgravity,and, as of incapability of crystallization. generally believed, The water present varies from 2 to 13 Small quantitiesof ferric oxide,alumina,lime p. c. or more, but mostly from 3 to 9 p. c. and

alkalies are usuallypresent as impurities. Precious Opal Exhibits a play of delicate colors. Fire-opal Hyacinth-red to honey-yellowcolors,with fire-like reflections, somewhat

magnesia,

Var.

"

"

"

insed

on

turning.

Gir'asol.

Bluish white,translucent, with reddish reflections in a bright light. In part translucent; Opal (a) milk-opal,milk-white to greenish,yellowish, bluish; (6) Resin-opal, with a resinous luster; (c) dull olivewax-, honey- to ocher-yellow, and mountain-green; (d) brick-red. green Includes Semiopal; (e)Hydrophane, a variety "

Common

which

"

becomes

more

translucent

or

transparent in water.

Cacholong. Opaque, bluish white, porcelain-white, pale yellowishor "

Upal-agate.

"

Memlite.

"

reddish.

Agate-likein structure, but consisting of opal of differentshades of color. In concretionaryforms; dull grayish. opaque,

409

OXIDES

J asp-opal. Opal-jasper. Opal containingsome yellowiron oxide and other having the color of yellow jasper,with the luster of common opal. "

and

impurities,

Wood petrified by opal. Wood-opal. Clear as glass and colorless, Hyalite. Muller's Glass. constitutingglobular concretions, and crusts with a globularor botryoidalsurface; also passing into translucent, and Less readilydissolved in caustic alkalies than other varieties. whitish. A porous German East Africa. varietyfrom the Virunga district, Schaumopal. Siliceous Sinter. Includes translucent to opaque, grayish,whitish or brownish Fiorite, fibrous-like or filamentous, incrustations, and, when porous, to firm in texture; sometimes deposited from the siliceous.waters of hot so, pearly in luster (then called Pearl-sinter)', springs. Geyserite. Constitutes concretionary depositsabout the geysers of the Yellowstone white or grayish, porous, mentous, filaPark, Iceland, and New stalactitic, Zealand,s_presenting cauliflower-like forms, often of great beauty: also compact-massive, and scaly"

"

"

"

"

massive. Float-stone.

white In light porous or concretionary masses, grayish,sometimes rough in fracture. from the siliceous shells of diatoms (hence called diatomite)and Tripolite. Formed other microscopicspecies,and occurringin extensive deposits. Includes InfusorialEarth, earth looking often like an earthy chalk,or a clay, or a very Earthy Tripolite, fine-grained but harsh to the feel,and scratchingglasswhen rubbed on it. B.B. Yields water. but becomes Some eties, infusible, Pyr., etc. yellow variopaque. acid somewhat more containingiron oxide,turn red. Soluble in hydrofluoric readily than quartz; also soluble in caustic alkalies, but more varieties than in readilyin some "

cavernous,

"

"

others. in igneous rocks,as trachyte,porOccurs filling cavities and fissures or seams phyry, where it has probably resulted from the action of hot,magmatic waters upon the silicatesof the rocks,the liberated silica being deposited in the cavities in the form of opal. Also in some metallic veins. Also embedded, like flint, in limestone,and sometimes, like other quartz concretions,in argillaceous beds; formed from the siliceous waters of hot springs; often resultingfrom the mere some accumulation,or accumulation and partial solution and solidification, of sponge spicules, of the siliceous shells of infusoria, etc.,which consist essentially of opal-silica.The last mentioned is the probable source of the opal of limestones and argillaceous beds (as it is of flint in the same rocks),and of part of that in igneous rocks. It exists in most chalcedony and flint. in porphyry at Czerwenitza, near Precious opal occurs Kashau in Hungary; at Gracias in Honduras; Queretaro in Mexico; a beautiful blue opal on Bulla Creek, Queensa Dios land; from White New South Wales, as filling openings in sandstone,in fossilwood, Cliffs, in the material of various fossil shells and bones and in aggregates of radiatingpseudoSan at Zimapan in Mexico; the Faroe Islands; near morphic crystals. Fire-opaloccurs from Humboldt Gem Co., Antonio, Honduras. opal, often of "black opal" type, comes Nev. Common at Telkebanya in Hungary; near Pernstein,etc., in opal is abundant Moravia; in Bohemia; Stenzelberg in Siebengebirge,Germany; in Iceland. Hyalite in amygdaloid at Schemnitz, Hungary; in clinkstone at Waltsch, Bohemia; at San occurs Luis Potosi,Mexico; Kamloops, British Columbia. In the United States,hyalite occurs sparinglyin connection with the trap rock of N. J. and Conn. A water-worn has been found on the John Davis river, specimen of fire-opal in Crook Co., Ore. Common Co., Pa.; at Aquas Calientes,Idaho opal is found at Cornwall, Lebanon Hill,Calaveras Co., Cal., and on the Mt. Springs,Col.; a white variety at Mokelumne in great abundance Diablo range. and varietyin the Yellowstone region Geyseriteoccurs Springs,Nev. (cf.above); also siliceous sinter at Steamboat In the colored varieties as a highly prizedgem-stone. Use. Obs.

"

"

II.

Oxides

of the

or

=

37.

n

=

Tungsten

In isometric octahedrons;in crusts and Occurs with arsenical ores. 1755.

trioxide,As2Os.

Arsenic white. G.

Arsenolite.

Colorless

Semi-Metals; also Molybdenum,

earthy.

In thin plates. Also As2O3,but monoclinic in form. Antimony trioxide. Sb2O3. In isometric octahedrons;hi crusts and Occurs with ores 2P087. of antimony. G. granular massive. 5;3. Colorless,grayish, n Claudetite.

Senarmontite.

=

=

From

Algeria;South

Ham,

Quebec.

410

MINERALOGY

DESCRIPTIVE

Sb2O3, in prismaticorthorhombic

Valentinite.

crystals. Index

2-34.

=

From

South

Ham, Quebec.

trioxide,Bi2O3. Pulverulent,earthy; color straw-yellow. From silverywhite, pearly scales that are hexagonal, rhombomuth of so-called bismites show them to be bisAnalyses of a number other or compounds. hydroxide In white to yellowslender prismatic crystals. Tellurite. Tellurium dioxide,TeO2. In capillary tufted forms and MoO3. earthy. trioxide, Molybdite. Molybdenum Color straw-yellow. Analyses of molybdic ocher from various localitiesshow it to be not the oxide but a hydrous ferric molybdate, Fe2O3.3MO3.7H2O. Indices,178-1 '90. WO3. Pulverulent,earthy; color yellow or yellowish Tungstite. Tungsten trioxide, Analysis of tungstic ocher from Salmo, B. C., prove it to Indices,2'09-2'26. green. have the composition WO3.H2O; perhaps identical with meymacite (a hydrated tungstic oxide from Meymac, Correze,France). Cervantite. Sb2O3.Sb2O6. In yellow to white acicular crystals; also massive, pulverulent Bismite.

Bismuth

Goldfield,Nevada, hedral; optically

in minute

"

Stibiconite.

.

H2Sb2O6.

Massive, compact.

Color

pale yellow

to

yellowish white.

Index, 1-83.

HI. A. I. H.

Oxides

of the

ANHYDROUS

IV.

OXIDES

Protoxides, R2O and RO. Sesquioxides,R^Oa. ii

m.

Metals

in

Intermediate, RR-A

or

RO.RgOg,

etc.

Dioxides, RO2.

The

Anhydrous Oxides include,as shown above, three distinct divisions, mediate Protoxides,the Sesquioxidesand the Dioxides. The remaining Interdivision embraces a number of oxygen compounds which are properly be regardedchemicallyas salts of certain acids (aluminates, ferrates, etc.) ;

the to

here is included the well-characterized

SPINEL GROUP. the Protoxides the only distinct group is the PERICLASE GROUP, which includes the rare speciesPericlase, MgO, Manganosite, MnO, and All of these are isometric in crystallization. Bunsenite,NiO. The Sesquioxides include the well-characterized HEMATITE GROUP, R2O3, The Dioxides include the prominent RUTILE Both of these GROUP, R02. groups are further defined later.

Among

I. CUPRITE.

Red

Copper

'Protoxides,RaO and RO

Ore.

Isometric-plagiohedral. Commonly in octahedrons; also in cubes and dodecahedrons,often highly modified. Plagiohedralfaces sometimes distinct (see p. 71). At times in capillary crystals. Also massive,granular; sometimes earthy. Cleavage: o(lll) interrupted.Fracture conchoidal,uneven. Brittle. H. 3*5-4. G. 5'85-6*15. Luster adamantine submetallic to earthy. or Color red, of various shades, particularly sometimes almost cochineal-red, crimson-red by transmitted light. Streak several shades black; occasionally of brownish red, shining. Subtransparentto subtranslucent. Refractive 2*849. index,n =

=

=

411

OXIDES

Var.

in octahedrons,dodecahedrons, forms; the crystalsoften with a crust of malachite; (6) massive. In cap2. Capillary; Chalcotrichite. Plush Copper Ore. illary which sometimes cubes acicular crystallizations, or are elongated in the direction of the cubic axis. reddish 3. Earthy; Tile Ore. Brick-red brown and or earthy, often mixed with red oxide of iron; sometimes nearly

Ordinary, (a) Crystallized;commonly

1.

"

cubes,and

intermediate

black.

,

Comp.

Cuprous oxide, Cu2O

"

88'8

copper

Pyr.,etc.

Oxygen

=

11*2,

100.

=

Unaltered

"

in the closed tube.

B.B.

hi

the

coal charforceps fuses and colors the flame emerald-green. On first blackens, then fuses,and to is reduced metallic With the fluxes gives reactions for copper. Soluble copper. in concentrated Arizona hydrochloricacid,and a strong solution when cooled and diluted with cold water yields a heavy, white precipitateof cuprous chloride. Diff Distinguishedfrom hematite by inferior hardness, but is harder than cinnabar and proustiteand differsfrom them in the color of "the streak; reactions for copper, B.B., "

.

are

conclusive. In polished sections shows Micro.

white with shiningsurface,usuallypitted. With HNO3 oblique illumination, transparent deep red. With instantlyplated with metallic remains. With HC1 copper which blackens and dissolves. On drying a thin film of copper darkens and is coated with white, seen by oblique light. Obs. Cuprite is a mineral of secondary origin. It is often formed as a furnace product and has been rioted as a coating upon ancient copper bronze objects. Occurs at or in Thuringia; in Cornwall, in fine crystals, Gorland and other mines; at Wheal Kamsdorf in Devonshire less altered to malachite, at near or Tavistock; in isolated crystals,more Chessy, near Lyons, France; in the Ural Mts.; South Australia;also abundant in Chile, Peru, Bolivia. In the United States observed at Somerville,etc.,N. J.; at Cornwall, Lebanon Co., Ariz, with malachite,limonite,etc.,at the Copper Pa.; in the.Lake Superior region. From in fine crystals;beautiful chalcotrichite at Morenci; Queen mine, Bisbee, sometimes Graham and massive. at Clifton, Co., in crystals, "

"

Use.

An

"

ore

of copper.

in six-rayed snow Hexagonal. Familiarlyknown ponds in whiter,further as glaciersand icebergs.

H2O.

Ice.

Periclase

crystals;also coating

Group

In cubes or octahedrons, and in grains. Cleavagecubic'. Periclase. Magnesia, MgO. Artif. from a melt containingmagne3'67-3'90. 174. H. =6. G. Crystallized n sium chloride and silica. Occurs in white limestone at Mte. Somma, Vesuvius; at the Kitteln manganese mine, Nordmark, Sweden. =

=

Manganese

Manganosite cubic.

H.

=

5-o.

From Bunsenite.

G.

Langban Nickel

=

5'18.

"

In

protoxide,MnO. n

=

2'18.

Color

and Nordmark, Sweden; In green protoxide,NiO.

isometric

octahedrons. Cleavage black on exposure. Furnace, N. J.

emerald-green, becoming Franklin

octahedrons.

From

Johanngeorgen-

stadt,Germany. Cadmium

color and

In minute octahedrons. Forms Isometric. oxide. a thin coating of black brilliant metallic luster upon calamine from Monte Poni, Sardinia. Also formed

artificially.

ZINCITE.

Red

Oxide

of Zinc.

Axis Hexagonal-hemimprphic.

c

=

44, p. 22); usuallyfoliated massive,or in

granularstructure.

1*5870. coarse

Natural crystalsrare (Fig. and grains;also with particles

412

MINERALOGY

DESCRIPTIVE

distinct. Fracture subLuster subadamantine. also Translucent to orange-yellow. deep red,

sometimes Cleavage: c(0001)perfect;prismatic, Brittle.

conchoidal.

H.

4-4'5.

=

G.

=

5-43-57.

Streak orange-yellow. Color subtranslucent. Optically+. Zinc oxide, ZnO Oxygen Comp. protoxideis sometimes present.

197,

=

"

zinc

80*3

=

100.

nese Manga-

infusible;with the fluxes,on the platinum wire,gives reactions for charcoal in R.F. gives a coating of zinc oxide, yellow while hot, and sumes cooling. The coating,moistened with cobalt solution and treated in O.F., ascolor. Soluble in acids. a green Characterized Diff. by its color,particularlythat of the streak; by cleavage; by reactions B.B. Zincite is often formed a furnace as product. It is also produced when zinc Artif. lime at red heat. act upon chloride and water vapor Obs. Occurs with franklinite and willemite,at SterlingHill near Ogdensburg, and at in -lamellar in pink Mine masses Hill,Franklin Furnace, Sussex Co., N. J., sometimes A not uncommon furnace product. calcite. Has been reported from Poland. An ore of zinc. Use.' Pyr., etc.

"

and

manganese, white on

B.B. on

"

"

"

"

"

Lead monoxide, PbO. Massive, scaly or earthy. Color yellow, reddish. Index, 1735. Optically". Probably orthorhombic. In minute black scales with metallic luster; from Tenorite. Cupric oxide, CuO. Also black earthy massive Vesuvius. of copper at (melaconite) ores as ; occurring with Point, Lake Superior. Pitchy black material Ducktown, Tenn., and Keweenaw ciated assowith cuprite,chrysocollaand malachite from Bisbee,Ariz.,has been called melanoMassicot.

chaldte.

essentially cupric oxide, CuO, occurring in black pyramidal crystals From the Copper Queen mine, Bisbee, Ariz. Orthorhombic. In minute highly modified crystals. H. Montroydite.HgO. Color and streak orange-red. Index, 2'55. T5-2. Volatile. Found at Terlingua, Tex. Paramelaconite

is

referred to the tetragonalsystem.

=

Hematite

Group.

R203.

Rhombohedral rr'

c

Corundum

A1203

93"

56'

Hematite

Fe2O3

94"

0'

1*3656

29'

1*3846

Ilmenite

(Fe,Mg)O.Ti02 Tri-rhombohedral

94"

Pyrophanite

MnO.Ti02

94"

"

5J'

1*3630

1'3692

The HEMATITE GROUP embraces the sesquioxides of aluminium and iron. These compounds in the rhombohedral crystallize class,hexagonal system, with a fundamental rhombohedron but littlein angle from a cube. differing Both the minerals belonginghere,Hematite and Corundum, are hard. To these speciesthe titanates of iron (and magnesium) and manganese, Ilmenite and Pyrophanite,are closely related in form though belongingto the tri-rhombohedral class (phenacite type) ; in other words, the relation between hematite and ilmenite may be regarded as analogous to that between calcite and dolomite. It is to be noted, further, that hematite often contains titanium, and an artificialisomorphouscompound, Ti203, has been described. Hence the ground for writingthe formula of ilmenite is done by as (Fe,Ti)2O3, authors. It isshown by Penfield, some however, that the formula (Fe,Mg)Ti02 is

more

correct.

OXIDES

413

CORUNDUM.

Rhombohedral.

Axisc

1-3630.

=

694

695

697

cr,

0001

A

en, rr'

0001

A

1011 2243

=

=

1011

A

1101

nn', 2243 w', 4483 zz', 2241

A

2423

=

A A

4843 2421

=

=

=

57" 34'

6l" 11' 93" 51" 57" 58"

56'

58' 38' 55'

sometimes often polysynthetic, pi.r(10ll), penetration-twins; producing a laminated structure. Crystals usually rough and Also massive,with nearlyrectangularpartingor pseudo-cleavage;

Twins: thus rounded.

tw.

and

fine. or granular,coarse Parting: c(0001),sometimes perfect,but interrupted;also r(1011) due to twinning, often prominent; a(1120) less distinct. Fracture to uneven conchoidal. when G. 3-95-4-10. Brittle, compact very tough. H. =9. Luster adamantine to vitreous;on c sometimes ing pearly. Occasionallyshowasterism. Color blue,red,yellow,brown, gray, and nearlywhite; streak uncolored. Pleochroic in deeply colored varieties. Transparent to translucent. 17676 to 1*7682 and Normally uniaxial, negative;for sapphireco 17594 to 17598. Often abnormally biaxial. e =

=

=

Var. There are three subdivisions of the speciesprominently recognized in the arts, but differing structure. or only in purity and state of crystallization VAR. 1. SAPPHIRE, RUBY. Includes the purer kinds of fine colors,transparent to Stones named useful as gems. are translucent, according to their colors: Sapphire blue; true Ruby, or Oriental Ruby, red; Oriental Topaz, yellow; Oriental Emerald, green; Oriental Amethyst,purple. The term sapphireis also often used as a generalterm to indicate corundum of any color except red. A varietyhaving a stellate opalescencewhen viewed in gems the direction of the vertical axis of the crystalis the Asteriated Sapphire or Star Sapphire. 2. CORUNDUM. Includes the kinds of dark or dull colors and not transparent, colors lightblue to gray, brown, and black. The originaladamantine spar from India has a dark grayish smoky brown tint,but greenishor bluish by transmitted light,when translucent. 3. EMERY. Includes granularcorundum, of black or grayish black color,and contains Sometimes associated with iron spinelor hercymagnetite or hematite intimatelymixed. nite. Feels and looks much like a black fine-grained iron ore, which it was long considered to kinds in which the corunto be. There are gradationsfrom the evenly fine-grained dum emery is in distinct crystals. "

"

"

"

Oxygen 47' 1, aluminium Comp. Alumina, A12O3 varieties are crystallized essentially pure; analysesof emery impurity,chieflymagnetite. =

"

Artif

.

ways.

and

"

dissolved

potassiumcarbonate

or

show

=

100. more

or

The less

of differin a number ent has been produced artificially sodium sulphide,in a fused mixture of a fluoride in fused lead oxide,will separateout as crystallized corundum.

Crystallizedcorundum Alumina

52'9

in molten

414

DESCRIPTIVE

MINERALOGY

salt,or blue has been produced in this way, colored red, with a chromium Crystallizedmaterial can also be produced by fusing alumina in an electric in an by heating bauxite to 5000"-6000" The artificialabrasive, alundum, is made arc. by fusing together small electric furnace. Pear-shaped drops of gem material are made known structed "reconare as. Gems cut from them fragments of natural or artificialstones. and other physical propertiesof the natural and have the crystalline stones material

Gem

by cobalt.

"

mineral. B.B. unaltered; slowly dissolved in borax and salt of phosphorus to a Pyr., etc. The finely glass,which is colorless when free from iron; not acted upon by soda. pulverizedmineral, after long heating with cobalt solution,gives a beautiful blue color. Not acted upon by acids,but converted into a soluble compound by fusion with potassium bisulphate. tine Characterized Diff. by its hardness (scratchingquartz and topaz), by its adamangravity and infusibility.The massive variety with rhombohedral luster,high specific partingresembles cleavable feldsparbut is much harder and denser. ence In thin sections appears Micro, nearly colorless with high relief and low interfer"

clear

"

"

colors. in crystalline Obs. rocks, as granular limestone or dolomite, gneiss, Usually occurs speciesof granite,mica slate,chlorite slate. The associated minerals often include some the chlorite group, as prochlorite,corundophilite,margarite, also tourmaline, spinel, cyanite,diaspore,and a series of aluminous minerals,in part produced from its alteration. Occasionallyfound as an originalconstituent of igneous rocks containinghigh percentages of alumina. In the Ural Mts. are found an anorthite rock containingnearly 60 per cent of corundum, a corundum syenite with 18 per cent, and a pegmatite with 35 per cent. A corundum anorthosite and corundum Important deposits syenitesare found in Canada. of corundum in North Carolina and Georgia are associated with dunite rocks. Rarely from the beds of observed as a contact-mineral. The fine sapphiresare usuallyobtained rivers,either in modified hexagonal prisms or in rolled masses, accompanied by grains of in magnetite,and several kinds of gems, as spinel,etc. The emery of Asia Minor occurs granularlimestone. The best rubies come from the mines in Upper Burma, north of Mandalay, in an area The rubies occur in situ in covering25 to 30 square miles,of which Mogok is the center. crystalline limestone,also in the soil of the hillsidesand in gem-bearing gravelsof the Irrawaddy River. Blue sapphires are brought from Ceylon from the Ratnapura and Rakwena often as rolled pebbles,also as well-preservedcrystals.Corundum in the districts, occurs Carnatic on the Malabar hillsin Siam, and elsewhere in the East coast, on the Chantibun Indies; also near Canton, China; from Naegi, Mino, Japan. At St. Gothard, Switzerland, it occurs of a red or blue tinge in dolomite,and near Mozzo in white in Piedmont, Italy, with in large,coarse, hexagonal pyramids in compact feldspar. Adamantine spar is met Other localities are in Bohemia, near Gellivara,Sweden. Petschau, in Russia,in the Ilmen mountains, not far from Miask and in the gold-washings northeast of Zlatoust. Corundum, sapphires,and less often rubies occur in rolled pebbles in the diamond gravels the Cudgegong river,at Mudgee and other points in New on South Wales. Emery is found in largebowlders at Naxos, Nicaria, and Samos of the Grecian islands ; also in Asia Minor, E. of Ephesus, near 12 m. Gumuchdagh and near Smyrna, associated with margarite, chloritoid, pyrite. -" In North America, in Mass., at Chester, with magnetite, diaspore,ripidolite, garite, 'marIn Conn, near etc.,was mined for use as emery. Litchfield. In N. Y., at Warwick, bluish and pink, with spinel; Amity, in granular with magnetite and limestone; emery in Westchester spinel (hercynite) green In Co., near Cruger's Station, and elsewhere. N. J.,at Newton, blue crystalsin granular limestone;at Vernon, at Sparta and elsewhere In Pa.,in Delaware in Sussex Co. Co., in Aston, near VillageGreen, in largecrystals;at Mineral Hill,in loose crystals;in Chester Co., at Unionville,abundant in crystals;in large crystalsloose m the soil at Shimersville, In Va., in the mica schists of Bull Mt., Lehigh Co. "

Patrick Co. Common at many South Carolina and

Haywood, most

work

pointsalong a belt extending from Virginiaacross

western

North

and

Georgia to Dudleyville, Alabama; especiallyin Madison, Buncombe, Jackson, Macon, Clay, and Gaston counties in N. C. The localities at which has been done are the Culsageemine, Corundum hill, near Franklin,Macon Co.,

U'1!md26

miles S

E. of

this,at Laurel Creek, Ga.

The

corundum

occurs

in beds in

ik chrysolite(and serpentine)and hornblendic gneiss,associated with a speciesof the chlorite group, also spinel,etc.,and here as elsewhere with many minerals resultingfrom its alteration.

Some

fine rubies have

been

found.

Fine

of pink crystals

corundum

occur

at Hia-

416

MINERALOGY

DESCRIPTIVE

often long radiating;luster submetallic The masses or fibrous. 2. Compact Columnar; to contrast it called red hematite, metallic;color brownish red to iron-black. Sometimes called kidney ore. with smooth fracture, with limonite and turgite. Often in reniform masses Red and earthy. Reddle and red chalk are red ocher, mixed with 3. Red Ocherous. less clay. or more Hard, brownish black to reddish brown, 4. Clay Iron-stone; Argillaceoushematite. often in part deep red; of submetallic to nonmetallic luster; and affording,like all the other It consists of oxide of iron with clay or sand, and sometimes a red streak. preceding, to

impurities. 100. times SomeFe203 Iron sesquioxide, Oxygen 30, iron 70 r elated is thus closely to ilmenite, contains titanium and magnesium, and

Comp.

=

=

"

p. 417.

charcoal in R.F. becomes B.B. infusible;on magnetic; with borax gives Pyr., etc. With soda on charcoal in R.F. is reduced to a gray magnetic powder. the iron reactions. Slowly soluble in hydrochloricacid. Diff. Distinguishedfrom magnetite by its red streak,also from limonite by the same from turgiteby its greater hardness and by well as by its not containingwater: as means, varieties (henceeasily distinguished micaceous B.B. It is hard in all but some not decrepitating and B.B. becomes strongly magnetic. from the black sulphides);also infusible, affected UnIn polished sections shows white color with a shining,pitted surface. Micro. "

"

"

by reagents. Artif Crystals of hematite have been made by decomposing ferric chloride by steam iron. at a high temperature; also by the action of heated air and hydrochloricacid upon which must contain little from various artificialmagmas, has been crystallized Hematite "

.

or

no

ferrous iron.

in rocks of all ages. This ore The specularvariety is mostly confined occurs canoes, volor metamorphic rocks,but is also a result of igneous action about some crystalline formations contain the argillaceous variety as at Vesuvius. Many of the geological the bottom of or clay iron-stone,which is mostly a marsh-formation, or a deposit over shallow,stagnant water; but this kind of clay iron-stone (that giving a red powder) is The in metamorphic beds that occur than the correspondingvariety of limonite. less common of very rocks are sometimes great thickness,and, like those of magnetite in the same situation,have resulted from the alteration of stratified beds of ore, originallyof which marsh formed at the same time with the enclosingrocks,and underwent were origin, time. metamorphism, or a change to the crystalline condition,at the same of this speciesare brought from the island of Elba, which has Beautiful crystallizations afforded it from a very remote period; the surfaces of the crystalsoften present an irised in Switzerland tarnish and brilliant luster. St. Gothard affords beautiful specimens, composed of crystallized tables grouped in the form of rosettes; near Limoges, France, in large Arendal in crystals;fine crystalsare the result of volcanic action at Etna and Vesuvius. in Sweden; Dognacska, Hungary; Framont in Lorraine, Norway, Langban and Nordmark land, Dauphine, France; Binnental and Tavetsch, Switzerland;also Cleator Moor in Cumberand Minas Geraes,Brazil, afford splendidspecimens. Crystalsfrom Ascension Island Obs.

"

to

and

from Cernero do Campo, Brazil. concentric structure, near Ulverstone

Red in

hematite

occurs

in reniform

of

masses

Lancashire, in Saxony, Bohemia,

and

a fibrous the Harz

Mts., Germany. In North America, widelydistributed, and sometimes in beds of vast thickness in rocks of the Archaean age. Very extensive and important hematite depositsare found along the southern and northwestern shores of Lake Superior. The various districts are known as and are located as follows : The Marquette and Menominee ranges Ranges in northern Mich., the Penokee-Gogebic Range in Northern Wis.,the Mesabi, Vermilion and Cuyuna Ranges Another district, in Minn. the Michipico en, is farther north in Canada. The ore bodies the results of the concentration in favorable localitiesof the iron content of the original are sedimentaryrocks. These rocks contained cherty iron carbonates,pyrite-bearmg iron carbonates and ferrous silicates. The ore bodies of them lying vary widely in form, many in trough-likestructures formed by the deformation of an impervious rock strata. The character of the ores varies from hard specularhematites to soft earthy ores. The latter often mined by the use are of steam shovels. Hematite is found in Wyoming in schist formations In N.

in Lararnie and Carbon

Counties.

Y., in Oneida,Herkimer, Madison, Wayne Cos., a lenticular argillaceous variety, constituting one or two beds in the Clinton group of the Upper Silurian;the same in Pa., and as far south as Ala.,and in Canada, and Wis., to the west; in Ala. there are extensive

417

OXIDES

Besides these regions of enormous Birmingham. beds, value, either crystallized or argillaceous.Some of these localities, interestingfor their specimens, are in northern N. Y., at Gouverneur, and Aroostoqk, Me.; at Antwerp, Hermon, Edwards, Fowler, Canton, etc.; Woodstock Hawley, Mass., a micaceous variety; in N. and S. C. a micaceou varietyin schistose rocks, itabirite. Hematite is mined in Nova or Scotia constitutingthe so-called specularschist,

beds; prominent mines there

are

near

others of workable

numerous

are

Newfoundland.

and

Named Use.

hematite

from

cu^a,

blood.

Used also in red paints, as important iron ore. polishing rouge, etc. isometric form, occurring in octahedrons Iron sesquioxide under an MARTITE. or like magnetite,and believed to be pseudomorphous after magnetite; perhaps dodecahedrons in part also after pyrite. Parting octahedral like magnetite. Fracture conchoidal. H. Color iron-black, sometimes with a bronzed tarnish. Luster submetallic. 4 '8-5*3. 6^7. G. Not The Streak reddish brown or magnetic, or only feeblyso. purplishbrown. in the massive sesquioxide. They are distinguished from crystalsare sometimes embedded magnetite by the red streak,and very feeble,if any, action on the magnetic needle. Found in the Marquette iron regionsouth of Lake Superior,where crystals in the ore; are common Monroe, N. Y.; Twin Peaks, Milliard Co., Utah; Digby Co., N. S.; at the Cerro de Mercado, Durango, Mexico, in largeoctahedrons; in the schists of Minas Gera s, Brazil; near Saxony. Rittersgriin, The

"

most

=

=

ILMENITE

or

Titanic Iron Ore.

MENACCANITE.

Axis Tri-rhombohedral;

c

1'3846.

=

0001

A

1011

rr',1011

A

TlOl

0001

A

2243

cr, en,

Crystalsusuallythick tabular; also platesor laminae. Massive, grains, compact ; in embedded also loose

=

=

=

57" 58*'. 94" 29'. 61" 33'.

rhombohedral.

acute 704

Often

in thin

705

sand.

as

H. Fracture conchoidal. Luster 5-6. 4-5-5. G. submetallic. Color iron-black. Streak submetallic,powder red. black brownish to -

=

Opaque. Influences slightly magnetic needle. If normal, FeTi03 Comp.

the

"

or

FeO,Ti02

=

Oxygen 31-6,titanium

31-6,

but probably to be regarded written (Fe,Ti)2O3, iron 36 *8 Sometimes 100. contains also iron titanate. Sometimes magnesium (picrotitanite) an as replacingthe ferrous iron; hence the generalformula (Fe,Mg)O.Ti02 (Pen=

,

field).(Compare geikielite, p. 586.) the edges in R.F. on B.B. infusible in O.F., although slightlyrounded salt of phosphorus reacts for iron in O.F., and with the latter flux assumes red color in R.F.; this treated with tin on charcoal changes a more or less intense brownish The pulverizedmineral, of titanium is not too small. to a violet-red color when the amount which, filtered from heated with hydrochloricacid,is slowly dissolved to a yellow solution, a beautiful blue assumes the undecomposed mineral and boiled with the addition of tin-foil, violet color. Decomposed by fusion with bisulphateof sodium or potassium. or Diff. Resembles hematite, but has a submetallic,nearly black,streak; not magnetic like magnetite. Obs. Occurs,as an accessory component, in many igneous rocks in grams, assuming it is often in gabbros and diorites. In these occurrences, the place of magnetite, especially the borders of the igneous rock where it is near found in veins or largesegregated masses in the molten supposed to have formed by local differentiation or fractional crystallization Some principal European localities It is also found at tunes in metamorphic rocks. mass. in in the Ilmen Mts. (ilmenite)} St. Cristophe,Dauphine, France (cricktonite) are ; Miask

Pyr., etc.

With

borax

"

"

"

and

418

MINERALOGY

DESCRIPTIVE

(menaccanite) ; Gastein in Tyrol (kibdelophane) ; it remarkable is at Kragero, Norway, where afford crystals 16 pounds. which sometimes in veins or bed 3 in diorite, weighing over occurs in Norway; St. Gothard, Switzerland,etc. Others are Egersund,Arendal, Snarum in Warwick, Amity, and Monroe, inch in diameter, occur sometimes an Fine crystals, from Chester and Quincy, Conn, N. Crystals (washingtonite) Litchfield, Y.; Co., Orange in Quebec, Canada, in at Bay St. Paul Vast depositsor beds of titanic ore occur Mass. Grains are found in the gold sand tyenite;also in the Seignory of St. Francis,Beauce Co. th'e form

of sand

at

Cornwall

Menaccan,

Binnental, Switzerland.

One

of the

most

.

of California. The titanic iron of massive

rocks is extensivelyaltered to a dull white opaque substance, for the most part is to be identified with titanite.

This

by Gumbel.

called leucoxene

H. =6. G. 5'3. Color black. Senaite. (Fe,Mn,Pb)O.TiO2. Tri-rhombohedral. in the diamond-bearing sands of Diamantina, Brazil. Found Streak brownish, black. =

Monoclinic? 5'5. G. 4'25. Fe2O3.3TiO2. Crystal faces rough. H. dark steel-gray. Streak brown. Decomposed by hot concentrated sulphuric acid. 25 miles southeast of Hackberry, Ariz. with gadolinite,

Arizonite.

Color Found

=

Pyrophanite. Manganese

=

In thin tabular rhombohedral titanate,MnTiOa. crystals 4'537. Luster vitreous to sub(p.417). H. =t 5. G. Streak ocher-yellow. From the Harstig mine, Pajsberg,

ilmenite in form and scales, near metallic. Color deep blood-red. Sweden.

=

9Mn2O3.4Fe2O3.MnO2.3CaO. SITAPARITE. Streak black. Color deep bronze. 5*0. G. District Chhindwara, India. =

Notary stallized. Weakly

Good

magnetic.

7. cleavage. H. at Sitapdr, ="=

Found

VREDENBURGITE. 3Mn3O4.2Fe2O3. Cleavage parallel to octahedron or tetragonal G. 6-5. 4 '8. Color bronze to dark pyramid. H. steel-gray.Streak dark brown. at Beldongri,District Ndgpur Strongly magnetic. Completely soluble in acids. Found and at Gravidi,District Vizagapatam, India. =

=

III. Intermediate

Oxides

The specieshere included are retained among the oxides,although chemically considered they are properlyoxygen-salts, aluminates,ferrates, manganates, etc.,and hence in a strict classificationto be placed in section 5 of the Oxygen-salts. The one well-characterized group is the SpinelGroup. ii in

Spinel Group.

RR204

Spinel Ceylomte Chlorospinel Picotite

Hercynite Gahnite (Automolite) Dysluite Kreittonite

ii

or

in

RO.R2O3.

Isometric

MgO.Al2O3 (Mg,Fe)O.Al2O3 MgO. (Al,Fe)2O3

(Mg,Fe)0.(Al,Cr)203 FeO.Al2O3 ZnO.Al2O3

(Zn,Fe,Mn)0.(Al,Fe)2O3 (Zn,Fe,Mg)0.(Al,Fe)2O3

Magnetite

FeO.Fe2O3

Magnesioferrite

(Fe,Mg)O.Fe203 MgO.Fe2O3

Franklinite

Jacobsite

(Fe,Zn,Mn)O.(Fe,Mn)2O3 (Mn,Mg)O.(Fe,Mn)2O3

Chromite

FeO.Cr203

(Fe,Mg)0.(Cr,Fe)203

419

OXIDES

The

speciesof the SpinelGroup

characterized by isometric crystallisation,

are

the octahedron is throughout the common form. All of and, further, the speciesare hard; those with nonmetallic luster up to 7*5-8, the others from

5*5 to 6*5.

SPINEL.

Usually in octahedrons,sometimes with dodecahedral truncations, tw. pi. and cubic. Twins: face o(lll) common .rarely (Fig. comp. 707),hence often called spinel-twins;also repeated and polysynthetic, ducing protw. lamellae. Isometric.

Cleavage: o(lll) imperfect. Fracture Luster 3'5-4'L vitreous; to Color splendent nearlydull. red of various shades,passinginto and blue, green, yellow, brown white. a lmost black; occasionally G.

conchoidal.

=

Streak

white.

nearly opaque.

Transparent

Brittle.

706

H.

=

8.

707

to

Refractive index

:

17155.

n=

aluminMagnesium Comp. ate, MgAl2O4 or MgO.Al2O3 Alumina 71*8, magnesia 28*2 100. The magnesium may be in part replaced by ferrous iron and the aluminium by ferric iron and chromium. "

=

=

or

ganese, man-

""

.

SPINEL RUBY or Magnesia Spinel. Clear red or reddish; transparent to 3 '63-3 71. subtranslucent. G. Compo ition normal, with translucent; sometimes littleor no iron,and sometimes chromium oxide to which the red color has been ascribed. The varieties are: (a) Spinel-Ruby, deep red; b) Balas-Ruby, rose-red; (c) Rubicette, yellow or orange^red; (d) Almandine, violet. to black, CEYLONITE or Pleonaste,Iron-Magnesia Spinel. Color dark green, brown G. 3 '5-3 '6. Contains iron replacingthe magnesium and or mostly opaque nearly so. or (Mg,Fe)O.(Al,Fe)2O3. perhaps also the aluminium, hence the formula (Mg,Fe)O.Al2C"3 CHLOROSPINEL or Magnesia-Iron Spinel. Color grass green, owing to the presence of 3'591-3*594. Contains iron replacingthe aluminium, MgO.(Al,Fe 3O3. G. copper. and also has the magnesium largely Contains chromium PICOTITE or Chrome-Spinel. and chromite. hence lying be ween spinelprope repla ed by iron (Mg,Fe)O.(Al,Cr)2O3, Translucent to nearlyopaque. G. 4 '08. brown or greenishbrown Color dark yellowish B.B. alone infusible. Slowly soluble in borax, more readily in salt of Pyr., etc. phosphorus, with which it gives a reddish bead while hot, becoming faint chrome-green on cooling. Black varieties give reactions for iron with the fluxes. Soluble with difficulty in concentrated sulphuricacid. Decomposed by fusion with potassium bisulphate. Diff. ; zircon Jiasa Distinguishedby its octahedral form, hardness, and infusibility higher specificgravity; the true ruby (p. 413) is harder and is distinguishedoptically; garnet is softer and fusible. Micro. In thin section shows lightcolor and high relief. Isotropic. from the be obtained by direct crystallization Artif Artificial spinel crystalsmay They also form from melts of the oxides or fluorides of pure melt fused in the electric arc. and iron dissolved in boric acid. The addition of chromium magnesium and aluminium oxides will produce various colors. in granular limestone,and with calcite hi serpentine, Obs. embedded Spinel occurs associate of the true ruby. Common gneiss,and allied rocks. Ruby spinelis a common It also occupies the cavities of masses ejected spinelis often associated with chondrodite. from as an volcanoes. some spinel,also picotiteand chromite,occurs Spinel (common those of the peridotite basic igneous rocks especially constituent in many group; accessory taining it is the result of the crystallization of a magma high in magnesia and convery low in silica, of the peridotites alkalies are absent,feldsparscannot alumina; since,as in many dum). form, and the A12O3 and Cr2Os (alsoFe2O3 perhaps) are compelled to form spinel (orcorunThe serpentines which yieldspinelare altered peridotites. Var.

"

"

=

"

=

"

"=

"

=

"

"

"

"

.

"

420

MINERALOGY

DESCRIPTIVE

with beautiful colors, rolled occurs In Ceylon, in Siam, and other eastern countries, as is found at Candy, in with the ruby (cf.p. 414)* Plepnaste pebbles; in upper Burma variety in limestone;small black Ceylon; at Aker, in Sweden, a pale blue and pearl-gray Monte in the of ancient masses Somma, Vesuvius; also at o ccur ejected splendentcrystals Pargas, Finland, with chondrodite,etc.; in compact gehleniteat Monzoni, in the Fassa valley,Austria. From Amity, N. Y., to Andover, N. J.,a distance of about 30 miles,is a region of granular limestone and serpentine,in which localities of spinelabound; colors, green, black, Localities brown, and less commonly red, along with chondrodite and other minerals. and Cornwall; Gouverneur, 2 m. N. and about Warwick, and also at Monroe are numerous f m. W. of Somerville,St. Lawrence Co.; green, blue,and occasionallyred varieties occur at Bolton,Boxborough, etc.,Mass. Franklin,N. J.,affords crystalsof various shades of black,blue,green, and red: Newton, Sterling,Sparta, Hamburgh and Vernon, N. J., are of N. C. as at the Culsagee mine, near other localities. With the corundum Franklin, Ala. Macon Spinelruby at Gold Bluff,Humboldt Co., Cal. Co.; similarlyat Dudleyville, Good black spinelis found in Burgess, Ontario; a bluish spinelhaving a rough cubic form occurs at Wakefield, Ottawa Co.; blue with clintonite at Daillebout,Joliette Co., Quebec. 0

Use.

The

"

colored transparent varieties

are

used

as

gems.

7-5-8. Isometric; massive, fine granular. H. From 3 '91-3 '95. Color black. G. Ronsberg, at the eastern foot of the Bohmerwald, A related iron-alumina spinel,with about 9 p. c. MgO, occurs with magnetite Bohemia. in Cortlandt the tin drift, and corundum township, Westchester Co., N. Y. From Moorina, Tasmania. .

Hercynite.

Spinel, FeAl2O4.

Iron

=

=

Zinc-Spinel. Isometric. Habit octahedral, often with faces striated ||edge between dodecahedron and octahedron; also less commonly in dodecahedrons and modified cubes.- Twins: tw. pi.0(111). Brittle. Cleavage: o(lll) indistinct. Fracture conchoidal to uneven. H. 7-5-8. G. 4-0-4-6. ngr 1'82 (Finland). Luster vitreous, or what someColor dark green, grayish green, deep leek-green,greenish greasy. or black,bluish black,yellowish, grayishbrown; streak grayish. SubtransGAHNITE.

=

=

=

nearlyopaque. Zinc aluminate, ZnAl204 Alumina 55-7, zinc oxide 44-3 The 100. zinc is sometimes ferrous iron,the or replacedby manganese aluminium by ferric iron. to

parent

Comp.

Var.

=

"

AUTOMOLITE,

"

Colors

4-1-4 '6.

or

Zinc Gahnite.

ZnAl2O4,with

"

sometimes

a

littleiron.

G.

=

above

given. DYSLUITE, or Zinc-Manganese-Iron Gahnite. brown G. 4-4*6. or grayishbrown. as

=

"

(Zn,Fe,Mn)O.(Al,Fe)2O3.Color yellowish

=

KREITTONITE,

or

Zinc-Iron

Gahnite.

"

(Zn,Fe,Mg)O.(Al,Fe)2O3.In

crystals,and

H. 4 '48-4 '89. 7-8. G. Color velvet-black to greenish black; granular massive. powder grayishgreen. Opaque. Gives a coating of zinc oxide when treated with a mixture of borax and Pyr., etc. soda on charcoal;otherwise like spinel. Obs. Occurs at Falun and Farila parish,Helsingland, Sweden (automolite) ; Traskbole,Finland; at Tiriola,Calabria,Italy; at Bodenmais, Bavaria (kreittonite)Minas Geraes,Brazil; Ambatofisikely, Madagascar. In the United States,at Franklin Furnace, N. J.,with franklinite and willemite;also at Sterling with pyriteat Hill,N. J. (dysluite); Rowe, Mass.; at a feldsparquarry in Delaware Co., Pa.; sparingly at the Deake mica mine, Mitchell Co.,N. C.; at the Canton Mine, Ga.; with galena,chalcopyrite, pyrite at the Cotopaxi mine, Chaffee Co., Col. In Canada at Raglan, Renfrew Co., Ontario. =

=

"

"

',

Named

after the Swedish ,

a

chemist

Gahn.

The

name

of Ekeberg, is Automolite,

deserter, alludingto the fact of the zinc occurringin

MAGNETITE.

an

from

unexpected place.

Magnetic Iron Ore. Isometric. Most commonly in octahedrons,also in dodecahedrons with faces striated ||edge between dodecahedron and octahedron (Fig.710); in dendrites between platesof mica; crystals sometimes highlymodified; cubic

421

OXIDES

forms

Twins: tw. pi.o(lll),sometimes rare. as striations octahedral face lamellae, on an producing 708

age or

polysynthetictwinning often a pseudo-cleav-

and

709

710

(Fig.474, p. 176). Massive with laminated structure;granular,coarse fine;impalpable. often highlydeveloped. FracCleavage not distinct;partingoctahedral, ture subconchoidal

Brittle. H. 5 '5-6*5. metallic and 5-168-5-180, crystals. Luster splendent to submetallic and rather dull. Color ironblack. Streak black. Opaque, but in thin dendrites in mica nearly transparent and pale brown to black. Strongly magnetic; sometimes possessing polarity G.

to

uneven.

=

=

711

(lodestone) .

ii

in

FeFe2O4

Iron sesquioxide Oxygen 27-6, iron or, The 72 '4 100. ferrous iron sometimes replacedby contains magnesium, and rarelynickel;also sometimes titanium (up to 6 p. c. TiO2).

Comp.

"

or

69.0, iron protoxide 31 '0

FeO.Fe2O3 =

=

100;

=

Ordinary. (a) In crystals. (") Massive,with pseudo-cleavage,also granular, fine, (c) As loose sand, a black earthy kind. Ordinary magne(d) Ocherous: tite 6f attractingparticles of iron itself. The is attracted by a magnet but has no power property of polaritywhich distinguishesthe lodestone (lessproperly written loadstone) is Var.

coarse

"

"

or

exceptional. G. 4-41-4*42; luster submetallic; weak magnetic; in crystalsfrom Magnesian. Sparta, N. J.,and elsewhere. Containing 3'8 to 6 '3 p. c. manganese (Manganmagnetite). From Manganesian. Sweden. Vester Silfberg, B.B. very difficultly fusible. In O.F. loses its influence on the magnet. Pyr., etc. Soluble in hydrochloricacid and solution reacts for With the fluxes reacts like hematite. =

"

"

"

both

ferrous and

ferric iron.

also from garnet, by of the spinelgroup, as Distinguishedfrom other members its being attracted by the magnet, as well as by its high specific gravity; franklinite and chromite are only feeblymagnetic (ifat all),and have a brown or blackish brown streak; also,when massive, by its black streak from hematite and limonite; much harder than Diff.

"

tetrahedrite. In polished sections shows Micro. "

cone.

HC1 Artif.

white

brown. is frequently formed as when they are low in the

slowly turns Magnetite

color with

a

shining,pitted surface..

With

a furnace product. It is easilyformed in artificialmagmas percentage of silica. It is formed by the lar minerals in processes simibreaking down of various minerals or by interreactions among to those of contact metamorphism. in Obs. Magnetite is mostly confined to crystallinerocks, and is most abundant It is found metamorphic rocks,though widely distributed also in grainyin eruptiverocks. most abundantly in the ferro-magnesian rocks, occurring at times in large segregated "

"

422

DESCRIPTIVE

MINERALOGY

mense often highly titaniferous. In the Archaean rocks the beds are of imIt is an ingreunder the same conditions as those of hematite. dient The called emery. in most of the massive variety of corundum earthy magnetite Occurs in meteorites,and forms the crust of meteoric is found in bogs like bog-iron ore.irons. in the mica of many localitiesfollowing the direction of in dendrite-like forms Present alterationand perhaps of secondary origin. A common the lines of the percussion-figure, product of minerals containing iron protoxide, e.g., present in veins in the serpentine resultingfrom altered chrysolite. The beds of ore at Arendal, Norway, and nearly all the celebrated iron mines of Sweden, and the Taberg in Smaland. consist of massive magnetite, as at Dannemora Falun, in chlorite slate. Splendid embedded in Sweden, and Corsica,afford octahedral crystals, in Wermland. The most dodecahedral at Nordmark crystals occur powerful native they are also obtained on magnets are found in Siberia,and in the Harz Mts., Germany; mineral are Traversella in Piedmont, the island of Elba. Other localitiesfor the crystallized Predazzo, at Rothenkopf and WildItaly; Achmatoysk in the Ural Mts.; Scalotta,near kreuzjoch,Austrian Tyrol; the Binnental,Switzerland; Sannatake, Bufen, Japan. In North America, it constitutes vast beds in the Archaean, in the Adirondack region, Co. the iron Warren, Essex, and Clinton Cos., in Northern N. Y., while in St. Lawrence is mainly hematite; fine crystalsand masses ore showing"broad parting surfaces and yielding in N J.; in large pseudo-crystalsare obtained at Port Henry, Essex Co.; similarly It Canada, in Hull, Greenville,Madoc, etc.; at Cornwall in Pa., and Magnet Cove, Ark. also in N. Y., in Saratoga,Herkimer, Orange, and Putnam occurs Cos.; at the TillyFoster iron mine, Brewster, Putnam Co., in crystalsand massive accompanied by chondrodite, etc. In N. J.,at Hamburg, near Franklin Furnace and elsewhere. In Pa., at Goshen, Chester Co., and at the French Creek mines; delineations forming hexagonal figuresin mica at In Cal.,in Sierra Co., Pennsbury. Good lodestones are obtained at Magnet Cove, Ark. In Wash., in large abundant, massive, and in crystals;in Plumas Co.; and elsewhere. Fine crystals deposits. In crystalsfrom Millard Co., Utah. from Fiqrmeza, Cuba. from the loc. Magnesia bordering on Macedonia. Named But Plinyfavors Nicander's derivation from Magnes, who firstdiscovered it,as the fable runs, by finding,on takinghis herds to pasture, that the nails of his shoes and the iron ferrule of his staff adhered to the These

masses.

are

extent, and

occur

ground. Use.

important

An

"

ore

of iron.

FRANKLINITE.

Isometric. into rounded

Habit octahedral;edges often rounded, and crystals passing grains. Massive,granular,coarse or fine to compact. or Pseudo-cleavage, parting,octahedral,as in magnetite. Fracture conchoidal to uneven. Brittle. H. 5'5-6'5. G. 5-07-5-22. Luster metallic, sometimes dull. Color iron-black. Streak reddish brown or black. Opaque. Slightlymagnetic. Comp. but varying rather widely in the (Fe,Zn,Mn)O.(Fe,Mn)2O3, =

=

"

relative quantitiesof the different metals general formula of the spinelgroup.

present, while

conforming to

the

Pyr., etc." B.B. infusible. With borax in O.F. gives a reddish amethystine bead (manganese), and in R.F. this becomes bottle-green (iron). With soda gives a bluish green manganate, and on charcoal a faint coatingof zinc oxide,which is much marked more when a mixture with borax and soda is used. Soluble in hydrochloric acid, sometimes with

evolution of a small amount of chlorine. Diff. Resembles magnetite, but is only slightly attracted dark brown streak; it also reacts for zinc on charcoal B.B. "bs" in cubic occurs "

T"*1^ (^ermany

at

masses JN.

Altenberg,near

J., with

wulemite

associated distant,

Use. *;' about at

An

"

ore

and

crystalsnear

Eibach

by the magnet, and in Nassau;

has

a

in amorphous

Aix-la-Chapelle.Abundant at Mine Hill, Franklin Furnace in granular limestone;also at SterlingHill,two miles zmcite

with willemite. of zinc.

Magnofernte.

H. 6-6'5 G. MgFe?O4. In octahedrons. streak as in magnetite. Strongly magnetic. Formed the fumaroles of Vesuvius-, and especiallythose of the eruption of 1855; also found

H4t"54.

iviont

jJor

Luster

color, and

=

=

MINERALOGY

DESCRIPTIVE

424

tabular 11a(100) Face angles(Fig.395, p. 164) Crystalsgenerally striation (Fig.713). in twins a feather-like vertically, quitedistinct;6(010)imperfect;a(100) more Cleavage: ""(QH)

striated

a

.

.

conchoidal.

to

uneven

Brittle.

H.

8-5.

=

G.

ture FracLuster

so.

3'5-3'84.

=

grass-green, emerald-green, greenishwhite, vitreous. Color asparagus-green, bine-red yellow;sometimes raspberry-or columbrown; greenish and yellowish green; to lucent. transuncolored. Streak Transparent transmitted light. by asteriated. and or bluish chatoyancy, Sometimes a opalescence Z (= c axis)emeraldPleochroic,vibrations ||Y (= b axis) orange-yellow, Ax. +. pi.||6(010). Bx. _L Optically X ( a axis)columbine-red. green, 43'. 84" 2E 1'757. 1748. 1747. 0 7 c(001). a =

Var.

Color

Ordinary.

1.

"

and then used

as

a

=

=

=

=

pale green, being colored by iron; also yellow and

parent trans-

gem.

Color emerald-green,but columbine-red by transmitted light;valued Crystals of results, ^upposed to be colored by chromium. 3 G. '644, mean as a gem. often very large,and in twins,like Fig. 395, either six-sided or six-rayed. 3. Cat's-eye. Color greenishand exhibitinga fine chatoyant effect;from Ceylon. 2.

Alexandrite.

"

=

"

Beryllium aluminate,BeAl2O4 Comp. 100. glucina19 '8 "

BeO.Al203

or

Alumina

=

80'2,

=

dull. B.B. alone unaltered; with soda, the surface is merely rendered tion, salt of phosphorus fuses with great difficulty.Ignited with cobalt soluthe powdered mineral gives a bluish color. Not attacked by acids. Diff. Distinguishedby its extreme hardness, greater than that of topaz; by its inin contrast with beryl. also characterized by its tabular crystallization, fusibility; In Minas Obs. Geraes,Brazil,in rolled pebbles; from Ceylon in pebbles and crystals; in Moravia; in the Ural Mts., 85 yersts from Ekaterinburg, in mica slate at Marschendorf southern Ural with beryl and phenacite,the varietyalexandrite;in the Orenburg district, Mts., yellow; in the Mourne Mts., Ireland. In the United States at Haddam, Conn., in granitetraversinggneiss,with tourmaline, Saratoga, N. Y., with tourmaline,garnet, and apatite; garnet, beryl; at Greenfield,near has been found in crystalsin the rocks of New York City; in Me. at Norway, in granite with garnet and at Stoneham, with fibrolite, at Topsham, Buckfield and Greenwood. Chrysoberylis from xpvvos, golden,ftrjpvXXos, beryl. Cymophane, from Kv/j.a, wave, and sometimes exhibit. Alexandrite "f"aij"a), appear, alludes to a peculiaropalescencethe crystals is after the Czar of Russia,Alexander I. Use. As a gem stone; see under Var. above.

Pyr., etc.

With

borax

"

or

"

"

"

Hausmannite.

167);

E. uster

also

In tetragonaloctahedrons Mn3O4 or MnO. Mn2O3. H. granular massive, particlesstrongly coherent. =

submetallic.

Color

brownish black. Streak chestnut-brown. in Thuringia, Germany; .Ilefeld in the Harz nau Mts., Germany; Nordmark, in Sweden; from Brazil.

and

twins

5-5'5. Occurs

(Fig.414,

G.

4'856.

=

Ilme-

near

Filipstad,Langban,

Coronadite. Massive H. with delicate fibrous structure. (Mn,Pb)Mn3O7. 4. G. 5'2. Color black. Streak brownish black. vein of the CliftonOccurs in Coronado Morenci district, Arizona. Hollandite is a similar manganate of manganese, barium 'and ferric iron from the Kaljlidongrimanganese mine, Central India. =

=

Cesllrolite. H2PbMn3O8. In cellular masses. From Sidi-Amer-bers-Salem, Tunis. Minium. vivid

Pb304

red, mixed

or

with

Badenweiler Jjjifel;

in

Color,steel-gray.H.

=

4'5.

G.

5'29.

=

2PbO.PbO2. scales. G. 4'6. Color as crystalline Pulverulent, yellow; streak orange-yellow. Occurs in Germany at Bleialf in the =

Baden, etc.

Crednerite. Cu3Mn4O9 or 3CuO.2Mn2O3. Foliated crystalline.H. 4'5. G. 5*1. Luster metallic. Color iron-black to steel-gray. Streak black, brownish. =

=

4'9From

Fnednchroda,Germany. Pseudobrookite. Probably Fe4(TiO4)3. Usually in minute orthorhombic crystals, tabular ||a(100) and often prismatic|| the macro-axis. G. 4-4-4'98. Color dark brown to black, btreak ocher-yellow.Found with hypersthene(szaboite) in cavities of the andesite ot Aranyer Berg, Transylvania, and elsewhere;on recent lava (1872) from Vesuvius; at Havredal, Bamle, Norway, embedded in kjerulfine (wagnerite)altered to apatite. =

425

OXIDES

BRAUNITE.

metric Tetragonal. Axis c 0;9850. Commonly in octahedrons,nearly iso70" 7'). Also massive. in angle (ppf 111 A 111 to subconchoidal. Brittle. Cleavage : p(lll) perfect. Fracture uneven Luster submetallic. 4-75-4-82. H. Color and streak,dark G. 6-6-5. black to steel-gray. brownish Silica lO'O,manganese 3Mn203.MnSiO3 ganese protoxide11 '7,manComp. 78 -3 100. sesquioxide =

=

=

=

=

"

=

B.B. infusible. With borax and salt of phosphorus gives an amethystine Pyr., etc. in O.F., becoming colorless in R.F. With soda gives a bluish green bead. Dissolves in hydrochloric acid leavinga residue of gelatinoussilica. Marceline gelatinizes with acids. Obs. Occurs in veins traversingporphyry, at Oehrenstock, near Ilmenau, Thuringia, and near Ilefeld in the Harz Mts., Germany; St. Marcel in Piedmont, Italy; at Elba; at the manganese mines of Jakobsberg, also at at Botnedal, Upper Tellemark, in Norway; from Marceline (heterocline) Langban, and at the Sjo mine, Grythyttan, Orebro, Sweden. St. Marcel, Ptedmont, is impure braunite. In black isometric crystals. H. G. 6-6'5. Bixbyite. EssentiallyFeO.MnO2. "

bead

"

=

=

4'945.

with topaz in cavities in

Occurs

Utah.

Dioxides, RO2.

IV. Rutile

from rhyolite;

Group.

Tetragonal c

c

Cassiterite

SnO2

0-6723

Rutile

TiO2

0-6442

Polianite

MnO2

0'6647

Plattnerite

PbO2

0'6764

includes the dioxides of the elements tin,manganese, GROUP in the tetragonalsystem lead. These compounds crystallize similar anglesand axial ratio;furthermore in habit and method with closely between the two best known of twinning there is much species similarity considered as salts here. minerals sometimes these included are Chemically of their respective acids,as stannyl metastannate, (SnO)SnO3, for cassiterite and titanylmetatitanate, (TiO)TiO3,for rutile. '

The

RUTILE

titanium,and

included Zircon. 0'6404. the Rutile Group is also sometimes ZrO2SiO2; c the silicates, with the allied speciesThorite, work, however, Zircon is classed among 0-6402. ThO2.SiO2, c A tetragonalform, approximating closelyto that of the speciesof the Rutile Group, of other species, as Xenotime, YPO4; Sellaite, MgF2; Tapiolite, belongs also to a number With

=

In this

=

Fe(Ta,Nb)2O6. It may

be

added

that

ZrO2,

as

in the monoclinic the speciesBaddeleyite, crystallizes

system. CASSITERITE.

Tin-stone,Tin Ore

Tetragonal. Axis ee', 101 ee", 101 ""', 111 ss", 111

c

0-6723.

=

A

Oil

=

46" 28'.

ms,

110

A

111

=

A

101

=

67" 50'.

A

231

=

A

111

=

58" 19'.

zz', 321 zzv",321

A

321

=

A

111

=

87"

46" 27'. 20" 53"' 61" 42'.

7'

tw. pi.e(101);both contact- and penetration-twins Twins common: (Fig. 717); often repeated. Crystalslow pyramidal; also prismaticand acutely sive, Often in reniform shapes, structure fibrous divergent;also masterminated. in rolled or grains. granular impalpable;

426

MINERALOGY

DESCRIPTIVE

Cleavage: a(100) imperfect;8(111) more

m(110) hardly distinct.

so;

Brittle. H.

6-7.

Fracture subconchoidal to uneven. usuallysplendent. Color adamantine, and crystals

times red, gray, white, or

transparent

to opaque.

G.

Luster

6-8-71.

=

brown

or

black;

some-

717

716

715

714

=

Nearly yellow. Streak white,grayish,brownish. 2-0934. Indices: e co 1-9966, + Optically =

=

.

In crystalsand massive. Ordinary. Tin-stone. and reniform shapes, concentric in structure, and radiated In botryoidal Wood-tin. fibrous internally, although very compact, with the color brownish, of mixed shades,looking like dry wood in its colors. Toad's-eyetin is the same, on a smaller scale. Streamsomewhat along the beds of streams or in gravel. tin is the ore in the state of sand, as it occurs Var.

"

Comp.

Tin

"

Ta2O5 is sometimes

dioxide,Sn02

=

Oxygen

21'4, tin 78'6

B.B. alone unaltered. On charcoal with soda reduced Pyr.,etc. gives a white coating. With the fluxes sometimes gives reactions for Only slightlyacted upon by acids. "

=

100.

A

little

present,also Fe2O3. to

metallic tin,and

iron and

manganese.

Artif Cassiterite has been artificially prepared by the action of aqueous upon vapor tin tetrachloride in a heated tube and by other similar methods employing heated vapors. Obs. Cassiterite has been noted as an originalconstituent of igneous rocks but usually in veins traversinggranite,rhyolite, it occurs quartz porphyry, pegmatite, gneiss,mica schist,chlorite or clay schist; also in finelyreticulated veins forming the ore-deposits called stockworks, or simply impregnating the enclosing rock. It is most commonly found in quartz veins traversinggranite,accompanied by minerals containing boron and fluorine which indicates a pneumatolytic origin. The commonly associated minerals are quartz, wolframite, scheelite;also mica, topaz, tourmaline, apatite,fluorite;further pyrite,arsenopyrite, sphalerite;molybdenite,native bismuth, etc. less so, in Cornwall, in fine crystals, and also as wood-tin Formerly very abundant, now and and Tavistock stream-tin; in Devonshire, near elsewhere; in pseudomorphs after St. Agnes, Cornwall; in fine crystals,often twins, at feldspar at Wheal Coates, near Schlackenwald,Graupen, Joachimstal, Zinnwald, etc.,in Bohemia, and at Ehrenfriedersdorf, Altenberg,etc.,in Saxony; at Limoges, France, in splendid crystals;Sweden, at Fmbo; Finland,at Pitkaranta. In the East Indies,on the Malay peninsula of Malacca and the neighboring islands, Banca, and Bilitong In New Borneo. near South Wales abundant of 8500 sq. over an area miles,also in Victoria, In Bolivia in veins containing silver, Queensland and Tasmania. lead,and bismuth; Mexico, in Durango, Guanajuato,Zacatecas,Jalisco. In the United States,in Me., sparinglyat Paris, Hebron, etc. In Mass., at Chesterfield and Goshen, rare. In N. H., at Jackson. In Va.. on Irish Creek, Rockbridge Co., with wolframite,etc. In N. C. and S. C. In Ala.,in Coosa Co. In S. D., near Harney Peak and near Custer City in the Black Hills, where it has been mined. In Wy., in Crook Co.; in Dillon. In Cal.,in San Bernardino Mon., near Has been mined in Co., at Temescal. the York district, Seward Peninsula,Alaska. Use. The most important ore of tin. "

.

"

"

427

OXIDES

In composite parallelgroupings of minute Polianite. Manganese dioxide, MnO2. 6-6'5. crystals;also forming the outer shell of crystalshaving the form of manganite. H. Color lightsteel-grayor iron-gray.Streak black. Luster metallic. From 4'992. G. It is distinguishedfrom pyrolusiteby its hardness and its anhydrous Flatten, Bohemia. Like pyrolusiteit is often a pseudomorph after manganite. character. =

=

RUTILE.

0-64415.

Tetragonal. Axis_c =

"vu, 310 ee't 101 ee", 101

A

310

=*

A

Oil

=

A

101

=

36" 54'. 45" 2'. 65" 34*'.

tw.

A

111

A

111 133

A

=

=

=

56

25|'.

84" 40'. 29" 6'.

719

718

Twins:

ss', 111 """, 111 it', 313

720

pi.(1)e(101);often geniculated(Figs.720,

721

also contact-twins of very varied habit,sometimes and eightlings sixlings (Fig.399, p. 164; Fig.413, p. 166).

721) ;

(2)v(301) rare, contact-twins (Fig.415, p. 167). Crystals rowed; furcommonly prismatic,verticallystriated or often slender acicular. Occasionallycompact, massive.

Cleavage: a(100) and w(110) distinct;s(lll) in conchoidal

Brittle. H. 6y6'5.G. metallic-adamantine. Color reddish brown,

Luster

to

uneven.

=

=

traces.

Fracture

4'18-4'25; also

subto 5'2.

times passing into red; someyellowish, bluish,violet, black,rarelygrass-green; by transmitted light deep red. Streak pale brown. Optically+. Transparent to opaque. Refractive indices high: co 2-9029. 2-6158, e Birefringencevery high. Sometimes abnormally biaxial. Titanium 100. Comp. dioxide,Ti02 Oxygen 40'0, titanium 60'0 A littleiron is usuallypresent, sometimes to 10 iron While the present up p. c. is often reported as ferric the probability is that in the unaltered mineral it =

"

=

=

=

existed in the ferrous state. The formula for rutile may be written as a titanylmetatitanate (TiO)TiO3 With this the ferrous titanate FeTiO3 may be considered isomorphous and so account for the iron frequentlypresent. It has been suggested that the tapiolitemolecule, FeO.Ta2O5 is also rutile and cassiterite, isomorphous and that tapiolitebelongs in the same as see group below. ilmenorutile, Var. 4* lS-4'25. parent TransOrdinary. Brownish red and other shades,not black. G. is sometimes quartz (sagenite) penetrated thicklywith acicular or capillarycrystals. Dark smoky quartz penetrated with the acicular rutile or "rutilated quartz,"is the Filches d'amour Fr. (or Venus hair-stone). Acicular crystalsoften implanted in parallel position tabular crystalsof hematite; also somewhat on on magnetite. similarly contains up to 30 p. c. of Ferriferous, (a) Nigrine is black in color,whence the name; ferrous titanate. ing (b) Ilmenorutile is a black varietyfrom the Ilmen Mts., Russia; containiron in the form of ferrous titanate,niobate and tantalate. 5'14. G. Struverite is the same mineral with greater amounts of the niobate present, (c) Iserine from Iserweise, Bohemia, formerly considered to be a varietyof ilmenite is probably also a ferriferous rutile. "

=

=

428

MINERALOGY

DESCRIPTIVE

B.B. infusible. With salt of phosphorus gives a colorless bead, which in varieties contain iron,and give a brownish violet color on cooling. Most of the bead with after treatment in violet the bead red only appearing R.F., or yellow alkali or soluble by fusion with an Insoluble in acids; made metallic tin on charcoal. foil, of acid,with the addition of tinThe solution containing an excess alkaline carbonate. gives a beautiful violet color when concentrated. red color. luster and brownish Characterized by its peculiar sub-adamantine Diff. alone heated unaltered when in being entirely Differs from tourmaline,vesuvianite,augite etc.

pyr

R.F.

assumes

"

a

"

B.B. Specificgravityabout 4, of cassiterite 6'5. In thin sections shows red-brown to Micro. order of interference color. "

yellow color,very

high relief and

high

Rutile has been formed artificially by heating titanic oxide with boric oxide, Artif ing sodium tungstate, etc. Rutile,octahedrite and brookite have all been formed by heatpotassiumtitanate and calcium chloride in a current of hydrochloricacid gas and air. RutUe is formed at the highesttemperature, brookite at lower temperatures, and octahedrite at the lowest of all. in granite,gneiss,mica mineral Obs. Rutile occurs schist,and syeas an accessory in granular limestone and dolomite; common, nitic rocks,and sometimes a secondary as slates. A dike rock from Nelson Co.,Va., consists product,in the form of microlites in many often in of rutile and apatite. It is generallyfound in embedded essentially crystals, of quartz or feldspar, and frequentlyin acicular crystalspenetrating quartz ; also masses It has also been met with in in phlqgopite (which see),and has been observed in diamond. It is common in grains or fragments in many hematite and limenite,rarelyin chromite. auriferous sands. localitiesare: Arendal and Kragero in Norway; Horrsjoberg,Sweden, with Prominent lazulite and cyanite; Saualpe, Carinthia;in the Ural Mts.; in the Tyrol, Austria; at St. Gothard and Binnental,Switzerland; at Yrieux, near Limoges in France; at Ohlapian in Transylvania,nigrine in pebbles;in largecrystalsin Perthshire,Scotland;in Donegal Co., Ireland. In Ver., at Waterbury; In Me., at Warren. in middle also in loose bowlders and northern Vermont, acicular, some specimens of great beauty in transparent quartz. In In N. Y., in Orange Co., at Chester. Mass.,at Barre,in gneiss;at Shelburne,in mica slate, Edenville;Warwick; east of Amity. In Pa., at Sudsbury,Chester Co., and the adjoining districtin Lancaster Co.; at Parksburg, Concord,West Bradford, and Newlin, Chester Co.; House at the Poor In N. J.,at Newton, with spinel. In N. C., at quarry, Chester Co. Crowder's Mountain; at Stony Point,Alexander Co., in splendent crystals. In Ga., in Habersham Co.; in Lincoln Co., at Graves' Mountain, with lazulite in largeand splendent crystals. In Ark.,at Magnet Cove, commonly in twins,with brookite and perovskite, also "

.

with

"

as

paramorphs after brqokite. Fine specimens of "rutilated

Tavetch Use.

"

and A

5-5*5.

Lead G.

dioxide, PbO2.

8'5.

Luster

Geraes, Brazil; Madagascar; Co., N. C.

Alexander

Rarely

submetallic. From Leadhill and Wanlockhead, Scotland. Cceur d'Alene Mts., Idaho. =

Minas

of titanium.

source

Plattnerite. H.

quartz," from

elsewhere, Switzerland;West Hartford,Ver.;

=

in prismatic crystals,usually massive. Color iron-black. Streak chestnut-brown. Also at the "As You Like" mine, Mullan,

Baddeleyite. Zirconium dioxide, ZrO2. In tabular monoclinic crystals.H. 6'5. "t. Colorless to yellow,brown and black. From Index,174. Ceylon; from Brazil near Caldas, Minas Geraes and Jacupiranga, where it is associated with zirkelite, (brazilite) Noted at Mte. (Ca,Fe)0.2(Zr,Ti,Th)O2. Also near Somma, Vesuvius. Boseman, Mon. Various minerals occurringas rolled pebbles in the diamond sands of Brazil are known as favas (beans). Some of them consist of nearlypure TiO2 others of nearly ZrO2, while pure others are various phosphates. Paredrite is a "fava," composed of TiO2 with a little =

=

5-5-6-0.

water.

Uhligite. Ca(Ti Zr)05.Al(Ti,Al)06.Isometric. Octahedral. Color black. Brown transparent on thin edges. Found in a nephelinesyeniteon the shore of Lake Magad, ri.QQt. A

and

TT1OQ

OCTAHEDRITE.

Anatase.

Tetragonal. Axis c Commonly octahedral =

17771. in

habit,either

acute

(p,111),or obtuse (v,117);

429

OXIDES

also tabular,c(001) predominating;rarely prismaticcrystals; frequently highlymodified. 101 ee',. ee", 101 ppf, 111 pp",Ul zz', 113

vv'

A

117

A

Oil

A

101

=

A

111

=

A

111

=

A

113 117

Cleavage:

c

76"

5'

121"

16'

82"

9' 36'

=

136"

722

723

1' 54" 27" 39'

=

=

and

(001)

p

(111)

subconchoidal. perfect. Brittle. H. 5-5-6. G. 3-82-3-95; sometimes 4-11-4-16 after heating. Luster adamantine amantine. metallic-ador Color various shades of and brown, passing into indigo-blue, black; greenishyellowby transmitted light. Streak uncolored. Transparent to nearly opaque. Optically 2-493. Sometimes rather high. Indices: o" mally abnorBirefringence 2-554,e biaxial. Titanium 100. Comp. Oxygen 40'0, titanium 60*0 dioxide,TiO2 Fracture =

=

"

.

=

=

=

"

=

Same as for rutile. See under rutile. Obs. Most abundant at Bpurgd'Oisans,in Dauphine, France, with feldspar, axinite, and ilmenite; Hof in the Fichtelgebirge, near zerland; SwitGermany; at Selva and Naderanertal, Norway; the Ural Mts.; in chlorite in Devonshire, near Tavistock; with brookite at Tremadoc, in North Liskeard and at Tintagel Cliffs; in Brazil Wales ; in Cornwall, near in quartz, and in detached crystals. In Switzerland in the Binnental the variety wiserine, long supposed to be xenotime; also Cavradi, Tavetsch; Rauris, Salzburg,in the Eastern Alps; also at Pfitsch Joch. In the United States,at the Dexter lime rock,Smithfield, R. L, in dolomite; from granite pegmatite, Quincy, and from Somerville,Mass.; in the washings at Brindletown,Burke Co.,N. C.,in transparent tabular crystals;at Magnet Cove, Ark.; in unusual crystalsfrom Beaver Creek, Gunnison Co., Col.

Pyr.,etc. Artif.

"

"

"

BROOKITE.

Orthorhombic.

Axes

a

:

mm'", zz',

110

A

lIO

112

A

112

=

zz"'

112

A

112

=

=

b

: c

=

0-8416

:

1

:

0-9444.

80" 10'. 53" 48'.

ee', 122 ee'", 122

A

122

=

A

122

=

44" 46'.

110

A

122

=

725

me,

of varied habit. Only in crystals, Cleavage: w(110) indistinct; c(001) still more adamantine

to

78" 57'. 45" 42'. 727

726

to uneven.

44" 23'.

Fracture choidal subconso. 5-5-6. Luster metallicG. Brittle. H. 3-87-4-08. Color hair-brown,yellowish;reddish,reddish submetallic. =

=

and translucent;also brown

brown to

MINERALOGY

DESCRIPTIVE

430

grayishor yellowish,a

characters,

Comp. Pyr.

Titanium

Same

"

iron-black, opaque. 0

2*586.

=

7

=

2741.

Streak uncolored Other optical

p. 298.

see "

to

2-583.

=

as

dioxide,TiO2

=

Oxygen 40*0, titanium

60'0

==

100.

for rutile.

at Bourg d'Oisans in Dauphine, France; in Switzerland at St. Gothard, and albite quartz, and Maderanertal; in the Ural Mts.; district of Zlatoust,near Miask, with river and elsewhere; at Fronolen, near Tremadoc, in the Sanarka and in the gold-washings Brazil. Bahia, Lencoes, From Companhia, Wales. at Magnet Cove, Ozark Mts., (arkansite) In the United States in thick black crystals black garnet, schorlomite,rutile, etc.; in small crystalsfrom the goldArk. with elaeolite, Ulster Co., N. Y., on quartz, with chalof N. C.; at the lead mine at Ellenville,

Obs.'"Occurs

washings copyriteand galena; after the

Named

at

Paris,Me., Somerville,Mass.

Englishmineralogist,H.

J. Brooke

(1771-1857).

PYROLUSITE.

Orthorhombic, but perhapsonly pseudomorphous.

Commonly

columnar,

often divergent;also granularmassive,and frequentlyin reniform coats. Luster 473-4-86. 2-2-5. G. Soft, often soilingthe fingers. H. black Streak sometimes bluish. dark metallic. Color iron-black, steel-gray, submetallic. Opaque. or bluish black, sometimes (p.427). Commonly Manganese dioxide,MnO2, like polianite Comp. contains a little water (2 p. c.),it having had usually a pseudomorphous =

=

"

origin(aftermanganite). is an independent species, form of with a crystalline It is uncertain whether pyrolusite from the dehydration of manganite; its own, or only a secondary mineral derived chiefly also from polianite (Breith.).Pseudomorphous crystalshaving distinctlythe form of

manganite

common.

are

etc. I^r.,

in the closed tube. but most varieties yieldsome Like polianite, water in its reaction Hardness less than that of psilomelane. Differs from iron ores B.B. for manganese Easilydistinguishedfrom psilomelane by its inferior hardness, and less brown. or usuallyby being crystalline.Its streak is black; that of manganite is more Diff.

"

"

Obs.

Manganese

"

ore

deposits in general

are

secondary

in

origin,the

manganese

of the rocks having been concentrated in favorable places. They often occur as at Elgersberg near irregularbodies in residual clays. Pyrolusiteis extensivelyworked Ilmenau, and other places in Thuringia, Germany; at Vorderehrensdorf in Moravia; at Flatten in Bohemia, and elsewhere; near phalia, Johanngeorgenstadt,at Hirschberg in Westcontent

Germany; Matzka, Transylvania; in Australia; in India. Occurs in the United States' with psilomelane, abundantly in Ver., at Brandon, etc.; at Plainfield and West Stockbridge,Mass.; Augusta Co.,Va.; Pope, Pulaski,Montgomery Cos.,Ark. In New Negaunee, Mich.; Lake Co., N. M. Brunswick, 7 m. from Bathurst. In Nova

Scotia,at Teny Cape; at Walton, etc. is from -nvp, fire,and \oveiv,to wash, because used to discharge the brown (FeO) tints of glass;and for the same green it is whimsically entitled by the reason

The and

name

French le savon de verriers. An ore Use. of manganese; as an mine oxidizingagent in manufacture of chlorine,broand oxygen; as a drier in paints, a decolorizer in glassand in electric batteries, ing as colormaterial in bricks,pottery, glass, etc. "

B. HYDROUS

OXIDES.

ddes the DIASPORE Among the hydrous oxides Gi GROUP is well characterized. belongthe hydroxides 3 of aluminium, iron and an The general manganese.

Here

in

formula

is

properlywritten RO(OH).

The

three

specieshere included

are

432

MINERALOGY

DESCRIPTIVE

In thin scale-like or tabular crystals, usually attached by one edge. Also in Var. slender prisms,often radiatelygrouped: the or acicular or capillary(not flexible) crystals, (SammetIt passes into a varietywith a velvetysurface;the Przibramite Needle-Ironstone. Also columnar, fibrous,etc.,as above. blende) of Pfibram,Bohemia, is of this kind. "

Comp.

FeO(OH) or Fe203.H2O sesquioxide89*9,water

"

Oxygen 27'0, iron 62'9, water

=

10*1

Iron

100, or

=

101

100.

=

and is converted into red iron sesquiIn the closed tube gives off water oxide. reaction,and some, With the fluxes like hematite; most varieties give a manganese treated in the forceps in O.F., after moistening in sulphuricacid, impart a bluish green acid. color to the flame (phosphoric acid). Soluble in hydrochloric Diff. Distinguishedfrom hematite by its yellow streak; from limonite by crystalline nature; it also contains less water than limonite. with the other oxides of iron,^ Obs. Found especiallyhematite or limonite. Occurs at Eiserfeld near Siegen,in Nassau, Germany; Pfibram, Bohemia; at Clifton,near Bristol, Iron mine, Negaunee, Lake In the United States,at the Jackson England; in Cornwall. Easton; in the Pike's Peak region and at Superior; in Conn., at Salisbury;in Pa., near Gothite (Goethite)after the poet-philosopher Goethe (1749-1832) CrystalPeak, Col. Named A colloidal form of iron hydroxide having the composition of goethite and occurring as pseudomorphs after pyritehas been called ehrenwerthite. Use. An ore of iron.

Pyr., etc.

"

"

.

"

.

"

but Lepidocrocite. A dimorphous form of goethite. Orthorhombic 4'09. 2*20. Strongly pleochroic. Scaly,fibrous. G "

axial ratio.

=

with

different

=

MANGANITE.

Orthorhombic.

Axes

a

:

b

: c

=

0*8441

730

729

1

:

0-5448.

hh'", mm'", ee', ee', ppf,

410

A

410

=

110

A

110

=

205

A

205

Oil

A

Oil

111

A

Til

23" 80" 28" 57" 59"

=

=

=

50'. 20'. 57'. 10'.

5|'.

Crystals commonly prismatic,the faces deeply striated vertically; often in bundles. Twins: tw. pi. grouped e(011). Also columnar; stalactitic. Cleavage:6(010)very perfect; w(110) Brittle. perfect. Fracture uneven. H. 4. G. 4-2-4-4. Luster submetallic. Color dark Streak reddish steel-grayto iron-black. brown, sometimes nearly black. Opaque; in minute splinterssometimes brown by transmitted light. =

Comp.

"

Pyr.,etc.

MnO(OH) or Mn2O3.H20 Oxygen 27'3, manganese 100, or Manganese sesquioxide897, water 10-3 100. =

10'3

water

=

=

62'4,

=

In the

closed tube yieldswater; manganese reactions with the fluxes, p. 339, Obs. Occurs in Germany at Ilefeld in the Harz Mts.; Ilmenau in Thuringia; Langban and Bolet, Sweden; Cornwall,at various places; also in Cumberland, etc. In the Lake Superior mining region at the Jackson Devil's "

"

mine, Negaunee;

Col.

In Nova

Scotia, at Cheverie,Hants ody mountain, Albert Co., etc.

Co., and

Sphenomanganiteis a varietyof manganite

from

Walton.

In New

Head, Douglas Co., Brunswick, at Shep-

Langban, Sweden, showing sphenoidal

forms.

Use.

"

An

LIMONITE.

ore

of manganese.

Brown

Hematite.

Not

crystallized.Usually in stalactitic and botryoidalor mammillary torms, having a fibrous or subfibrous structure; also concretionary,massiveand

occasionally earthy.

433

OXIDES

Luster G. 3'6-4-0. silky,often submetallic; sometimes Color of surface of fracture various shades of brown, comearthy. monly dark, and none bright; sometimes with a nearly black varnish-like yellow, ocher-yellow. Streak yellowish exterior;when earthy, brownish brown. Opaque.

H. dull and

5-5*5.

=

=

Var. (1) Compact, Submetallic to silkyin luster;often stalactitic, etc. botryoidal, often impure from the presence of (2) Ocherous or earthy,brownish yellow to ocher-yellow, The ore from marshy places,generally loose or porous in clay,sand, etc. (3) Bog ore. in compact texture, often petrifyingleaves,wood, nuts, etc. (4) Brown clay-ironstone, "

often

masses,

Comp.

in

nodules. concretionary

Approximately 2Fe203.3H2O Oxygen 257, iron 59'8, water 100. The water content 100, or Iron sesquioxide85 '5,water 14*5 varies widely and it is probable that limonite is essentially an amorphous form of goethitewith adsorbed and capillary In the bog ores water. and and humic other ochers,sand, clay,phosphates,oxides of manganese, or acids of organicoriginare very common impurities. 14'5

=

"

=

=

Like gpthite.Some varieties leave a siliceous skeleton in the salt of phosPyr., etc. phorus bead, and a siliceous residue when dissolved in acids. Diff Distinguishedfrom hematite by its yellowishstreak,inferior hardness,and its reaction for water. Does not decrepitateB.B., like turgite. Not crystallized like gothite and yieldsmore water. "

"

.

Obs.

In

all

result of the alteration of other ores, or minerals containing moisture, air,and carbonic or organic acids; derived largely from the change of pyrite,magnetite, siderite, ferriferous dolomite,etc.; also various which contain iron in the ferrous state (FeO). species(asmica, pyroxene, hornblende,etc.), Waters containing iron in solution when brought into marshy places deposit the metal usually in the form of limonite. The evaporation of the carbonic acid in the water which held the iron in solution is one for the separationof the iron oxide. This separation cause is also aided by the so-called "iron bacteria" which absorb the iron from the water and later deposit it again as ferric hydroxide. Limonite consequentlyoccupies,as a bog ore, It is marshy places,into which it has been borne by streamlets from the hills around. also found in depositsassociated with iron-bearinglimestones where the originaliron content of the rock has been largelydissolved and redepositedlater in some favorable spot. Limonite forms the capping or gossan, iron hat,of many metallic veins. It is often associated with manganese Limonite is a common in Bavaria, the Harz Mts., Germany, ores. ore "

iron,through

cases

a

to

exposure

Luxemburg, Scotland,Sweden,

etc.

Abundant in the United States. Extensive beds exist at Salisbury and Kent, Conn., also in the neighboring towns of N. Y., and in a similar situation in Berkshire Co., Mass., and in Ver.; in Pa., widely distributed;also in Tenn., Ala.,Ohio, etc. Named Limonite from Xei/icoi", meadow. Use. An ore of iron; as a yellow pigment. "

TURGITE. Probably to be considered Hydrohematite. Approximately 2Fe2O3.H2O. as a solid solution of goethitewith hematite together with enclosed and adsorbed water. Resembles the limonite but has a red streak. From 4'14-4'6. G. DecrepitatesB.B. Intermediate between Turginsk mine in the Ural Mts., etc.; also from Salisbury,Conn. hematite and limonite. =

G. HYDRO GOETHITE. 3Fe203.4H20. Orthorhombic, radiating fibrous. H. =4. Color and streak brick-red. With limonite at various localities in Tula, Russia. stellate and concentric; also In fine needles or fibers, Xanthosiderite. Fe2O3.2H2O. ocher. red. Associated with manganese Color golden yellowish, brown to brownish an =

37.

as ores

at

Ilmenau,Thuringia, Germany,

Esmeraldaite. choidal fracture. Esmeralda Co., BAUXITE.

Fe203.4H2O. H.

=

2'5.

G.

=

etc.

In small

pod-shapedmasses

2 '58.

Color coal black.

enclosed in limonite. streak. Yellow-brown

ConFrom

Beauxite.

concretionarydisseminated grains. Also massive,oolitic;and to ocher-yeHow,brown, Color whitish, G. 2'55. earthy,clay-like. grayish, In round

=

and

red.

434

MINERALOGY

DESCRIPTIVE

Var.

2 Clay-like,wocheinite;the concretionarygrains,or oolitic;bauxite. containing very little iron oxide; also red from the iron grayish,clay-like,

1. In

"

kind

purer

oxide present.

EssentiallyA1203.2H2O Comp. however, give A12O3.H2O analyses,

some

Alumina

=

"

like

73'9, diaspore.

26'1

water

=

100;

of Bauxite is probably a mixture of varying character but containinglarge amounts This substance has been called sporogelite or colloidal form of Al2Os.H2O. diasporogelite, cliachite and alumogel. in large amount, in part replacing Iron sesquioxideis usually present,sometimes has been suggested for this hematogelite alumina, in part only an impurity. The name colloidal form of ferric oxide. Silica, phosphoricacid, carbonic acid,lime, magnesia are '

a

impurities.

common

Bauxite is a product of the decomposition of certain rocks,particularlythose The laterites and has been found under various conditions. feldspars, plagioclase of India,etc.,are probably similar in originand might be considered as iron-rich bauxites. Bauxite is certainlynot a definite mineral speciesbut consists of a mixture of several From Baux different materials. nated (orBeaux), near Aries,and elsewhere in France, dissemiin grains in compact limestone,and also oolitic. Wocheinite occurs in Carniola, The purest bauxite is used for the manuFeistritz and Lake Wochein. facture Austria,between In the United of aluminium ore. (aluminum), and is called aluminum States, in Saline and Pulaski Cos.,Ark.; also in Cherokee bauxite occurs and Calhoun Cos.,Ala., and Walker and in Floyd, Barton Cos.,Ga. Obs. rich in

"

Use.

As

"

an

aluminum

ore.

Brucite

R(OH)2. Rhombohedral

Group.

BRUCITE.

Jlhombohedral. Axis

c

1-5208; cr 0001

=

H. and

=

2-5.

=

A

G.

=

2-38-2-4.

flexible, nearly as

Also

60"

=

20i',rr' 1011

commonly foliated massive; fibrous,

Cleavage:c(0001)eminent.

in gypsum.

Sectile.

Luster

to vitreous. Color white,inclining to gray, waxy to translucent. Indices: o"r Optically+ =

.

Comp. --Magnesium 69*0,

1011

97"

37J'. Crystalsusuallybroad tabular. fibers separableand elastic. 1101

A

31*0

water

=

100.

hydroxide, Mg(OH)2 Iron

and

blue,or

1-559,er

manganese

Folia separable

||c pearly,elsewhere green.

=

MgO.H2O protoxide are

or

Transparent

1-5795. =

Magnesia sometimes

present. Var-

Ordinary,occurringin plates,white

to pale greenish in color; strong pearly cleavage surface. Nemalite is a fibrous varietycontaining 4 to 5 p. c. iron 2 "44. Manganbrucite contains protoxide, with G. occurs granular; color manganese; luster

on

"

the

=

honey-yellowto

brownish red. Ferrobrucitecontains iron. In the closed tube givesoff water, Pyr.,etc. becoming opaque and friable, sometimes the manganesian varietybecomes turning gray to brown; dark brown. B.B. infusible, glows with a bright light, and the ignitedmineral reacts slightly alkaline to test-paper. ignited with cobalt solution gives the pale pink color of The pure mineral is magnesia. soluble in acids without effervescence. "

i,

by -its. infusibility, D/SitingUiS^ P^vT softness, cleavage,and than talc and

harder

differs in separate it from gypsum,

its

in acids; the magnesia solubility

which

foliated structure. Is test and opticalacters char-

is also somewhat softer. other magnesian minerals in serpentine, Swmaness in Unst, Shetland Isles;at the iron mine of Cogne Aosta Italy;near Fihpstadt in Sweden. At Hoboken, N. J, in serpentine; at the Tilly Foster iron N. Y, well crystallized; nime, Brewster Richmond Co , N. Y.; at Wood's e *' m "r several inches across, m-asses'and often crystallizations ? 5 From rom Riverside Crestmore, verse resmore, a. Co., Nemalite, o., Cal. fibrvHHp variety, occurs the fibrous at Hoboken, N. J.,and at Xettes in the ur Vosges Mts. Mangos

dary mm"f a.1 accompanying Arsecon "l"n f^'r^also found m limestone. At

hydjomagnesite

435

OXIDES

with hausmannite and other manganese minerals in the granular limestone occurs Jakobsberg, Nordmark, Sweden. Named after the early American mineralogist,A. Bruce (1777-1818). like brucite. Luster Pyrochroite. Manganese hydroxide, Mn(OH)2. Usually foliated, 1723. In 1'681. pearly. Color white, but growing dark on exposure, e in magnetite at Pajsberg, also at Nordmark Sweden and occurs Langban; in N. J. at brucite of

"

to

Franklin

=

=

Furnace.

Backstromite. Sweden.

Manganese

GIBBSITE.

Hydrargillite.

hydroxide, Mn(OH)2.

Orthorhombic.

From

Langban,

Monoclinic. Axes a : b : c 17089 85" 29'. Crystals: 1 : 1-9184; 0 tabular |c(001), in spheroidal concretions. hexagonalin aspect. Occasionally Also stalactitic, small mammillary, incrusting, with smooth or surface,and often a faint fibrous structure within. 2-5-3 -5. G. 2-3-2-4. Cleavage: c(001) eminent. Tough. H. Color white,grayish, reddish white. Luster of c(001)pearly;ot or greenish, other faces vitreous;of surface of stalactites faint. Translucent;sometimes A strong argillaceous odor transparent in crystals.Indices,1-535-1-558. when breathed on. Aluminium Alumina Comp. hydroxide, A1(OH)3 or A1203.3H20 =

=

=

=

=

"

34-6

65-4,water Pyr.,etc.

"

100.

=

In the closed tube

B.B. inand yieldswater. white and opaque, color to the flame. Ignited with cobalt in concentrated sulphuricacid. aluminate are slowlydecomposed by carbon dioxide

becomes

''usible, whitens, and does not impart a solution gives a deep blue color. Soluble Artif

When

"

.

solutions of sodium

green

gibbsiteis precipitated. The crystallized Obs. in the Shishimsk mountains near occurs gibbsite(hydrargillite) Zlatoust in the Ural Mts. ; also in crystalsfilling cavities in natrolite at Langesundfiord, Norway; Ouro Preto, Minas Geraes, Brazil. Occurs in nodular platesat Kodikanal, Palni Hills,Madras, and at Talevadi,Bombay, India. In the United States,in stalactiticform at Richmond, Mass., in a bed of limonite ; at the Clove Mine, Union Vale, Dutchess Co., N. Y., on limonite;in Orange Co., N. Y. Named after Col. George Gibbs. Sassolite. Boric acid,B(OH)3. Usually small, Crystalstabular ||c(001) (triclinic). 1'48. the waters of the Tuscan lagoons white, pearly scales. G. Index, 1*46. From of Monte Rotondo and Castelnuovo,Italy. Exists also in other natural waters, as at Clear Lake, in Lake Co., Cal. Occurs also abundantly in the crater of Vulcano, Lipariisles. what someHydrotalcite. Perhaps Al(OH)3.3Mg(OH)2.3H2O. Lamellar-massive,or foliated, fibroiR. H. =2. Luster G. 2 -04-2 '09. Color white. pearly. Uniaxial, 1'47. Occurs at the mines of Shishimsk,district of Zlatoust,Ural Mts.; at Snarum, w Norway, in serpentine. Thin tabular crystals. Pyroaurite. Perhaps Fe(OH)3.3Mg(OH)2.3H2O. Rhombohedral. G. H. 2-07. 2-3. Luster pearly to greasy. Color yellow to yellow-brown. subOccurs at the Langban iron-mine,Wermland, Sweden, in gold-like Optically of a silvery metallic scales (pyroaurite) From the Moss mine, Norway. In thin seams white color in serpentinein the island Haaf-Grunay, Scotland (igelstromite). In druses of minute Chalcophanite. Hydrofranklinite. (Mn,Zn)O.2MnO2.2H2O. tabular rhombohedral gates; crystals;sometimes octahedral in aspect. Also in foliated aggrestalactitic and 3 '907. Luster metallic,brilliant. Color oluish plumose. G. Streak chocolate-brown,dull. Occurs at SterlingHill,near black to iron-black. Ogdensburg, Sussex Co., N. J. From Leadville,Col. BrownHetserolite. In radiating botryoidal masses. Black. 2ZnO.2Mn2O3.lH2O. 4 '85. Col. (Wolfblack streak. H. =5. G. From Franklin,N. J., and Leadville, tonite). "

=

=

-.

=

=

=

"

.

.

=

=

436

DESCRIPTIVE

V^Oe.H^O.

ALAITE.

Found

Rare.

MINERALOGY

bluish red moss-like

in dark

in Alai Mts.,

masses

Turkestan.

near

Amorphous,

A12O8.4H2O. SHANYAVSKWE. Moscow, Russia.

transparent material

found

in

dolomite,

PSILOMELANE.

5-6. G. 37-4-7. botryoidal;reniform;stalactitic. H. dull. Streak brownish black, shining. Color iron-black, Luster submetallic, passinginto dark steel-gray.Opaque. ganese A hydrous manganese manganate in wjrichpart of the manComp. or is often replaced by barium potassium, perhaps conforming to The material is generally H4Mn06. very impure, and the compositionhence

and

Massive

=

=

"

doubtful. varieties yield water, and all lose oxygen In the closed tube most on tion; igniSoluble in hydrochloricacid,with evolution with the fluxes reacts for manganese. of chlorine. A common but impure ore of manganese; Obs. frequentlyin alternating layerswith In Germany and Cornwall. at Ilefeld in the Harz Devonshire Mts., pyrolusite. From From the Crimea, Russia; also various localities in India. at Ilmenau, Siegen, etc. In Independence Co., and elsewhere in at Brandon, etc.,Vt. Forms mammillary masses Scotia. Named from ^i\6s,smooth Ark. With pyrolusiteat Douglas, Hants Co., Nova

Pyr., etc.

"

"

or

naked, and ne\as, black. Use.

"

An

ore

of manganese.

followingmineral substances here included are mixtures of various oxides,chiefly of manganese (MnO2, also MnO), cobalt,copper, with also iron,and from 10 to 20 p. c. These results of the decomposition of other ores water. are phides, partlyof oxides and sulpartly of manganesian carbonates, and can hardly be regarded as representing distinct mineral species. WAD. In amorphous and reniform masses, either earthy or compact; also in crusting or as stains. G. 3'0Usuallyvery soft,soilingthe fingers;less often hard to H. =6. Color dull black, 4-26; often looselyaggregated, and feelingvery light to the hand. The

"

=

bluish or brownish black. BOG MANGANESE consists mainly of oxide of manganese and water, with iron,and often silica, alumina, baryta. ASBOLITE, or Earthy Cobalt,contains oxide of cobalt,which sometimes 32 p.

oxide of

some

amounts

to

c.

LAMPADITE,

or

Cupreous Manganese, is a wad

containing4

to 18 p.

c.

of oxide of copper,

and often oxide of cobalt also. SKEMMATITE. Color black. Streak dark 3MnO2.2Fe2O3.6H2q. Fusible to magnetic globule. Alteration product of pyroxmangite. Co.,S. C. BELDONGRITE. 6Mn306.Fe2O3.8H20. District Ndgpur, India.

VI.

Luster

pitchy.

Color

H. brown. 5'5-6. From Iva, Anderson

black.

=

From

Beldongri,

OXYGEN-SALTS

The Sixth Class includes the salts of the various acids. oxygen into the following sections: 1. Carbonates;2. Silicates and seven 3. Niobates and Tantalates;4. Phosphates, Arsenates,

Titanates;

Nitrates;5. Borates and Uranates;6. Sulphates,Chromates 7. Tungstatesand Molybdates.

Tellurates;

These

fall

etc.; also the and

1. CARBONATES A.

the

Anhydrous Carbonates

The Anhydrous Carbonates include two distinct isomorphous groups, CALCITE GROUP and the ARAGONITE GROUP. The metallic elements

437

CARBONATES

present

cobalt; The

in

former

the

in the

calcium, magnesium, iron, calcium, barium, strontium

are

latter,they

species included 1.

as

are

Calcite

zinc

manganese, and lead.

are

follows:

RCO3.

Group.

Rhombohedral rr'

CaC03

Calcite

Normal

Tri-rhombohedral

(Ca,Mg)C03 CaC03.MgC03

Dolomite Dolomite

and

c

74"

55'

0-8543

73"

45'

0-8322

Ankerite

CaC03.(Mg,Fe)C03

73"

48'

0-8332

Magnesite

MgC03 (Mg,Fe)C03 2MgC03.FeC03 MgCO3.FeCO3

72"

36'

0-8112

72"

46'

0 -8141

72"

42'

0-8129

Breunnerite Mesitite Pistomesite

FeCO3

Siderite

MnCO3

Rhodochrosite

Manganosiderite Manganocalcite

0-8184

73"

0'

0-8184

72"

20'

0-8063

of the

isomor-

(Mn,Fe)C03 (Mn,Ca)CO3

pt.

ZnCO3

Smithsonite

(Zn,Fe)C03

Monheimite

CoCO3

Sphaerocobaltite

This list gives not only the compounds. phous intermediate

the species show, cleavage, the angle varying

2.

group,

but

also

in the

is exhibited

Group.

Aragonite

above.

table

Orthorhombic

RC03.

:

b

: c

48'

0-6224

:

1

:

07206

:

07302

mm'"

63"

CaCO3

Aragonite

some

by rhombohedral crystallization. distinctly crystallized, perfect rhombohedral 75" (and 105") in calcite to 73" (and 107") from

when

This

species of this

prominent

is characterized

GROUP

CALCITE

All

in siderite.

0'

(Fe,Mn)C03

Oligonite

The

73"

a

Bromlite

(Ca,Ba)CO,

Witherite

BaCO3

62"

12'

0-6032

:

1

SrC03

62"

41'

0-6090

:

1

:

0*7239

PbC03

62"

46'

0-6100

:

1

:

07230

Strontianite Cerussite

crystallize in the orthorhombic close by more Group is made system, 60" (and 120") the fact that the prismatic angle varies a few degrees only from with the fundamental forms and the twinned prism as twinning-plane are The

species of

but

the

pseudo-hexagonal

the

relation

ARAGONITE to

those

in character.

GROUP

of the

Calcite

438

MINERALOGY

DESCRIPTIVE

CALCITE.

Calc Spar; Calcareous

Axis

Rhombohedral.

c

ce, me,

rr'.

MM', ff',

=

0001 0001

A

1011

A 1010 A 1011 A 4041 A

0112 0112

=

1101

=

0112 0554

A

1012

0221

A

*

A

4401 5054 2021

=

=

=

=

=

=

Rhombohedral

Spar.

0*8543.

44" 36"'. 26" 15'. 63" 45'. 74" 55'. 114" 10'. 45" 3' 84" 101"

324'. 9'.

735

734

733

732

731

cr*

RC03.

Group.

Calcite

1.

w',

2131

A

wv,

2131

A

wvi, yy't

2131

A

3251

A

yyv,

3251 3251

A

5231

A

2351

A

3124 4135

yy*,

v, 2134 wv, 3145

A

2311 3121 1231 3521

See the stereographic projection, Fig. 269, p. 108.

=

=

75" 22'. 35" 36'. 47"

=

=

=

=

=

=

1|'.

70" 59'. 45"

32'.

29" 16'. 20" 36f '. 16" 0'.

440

MINERALOGY

DESCRIPTIVE

or less undulating; color white, the lamellae more Argentineis a pearlylamellar calcite, variety,is a foliated white sparry grayish,yellowish.Aphrite, in its harder and more it approaches chalk, though lighter, in kinds its softer n ear argentine; calcite, pearly

silverywhite or yellowishin color,soft and greasy to the touch, and more pearly in luster, less scaly in structure. Aphrite has been thought to be aragonite pseudomorphous

or

after gypsum. kinds: Limestone, Marble, Chalk. 3. Granular massive to cryptocrystalline because like loaf sugar in fracture, named so Granular limestone or Saccharoidal limestone, hence to compact limestone; colors to varying from coarse very fine granular,and

various,as white,yellow,reddish,green; usuallythey are clouded and give a handsome fit for polishing,or for such limestones are the material is polished. When called marbles. Many varietieshave special architectural or ornamental use, they are or fire-marbleis a dark Shell-marble consists largelyof fossil shells;Lumachelle names. with brilliant fire-likeor chatoyant internal reflections. Ruin-marble brown shell-marble, blance resemis a kind of a yellow to brown color,showing, when polished,figuresbearing some to fortifications, temples,etc.,in ruins,due to infiltrationof iron oxide,etc. Lithographicstone is a very even-grainedcompact limestone,of buff or drab color;as tion that of Solenhofen,Bavaria. Hydraulic limestone is an impure limestone which after ignitakes a solid form under water, due to the formation of a silicate. The sets, i.e., French varieties contain 2 or 3 p. c. of magnesia, and 10 to 20 of silica and alumina (or clay). The varieties in the United States contain 20 to 40 p. c. of magnesia, and 12 to 30 Hard compact limestone varies from nearly pure white,through p. c. of silicaand alumina. and reddish shades,to bluish gray, dark brownish gray, and grayish,drab, buff,yellowish, beautiful marble when ished. polblack, and sometimes variouslyveined. Many kinds make Shades of green are due to Red oxide of iron produces red of different shades. iron protoxide,chromium oxide,iron silicate. and soft enough to leave a trace on a board. Chalk is white,grayishwhite,or yellowish, It is composed of the shells of minute sea organisms. Calcareous marl is a soft earthy deposit,with or without distinct fragments of shells;it generallycontains much clay,and graduatesinto a calcareous clay. Oolite is a granularlimestone,its grainsminute concretions, like the lookingsomewhat of fish, the name roe coming from u6i",egg. Pisolite consists of concretions as largeoften or larger, as a small pea, having usuallya distinct concentric structure. careous Depositedfrom calcareous springs,streams, or in caverns, etc. (a) Stalactites are calthat hang from the roofs of limestone caverns, and which are cylindersor cones formed from the waters that drip through the roof; these waters hold some calcium bicarbonate in solution, and leave calcium carbonate to form the stalactite when evaporation takes place. Stalactites vary from transparent to nearly opaque; from a crystalline structure with singlecleavage directions to coarse ating fine granular cleavable and to radior fibrous;from a white color and colorless to yellowishgray and brown. mite (6) Stalagis the same material from the waters covering the floors of caverns, it being made that drop from the roofs,or from sources the bottom or sides; cones of it sometimes over rise from the floor to meet the stalactites above. It consists of layers, curved, irregularly or bent. or a solid kind of travertine (seebelow) when Stalagmite, is the on a largescale, alabaster stone of ancient writers,that is,the stone of which ointment vases, of a certain form called alabasters, made. A locality were well known, was near Thebes, now largely and the material has often been hence called Egyptian alabaster. exploredby the ancients, It was also formerlycalled onyx and onychitesbecause of its beautiful banded structure. In the arts it is often now called Oriental alabaster or onyx marble. Very beautiful marble of this kind is obtained in Algeria. Mexican is a similar material obtained from onyx lecah, Puebla,Mexico; also in a beautiful brecciated form from the extinct crater of Zempoaltepecin southern Mexico. Similar kinds occur in Missouri, Arizona, San Luis Obispo Co., California, (c) Calc-sinter, Calc Tufa. Travertine is of essentially the Travertine, same but is distinctively origin with stalagmite, a depositfrom springsor rivers,especially where m largedeposits, as along the river Anio, at Tivoli, near Rome, where the depositis ot feet in thickness. icores Similar material is being deposited at the Mammoth Hot Springs,Yellowstone Park, (d) Agaric mineral; Rock-milk is a very soft white material, breaking easilym the fingers, deposited sometimes in caverns, or about sources holding lime in solution, (e) Rock-meal is white and light, like cotton, becoming a powder on the slightest pressure. are

effect when

B.

These toward

VARIETIES

include: Dolomitic

true

dolomite.

Also

BASED

UPON

COMPOSITION

calcite. Contains magnesium baricalcite (which contains some

carbonate, thus graduating BaCO3); similarly,stron-

441

CARBONATES

tianocalcite

(SrCO3), ferrocalcite(FeCO3), manganocalcite (MnCOa) (see under agnolite, 582), zincocalcite (ZnCO3), plumbocalcite(PbCOs), cobal'ocalcite (CoCO3). B.B. infusible, Pyr., etc. glows, and colors the flame reddish yellow; after ignition the assay reacts with alkaline; moistened hydrochloric acid imparts the characteristic p.

"

lime color to the flame. In the solid mass effervesces when moistened in cold acid. acid,and fragments dissolve with brisk effervescence even aragonite, p. 447.

with hydrochloric See further under

Diff. Distinguishing characters: perfect rhombohedral be cleavage; softness,can scratched with a knife; effervescence in cold dilute acid; infusibility. Less hard and of lower specific in its different varieties the gravity than aragonite (which see). Resembles other rhombohedral carbonates, but is less hard, of lower specificgravity, and more varieties of barite,but has lower specific readily attacked by acid. Also resembles some gravity; it is less hard than feldsparand harder than gypsum. "

Micro. Recognized in thin sections by its low refraction and very high birefringence, the polarizationcolors in the thinnest sections attaining white of the highest order. The colored rings,is also characteristic. negative interference figure,with many closelycrowded The rhombohedral cleavage is often shown in the fine fracture lines;systems of twinned lamellae often conspicuous (Fig.750), especiallyin crystalline limestone. "

Crystals of calcite are formed when a solution of calcium carbonate in dilute acid is evaporated slowly at ordinary temperatures. Calcite is formed when aragonite is heated, the transformation being complete at 470". Artif

"

.

carbonic

Calcite, in

its various forms, is one formed sedimentarylimestone,

of the most widely distributed of from organic remains, shells,crinoids, corals,etc., yield on metamorphism crystallinelimestone or marble, and in connection calcite and also depositsin caves with these crystallized of stalactites and stalagmitesoften Common with the zeolites in cavities and veins of igneous rocks as a result of occur. A frequent with granite, syenite, etc. alteration,and similarlythough less abundant mineral in metalliferous deposits,with lead, copper, silver,etc. Deposited from limebearing waters as calc sinter,travertine, etc.,especiallyin connection with hot springs as Hot at the Mammoth Springs in the Yellowstone region. localities for crystallized calcite are the following: Andreas^Some of the best known berg in the Harz Mts.; the mines of Freiberg, Schneeberg, etc., in Saxony; Kapnik in Hungary; Aussig in Bohemia; Bleiberg in Carinthia; Traversella in Piedmont, Italy; and Elba. In England at Alston Moor Matlock, Derbyshire; Egremont in Cumberland; in Durham; Beer Alston in Devonshire; at numerous points in Cornwall; Weardale Stank mine, Lancashire, In twin crystalsof great variety and beauty at Guanajuato, The Iceland spar has been obtained from Iceland near Mexico. Helgustadir on the Eskein a largecavity in basalt. The crystals, fiord. It occurs usuallyshowing the fundamental rhombohedron, are often coated with tufts of stilbite. in N. Y., in St. Lawrence calcite occurs In the United States,crystallized Co., especially at the Rossie lead mine; in Jefferson Co., near dog-toothspar, in Niagara Co., Oxbow; nd Lowville, and near Lockport, with pearlspar, celestite,etc.; in Lewis Co., at Leyden of the Hudson, formerly groups at Anthony's Nose at the Martinsburg lead mine; on In N. J.,at Bergen, yellow large tabular crystals;twins from Union Springs, Cayuga Co In Va., at Wier's cave, stalactitesof great beauty; also in calcite with datolite,etc. In pyramidal crystalsfrom of Ky. the large caves Kelly's Island, Lake Erie. At the Lake mines, complex crystalsoften containing scales of native copper. Superior Copper Obs. minerals.

"

Beds

of

in great variety of form, lininggeodes and implanted on quartz crystals; Warsaw, 111., Quincy. In Mo., with dolomite,near St. Louis; also with sphaleriteat Joplin and other points in the zinc region in the south-western part of the state,the crystalsusually scalenothe Bad From Hazel Green. Lands, of a wine-yellow color. Wis., from hedral and S. p. In Nova Scotia,at Partridge Island, a wine-colored calcite,and other interesting At at

varieties. Use.

"

In

the

manufacture

of mortars

and

cements;

material; as a flux in metallurgicaloperations; Iceland in whitewash, etc. prisms; chalk as a fertilizer,

as

spar

a

building and

is used

to

make

ornamental

polarizing

scale in carbonate A tufa deposit of calc um occurring on an enormous Mono about Lake, Cal. It forms layers of interlaced Nev.; also occurs color and often skeleton structure except when crystalsof a pale yellow or light brown covered by subsequent deposit of calcium carbonate. THINOLITE.

north-western

MINERALOGY

DESCRIPTIVE

442

Pearl Spar pt.

DOLOMITE.

Tri-rhombohedral. 0001

or

10T1 A Ilt)l

A

rr\lOll

Axis =

=

c

=

0-8322. MM',

43" 52'. 73" 45'.

4041

A

4401

113"

=

53'.

the presence of rhomthe second or third of bohedrons series after the phenacitetype very faces comcharacteristic. The monly r curved or made up of suband thus passing into individuals,

or M(4041); rhombohedral,usuallyr(10ll)

Habit

752

751

(Fig. 752). saddle-shaped forms or Also granular, coarse fine, marble. resemblingordinary r(1011)perfect. Cleavage: Brittle. subconchoidal. eties. varito pearlyin some Luster vitreous,inclining 2-8-2-9. G. 3-5-4. Color white, reddish,or greenishwhite; also rose-red,green, brown, 1-68174. w and black. Transparent to translucent. Optically Fracture

H.

=

=

=

"

gray e

=

.

1-50256.

Comp.

Carbonate

"

dolomite

CaMgC2O6

of calcium or

and

CaC03MgCO3

magnesium =

Carbon

for normal dioxide 47-9,lime 30-4,

(Ca,Mg)CO3;

45*65 carbonate 54-35,magnesium carbonate from carbonates of varies the two in which the ratio Varieties occur 100. also frequentlyenter replacing The carbonates of iron and manganese 1:1. the magnesium carbonate and grading to ankerite ; rarelycobalt and zinc

magnesia 21'7

=

100,or Calcium

=

carbonates. B.B. acts like calcite. In solution gives tests for magnesium and usually Pyr.tetc. are only very slowly acted upon, Fragments thrown into cold acid,unlike calcite, acid the mineral is readilydissolved with effervescence. while in powder in warm if at all, "

for iron.

brown on ferriferous dolomites become exposure. calcite (seep. 441), but generallyto be distinguishedin that it does Resembles in cold acid. not effervesce readilyin the mass The results of many periments exArtif. Artificialdolomite has been formed in several ways. Sea favorable for its formation. would indicate that heat and pressure are heated in a sealed tube produced dolomite. water in contact with calcium carbonate when observed that such reactions take place more It has been readily with aragonite than with calcite, indicatingthe possibilityof coral deposits (aragonite)being transformed into dolomite. Micro. often shows Similar to calcite in thin sections except that it more crystal outlines and less commonly polysynthetictwinning. Obs. Massive dolomite constitutes extensive strata,called limestone strata,in various and compact varieties regions,as in the dolomite regionof the southern Tyrol. Crystalline often associated with serpentineand other magnesian rocks,and with ordinary limestones. are Dolomite, as a rock,is of secondary origin,having been transformed from ordinary limestone by the action of solutions containingmagnesium. This change, called dolomititake place in various ways. involve The more favorable conditions would zaiion,may heat,pressure, high magnesium content of waters and long periodsof time. Consequently the older and more stone deeply buried in the earth's crust the greater is the probabilityof a limeDolomite is also commonly a vein mineral,frequently being converted into dolomite. Some occurringwith various metallic ores. prominent localitiesare: Leogang in Salzburg, In Switzerland, Austria; Schemnitz and Kapnik in Hungary; Freibergin Saxony, Germany. at Bex, in crystals; also in the Binnental; Traversella in Piedmont and Campolongo, Italy. In unusual dark colored crystalsfrom Teruel,Spain. In the United States,in Ver.,at Roxbury. In N. J.,at Hoboken. In N. Y. at Lockport, Niagara Falls,etc.; at the TillyFoster iron mine, Brewster, Putnam Co., with magnetite, chondrodite. In Pa. at Phoenixville. In saddle-shapedcrystalswith the sphalerite The

Diff.

"

"

"

"

CARBONATES

443

In fine crystalsfrom Alamosa, In N. C. at Stony Point, Alexander Co. of Joplin,Mo. Alaska. who announced of the marked Named after Dolomieu (1750-1801), some characteristics its not effervescingwith acids,while burning like limestone, of the rock in 1791 and after heating in acids. solubility Use. of certain cements; As a building and ornamental stone; for the manufacture for the production of magnesia used in the preparationof refractory in metallurgical linings furnaces "

"

.

CaCO3.(Mg,Fe,Mn)CO3,_or for normal ankerite 2CaCO3.MgCO3.FeCO3. 48' also crystallinemassive, granular, rhombohedral crys als; rr' 1011 A 1101 =73" Color white,gray, reddish. Occurs with siderite at the Styrian 2 -95-31. G. compact. From mines. Traversella,Italy. With the hematite of northern New York/ Ankerite.

In

=

MAGNESITE.

rr' 1011 A TlOl Axis: c 0-8112. 72" 36'. Crystals usuallyrhombohedral, also prismatic. Commonly massive; granular cleavable to very compact; earthy. 3-5Cleavage: r(1011)perfect. Fracture flat conchoidal. Brittle. H. 4-5. G. 3-0-3-12, cryst. Luster vitreous; fibrous varieties sometimes silky. Color white, yellowish,or grayish white, brown. Transparentto 1*717. 1*515. c co Optically opaque. Carbon dioxide 52'4,magMagnesium carbonate,MgC03 Comp. nesia Rhombohedral

=

=

rare,

=

=

=

=

"

.

=

"

47-6

100.

=

carbonate

Iron

is often present.

Breunnerite contains several p. c. of FeO; G. 3-3 '2; white, yellowish, brownish, rarelyblack and bituminous; often becoming brown on exposure, and hence called Brown Spar. B.B. resembles calcite and dolomite,and like the latter is but slightly acted Pyr.,etc. cold in powder is readilydissolved with effervescence in warm by acids; upon chloric hydroacid. In solution gives strong test for magnesium with littleor no calcium. Obs. formed Found as a secondary mineral by the alteration of various magnesian veins minerals;in talcose schist,serpentineand other magnesian rocks, also gypsum; as in serpentine,or mixed with it so as to form a variety of verd-antique marble. Occurs and Maria-ZeU, Styria; Greiner in the Zillertal, at Hrubschiitz in Moravia; at Kraubat Tyrol, Austria; Snarum, Norway. In the United States,in Mass., at Bolton; at Roxbury, veining serpentine;in Md., atat West near Barehills, Goshen, Chester Co., near Baltimore; in Pa., in crystals, Texas, Lancaster Co.; in Cal. it is mined in Tulare, Kern, Santa Clara,Sonoma Cos. and elsewhere. A white saccharqidal magnesite resembling statuary marble has been found as loose blocks on an island in the St. Lawrence Island Park. River, near the Thousand In Nova Scotia. small prismaticcrystalsfrom Orangedale, Use. In the preparationof magnesite brick for the liningsof metallurgical furnaces; in the manufacture of various chemical compounds, as epsom salts,magnesia, etc. Intermediate between magnesite and siderite are: MESITITE. 72" 46'. G. rr' lOll A TlOl 3-35-3-36. 2MgCO3.FeCO3. Usually in flatrhombohedrons Piedmont, Italy. (e,0112) with rounded faces. Traversella, PISTOMESITE. 100. Magnesium carbonate 42'0,iron carbonate 58'0 MgCOs.FeCOs rr' 1011 A TlOl 3 '42. 72" 42'. G. Thurnberg, Salzburg,Austria; also Traversella, Italy. =

"

"

"

=

=

=

=

Chalybite,SpathicIron.

SIDERITE.

Rhombohedral.

Axis

c

=

0001

A

lOTl

cM,

0001

A

4041

cs,

0001 0001

A

0551

=

A

0881

=

"cr,

cd,

Crystals commonly curved and

=

=

=

=

0-8184. 43" 23'. 75" 11'. 78" 3'. 82" 28'.

rhombohedral

rr', 1011 MM', 4041 ss', 0551 dd', 0881 r

A

1101

A

4401

A

5051 8081

A

(1011) or

built up of sub-individuals like dolomite.

=

=

=

=

73" 0'. 113" 42'. 115" 50'. 118" 18"'.

e(0112) the

faces,often Often cleavable massive

444

MINERALOGY

DESCRIPTIVE

forms,subfibrous granular. Also in botryoidaland globular and earthy. silkyfibrous;compact within,occasionally subconchoidal. Brittle. or Cleavage: r(1011)perfect. Fracture uneven to Luster G. 3-83-3-88. vitreous,inclining pearly. Color 3'5-4. H. ash-gray,yellowishgray, greenishgray, also brown and brownish red,rarely to

fine

or

coarse

=

=

and sometimes

green;

Optically

"

-.

=

Streak white.

white.

1'873.

"

=

Translucent

to subtranslucent.

1-633.

dioxide 37-9, iron proCarbon toxide protocarbonate,FeC03 be present (as in 48'2 p. c.). Manganese may 100 (Fe 62-1 manganospherite)also magnesium and calcium. oligonite,

Comp.

Iron

"

=

=

=

,

decrepitates, gives off CO2, blackens and becomes magnetic. With the fluxes reacts for iron,and with soda and fuses at 4 '5-5. reaction. Only slowlyacted upon and niter on platinum foil generallygives a manganese in effervescence acid. Exposure to hot brisk with but dissolves hydrochloric cold acid, by brownish red or the atmosphere darkens its color,rendering it often of a blackish brown color. form and cleavage. Specificgravity higher Characterized Diff. by rhombohedral Resembles dolomite and ankerite. some than that of calcite, sphaleritebut lacks the differs in cleavageangle and yieldsCOa (not H^S) with hydrochloric acid. resinous luster, form as Obs. bog ore by the action,out of contact with the air,of ,Siderite may organic matter in a bicarbonate solution. It may also be formed by the action of ferrous in many It frequentlyoccurs It occurs also as a vein mineral. limestones. solutions upon and as clay iron-stone in connection with of the rock strata,in gneiss,mica slate,clay slate, and many other stratified deposits. It is often associated with metallic the Coal formation in silver mines. In Cornwall At Freiberg,Saxony, it occurs it accompanies tin. It ores. is also found accompanying copper and iron pyrites, tetrahedrite. sionally Occagalena,chalcocite, it is to be met with in trap rocks as spherosiderite in globularconcretions. sive Extenin the Eastern depositsoccur Alps, in Styria and Carinthia at Tavetsch, Switzerland. At Harzgerode and elsewhere in the Harz in fine crystalsin gray-wacke; Mts., it occurs also in Cornwall of varied habit at many shire. at Alston-Moor,and Tavistock, Devonlocalities; In largerhombohedrons from Allevard,France. with Fine cleavage masses occur cryolitein Greenland. In the United in Ver.,at Plymouth. In Mass., at Sterling. In Conn., at RoxStates, bury,an extensive vein in quartz, traversinggneiss. In N. Y., a series of depositsoccur in Columbia In N. C., at Fentress lem Co.; at the Rbssie iron mines, St. Lawrence Co. and Harmines. The argillaceous carbonate,in nodules and beds (clayironstone),is abundant in the coal regionsof Pa., Ohio, and many parts of the country. In a clay-bed under the Tertiaryalong the west side of Chesapeake Bay for 50 m. Use. An ore of iron. Pyr., etc.

"

In the closed tube

blackens

B.B.

"

"

"

"

"

RHODOCHROSITE.

Dialogite. Axis c 0-8184, rr' 1011 A TlOl =_73" 0'. Distinct crystals not common; usually the rhombohedron r(1011); also e(0112), with rounded striated faces. Cleavable,massive to granular-massiveand Also globularand botryoidal, compact. with columnar structure,sometimes Rhombohedral.

=

indistinct; incrusting. Cleavage: r(10Tl) perfect. Fracture uneven. 3-5-4-5. Brittle. H. G. 3-45-3*60 and higher. Luster vitreous,incliningto pearly. Color shades of rose-red;yellowish dark red, brown. Streak gray, fawn-colored, white. Translucent to subtranslucent. 1-820. 1*600. e Optically co Comp. Manganese protocarbonate,MnCO3 Carbon dioxide 38'3, 100. manganese protoxide61-7 Iron carbonate is usuallypresent even up to 40 p. c in manganosiderite; sometimes as the carbonate of calcium,as in also magnesium, zinc,and rarelycobalt. manganocalcite, =

=

=

-.

"

=

=

,

green

manganate.

=

445

CARBONATES

effervescence in

acid. hydrochloric

warm

varieties become Characterized by its pink

bright rose-red

some

Diff. in acids.

"

On

exposure

paler. color,rhombohedral

to the air

form

changes to brown,

and

and cleavage,effervescence

Occurs commonly in veins along with ores of silver, lead and copper, and with and Kapnik in Hungary ; Nagyag in Tranof manganese. sylvania; Found at Schemnitz ony; ponite is a ferriferous varietyfrom Roumania; in Germany at Freiberg in Saxin Nassau; at Daaden, Rheinprovinz ; in Belgium at Oberneisen at Diez near in the Ardennes. A varietycontaining 45 per cent of zinc carbonate Moet-Fontaine from Rosseto, Elba, has been called zincorodochrosite. In the United States at Branchville, Obs.

other

"

ores

In Col., at the John Conn.; in N. J.,with franklinite at Mine Hill,Franklin Furnace. Reed mine, Alicante,Lake Co., in beautiful clear rhombohedrons ; also at the Oulay mine, In Mon., at Butte Lake City and Alma, Park Co.; in Chaff ee, Gilpinand Ouray Cos. near At Placentia Bay, Newfoundland. at the silver mines of Austin, Nev. City. Abundant rhodochrosite from podov, a rose, and xpoxris, color;and dialogite, Named from 5ux\oyrj, doubt.

Use.

A

"

minor

ore

of manganese. Calamine

SMITHSONITE.

pt.

Dry-bone

ore

Miners.

72" 20'. Rarely Rhombohedral. Axis c 0-8063. rrf lOll A IlOl well crystallized; faces r(1011)generallycurved and rough. Usually renialso granular, and in crystalline or form,botryoidal, stalactitic, incrustations; and sometimes impalpable,occasionally friable. and earthy conchoidal. Cleavable: r(1011)perfect. Fracture to imperfectly uneven =

=

Brittle. H. Luster 5. G. 4*30-4 '45. vitreous, incliningto pearly. Streak white. Color white, often grayish,greenish,brownish times white, someSubtransparentto translucent. Optically green, blue and brown. =

"

=

"

.

co

1-818.

=

e

-

1-618.

dioxide 35-2, zinc protoxide Zinc carbonate,ZnCO3 Carbon Iron carbonate is often present (asin monheimite) also manganese and cobalt carbonates; further calcium and magnesium carbonates in and indium. traces; rarelycadmium

Comp.

64-8

=

"

100.

=

',

In the closed tube loses carbon dioxide,and, if pure, is yellow while hot Pyr., etc. balt and white on cooling. B.B. infusible, giving characteristic zinc flame; moistened with cosolution and heated in O.F. gives a green color on cooling. With soda on charcoal coats the coal with the oxide,which is yellow while hot and white on cooling; this coating, Soluble in moistened with cobalt solution,gives a green color after heating in O.F. hydrochloricacid with effervescence. cence Diff. Distinguishedfrom calamine, which it often closelyresembles,by its effervesin acids. Obs. with galena and sphalerite; Found both in veins and beds,especially in company also with copper and iron ores. ciated It usuallyoccurs in calcareous rocks,and is generallyassowith calamine,and sometimes It frequently with limonite. limestone,pseureplaces Commonly a secondary mineral and domorphs after calcite crystalsbeing often observed. is often produced by the action of carbonated waters zinc sulphide. Often is in a upon "

"

"

honey-comb-like material,known commonly as "dry-bone" ore. at Nerchinsk in Siberia; at Dognaczka in Hungary; Bleiberg and Raibel in in Belgium and Moresnet and at AJtenberg, Germany. Carinthia; Wiesloch in Baden Viesgo. In England, at Altenberg. In the province of Santander, Spain, at Puente Roughten Gill,Alston Moor, near Matlock, in the Mendip Hills,and elsewhere; in Ireland, Broken at Donegal. At Laurion, Greece, varieties of many colors;from Sardinia. From Hill,New South Wales. In the United States,in Pa., at Lancaster abundant, the varietycalled "dry-bone"; at the Ueberroth In Wis., at Mineral Point, mine, near Bethlehem, in scalenohedrons. Shullsburg,etc.,pseudomorphs after sphaleriteand calcite. In la.,at Swing's diggings, and calamine. N. W. of Dubuque, etc. In south-western Mo., associated with sphalerite In Ark., at Calamine, Lawrence A pink cobaltiferous variety occurs Co. Co.; in Marion at Boleo, Lower California. In N. M. from Socorro Co. and in translucent green botryoidal from Kelly. In Tooele Co., Utah. masses porous,

Found

MINERALOGY

DESCRIPTIVE

446

Institution in p. 539.

founded the Smithsonian

who after James Smithson (1754-1829), used is frequently calamine The name Washington. zinc. of An ore Use. Named

in

England, cf. calamme,

"

Rhombohedral CoCO3. protocarbonate, 4 '02-4-13. surface,rarelyin crystals.G. crystalline

Sphserocobaltite.Cobalt

masSswith

From

=

Schneeberg, Saxony.

California.

Boleo, Lower

From

For listof

Orthorhombic

RC03.

Aragonite Group.

2.

small spherical Color rose-red.

In

p. 437.

see species,

ARAGONITE.

Axes

Orthorhombic.

or

a

:

b

: c

0'62244

=

mm"',

110

A

110

=

kk'

Oil

A

Oil

=

pp'

111

A

111

pp"',

111

A

111

:

1

63" 71" 86" 50"

=

=

:

072056.

48'. 33'.

24"'. 27'.

and characterized by the presence of acute domes often acicular, Crystals tw. Twins: pi.ra(110)commonly repeated,producing pseudopyramids. 763

'

756

755

754

757

m

\

\

reniform, and coralloidal hexagonalforms (seeFigs.755-757) Also globular, incrusting. or divergent; alsostalactitic; shapes;sometimes columnar,straight Cleavage: 6(010) distinct;also ra(110);fc(Oll)imperfect. Fracture Luster 2*93-2-95. 3'5^. Brittle. H. G. subconchoidal. vitreous, Color white; also gray, yelsurfaces of fracture. to resinous on low, inclining translucent. and streak to uncolored. tically OpTransparent violet; green 2 E Ax. pi.||a(100). Bx J_ c(001). Dispersionp " v small. .

=

=

-.

=

30" 54'.

a

=

1-531.

0

=

1-682.

=

7

1-686.

=

dioxide 44'0, lime 56*0 Calcium Carbon Comp. carbonate,CaCO3 100. Some varieties contain a littlestrontium,others lead,and rarelyzinc. =

"

Aragonite changes to calcite at 470". the the latter much Ordinary, (a) Crystallizedin simple or compound crystals, most often in radiatinggroups of acicular crystals.Columnar; also fine fibrous common; with silkyluster, (c)Massive. Stalactiticor stalagmitic: Either compact or fibrous in structure,as with calcite;Sprudelstein is stalactitic from Carlsbad, lacing Bohemia. Coralloidal: In groupings of delicate interand coalescing stems, of a snow-white color,and lookinga littlelike coral; often called Flosferri.Tarnowitzite is a kind containinglead carbonate (4 to 8 p. c.),from Tarnowitz in Silesia; with G. 2 '99. Zeyringiteis a calcareous sinter,probably aragonite,colored greenish white or sky-bluewith nickel,from Zeyring, Styria. Nicholsonite is aragonite Var.

"

=

zinc containing

from

Leadville, Col.,and

the Tintic

Utah. District,

448

MINERALOGY

DESCRIPTIVE

Color pale asparagus-green, also faces of fracture. apple-green; Streak white. brown. and Transparent to yellowish white, gray, yellow, Bx Ax. _L Z"("10). c(001). Dispersion pi.|| translucent. Optically T667. T667. 12" 17'. a t'52f6. 2Er (3 y p " v small. diozide Carbon Strontium carbonate, SrCOs 29*9, strontia Comp. resinous

on

-.

=

"

70-1

is sometimes

A littlecalcium

100.

=

=

=

=

=

present.

B.B. swells up, throws out minute sprouts, fuses only on the thin edges, and Pyr.,etc. with colors the flame strontia-red;the assay reacts alkaline after ignition. Moistened hydrochloricacid and treated either B.B. or in the naked lamp gives an intense red color. Soluble in hydrochloric acid; the mediumly dilute solution when treated with sulphuric acid gives a white precipitate. with acids; has a Differs from related minerals,not carbonates,in effervescing Diff. gravity than aragonite and lower than witherite; colors the flame red B.B. higher specific Obs. Occurs at Strontian in Argyllshireand in Yorkshire, England; Claustal in the "

"

"

Freiberg,Saxony; Leogang in Salzburg,Austria; Mts., Germany; Braunsdorf, near in fine crystals near Brixlegg,Tyrol, Austria (calciostrontianite) ; in Westphalia, Germany near Hamm, and at the Wilhelmine mine near Altahlen. in N. Y. at Schoharie,at Muscalonge Lake, Chaumont In the United States, occurs Bay and Theresa, in Jefferson Co.; Mifflin Co., Pa. A minor source Use. of strontium compounds. Harz

"

CERUSSITE.

White

Orthorhombic.

Lead

Axes

758

Ore. a

:

6

: c

=

0-60997

759

:

1

:

072300.

mm'", J*', ii', cp,

pp'j pp'",

760

110

A

110

oil

A

Oil

021

A

021

=

001

A

111

=

111

A

111

111

A

111

62" 46'. 71" 44'. 110" 40'. 54" 14'. 87" 42'. 49" 59"'.

=

=

=

=

Simple crystalsoften || 6(010), prismatic ||caxis; also pyramidal. Twins: tw. pi. m(110) very common, tabular

and penetrationoften twins, repeated yielding six-rayed stellate groups. Crystals grouped in clusters,and aggregates. Rarely fibrous,often granular massive and compactearthv Sometimes stalactitic. contact-

Cleavage: m(110) and {(021) distinct;6(010) and z(012) in traces. conchoidal. 3-3-5. Very brittle. H. G. 6-46-6-574. Luster to adamantine, inclining vitreous,resinous, or pearly;sometimes submetallic. Color white gray, grayish black,sometimes tingedblue or green (copper); streak uncolored. Transparent to subtranslucent. Optically-. Ax. nil 6(010). Bx _L c(001). Dispersionp " v large. 2 V 8" 14'. a 1-804 Fracture

=

=

=

p

=

Q

oo.o

2*076.

7

=

Lead carbonate"pbC03 rF"miPnVT~ =

=

2-078. =

Carbon

dioxide 16-5, lead

oxide

1UU-

loses carbon "ecrepitates,

at

n -

d'

turns dioxide,

yellow on Soluble

firstyellow,and cha"al on in dilute nitric acid with

coolin^ B'B'

Aiding

449

CAEBONATES

Artif Cerussite has been produced artificially by the slow diffusion of a carbonate solution into a lead solution through a porous membrane; by the action of a carbonate solution upon a lead plate. Obs. A secondary mineral occurring in connection with other lead minerals,and is formed from galena,which, as it passes to a sulphate,may be changed to carbonate by of solutions of calcium bicarbonate. It is tound in Germany at Johanngeorgenstadt means in beautiful crystals;Friedrichssegen,Nassau; Badenweiler, Baden; at Claustal in the Harz Other important localitiesare Mts. Monte Poni,Sardinia; at Bleibergin Carinthia; at Mies and Pfibram,Bohemia; in England, in Cornwall; at East Tamar mine, Devonshire; and Matlock near Wirksworth, Derbyshire; at Leadhill and Wanlockhead, Scotland. Fine crystalsfrom Broken Hill,New South Wales. In Va.,at Austin's mines,Wythe Co. In N. C.,in King's Found in Pa.,at Phenixyille. In lead mines of Wis. but rarelyin crystals;at Hazelgreen,crystalscoatinggalena. mine. In Col.,at Leadyille, In Ariz., and elsewhere. at the Flux mine, Pima Co.,in largecrystalline in crystals In Utah Cloud mine, Yuma Co. at the Red from Flagstaff masses; and Kingston. mine; in Idaho at Wardner Use. An ore of lead. "

.

"

"

BARYTOCALCITE.

Axes Monoclinic. also massive.

a

:

b

: c

07717

=

:

1

0-6254; /3

:

73" 52'.

=

In

tals; crys-

Fracture uneven to subconCleavage: ra(110) perfect;c(001)less so. 4. 3 -64-3 '66. Luster choidal. Brittle. H. G. vitreous,incliningto parent TransStreak resinous. Color white,grayish, white. or greenish yellowish. 1'684. 1-686. 1-525. to translucent. a 0 Optically 7 Carbon Carbonate of barium and calcium, BaCO3.CaCO3 Comp. 100. dioxide 29'6,baryta 51 '5,lime 18'9 =

=

=

=

=

-.

=

"

=

B.B. colors the flame yellowishgreen, and at a high temperature fuses on Pyr., etc. the thin edges and assumes a pale green color; the assay reacts alkaline after ignition. Soluble in dilute hydrochloricacid with effervescence. Dilute solution gives an abundant precipitate, BaSO4, with a few drops of sulphuricacid. Obs. Occurs at Alston Moor in Cumberland, England, in limestone with barite and fluorite. "

"

ROSASITE. 2CuO.3CuC03.5ZnC03?. Mammillary blue color. From Sardinia. Rosas mine at Sulcis,

fibrous of

bright

a

green

to

sky-

with radiated structure. Bismutospharite. Bi2(CO3)3.2Bi2O3. In spherical forms 7 '42. Color yellow to gray or blackish brown. From Schneeberg, Saxony. Also sparinglyat Willimantic and Portland,Conn., as a result of the alteration of bismuthinite. From the Stewart mine, Pala,San Diego Co.,Cal. Rutherfordine. A yellow ocher resultingfrom alteration Uranyl carbonate,UO2CO3. 4*8. G. of uraninite. From Uruguru Mts., German East Africa. Rhomboof the cerium metals, [(Ce,La,Di)F]2Ca(C03)2. Parisite. A fluocarbonate hedral. Crystalssmall and slender. Habit pyramidal or prismatic. Crystalshorizontally 4*358. Color brownish 4'5. combination of faces. H. G. grooved due to oscillatory bia; 1*676. 1757. From the emerald mines, Muso, Colomyellow. Optically+ co e Ravalli, Mon.; Quincy, Mass.; Montorfano, Italy; Narsarsuk, Greenland (synG.

=

=

=

=

=

=

.

chisite) .

Other parisitecontaining barium from Narsarsuk, South Greenland. is parisite. thought to be a new speciesand named synchisite 4 '5H. A fluocarbonate of the cerium metals (RF)COs. Bastnasite. Hamartite. G. 4 '948. Color wax-yellow to reddish brown. Strong birefringence. Uniaxial,+. the Bastnas Also in parallel 1715. From growth with mine, Riddarhyttan, Sweden. cc to the east of AmboFound tysonitein the graniteof the Pike's Peak region in Colorado. sitra,Madagascar. In small pyramids with curved Orthorhombic. Ancylite. 4Ce(OH)CO3.3SrCO3.3H2O. sible. Infufaces and 3 '9. Color lightyellow, orange, G. brown, gray. edges. H. =4'5. From Narsarsuk, Greenland. WeibyeUe is a related mineral.

Cordyliteis

material from

a

Narsarsuk

=

=

=

=

Ambatoarinite.

A

carbonate

of strontium

and

crystalswith parallelaxes, forming skeleton-like toarina,near Ambositra, Madagascar.

the groups.

rare

earths.

Index,

"

Orthorhombic? 1'66.

From

In Arnba-

MINERALOGY

DESCRIPTIVE

450 PHOSGENITE.

Tetragonal. Axis

c

tabular

Crystals prismatic;sometimes

1-0876.

=

"

sectile. H. Rather Cleavage: m(110), a(100) distinct;also c(001). Color white, adamantine. Luster gray, and yellow. 6-0-6-3. G. 275-3. =

=

Transparent

Streak white.

Comp." carbonate

Optically+.

to translucent.

of lead, (PbCl)2CO3 Chlorocarbonate 100. 49'0,lead chloride 51*0

or

w

2-114.

=

PbCO3.PbCl2

=

e

=

Lead

=

white which on cooling becomes melts readily to a yellow globule, of lead white with coating metallic a in R.F. lead, On charcoal gives and crystalline. chloride. Dissolves with effervescence in dilute nitric acid and solution reacts for chlorine with silver nitrate. Pom and MonteMatlock in Derbyshire; at Gibbas, Monte At Cromford Obs. near South Wales; Dundas, Tasmania. Broken Hill,New From vecchio in Sardinia.

Pyr., etc.

"

B.B.

"

G. H. 3'5-4. octahedrons. In isometric Northupite. MgCO3.Na2CO3.NaCl. Borax From T514. Co.,Cal. Lake, San Bernardino White to yellow or gray, n H. G. 3'5. habit. Octahedral Tychite. 2MgCO3.2Na2CO3.Na2SO4. Isometric. associated San Bernardino Borax Co., Cal., From Lake, rare. 2'5. n l;51. Very with northupite. =

=

2'38.

=

=

=

=

ACID, BASIC,

B.

HYDROUS

AND

CARBONATES

carbonate, HNH4CO3. Indices, 1'423-1'536.

ammonium 1'45. to 'white crystals. G. Africa,Patagonia, the Chincha Islands. Acid

Teschemacherite.

=

Orthorhombic. From

guano

In yellowish deposits of

MALACHITE.

61" 50'. : 0-4012; $ acicular prisms (mm"' 110 A 110 Crystalsrarelydistinct, usuallyslender, 75" 40'),grouped in tufts and rosettes. Twins: tw. pi.a(100) common. and with surface botryoidal, or stalactitic, Commonly massive or incrusting, structure divergent;often delicately compact fibrous,and banded in color; Monoclinic.

Axes

a

:

b

: c

=

0-8809

1

:

=

=

frequentlygranularor earthy. Cleavage: c(001) perfect;6(010) less Brittle.

so.

Fracture

even. subconchoidal,un-

Luster of crystals 3-9-4-03. G. admantine, to vitreous;of fibrous varieties more less silky;often dull and inclining or subStreak Translucent to earthy. Color bright green. paler green. translucent to opaque. 1'88. /3 Optically Basic cupric carbonate, CuC03.Cu(OH)2 Carbon dioxide Comp. 100. 19-9,cupric oxide 71-9,water 8'2 H.

=

3-5-4.

=

=

"

.

=

"

=

In the closed tube Pyr.,etc. emerald-green;on charcoal

B.B. fuses at 2, coloringthe blackens and yieldswater. with the fluxes reacts like is reduced to metallic copper; cuprite. Soluble in acids with effervescence. Diff. Characterized by green color and -copper reactions B.B.; differs from other of a green color in its effervescence with acids. copper ores Artif. Malachite has been formed artificially ate carbonby heating precipitated copper with a solution of ammonium carbonate for several days. Obs. Common with other ores of copper and as a product of their alteration ; thus as a pseudomorph after cuprite and azurite. Occurs abundantly in the Ural Mts.; at Chessy in France; in Cornwall and in Cumberland, England; in Germany at Rheinbreitbach; Dillenburg, Nassau; Betzdorf near Siegen. At the copper mines of Nizhni Tagilsk, Russia; with the copper ores of Cuba; Chile; at the Cobar mines and elsewhere in New bouth Wales; South Australia; Rhodesia. In crystalsfrom Katanga, Congo, and Mindouh, French Congo. "

flame

"

"

"

451

CARBONATES

In Pa.,at Cornwall, Occurs in N. J., at Schuyler's Brunswick. mines, and at New In Wis., at the copper mines, Lebanon Co.; at the Perkiomen and Phenixville lead-mines. of Mineral and acicular crystals, with Abundantly in fine masses Point, and elsewhere. calcite at the Copper Queen mine, Bisbee, Cochise Co., Ariz.; also in Graham Co., at Morenci (6 m. from Clifton),in stalactitic forms of malachite and azurite in concentric bands. At the Santa Rita mines, Grant Tintic district, Co., and elsewhere in N. M. In pseudomorphs from Good Named Utah. from naXaxi), mallows, in Springs, Nev. allusion to the green color. An ore of copper; at times as an ornamental Use. stone. "

AZURITE.

Monoclinic.

Axes

a

:

b

: c

=

0-8501

761

:

1

:

0-8805; 0

87" 36'.

=

762

mm'",

110

A

110

=

ac,

100

A

001

=

101 023

ca,

001

A

II',

023

A

=

=

763

80" 41'. 87" 36'. 44" 46'. 60" 47'.

ppf,

021

A

021

cm,

001

A

110

=

cd, hhf,

001

A

243

=

221

A

221

=

120" 88" 54" 73"

=

47'. 10'. 29'. 56'.

in habit and highlymodified. Also massive, and presenting imitative shapes, having a columnar composition;also dull and earthy. Cleavage: p(021)perfectbut interrupted;a(100) less perfect;ra(HO) in ter Lus3-77-3-83. 3-5-4. conchoidal. Brittle. H. G. Fracture traces. Color shades of adamantine. various a lmost p assing azure-blue, vitreous, Streak blue, lighterthan the color. Transparent to subinto Berlin-blue.

Crystalsvaried

=

translucent,

a

=

1730.

0-=

1-758.

7

=

=

1-838.

Basic cupric carbonate, 2CuCO3.Cu(OH)2 Comp. 100. 25-6,cupricoxide 69-2,water 5 -2 "

=

Carbon

dioxide

=

Same as in malachite. Characterized by its blue

Pyr., etc. Diff.

"

"

color; effervescence

in nitric

acid;

copper

reactions

B.B. Azurite tact has been formed by allowing a solution of copper nitrate to lie in conwith fragments of calcite for several years. in France at Chessy, near Occurs in splendid crystallizations Obs. Lyons, whence it in derived the name Chessy Copper or chessylite.Also in fine crystalsin Siberia; Moldawa Redruth in Cornwall; in Devonshire and Derbythe Banat, Hungary; at Wheal Buller,near shire, England; at Broken Hill and elsewhere in New South Wales; South Australia. In Wis., New Brunswick. Occurs in Pa., at Phenixville,in crystals. In N. J.,near in Graham In Ariz.,at the Longfellow and other mines Mineral Point. Co.; with near In Grant at the Copper Queen mine, Bisbee; at Morenci. malachite in beautiful crystals In mine in the Tintic district and in Tooele Co., Utah. At the Mammoth Co., N. M. Artif

"

.

"

Cal.,Calaveras

Co., at Hughes's mine, in crystals.

of copper. of zinc and copper, basic carbonate 2(Zn,Cu)CO3,.3(Zn,Cu)(OH)2. Luster In drusy incrustations. G. 3'54-3'64. Orthorhombic? pearly. Color pale From the Altai Mts., Mongolia; Chessy, near to sky-blue. Indices,1 '634^1 '682. green In Lyons, France; Rezbdnya, Hungary; Ondarroa, Vizcaya, Spain; Chihuahua, Mexico. the United States,at Lancaster,Pa.; Salida,Col.; the Santa Caterina Mts., Ariz.; Beaver Use.

"

An

Aurichalcite.

ore

A

=

Co., Utah; Kelly, N. M. Hydrozincite. A basic zinc carbonate, perhaps ZnCO3.2Zn(pH)2. Massive, fibrous, 3'58-3'8. Color white, grayish or yellowish. earthy or compact, as incrustations. G. =

452

MINERALOGY

DESCRIPTIVE

Index, Dolores

Occurs

1-695.

of zinc,as

mines

at

mine, Santander, Spain. In the United

fidano,Sardinia.

In great quantitiesat the result of alteration. Chihuahua, Mexico; Bleyberg, Belgium; MalFriedensville, Pa.; at Linden, in Wis.; Granby, a

From

States at

Mo. ute carbonate of uncertain composition. In crusts showing minA basic cadmium OTAVITE. the Otavi district, German rhombohedral crystals. Color white to reddish. From Africa. Southwest

less Hydrocerussite. A basic lead carbonate, probably2PbCO3.Pb(pH)2.In thin colorhexagonal plates. Index, 2 '07. Occurs as a coating on native lead, at Langban, Sweden; with galena at Wanlockhead, Scotland. In of lead and aluminium, Pb(AlO)2(CO3)2.4H2O. A basic carbonate Dundasite. From Dundas and small sphericalaggregates of radiatingacicular crystals. Color white. Mt. Read, Tasmania, and from near Trefriw,Carnarvonshire,Wales; Wensley, Derbyshire; near Maam, County Gal way, Ireland. and of aluminium A Dawsonite. basic carbonate sodium, Na3Al(CO3)3.2Al(OH)3. In thin incrustations of white radiatingbladed crystals. Perfect cleavage, Orthorhombic. Found 2-40. McGill on a feldspathic dike near Indices, 1-466-1-596. ra(110). G. From the province of Siena,Pian Castagnaio, Tuscany, Italy College,Montreal. =

G. Occurs m l'S-1'6. carbonate, Na2CO3.H2O. the soil in many dry regions. In radiating groups Nesquehonite. Hydrous magnesium carbonate, MgCO3.3H2O. of prismaticcrystals. G. Colorless to white. 1 '83-1-85. Biaxial, Indices,1-4951'526. From See lansfordite, at Nesquehoning, SchuylkillCo., Pa. a coal mine p. 453. Natron. in carbonate, Na2CO3.10H2O. Hydrous sodium nature Occurring only in solution,as in the soda lakes of Egypt, and elsewhere,or mixed with the other sodium Thermonatrite. various lakes, and

Hydrous sodium

as

an

=

efflorescence

over

=""

"

.

carbonates.

CaCO3.Na2CO3.2H2O.

Pirssonite.

H.

G.

=3.

Lake, San

In

Colorless to white. Bernardino, Cal. =

2'35.

prismatic crystals,orthorhombic-hemimorphic. Optically +. Borax Indices,I'504-r575.

GAY-LUSSITE.

Monoclinic.

Axes

a

:

b

764

: c

=

1 -4897

:

1

1-4442;0

:

mm'", ee',

765

_78"27'.

=

110

A

UO

Oil

A

Oil

me,

110

A

Oil

rrf,

112

A

112

111"

10'. 109" 30'. 42" 21'. 69" 29'.

=

=

=

=

Crystalsoften elongated|| also a axis; wedge-shaped. Cleavage: m (110)perfect; c (001)rather difficult. Fracture conchoidal. Very brittle. flattened

H.

2-3. G. vitreous. Color Streak uncolored =

1-93-1-95.

=

cent. grayish. Translu-

to

Optically "

T517., Comp.

Hydrous

"

Calcium

Pyr.,etc. "

7

=

carbonate of calcium and carbonate 33-8,sodium carbonate

Heated

in

.

a

=

1*444

6

=

1-518.

sodium, CaCO3.Na2CO3. 100. 35-8, water 30-4 =

closed tube decrepitates and becomes the flame inten^ly yellow. effervescence; partly soluble in water, and reddens turmeric "

Luster

white,yellowish white.

a

B.B. fuses opaque. in acids with a

Dissolve! ^^'l ""Vu^ briskyeffervesoene brisk paper. "a^Merida"in Venezuela,in crystalsdisseminated at the botton" of r^ll aVLa?Un^ "f day' trona. Also abundant in Little Salt covermg So" iM ' 'SV1 ^ Desert Lake Ragtown, Nev, deposited upon the evapora'Fnth%Carsfm tion of the t"tPr Sweetwater "

or

near

cms

VaUey'

1850)

Wv'

Named

after

Gay Lussac,the

French

453

CARBONATES In thin tabular

La2(CO3)3.9H2O.

Lanthanite.

earthy. G.

Color

2 '605.

=

crystals;also granular, "

cerite at Bastnas, Sweden; with zinc Sandford iron-ore bed, Moriah, N. Y.

TRONA.'

orthorhombic

grayishwhite, pink, yellowish. Optically ores

of the Saucon

.

Found

valley,Lehigh Co., Pa.;

ing coatat the

Urao.

Monoclinic.

Axes

a

:

b

ca,

001

A

100

co,

001

A

Til

oo",

111

A

111

Often fibrous

: c

2-8460: 1:

=

77" 23'.

=

75" 53^.

=

47" 35|'.

columnar

or

=

2-9700;0

766

massive.

.

.

o (111) Cleavage:a (100)perfect; ; c (001)in traces.

Fracture uneven 2-11-2-14. G. =

subconchoidal.

to

Luster

77" 23'.

=

H.

=

2*5-3.

\

\

vitreous, glistening.Color

Translucent. alkaline. Optically". Taste or yellowish white. Index, 1-507. Carbon ide dioxNa2CO3.HNaCO3.2H2O or 3Na2O.4CO3.5H20 Comp.

gray

=

"

38-9,soda 41-2,water

19-9

=

100.

established the above composition for urao, and showed that trona, sometimes Chatard called sesquicarbonateof soda," is an impure form of the same compound. In the closed tube yieldswater and carbon dioxide. B.B. imparts an Pyr., etc. intenselyyellowcolor to the flame. Soluble in water, and effervesces with acids. Reacts alkaline with moistened test-paper. in the province of Fezzan, Africa, Obs. Found forming thin superficial crusts; Natroun lakes,Egypt; from Vesuvius; at the bottom of a lake at Lagunilla,Venezuela. An extensive Efflorescences of trona occur the Sweetwater near river,Rocky Mountains. In fine crystalsat Borax lake,San Bernardino bed in Churchill Co., Nev. Co., Cal.,with "

"

"

hanksite,glauberite,thenardite,etc. Basic magnesium Crystals Hydromagnesite. carbonate, 3MgCO3.Mg(OH)2.3H2O. small,tufted. Also amorphous; as chalky crusts. Color and streak white. Index, 1 '530. with serpentine; thus at Hrubschiitz,in Moravia; at Kraubat, Styria,etc. Often occurs Also similarlynear Texas, Pa.; Hoboken, N. J. Material closelysimilar from saline crusts lava at Alpharoessa,Santorin Island,has been called giorgiosite. on In lightgray From the Hydrogiobertite. MgCO3.Mg(OH)2.2H2O. sphericalforms. neighborhood of Pollena,Italy. Deposited from PhillipsSprings,Napa Co., Cal. H. Artinite. 2'0. Orthorhombic. MgCO3.Mg(OH)2.3H2O. Radiating fibrous. 1'54. From White, Val Laterna 2-0. and Emarede, Val Aosta, Piedmont, G. ft Italy. Occurs as Lansfordite. Biaxial 3MgCO3.Mg(OH)2.21H2O. Indices,1'42-1-503. small stalactites in the anthracite mine at Nesquehoning near Lansford, SchuylkillCo., Pa.; changed on exposure to nesquehonite. age. Brugnatellite.MgCO3.5Mg(OH)2.Fe(OH)3.4H2O. Micaceous/lamellar. Perfect cleavSanta T53. Found at Torre Color flesh-pink, in an old asbestos mine Maria, Val Malenco, Lombardy, Italy. A basic hydrous calcium,magnesium carbonate. GAJITE. Rhombqhedralcleavage. H. G. 3'5. 2'62. Granular structure. Color,white. Strong birefringence. Found near Plesce,in the district Gorskikotar,Croatia. =

=

=

-.

=

co

=

Stichtite.

=

2MgCO3.5Mg(OH)2.2Cr(OH)3.

Micaceous.

In scales.

G.=

2'16.

Color

feebly biaxial. Optically Index, 1'54. An alteration Dundas, Tasmania. Zaratite. also Emerald Nickel. NiCO3.2Ni(OH)2.4H2O. Inmammillary incrustations; at Texas, Lancaster Color emerald-green. Occurs on chromite Co., massive, compact. Pa.; at Swinaness, Unst, Shetland; Igdlokunguak, Greenland. A rose-colored incrustation,soft and Remingtonite. A hydrous cobalt carbonate. earthy. From a copper mine near Finksburg, Carroll Co., Md.; Boleo, Lower California. lilac. Optically uniaxial product of serpentinefrom

or

"

.

454

MINERALOGY

DESCRIPTIVE

Tengerite.

A

supposedyttrium carbonate.

linite at Ytterby, Sweden.

A

similar mineral

In white

On gadothe gadoliniteof Llano

pulverulentcoatings.

is associated

with

Co., Tex. or earthy carbonate,perhaps Bi2O3.CO2.H2O. Incrusting, low 6'86-6'9 Breith.; 7 '67 Rg. Color white,-green, yelin Germany, at Schneeberg and Johanngeorgenstadt, and gray. Index, 2'25. In the United States, in S. C., at with native bismuth, and at Joachimstal,Bohemia. Brewer's mine; hi Gaston Co., N. C. In scaly or granular crystallineaggregates. Uranothallite. 2CaCO3.U(CO3)2.10H2O. Color siskin-green.Occurs on uraninite at Joachimstal,Bohemia. In mammillary concretions, Liebigite. A hydrous carbonate of uranium and calcium. uraninite Occurs near Adrianople,Turkey; also on Color thin apple-green. or coatings. Germany, and Joachimstal,Bohemia. Johanngeorgenstadt, In aggregations of Voglite. A hydrous carbonate of uranium, calcium and copper. From Elias mine, near the to Color scales. bright emerald-green grass-green. crystalline Joachimstal,on uraninite,Bohemia.

Bismutite.

and

A

basic bismuth

pulverulent;amorphous.

G. Occurs

=

Oxygen 2.

Salts

SILICATES

anhydrous,in part hydrous,as the zeolites part strictly of the silicates a largenumber clays,etc. -Furthermore, and in many it is known that they or less water cases ignition, yieldmore upon The to be basic silicates. as therefore, regarded (oracid) line, however, are, and between the strictly silicates be cannot anhydrous hydrous sharplydrawn, since with many specieswhich yieldwater upon ignitionthe part played by the elements formingthe water is as yet uncertain. Furthermore,in the cases the several strict arrangement must of be deviated from, since the groups, relation of the speciesis best exhibited by introducingthe related hydrous immediatelyafter the others. species This chaptercloses with a section includingthe Titanates, Silico-titanates, the Silicates with the Niobates and etc., which connect Titano-niobates, Tantalates. Some Titanates have alreadybeen included among the Oxides. The Silicates are and the amorphous

in

Section

A. I.

ChieflyAnhydrous Silicates Disilicates, Polysilicates

II. Metasilicates

The

III.

Orthosilicates

IV.

Subsilicates

DISILICATES,RSi205,are

salts of disilicicacid,H2Si2O5,and have an when the formula is written 1, as seen

ratio of siliconto bases of 4 : oxygen after the dualistic method, RO.2Si02. The

POLYSILICATES,R2Si308,are

salts of polysilicic acid,H4Si3O8,and : 1, as seen in 2R0.3Si02. oxygen The METASILICATES, RSiO3, are salts of metasilicic acid,H2SiO3,and have an ratio of 2 : 1. They have hence been called bisilicates. oxygen The ORTHOSILICATES, R2Si04,are salts of orthosilicic acid,H4Si04, and have an oxygen ratio of 1 : 1. They have hence been called unisilicates. The majorityof the silicatesfall into one of the last two groups.

have

an

ratio of 3

MINERALOGY

DESCRIPTIVE

456

Feldspar Group a.

Monoclinic

Section a

0-6585

KAlSi3O8 {(K,Na) AlSi3O8

Orthoclase

Soda-Orthoclase

\(Na,K)AlSi3O8 (K2,Ba)Al2Si4Oi2

Hyalophane Celsian

BaAl2Si208

Microcline

KAlSi3O8

:

0*6584 0-657

0'5554

116"

0'5512

115" 35' 115" 2'

0'554

3'

j8. Triclinie Section

(K,Na)AlSi3O8 (Na,K)AlSi3O8

Soda-microcline Anorthoclase

PlagioclaseFeldspars

Albite-anorthite Series.

NaAlSi308

Albite

0*557794"* :'l: 3' 4'

116" 29' 116" 23'

88" 90"

93" 23'

116" 29'

89" 59'

0-6377:1:0-5547

93" 31'

116"

0-6347:1:0-5501

93" 13'

115" 55'

0'6335

0'6321: 1:0'5524

Oligoclasej ^ 0'6357 (n"faf!?J?9v8 Andesine Labradorite

are

as

1 : 0'5521

3'

9' 5'

89"54J'

J

CaAl2Si208

Anorthite The

:

93"

generalcharacters of the speciesbelongingin the follows

FELDSPAR

91" 12' GROUP

:

in the monoclinic 1, Crystallization

or

crystalsof the generalhabit,and

tricliniesystems, the

different species resemblingeach other closelyin

angle,in

differs but a few of twinning. The prismaticangle in all cases degreesfrom 60" and 120". to the base c (001)and clino2, Cleavagein two similar directions parallel pinacoid(orbrachypinacoid)6 (010),inclined at an angleof 90" or nearly90". 2"5 and Gravityvarying between 3, Hardness between 6 and 6'5. 4, Specific shades of 275. Color white 2-55 and between and or pale 2'9, 5, mostly of dark. In red minium alusilicates less or composition 6, yellow, commonly green, with either potassium,sodium, or calcium,and rarelybarium, while magnesium and iron are always absent. Furthermore, besides the several distinct species there are intermediate compounds having a certain many independenceof character and yet connected with each other by insensible not only gradations;allthe members of the series showing a close relationship in composition but also in crystalline form and opticalcharacters. The species of the FeldsparGroup are classified, firstas regards form, and second with reference to composition. The monoclinic speciesinclude (see above): ORTHOCLASE, potassiumfeldspar, and SODA-ORTHOCLASE, potassiumsodium feldspar;also HYALOPHANE and CELSIAN, barium feldspars. The tricliniespecies include : MICROCLINE and ANORTHOCLASE, potassiumsodium feldspars;ALBITE, sodium feldspar;ANORTHITE, calcium feldspar. Also intermediate between albite and anorthite the isomorphous subspecies, sodium-calcium calcium-sodium or feldspars: OLIGOCLASE, ANDESINE, in methods

LABRADORITE.

457

SILICATES

Section

Monoclinic

a.

ORTHOCLASE.

Monoclinic.

Axes

a

:

b

: c

=

0*6585

:

1

:

768

767

63" 57'.

0-5554; 769

770

m m

A

110

001

A A

130 101

001

A

201

mm'", 110 zz', 130 ex, cy,

61" 58" 50" 80"

=

=

=

=

13'. 48'.

001

A

021

=

nn', 021

A

021

=

001

A A

Til

cn,

16|'. 18'.

cm, co,

001

110

=

=

44" 89" 53 67" 47 55" 14

Carlsbad twins, Twins: tw. pi. (1) a (100),or tw. axis c, the common either of irregular penetratipm(Fig.772) or contact type; the latter usually often then (Fig.773) with c (001) and with b (010) as composition-face, be to in but a x distinguishedby luster,cleavage,etc. plane, (101)nearly forming nearlysquare prisms (Fig.774),since (2) n (021),the Baveno ..twins 89" 53'; often repeated as fourlings hence cc 44" SGJ'^and cn (Fig.447, axis. Manebach the a in*square p risms, c || elongated (3) (001), /also p. 171), =

=

771

twins laws.

772

773

(Fig.775),usuallycontact-twins with

774

c as

776

comp.-face. Also other

rarer

Crystalsoften prismatic ||c axis;sometimes orthorhombic in aspect (Fig. 770) since c (001)and x (101)are inclined at nearlyequalanglesto the vertical axis ; also elongated|| a axis (Fig. 771) with b (010)and c (001)nearlyequally 6 also thin tabular developed; || (010):rarelytabular ||a (100),a face not often observed. Often massive, coarselycleavable to granular; sometimes lamellar. and flint-likeor jasper-like. Also compact crypto-crystalline, less so; prismaticm (110) somewhat 6 Cleavage: c (001)perfect; (010) t o but one distinct parallel prismaticface than to the imperfect, usuallymore other. t o distinct Parting sometimes parallel a (100),also to a hemi-orthoinclined the to a few degrees dome, orthopinacoid;this may produce a satinlike luster or schiller (p.251),the latter also often present when the parting

MINERALOGY

DESCRIPTIVE

458 distinct.

is not 2'57.

Luster

conchoidal

Fracture

vitreous; on

c

to

H.

Brittle.

uneven.

G.

=6.

=

white,pale yellow pearly. Colorless,

(001)often

uncolored.

Streak gray; rarelygreen. (Fig.776). Ax. pi. usually J_ b (010), Opticallynegative in all cases from the former to the latter on increase of tem11 6, also changing sometimes and flesh-red common,

perature (see p

,*m"-,\

?i

297). For

"__"_ .7. adularia

Bxa.r "69"

axis direction c

776

T-"__

=

A

Ac

axis

.

=

-

i -i r

"!r"o 69"

ID,,

11',Bxa.w

A

A

Bxa and the.extinctioninclined a few degrees only

37'.

Hence

(Fig.776) axis, or the edge b/c; thus +3" to +7" usually,or up to +10" or +12" in varieties rich also horizontal, in Na20. Dispersion p "v\ accordingto position stronglymarked, or inclined, of ax. pi. Axial angles variable. Birefringence

to

a

low, 7

=

ay /.

2Vy

0-007

=

a

-

=

-

0-005.

adularia

For

1-5237, yy 1-5190, fty 121" 6'. 69" 43', 2Ey= =

=

1'5260.

and potasA silicate of aluminium sium, Silica K2O.Al2O3.6SiO2 or KAlSi308 16'9 100. Sodium alumina 18-4, potash 647,

Comp.

"

=

=

is often also present, replacing part of the potassium,and sometimes exceeds it soda-orthoclase under the name embraced these varieties are in amount; material whose as a barbieritehas been proposed for this existence, (thename to have been proven). distinct though rare mineral,seems habit and method of occurrence crystalline prominent varieties depend upon difference of composition. upon The 1. Adularia. pure or nearly pure potassium silicate. Usually in crystals,like parent TransG. 2 '565. twins common. Fig.770 inhabit; often with vicinal planes; Baveno Often with a pearly opalescentreflection or schiller or a delicate play or nearly so. of colors;some is here included,but the remainder moonstone belongs to albite or other of the triclinicfeldspars. The originaladularia (Adular) is from the St. Gothard region in Switzerland. from the silver mine of Valencia,Mexico, is adularia. Valencianite, in crystals,often transparent and 2. Sanidine or glassy, glassy feldspar. Occurs in rhyolite, Habit embedded trachyte (as of the Siebengebirge,Germany), phonolite,etc. often tabular ||6 (010) (hence named from (ravls, board) ; also in square a tablet, or prisms Most varieties contain sodium as a prominent constituent, (6,c); Carlsbad twins common. and hence belong to the soda-orthoclase. is a sanidine-like soda-orthoNatronsanidine clase from a soda liparite from Mitrowitza,Servia. from pva", Rhyacolite. Occurs in glassy crystalsat Monte Somma, Vesuvius; named stream (lavastream). 3. Isothose is said to be a variety having a different optical orientation than normal Var.

"

more

The

than

=

orthoclase. 4. Ordinary. In crystals, Carlsbad and other twins common; also massive or cleavable, varying in color from white to pale yellow,red or green, translucent;sometimes avent urine. Here belongs the common feldsparof granitoidrocks or graniteveins. Usually contains a greater or less percentage of soda (soda-orthoclase).Compact cryptocrystalline orthoclase makes up the mass of much felsite, but to a greater or less degree admixed with quartz; of various colors, from white and brown of what to deep red. Much has been called orthoclase, or common potash feldspar,has proved to belong to the related triclinic species, microcline. Cf. p. 461 on the relations of the two species. Chesterlite and Amazon stone are

also most microcline;

aventurine

orthoclase.

Loxoclase

contains sodium

in considerable

(7'6 Na2O); from Hammond, St. Lawrence Murchisonite is a fleshCo., N. Y. red feldspar similar to perthite(p.460),with gold-yellowreflections in a direction _|_b (010) and nearlyparallelto 701 or 801 (p.457) from Dawlish and Exeter,England. ; The spherulities noted in some volcanic rocks,as in the rhyoliteof Obsidian Cliff in the Yellowstone Park, are believed to consist essentiallyof orthoclase needles with quartz. amount

SILICATES

(from Iddings; much

459 magnified)

777

778

B.B.

fuses at 5; varieties containing much soda are acted upon by acids. Mixed with powdered B. B. gives violet potassium flame visible through blue glass.

Pyr.,

etc.

clase fuses

at

"

4.

Not

more

fusible.

gypsum

and

Loxoheated

Diff Characterized form and the two cleavages at rightangles to by its crystalline each other; harder than barite and calcite; not attacked by acids; difficultly fusible. Massive is much corundum harder and has a higher specific gravity. "

.

Micro. Distinguished in rock sections by its low refraction f erence-colors, which last scarcelyrise to white of the first order of quartz; also by its biaxial character in convergent lightand

and (low relief)

low'interhence lower than those by the distinct cleavages. It is colorless in ordinary lightand may be limpid, but is frequentlyturbid and brownish of very minute from the presence scales of kaolin due to alteration from weathering; this in the older granularrocks,as graniteand gneiss. change is especiallycommon Artif. Orthoclase has not been produced artificially by the methods of dry fusion. It can, however, be crystallized from a dry melt when certain other substances,like tungstic The function of these additions in the reactions acid,alkaline phosphates, etc.,are added. is not clear. Orthoclase is more It has been methods. easilyformed by hydrochemical produced by heating gelatinoussilica, alumina, caustic potash and water in a sealed tube. has also been formed Orthoclase by heating potassium silicate and water together with muscovite. Obs. in its several varieties belongs especiallyto the crystalline Orthoclase rocks, occurringas an essential constituent of granite,gneiss,syenite,also porphyry, further (var., sanidine) trachyte,phonolite,etc. In the massive granitoidrocks it is seldom in distinct, well-formed,separable crystals,except in veins and cavities;such crystalsare more mon, comhowever, in volcanic rocks like trachyte. Adularia in the crystalline rocks of the central and eastern Alps, associated with occurs smoky quartz and albite,also titanite,apatite,etc.; the crystalsare often coated with Fine crystalsof orthoclase,often twins, are obtained from Baveno, chlorite;also ^n Elba. "

"

"

"

Lago Maggiore, Italy; the Fleimstal,Tyrol, Austria, a red variety; Bodenmais, Carlsbad, and Elbogen in Bohemia; Striegau,etc.,in Silesia. Also Arendal in Norway, and near Shaitansk in the Ural Mts.; Land's End and St. Agnes in Cornwall; the Mourne Mts., Ireland,with beryl and topaz. From Tamagama Yama, Japan, with topaz and smoky is brought from quartz. Moonstone Ceylon. Crystalsof gem quality from Itrongahy, Valencianite from Guanajuato, Mexico. Madagascar Crystals from Eganville,Ontario. In the United States,orthoclase is common in the crystalline rocks of New England,also of States south, further Colorado, California,etc. Thus at the Paris tourmaline locality, Me. In N. H., at Acworth. In Mass., at South In Conn., at Royalston and Barre. Haddam and crystals. In N. Y., in St. Lawrence Middletown, in large coarse Co., at in Lewis Co., in white limestone near Natural Bridge; at Rossie; at Hammond (loxoclase)', In Pa.,in crystalsat Leiperville, Mineral Hill,Delaware Amity and Edenville. Co.; sunIn N. C., at Washington Mine, Davidson Co. In Col.,at the stone in Kennett Township. of Mt. Antero, Chaffee Co., in fine crystals,often twins; at Gunnison; Black summit

460

MINERALOGY

DESCRIPTIVE

Kokomp, Summit Co., Robinson, also at other points. Also similarlyin Nev. and Large twin crystalsfrom Barringer Hill,Llano Co., Texas. Orthoclase is frequentlyaltered,especially through the action of carbonated or Alter. of the potash and the formation of alkaline waters; the final result is often the removal kaolin. as pseudomorphs after Steatite,talc,chlorite,leucite,mica, laumontite, occur tion process of soluorthoclase;and cassiterite and calcite often replacethese feldsparsby some Hawk;

Cal.

"

substitution. In the manufacture its surface. and

Use.

on

of porcelain,both

"

in the

body

of the

and

ware

in the

glaze

first described,a flesh-red aventurine feldspar from Perth, Ontario, but shown clase soda-orthoclase, by Gerhard to consist of interlaminated orthosince been have and albite. Many similar occurrences noted, as also those in which microcline and albite are similarlyinterlaminated,the latter called microcline-perthite, or this is true in part of the originalperthite. When the structure microcline-albite-perthite; is discernible only with the help of the microscope it is called microperthite. Brogger has investigatednot only the microperthitesof Norway, but also other feldsparscharacterized he assumes the existence of an extremelyfine interlamination of albite by a marked schiller; and and orthoclase ||801, not discernible by the microscope (cryptoperthite), connected with secondary planes of parting ||100 or || 801, which is probably to be explained as due to incipientalteration. PERTHITE.

Canada, called

As

a

Silica 51 '6, alumina K2O.BaO.2Al2O3.8SiO2. or Hyalophane. (K2,Ba)Al2(SiO3)4 21'9, In crystals, like adularia in habit (Fig.770, p. 457); also 100. baryta 16*4,potash 101 massive. less so. H. 6-6*5. G. =2*805. Cleavage: c (001)perfect;b (010)somewhat 1-547. 1*542. 1*545. Occurs in a granular dolomite in the Optically ft a. 7 mine of Jakobsberg, Sweden. Binnental,Switzerland; also at the manganese Some other feldspars containing7 to 15 p. c. BaO have been described. Celsian. BaAl2Si2Og,similar in composition to anorthite,but containingbarium instead In crystalsshowing a number of calcium. Monoclinic. of forms; twinned according to Carlsbad, Manebach and Baveno laws. H. Usually cleavable massive. 6-6*5. G. 3'37. Extinction on 6 (010) 28" 3'. Colorless. 1*584. Optically+ a ft 1*589. From 1*594. Name Jakobsberg, Sweden. 7 baryta-orthoclase given to mixtures of celsian and orthoclase. Paracelsian from Candoglia,Piedmont, Italy, is the same species. =

=

-.

=

=

=

=

=

=

=

=

.

=

ft. Triclinic Section MICROCLINE.

Triclinic.

Near

orthoclase in

angles and habit,but the angle be (010 A about 89" 30'. 001) Twins: like orthoclase,also polysynthetic twinning according to the albite and pericline laws (p. 464), common, producing two series of fine lamellae nearly at right angles to each other, hence the characteristic gratingstructure of a basal section in polarized light(Fig.779). Also massive cleavable =

779

to

m

easy.

Fracture

granular compact.

Cleavage: c(001) perfect;6(010) somewhat less so; M (1TO) sometimes distinct; (110) also sometimes but less distinct,

Brittle. H. (001) sometimes pearly. uneven.

=

6-6'5.

G

=

2'54-2*57

Luster

vitreous,on c Color white to pale cream-yellow also red, green Transparent to translucent. Ax. pi.nearly Optically-. perpendicular (82"-83")to 6 (010). Bx0 inclined 15" 26' to a normal to 6 "

*'

Bx"-

Extinction-angle on

(001),+15"

c .

"=

1-522.

461

SILICATES

essential identityof orthoclase and microcline has been urged by Mallard and the ground that the propertiesof the former would belong to an aggregate of submicroscopictwinning lamellae of the latter, laws. accordingto the albite and pericline The

Michel-Levy on

Comp. alumina

Like

"

prominent,as

sometimes Pyr. Diff.

orthoclase,KAlSi3O8

-4,potash 16*9

18

Silica 647, or K2O.Al2O3.6Sip2 Sodium is usuallypresent in small amount: in soda-microcline. =

=

100.

for orthoclase. Resembles orthoclase but distinguishedby opticalcharacters (e.g., the grating in polarizedlight,Fig. 779); also often shows fine twinning-striations on a basal

"

As

"

"

structure

surface (albite law). In thin sections like orthoclase but usuallyto be distinguished Micro. by the gratingin polarizedlightdue to triclinictwinning. like structure conditions as much Obs. Occurs under the same orthoclase. The beautiful common from the Ural Mts., also that occurringin fine groups of largecrystalsof deep amazonstone color in the graniteof Pike's Peak, Col.,is microcline. Crystals from Ivigtut,Greenland. From Antsongombato and Antoboko (amazonstone), Madagascar. Chesterlite from Poorhouse quarry, Chester Co.,Pa.,and the aventurine feldsparof Mineral Hill,Pa.,belong here. at Magnet Cove, Ark. at many A pure varietyoccurs Ordinary microcline is common points. Same for orthoclase;sometimes Use. ornamental material (amazonstone). as as an "

"

"

A triclinicfeldsparwith a cleavage-angle, Anorthoclase. Soda-microcline. be,010 A 001, like that of the ordinary feldspars. Twinning as varying but little from 90". Form with orthoclase;also polysyntheticaccordingto the albite and pericline laws; but in many and hence not distinct. Rhombic section (seep. the twinning laminae very narrow cases 2 '57-2 "60. Cleavage,hardness,luster, 462) inclined on 6 (010)4" to 6" to edge b/c. G. =

of the group. Optically ._ Extinction-angleon c (001) izontal +5" 45' to +2"; on b (010)6" to 9.8". Bxa nearly _L y (201). Dispersionp " v; hor1'523. perature, 1'529. 1'531. Axial angle variable with temdistinct, a /3 7 becoming in part monoclinic in opticalsymmetry between 86" and 264" C., but again triclinicon cooling;this is true of those containinglittlecalcium. Chiefly a soda-potash,feldsparNaAlSisOs and KAlSi3p8, the sodium silicate usuallyin of albite and orthoclase molecules. cium Calas if consisting largerproportion(2 : 1, 3 : 1,etc.), small amount. is also present in relatively very (CaAl2Si2p8) from the andesitic lavas of These triclinic soda-potash feldsparsare chieflyknown from a rock,called pantellerite.Also prominent Most of these feldsparscome Pantelleria. of southern Chrisfrom the augite-syenite near Norway and from the " Rhomben-porphyr and twinned according tabular j| tiania. Here is referred also a feldsparin crystals, c (001), and less often Baveno laws occurringin the lithophysesof the rhyoliteof to the Manebach Park. It shows the blue opalescence in a direction parallel Obsidian Cliff.Yellowstone with a steep orthodome (cf.p. 457). and

color

as

with other

members

=

"

=

=

"

Albite-Anorthite

Between

the

Series.

Plagioclase Feldspars*

isomorphous species

ALBITE

NaAlSisOg

Ab

ANORTHITE

CaAl2Si208

An

of intermediate subspecies, a number regarded,as urged by Tscherisomorphous mixtures of these molecules,and defined accordingto the ratio in which they enter; their compositionis expressedin generalby the formula AbnAnm. They are:

there

mak,

are

as

LABRADORITE

Ab6Ani Ab3Ani AbiAni

to

Bytownite

AbiAn3

to

OLIGOCLASE ANDESINE and

to

Ab3Ani

to

AbiAn6

albite through the successive intermediate compounds to anorthite From with the progressivechange in composition (also specific gravity,melting * The triclinicfeldsparsof this series, in which the two cleavages6 (010)and c (001)are (from Tr\ayios,oblique). oblique to each other,are often called in generalplagioclase

DESCRIPTIVE

462

MINERALOGY

form, and change in crystallographic there is also a corresponding etc.), points, in certain fundamental opticalproperties. The axial ratios and anglesgiven on p. 456 show that Form. Crystalline triclinic feldspars these 781 780 ly approach orthoclase closein

form, the

most

vious ob-

being in the cleavage-angle6c010 difference

is 90" in A 001, which 86" 24' in albite, orthoclase, 50' in anorthite. a change in the axial angle 7, which is about 90" in 88" in albite, oligoclaseand andesine, This and 91" in anorthite. still transition appears c Plagioclasewith twinning lamellae. Fig. 780 section || the in more strikingly ary (001)showing vibration-directions(cf.Fig. 784),ordinof the rhombic in position section polarizedlight. light;Fig. 781 the section,"by which law united below. the to are as twins according pericline explained feldsparsare often twinned in accordance Twinning. The plagioclase laws common with orthoclase with the Carlsbad, Baveno, and Manebach is also almost universal according to the albite law (p.457). Twinning i.e., twinning plane the brachypinacoid; this is usually polysynthetic, givingrise to fine striations on the basal repeatedin the form of thin lamellae, accordingto the cleavagesurface (Figs.780, 781). Twinning is also common axis the axis law when twinning macrodiagonal polysynthetic 6; pericline this givesanother series of fine striations seen the brachypinacoid. on and

There

85"

is also

"

"

"

in this pericline The composition-plane twinningis a plane passingthrough the crystalin such a direction that its intersections with the prismaticfaces and the brachypinacoid make The positionof this rhombic section and the consequent equalplaneangleswith each other. direction of the striations on the brachypinacoid change rapidly with a small variation in be said to be approximatelyparallelto the base, but in the angle 7. In generalit may albite it is inclined backward (+, Figs. 782 and 784) and in anorthite to the front (" , Fig. 783); for the intermediate speciesits positionvaries progressivelywith the composition. 783

782

Fig.782, Rhombic

784

section in albite. 783, Same in anorthite. 784, Typicalform + and extinction-directions on c (001) and 6 (010).

showing

"

Thus

for the angle between the trace of this plane on the brachypinacoidand the edge have for Albite +22" to +20"; for Oligoclase+9" to +1" +3""; for Andesine to -2"; for Labradorite -9" to -10"; for Anorthite -15" to -17".

6/c,we

464

MINERALOGY

DESCRIPTIVE

Bx; for certain Bx, while anorthite is negative or X 90". is andesines sensibly angle Fig. 786 (afterIddings)shows the variation in the extinction angleson the cleavage faces,c (001) and b (010),for the different mixtures of the albite

itive,that is Z the

and

=

"

axial

anorthite molecule.

In rock sections the plagioclasefeldsparsare distinguishedby their lack of Micro. and low interference-colors, which in good sections are mainly color,low refractive relief, dark gray and scarcelyrise into white of the first order; also by their biaxial character in converging light. In the majority of cases they are easilytold by the parallelbands or fine due to the multiple twinning according to the albite lamellae which pass through them law; one set of bands or twin lamellae exhibits in general a different interference-color from the other (cf.Figs.780, 781). They are thus distinguishednot only from quartz and orthoclase,with which they are often associated,but from all the common rock-making To distinguishthe different speciesand sub-speciesfrom one minerals. another, as albite difficult. In sections having a definite orientation from laboradorite or andesine,is more c (001)and ||6 (010)) this can generallybe done by determining the extinction angles (cf (|| are required;these are p. 462 and Fig. 784). In general in rock sections specialmethods discussed in the various texts devoted to this subject. "

.

ALBITE.

=

Triclinic. 88" 9'.

Axed

a

:

b

: c

0*6335

=

:

1

:

0-5577; a

788

787

=

94"

3',(3

116"

=

be, mM, bm,

010

A

110

=

60"

cm,

001

A

110

=

65"

cM,

001

A

110

=

ex,

001

A

101

Twins also very

010

A

001

110

A

110

=

=

=

29',

86" 24'. 14'.

59"

26'.

17'. 10'. 52" 16'. 69"

with

orthoclase; the tw. pi. common, b (010),albite law (p. 462), usually contact-twins, and as

polysynthetic, consistingof thin

lamellae

and with sequent confine striations on c(001) (Fig.790); tw. axis b axis,peridine law,contact-twins whose composition-face is the rhombic section (Figs.782 and 792); often polysynthetic and showing fine striations which 6 (010) on inclined backward are +22" to the edge b/c. Crystals often tabular || b (010); also elongated||6 axis as in the variety pericline. Also massive,either lamellar or granular;the laminae often curved, sometimes divergent; granular varieties occasionallyquite fine to

impalpable. Cleavage: c(001)perfect;6(010)somewhat less so; m (110)imperfect. Fracture uneven conchoidal. Brittle. H. 6-6*5. G. 2-62-2-65. Luster vitreous; on a cleavage surface often pearly. Color white; also occasionally to

=

bluish,gray,

=

reddish,greenish,and

sometimes having a bluish opalescence or play of colors on c (001). Streak uncolored. translucent. green;

Transparent

to

sub-

465

SILICATES

30' to 2" on c, Optically-!-. Extinction-anglewith edge b/c =4-4" +20" to 15" on b (Fig. 782). Dispersion for Bxa, p " v; also clined, and inhorizontal; for Bx0, ^91 ^92 " inclined, crossed. v, p =

a=l-531.

l'"

J3

=

2V=

1-540.

77".

fringence weak,

y

"

a

=

0-009.

Comp.

A

"

aluminium

silicate of

and

sodium,

NaAlSi3O8 or NaaO.Al20". Silica 687, alumina 6SiO2 present in small amount,

Pericline

11 -8 =100. Calcium is usually creases this inas (CaAl2Si2O8),and sium it graduatesthrough oligoclase-albite to oligoclase (cf.p. 466). Potas-

=

may

also be

19'5, soda

as

present, and

anorthite

it is then

connected

with

anorthoclase

and

microcline. Var. The crystalsoften tabular ||b (010). The Ordinary. In crystalsand massive. Permassive forms are usuallynearly pure white, and often show wavy curved laminae. or from Trepto-repa, pigeon. isterite is a whitish adularia-like albite,slightlyiridescent,named Pericline from the chloritic schists of the Aventurine and moonstone varieties also occur. with characteristic elongation in the direction white crystals, Alps is in rather large opaque in Figs.791 and 792, and commonly twinned of the 6 axis,as shown with this as the twinning axis (pericline law). B.B. fuses at 4 to a colorless or white glass,imparting an intense yellow to Pyr., etc. the flame. Not acted upon by acids. Diff. Resembles barite in some forms, but is harder and of lower specificgravity; does not effervesce with acid (likecalcite). Distinguished opticallyand by the common twinning striations on c (001) from orthoclase; from the other triclinic feldsparspartially by specificgravity and better by opticalmeans (seep. 463). Artif. Albite acts, in regard to its artificialformation, like orthoclase,which see. Obs. Albite is a constituent of many igneous rocks,especiallythose of alkaline type, as granite,elaeolite-syenite, diorite,etc.; also in the corresponding feldspathiclavas. In with orthoclase or microcline,and similar aggregaperthite(p. 460) it is interlaminated tions, in many Albite is common also often on a microscopic scale,are rocks. common in gneiss, and sometimes in the crystallineschists. often Veins of albitic granite are maline, of gems, includingberyl,tourrepositoriesof the rarer minerals and of fine crystallizations in granular limestone. allanite, columbite, etc. It is found in disseminated crystals Some of the most prominent European localities are in cavities and veins in the granite or granitoidrocks of the Swiss and Austrian Alps, associated with adularia,smoky quartz, rarer chlorite,titanite, apatite,and many species: it is often implanted in parallelposition the orthoclase. Thus in the Alps the St. Gothard near Modane, region; Roc Tourne upon Greiner, Tyrol; Savoie; on Mt. Skopi (pericline); Tavetschtal; in Austria at Schmirnand also Pfitsch,Rauris, the Zillertal, Krimml, Schneeberg in Passeir,Tyrol, in simple crystals. Also Hirschberg in Silesia; Also in DaupLine, France, in similar association;Elba. Penig in the Ilmen in Saxony; with topaz at Mursinka Miask in the Ural Mts. and near Mts.; Mts. in Ireland. Fine crystalsfrom Greenland. Cornwall, England; Mourne In the United States,in Me., at Paris,with red and blue tourmalines,also at Topsham. In Mass., at Chesterfield, in lamellar masses bluish,also fine granu(cleavelandite) slightly lar. spar feldIn N. H., at Acworth In Conn., at Haddam; at the Middletown and Alstead. In N. Y., at Moriah, Essex quarries,at Branchville,in fine crystalsand massive. In Pa., at Co., of a greenish color;at Diana, Lewis Co., and Macomb, St. Laurence Co. in splendid Amelia Court-House In Va., at the mica mines Union ville,Chester Co. near In Col.,in the Pike's Peak region with smoky quartz and amazonstone. crystallizations. color. The albite is derived from name albus,white, in allusion to its common varieties which Use. Same orthoclase but not as so commonly employed; some material known show an opalescent play of colors when as polished form the ornamental "

"

"

"

"

,

"

moonstone.

466

MINERALOGY

DESCRIPTIVE

Oligoclase. 86" 32'. Twins observed be, 010 A 001 laws. a nd Crystalsnot common. pericline Carlsbad,albite, cleavable to compact. Usuallymassive, Fracture conchoidal Cleavage: c (001)perfect;6 (010)somewhat less so. Triclinic.

Axes,

p. 456.

see

=

accordingto the

21-65-2 '67. Luster vitreous to some6-6 -5. G. what of faint with Color a tinge grayish usuallywhitish, pearly or waxy. reddish;sometimes aventurine. green, grayishwhite, reddish white,greenish, see Opticalcharacters, Transparent, subtranslucent. p. 463. albite and anorthite and corresponding Intermediate between Comp.

Brittle. H.

to

uneven.

to

Ab6Ani

=

=

"

to

to Ab3Ani, Ab2Ani, but chiefly

p. 461.

1. Ordinary. In crystalsor more Var. commonly massive, cleavable. The varieties 2. Aventurine or sunoligoclase, containingsoda up to 10 p. c. are called oligoclase-albite. with internal yellowish stone,is of a grayish white to reddish gray color,usually the latter, reddish fire-likereflections proceeding from disseminated or crystalsof probably either hematite or gothite. B.B. fuses at 3-5 to a clear or enamel-like glass. Not materially acted Pyr., etc. by acids. upon Diff. See orthoclase (p.459) and albite (p.465); also pp. 456, 463. Obs. Occurs in porphyry, granite,syenite,and also in different effusive rocks,as It is sometimes andesite. associated with orthoclase in granite or other granite-like rock. Among its localitiesare Danviks-Zoll near Stockholm, Sweden; Pargas in Finland; Shaitansk,Ural Mts.; in syeniteof the Vosges Mts., France; at Albula in Orisons,Switzerland; Marienbad, Bohemia; in France at Chalanches in Allemont, and Bourg d'Oisans,Dauphine; at Hittero,Norway; Lake at Tvedestrand, Norway; as sunstone Baikal,Siberia. In the United States,at Fine and Macomb, St. Lawrence Co., N. Y., in good crystals; at Danbury, Conn., with orthoclase and danburite;Haddam, Conn.; at the emery mine, Chester,Mass., granular; at Unionville,Pa., with euphylliteand corundum; Mineral Hill, Delaware Co., Pa.; at Bakersville,N. C., in clear glassy masses, showing cleavage but no in 1826 by Breithauptfrom 0X1705,little, and /cXao-is, twinning. Named fracture. "

"

"

"

Andesine.

Triclinic. Axes, albite. Crystalsrare.

86" 14'. Twins with be, 010 A 001 as p. 456. Usuallymassive,cleavable or granular. Cleavage: c (001) perfect; b (010) less so; also M (110) sometimes observed. H. 5-6. G. 2'68-2'69. Color white,gray, greenish, ish, yellowflesh-red. Luster subvitreous to pearly. Opticalcharacters, see p. 463. Intermediate between albite and anorthite,corresponding to Comp. see

=

=

=

"

Ab

:

An

in the ratio of 3

:

2, 4

:

3 to 1

:

1,see

p. 461.

Fuses in thin splinters before the blowpipe. Imperfectlysoluble in acids: Observed in many granular and volcanic rocks; thus occurs in the Andes, at Marmato, Colombia, as an ingredient of the rock called andesite;in the porphyry of 1 JLsterel, Dept. du Var, France; in the syeniteof Alsace in the Vosges Mts.; at Vapnefiord, Iceland; Bodenmais, Bavaria; Frankenstein,Silesia. Sanford, Me., with vesuvianite Common in the igneous rocks of the Rocky Mts. Crystalsfrom Sardinia and Greenland. r., etc.

"

_

Obs.

"

Labradorite.

Labrador

Feldspar.

Triclinic. Axes, see 86" 4'. p. 456. Cleavage angle be 010 A 001 Forms and twinning similar to the other plagioclase species. Crystalsoften very thin tabular 11b (010); and rhombic in outline bounded by cy or ex (Fig. 455, p. 172). Also massive,cleavable or granular; sometimes crvptocrvstalhne or hornstone-like. =

Cleavage:c (001)perfect;b (010)less so; *T

~~

5~b"

G"

vitreous

=

or

270-272.

M

(110)sometimes

distinct.

Duster on c pearly,passinginto vitreous;elsewhere subresinous. Color gray, brown, or greenish;sometimes

467

SILICATES

colorless and glassy; rarelyporcelainwhite; usuallya beautiful colors in cleavable varieties, ||6 (010). Streak uncolored. especially subtranslucent. to see Opticalcharacters, p. 463. Play of colors

change of lucent Trans-

colorless cryscharacter,but sometimes wanting as in some tals. and pearl-gray the predominant colors; but yellow,fire-red, also blue color of labradorite as an interference-phenomoccur. Vogelsang regards the common enon due to its lamellar structure, while the golden or reddish schiller, with the other colors, is due to the presence of black acicular microlites and yellowishred microscopic lamellae, or effect of these with the blue reflections. Schrauf has examined to the combined the inclusions, Blue and

their of them.

a

common

are

green

position,etc.,and (See references on

Comp. chieflyto

given the 181.)

Intermediate

"

Ab

An

:

in

a

microplakiteand

names

to microphyllite

two

groups

p.

between

ratio of from

albite and 1

:

1 to 1

anorthite :

and

corresponding

3, p. 461.

labradorite proper and anorthite have been embraced The feldsparswhich lie between under the name by Tschermak bytownite. The originalbytownite of Thomson was a rio, greenishwhite feldspathicmineral found in a boulder near Bytown (now Ottawa) in OntaCanada. B.B. fuses at 3 to a colorless glass. Decomposed with difficulty by hydrochloric acid,generallyleaving a portion of undecomposed mineral. but not universal character. Diff. The beautiful play of colors is a common wise Otherdistinguishedas are the other feldspars(pp. 459, 465). Obs. Labradorite is an essential constituent of various igneous rocks,especiallyof the basic kinds, and usually associated with some member of the pyroxene or amphibole Thus with hypersthene in norite,with diallagein gabbro, with some form of groups. in diabase,basalt,dolerite, also andesite,tephrite,etc. Labradorite also occurs pyroxene in other kinds of lava,and is sometimes found in them in glassycrystals, as in those of Etna, Islands. Vesuvius, at Kilauea, Hawaiian

Pyr.,etc.

"

"

"

labradoritic massive rocks are most the formations of the Archaean common among Such are part of those of British America, northern New sas; York, Pennsylvania, Arkanthose of Greenland, Norway, Finland, Sweden, and probablyof the Vosges Mts. On the coast of Labrador, labradorite is associated with hornblende, hypersthene, and placesin Quebec. Occurs abundantly through the cenmagnetite. It is met with in many tral Adirondack region in northern N. Y.; in the Wichita Mts., Ark. the Isle of Paul, on the coast of Labrador,by Mr. first brought from Labradorite was missionary,about the year 1770. Wolfe, a Moravian Use. The varieties showing a play of colors are used as ornamental material. The

era.

"

MASKELYNITE.

In colorless isotropic grainsin

ANORTHITE.

Indianite.

Triclinic. 7

Axes

a

:

b

: c

=

0-6347

1

:

meteorites;composition near

0-5501;

a

=

93"

13',ft

=

labradorite.

115"

55|',

91" 12'.

=

be, mM, bm,

010

A

001

110

110

010

A A

110

=

cm,

001

A

110

=

cM,

001 001

A A

110 201

cy,

=

=

=

=

85" 59" 58" 65" 69" 81"

50'. 29'.

793

794

4'.

53'. 20'. 14'.

albite

(p. 462 and 464). Crystals usually p. prismatic ||c axis (Fig.793, also gated Fig. 364, p. 146),less often elon1 1 b axis,like pericline(Fig. Twins

Also

794). with

as

with

massive, cleavable,

granular or

coarse

lamellar

structure.

Cleavage: c (001)perfect;b (010)somewhat

less so.

Fracture

conchoidal

468 to

MINERALOGY

DESCRIPTIVE

H. Brittle. uncolored. Streak

=

uneven.

reddish.

G.

6-6'5.

=

Transparent

2-74-276.

Color

white, grayish,

to translucent.

60"

inclined to the Ax. pi.nearly _L e (021),and its trace Optically below. in front Extinction-angles to behind right edge c/e from left above to -43" b (010), -35" (Fig. with edge 6/c; on to -42" on c (001),-34" V 78". 2 inclined. 1'576. a 784, p. 462). Dispersion p " v, also 1*588. 1*584. Birefringencestronger than with albite. j8 7 -.

=

=

=

=

Comp.

A

"

and

silicate of aluminium

calcium, CaAl2Si2O8

or

CaO.Al203.

Soda 100. (as NaAlSi3O8) is Silica 43'2, alumina 367, lime 20-1 there is a gradual transition increases it and in small as amount, usually present labradorite. to bytownite through

2SiO2

=

=

Vesuvius; and described from the glassy crystalsof Mte. Somma, is the same from Iceland. Thiorsauite Inmineral. the same as the dianite is a white, grayish, granular anorthite from India, where it occurs or reddish in small, Bournon. of corundum, first described in 1802 by Count Cyclopiteoccurs gangue b (010),coating cavities in the dolerite of the tabular ||transparent, and glassy crystals, latrobite also belong to Etna. Trezza Amphodelite, lepolite, on Cyclopean Islands and near Var.

Anorthite

"

christianite

was

biotine

and

are

anorthite. from Mte. B.B. fuses at 5 to a colorless glass. Anorthite etc. Somma, and from the Carnatic, India, are decomposed by hydrochloric acid,with separation.of gelatinoussilica. is the easiest of the feldspars to be formed Artif. Anorthite artificially.Unlike the in a dry fusion of its constituents. be easilyformed This method alkalic feldsparsit can is added to the composition. difficult as the albite molecule becomes progressively more in artificial magmas. in slags and is easilyproduced Anorthite is frequently observed It further is often produced when more complex silicates are broken down by fusion. Obs. Occurs in some diorites;occasionallyin connection with gabbro and serpentine volcanic rocks, andesites,basalts, cases rocks; in some along with corundum; in many etc.;

Pyr.,

"

indianite

"

"

constituent

of

meteorites

(Juvenas, Stannern) Vesuvius in isolated blocks among at Mount biotine)occurs the old lavas in the ravines of Monte in the Albani Somma; Mts.; on the Pesmeda Alp, land; Monzoni, Tyrol, as a contact mineral; Aranyer Berg, Transylvania, in andesite; in IceIn the Cyclopean Islands (cyclopite). In the lava near Bogoslovsk in the Ural Mts. of the island of Miyake, Japan. In crystalsfrom Franklin, N. J.; from Phippsburg, Me. Anorthite named in 1823 was by Rose from avopdos, oblique, the crystallization being as

a

Anorthite

some

.

and (christianite

triclinic. A feldspar having the composition,Na2O.2CaO.3Al2O3.9SiO2. This does with of the albite-anorthite series. possible member This is explained by any agree of a sodium-anorthite assuming the presence in small amount molecule, Na2O.Al2O3.2SiO2, to which the name carnegieite has been 85" 59'. given. Cleavage angle G. 2 '68. 1-555. 1-559. 1'563. 2 V 82" 48'. a j8 Found loose crystals on Mte. as 7 Name derived from the ancient Greek Rosso, Island of Linosa. of the island. name negieite Caris named in honor of Andrew Carnegie. Anemousite.

not

=

=

=

=

=

=

;H. Metasilicates.

RSiO3

Salts of Metasilicic Acid, H^SiOs;characterized by an oxygen ratio of 2 : 1 for silicon to bases. The Division closes with a number of species,in part of somewhat doubtful composition,forming a transition to the Orthosilicates. The metasilicates include two and well-characterized prominent

viz.,the Pyroxene Group and the Amphibole less important.

groups,

Group.

There

are

also others

469

SILICATES

Leucite In several

Isometric

Group.

respects leucite is allied to the speciesof the FELDSPAR

GROUP,

which

diately imme-

precede. Leucite

Isometric KAl(SiO3)2 at ordinary temperatures. Isometric H2Cs4Al4(Si03)9

at 500"

Pseudo-isometric Pollucite LEUCITE.

Amphigene. at 500"

under ordinaryconditions (seep. C.; pseudo-isometric crystalsvarying in angle but the tetragonaltrisoctahedron little from n (211), with a (100),and d (110)as subordinate sometimes forms. Faces often showing fine striations due to twinning (Fig.795). Also in disseminated grains; rarelymassive granular. Cleavage: d (110) very imperfect. Fracture Isometric

in

302). Commonly

conchoidal. Brittle. H. 5'5-6. G. 2-45-2-50. Luster vitreous. Color white,ash-gray or smokeuncolored. Translucent to Streak gray. opaque. Usually shows very feeble double refraction: co =

=

=

1-508,6

1-509

=

(p.302).

KAl(Si03)2

Comp. potash 21'5 "

=

or

K2O.Al2O3.4Si02

=

Silica 55*0, alumina

23'5.

100.

traces of Soda is present only in small quantities,unless as introduced by alteration; Leucite and analcite are closely lithium,also of rubidium and caesium,have been detected. related chemically as is shown by the fact that the two speciescan be converted into each other when heated with sodium or potassium chlorides or carbonates. B.B. infusible;with cobalt solution gives a blue color (aluminium). Decomposed Pyr., etc. by hydrochloricacid without gelatinization. Diff Characterized by its trapezohedralform, absence of color,and infusibility.It and fuses. is softer than garnet and harder than analcite;the latter yieldswater ter, Micro. isotropiccharacRecognized in thin sections by its extremely low refraction, and the symmetricalarrangement of inclusions (Fig.796; also Fig.485,p. 180). Larger "

"

.

"

796

Leucite crystalsfrom the leucitite of the Bearpaw Mts., Montana (Pirsson). These show with glassinclusions the progressivegrowth from skeleton forms to complete crystals .

complicated systems of crystalsare commonly not wholly isotropicand, further,show twinning-lines(Fig.795); the birefringenceis,however, very low, and the colors scarcely rise above dark gray; they are best seen by introduction of the quartz or gypsum plate which lack this twinning or the inclusions, yieldingred of the firstorder. The smaller leucites, from sodalite or analcite by chemical tests. are only to be distinguished Artif Leucite is easilyprepared artificially ents by simply fusing together its constituin proper slowly. The addition of proportion and allowing the melt to crystallize produces largercrystals. Leucite has been formed when microcline potassium vanadate fused alone. muscovite was fused together and also when and biotite were Obs. Leucite occurs only in igneous rocks, and especiallyin recent lavas,as one of of magmas rich in potash and low in silica (forwhich reason the products of crystallization The largerembedded this speciesrather than orthoclase is formed) crystalsare commonly anisotropicand show twinning lamellae;the smaller ones, forming the groundmass, are in leucitites and leucite-basalts, twinning. Found isotropicand without leucitophyres, also in certain rocks occurringin dikes. Very rare and leucite-tephrites; leucite-phonolites "

.

"

.

470

MINERALOGY

DESCRIPTIVE

two instances being known; but its former presence or conditions is indicated by pseudomorphs, often of large size (pseudoleucite) also of anal cite. consistingof neph elite and orthoclase, The prominent localitiesare, firstof all,Vesuvius and Mte. Somma, where it is thickly disseminated through the lava in grains,and in large perfectcrystals; also in ejected also near Rome, at Capo di Bove, Rocca Monfina, etc. Further in leucite-tephrite masses; Lake at Proceno near Bolsena in central Italy; in Germany about the Laacher See and at several pointsin the Eifel;at Riedennear in Andernach; at Meichesin the Vogelsgebirge; Occurs in Brazil, the Kaiserstuhlgebirge; at Pinhalzinho. From the Wiesental,Bohemia. Cerro de las Virgines,Lower California. In the United States it is present in a rock in the Green River Basin at the Leucite Hills,Wy. ; also in the Absaroka western range, in northWy.; in the Highwood and Bearpaw Mts., Mon. (inpart pseudoleucite). On the shores of Vancouver Island,where magnificentgroups of crystalshave been found as drift boulders. Pseudoleucite (seeabove) occurs of the Serra de Tingua, in the phonolite(tinguaite) Brazil; at Magnet Cove, Ark.; near Hamburg, N.J.; Mon.; also in the Cariboo District, British Columbia. Named from Xewcos,white,in allusion to its color.

in intruded under such

igneousrocks,only one

Pollucite. EssentiallyH2O.2Cs2O.2Al2O3.9SiO2. Isometric;often in cubes; also massive. H. 6'5. G. 2-901. Occurs Colorless, n 1-525. in the island very sparingly of Elba,with petalite(castorite); also at Hebron and Rumford, Me. =

=

=

Ussingite.HNa2Al(Si03)3.

Triclinic. Three cleavages. G. violet. Indices,1-50-1 '55. Easilyfusible. Soluble in rolled masses from pegmatite at Kangerdluarsuk, Greenland.

reddish in

=

2-5.

H.

6-7.

=

Color Found

acid. hydrochloric

Pyroxene Group

Orthorhombic,Monoclinic,Triclinic Composition for the

part that of

most

also Mn,Zn. Ca,Mg,Fe chiefly,

Further

metasilicate, RSiO3, with R

a

=

RSiO3 with R(Fe,Al)2SiO6, less often

containingalkalies (Na,K),and then RSiO3 with RAl(Si03)2. Rarely including zirconium and titanium,also fluorine. ".

Orthorhombic

Section a

b

:

: c

b

or

_,

Enstatite

Bronzite

Hypersthene

MgSi03 (Mg,Fe)Si03

0'9702

:

1

:

0'5710

1'0307

(Fe,Mg)SiO3

0'9713

:

1

:

0'5704

T0319

ut the

of similarity

: a "

:

1 1

*

c

0'5885

"

:

the form

0'5872 to

the

0. Monoclinic Section

Pyroxene

.1-0921

I. NON-ALUMINOUS

Ayr

3.

':

0-5893

VARIETIES:

1. DIOPSIDE

2.

11

{CaMg(Si03)2 iCa(Mg,Fe)(Si03)2

, r, Malacohte, Sahte,Diallage, etc. HEDENBERGITE CaFe(SiO3)2 Manganhedenbergite Ca(Fe,Mn) (SiO3)2 SCHEFFERITE (Ca,Mg)(Fe,Mn)(SiO3)2 Jeffersomte (Ca,Mg)(Fe,Mn,Zn) (Si03)2 .

74" 10'

472

MINERALOGY

DESCRIPTIVE

797

Ill,Diopside, etc. II,Spodumene. V, Augite. VI, Acmite.

I,Enstatite,etc.

Section

Orthorhombic

a.

IV, Hedenbergite, Augite.

ENSTATITE.

Orthorhombic.

Axes

mm'", qqf,

110 023

a

:

110 023

A A

b

: c

0'9702

=

88" 16'. 241" 41'.

=

=

:

1

:

0'5710.

rr', 223 XT'",223

A

223

A

223

=

=

40" 16^. 39" H'.

tw. pi.h (014)as twinninglamellae; also tw. pi.(101)as -stellate at angles of nearly 60", sometimes cros'sing six-rayed. Distinct or lamellar. crystals rare, habit prismatic. Usuallymassive,fibrous, ture Cleavage: m (110)rather easy. Parting ||6 (010); also a (100). Frac-

Twins twins

rare:

Brittle.

uneven.

798

H.

G.

5*5.

=

31-3-3.

=

Luster, a littlepearly on

to vitreous; cleavage-surfaces in the often metalloidal bronzite variety. Color grayish,yellowish or greenish white, to olive-green and brown. Streak uncolored,grayish. Translucent to nearlyopaque. in Pleochroism weak, more marked varieties relatively rich in iron. Optically+. Ax. pi. 11 b (010) Bxa J_ c (001) Dispersionp " v weak. Axial angle large and variable,increasingwith the amount of iron,usually about 90" for FeO 10 p. c. .

=

Bamle

j8

Comp. MgSiO3 (Mg,Fe)SiO3with Mg "

8

=

:

Var.

1, 6 "

:

1, 3

1.

:

With

iron; Enstatite.

up

and

is the

magnesia

799

40

=

100.

Also

800

littleor

Color

90 p.

c.

001

no

001

white, 100

100

of the

x^-H"

Bishopvillemeteorite,belongs here

0'009.

Silica 60,

1, etc.

=

makes

=

Fe

=

a

-

MgO.SiO2

or :

1-669; 7

=

yellowish, grayish, or greenish white; luster vitreous to G. pearly; 3'10-3'13. Chladnite (Sheparditeof Rose), which

.

purest

*K

h-

kind.

Victorite, in the Deesa occurring meteoric iron in rosettes of acicular crystals, is similar. 2. Ferriferous; Bronzite. Color

grayishgreen and

brown.

to

Luster

t

olive-green on

cleav-

,-,

.,

.-"

^nstatite (Bronzite) Hypersthene age-surfaceoften adamantinepearly to submetallic or bronze-like; this,however, is usuallyof secondary origin and

is

473

SILICATES

With the increase 9f iron (above 12 to 14 p. c.) bronzite passes to hypernot essential. Bxa _L " (100). This is sthene,the optic axial angle changing so that in the latter X illustrated by Figs.799, 800. the thin edges; B.B. almost infusible,being only slightlyrounded on Pyr., etc. =

"

acid. Insoluble in hydrochloric Enstatite is formed from a melt having the proper composition at temperatures under 1100". At higher temperatures the monoclinic pyroxenes Enstatite slightly appear. has also been formed by fusing olivine with silica. When serpentineis melted it breaks into enstatite and olivine. down Micro. In thin sections is colorless or lightyellow or green; marked relief;prominent cleavage with parallelextinction;littlepleochroism but becoming stronger with increase of iron; inclusions common lyingparallelto brachypinacoid,producing characteristic schiller of mineral. Obs. constituent of peridotites and the Enstatite (includingbronzite)is a common in crystalline schists. It is often associated serpentinesderived from them; it also occurs in parallel mineral in meteoric growth with a monoclinic pyroxene, e.g., diallage. A common often occurringin chondrules with eccentric radiated structure. stones Occurs near Aloystalin Moravia, in serpentine;at Kupferberg in Bavaria; at Baste in the Harz of the Dreiser Weiher Mts., Germany (protobastite) ; in the so-called olivine bombs in immense in the Eifel,Germany; crystals,in part altered,at the apatite deposits of Kjorrestad near Bamle, Norway; in the peridotiteassociated with the diamond depositsof South Africa. In. the United States,in N. Y. at the TillyFoster magnetite mine, Brewster, Putnam Co., with chondrodite and at Edwards; Texas, Pa.; bronzite from Webster, N. C.; Bare Hills, F.

6. Artif

=

"

.

"

"

Baltimore, Md. Named

from opponent, because so refractory.The evaaTT-rjs, an luster is not essential, and is far from universal. a bronze

bronzite has

name

but priority,

HYPERSTHENE.

Orthorhombic.

Axes

mm

110

A

110

hh',

014

A

014

a

: =

=

b

: c

=

0-9713

:

1

88" 20'. 16" 14'.

:

0-5704.

oo'", 111 uu'"t 232

A A

111 232

=

=

52' 23'. 72" 50'.

less often ||b (010). often tabular ||a (100), Crystalsrare, habit prismatic, in foliated massive sometimes embedded forms. spherical Usually ; b distinct but interrupted. and m a (100) Cleavage: (010)perfect; (110) Luster 5-6. G. 3 '40-3 '50. somewhat and sometimes Color metalloidal. dark ish brownpearlyon a Cleavage-surface, grayishblack,greenishblack,pinchbeck-brown. Streak grayish, green,

Fracture

Brittle.

uneven.

H.

=

=

802

801

803

See. sions; 802, Malnas. 803, Section ||6 (010)showing inclufrom Lacroix. to actinolite; the exterior transformed

Laacher Figs.801, Amblystegite,

Pleochroism often strong, Translucent to nearly opaque. gray. in the kinds with high iron percentage; thus 11X or a axis brownish especially Ax. pi. || Optically red, Y or b axis reddish yellow,Z or c axis green. brownish

"

.

b

(010). Bxa

J_

a

(100). Dispersionp

"

v.

Axial

angle rather large and

MINERALOGY

DESCRIPTIVE

474

p. 472, and Figs.799, variable,diminishingwith increase of iron,cf enstatite, 0-013. a 1702; y 800, p. 472. 0 .

=

=

-

tabular scales,usuallyof a brown color,arranged encloses minute basal plane (Fig.803),also less frequentlyvertical or inclined 30" to They be brookite (gothite, hematite),but their true nature is doubtful. c axis;they may and are often of secondary origin, metalloidal luster or schiller, the of the peculiar cause are " (p. 189)'. being developed along the so-called solution-planes"

Hypersthene often to the mostly parallel

167 2 1 : 3(FeO (Fe,Mg)SiO3 with Fe : Mg p. c.),1 is Alumina sometimes '0 31 1 to c.). : l(FeO nearly p. (FeO p. c.) minous present (up to 10 p. c.)and the compositionthen approximates to the alu-

Comp.

=

=

"

.

217

=

=

pyroxenes. those with FeO " 12 to 15p. c. are Of the orthorhombic magnesium-iron metasilicates, which characterized by being optically with is further be to classed hypersthene, usually

negative and having dispersionp " v. B.B. fuses to a black enamel, and on "Pyr.,etc. of iron. fuses more easily with increasing amount

charcoal yields a magnetic mass; chloric Partially decomposed by hydro-

"

acid. In thin sections similar,to enstatite except shows distinct reddish or greenish color with stronger pleochroism and is optically Similar to enstatite, Artif which see. in Obs. is common Hypersthene, associated with a triclinic feldspar (labradorite), certain granulareruptiverocks,as norite,hyperite,gabbro,also in some andesites (hyperrather to occur sthene-andesite)a rock shown extensivelyin widely separated regions. It occurs way; at Isle St. Paul, Labrador; in Greenland; at Farsund and elsewhere in NorElfdalen in Sweden; Penig in Saxony; Ronsberg in Bohemia; the Tyrol; Neurode in Silesia;Bodenmais, Bavaria. SzaAmblystegiteis from the Laacher See, Germany. boite occurs with pseudobrookite and tridymite,in cavities in the andesite of the Aranyer Berg, Transylvania,and elsewhere. Occurs in the norites of the Cortlandt region on the Hudson river,N.' Y.; also common in with labradorite in the Adirondack Archa3an region of northern N. Y. and northward In the hypersthene-andesitesof Mt Canada.Shasta, Cal.; Buffalo Peaks, Col.,and other points. Hyperstheneis named from virep and "r0ei"os, very strong,or tough. Micro.

"

"

.

"

.

"

,

An altered enstatite (or BASTITE, or SCHILLER SPAR. having approximately brqnzite) the composition of serpentine. It occurs in foliated form in certain granular eruptive rocks and is characterized by a bronze-like metalioidal 'lusteror schiller on the chief 6 (010),which "schillerization" (p.251) isof secondary origin. H. cleavage-face 3'5-4. G. 2 '5-2 '7. Color leek-green to olive- and pistachio-green,and pinchbeck-brown. Pleochroism not marked. Ax. pi. ||a Double refraction weak. (010) Optically to that of enstatite).Bxa " b (010). Dispersion p " v. (hence normal The original bastite was from Baste near Harzburg in the Harz Mts., Germany; also from Todtmoos in the Schwarzwald,Germany. =

=

-.

of

PECKHAMITE, 2(Mg,Fe)SiO3.(Mg,Fe)SiO4.Occurs Emmet Estherville, Co., Iowa, May 10, 1879. G. )8. Monoclinic

in rounded =

3 '23.

nodules hi the meteorite Color lightgreenishyellow.

Section

PYROXENE.

Monoclinic.

: b Axes_a

: c

=

1-0921

:

1

:

74" 10'.

0-5893; J3

=

'

mm'",

110 A 001 A

110 100

001 Oil 021

A A

101

ee', 22',

A

Oil 021

cu,

001

A

111

co, cp, "

=

=

=

=

=

=

92" 50'. 74" 10'. 31" 20'. 59" 6'. 97" 11'. 33" 49*'.

"",

001

A

221

en,

001 001

A

110

a,

uu', 111 SSf,111 oo', 221

Til ill A TTl

A A

A

221

=

=

=

=

=

=

49" 54'. 79" 9"'. 42" 2'. 48" 29'/ 59" 11'. 84" 11'.

Twins: tw. pi. (1)a (100), common contact-twins, (Fig.810),sometimes polysynthetic. (2) c (001),as twinning lamellae producing striations on the vertical faces and

or pseudocleavage parting ||c (Fig.811); very

common,

475

SILICATES

often (4) W

not common secondary. (3)y (101)cruciform-twins, (Fig.451, p. 171). (122) the vertical axes crossingat anglesof nearly60"; sometimes repeated star (Fig.450, p. 171). Crystalsusuallyprismaticin as a six-rayed

804

805

806

807

808

100

habit,often short and thick,and either a square prism (a (100),6 (010)prominent), or nearlysquare (93",87") with m (110)predominating; sometimes a nearly symmetrical 8-sided prism with a, 6, m (Fig.811). Often coarsely or ||c (001) or a (100). Also granular,coarse lamellar, fine;rarely fibrous or

columnar.

but m (110) sometimes rather perfect, in thin sections J_ caxis (Fig.812). Parting ||c (001),due to twinning, often in largecrystals and prominent,especially lamellar masses (Fig.811); also ||a (100)

Cleavage:

often only interrupted,

observed

813

Fracture less distinct and not so common. 5-6. Brittle. H. to conchoidal. uneven G. 3*2-3*6, varying with the composition. Luster vitreous incliningto resinous; often dull; sometimes pearly || c(001) in kinds showing parting. Color usuallygreen of various dull shades,varying =

=

white, or grayish nearly colorless, and black; rarelybright to brown X in kinds containingchromium; as green, also blue. Streak white to gray and grayish PleoTransparent to opaque. green. chroism usuallyweak, even in dark-colored marked, especiallyin violet-brown kinds containing varieties; sometimes titanium. (Violaiteis name given to a highly pleochroicvarietyfrom the Caucasus Mts.) from

white

476

MINERALOGY

DESCRIPTIVE v,"

0'02 0'03. Ax. pi. || a) Birefringencestrong, (7 Optically+. in t o in axis Z augite diopside, A c (which b (010). Bxa or =^4-36" -j-52" with amount see),or Z A c (001) 20" to gg",the anglein generalincreasing 1-680. 1702. 1-673. 59-". a 0 of iron. For diopside2 V 7 normal For the most metasilicate, RSiO3, chieflyof Comp. g^rt a and zinc. The often calcium and magnesium, also iron, less manganese alkali metals potassium anc^sodium present rarely,except in very small the trivalent metals aluminium, Also in certain varietiescontaining amount. be most These last varieties may sidered ferric iron,and manganese. simply conas molecular compounds of Ca(Mg,Fe)Si2O6 and (Mg,Fe)(Al,Fe)2Si06, is sometimes Chromium Tschermak. present in small as suggested by "

=

"

=

=

=

=

=

"

silicon. "replacing

also titanium

amount;

The name stranger,and records Haiiy's idea that Pyroxene is from iryp,fire and "evps, of fire," the mineral was, as he expresses it,"a stranger in the domain whereas, in fact,it Tmiversal constituent of igneous rocks. most is,next to the feldspars, tjje variations in composition chiefly;the and depend upon The varieties are numerous more prominent of the varieties p*"perlyrank as sub-species from a melt having the Artif. The monoclinic pyroxene, MgSiOs, can be crystallized 1500" or at a lower temperature from solutheoretical composition at temperatures about tion in molten It is the most calcium or magnesium vanadate. stable form of MgSiO?. into forsterite and silica. It has no true meltingpoint but af about 1550" breaks down .

"

"

I. 1. DIOPSIDE.

Containinglittleor

no

Aluminium

Malacolite,Alalite.

mula ForCalcium-magnesium pyroxene. Silica 55-6, lime 25-9, magnesia 18-5 100. Color to dark green and white,yellowish, grayishwhite to pale green, and finally also rarelya fine blue. In nearlyblack; sometimes transparent and colorless, often slender;also granularand columnar to lamellar masprismaticcrystals, sive. G. 3-2-3-38. Bxa A c axis 0-03. + 36" and upwards. a 7 Iron is present usuallyin small amount noted below, and the amount as increases as it graduatestoward true hedenbergite.

CaM"g(Si03)2 =

=

=

=

-

=

The

followingbelong here: Chrome-diopside, contains chromium (1 to 2'8 p. c. C^Oa), bright green. Malacolite,as originallydescribed,was a pale-coloredtranslucent variety from Sala,

often

a

Sweden. Alalite

in broad right-angledprisms,colorless to faint greenish or clear green, in the Ala valley,Piedmont, Italy. from Trayersella, Traversellite, Piedmont, Italy,is similar. Violan is a fine blue diopsidefrom St. Marcel, Piedmont, Italy;occurring in prismatic crystalsand massive. Canaanite is a grayish-whiteor bluish-white rock occurring with dolomite at pyroxene Canaan, Conn. Lavrovite is a pyroxene, colored green by vanadium, from the neighborhood of Lake Baikal,in eastern Siberia. Diopside is named from 6is,twice or double,and o^is, Malacolite is from appearance. because softer than feldspar, na\otKos,soft, with which it was associated. from

occurs

the Mussa

Alp

2. HEDENBERGITE. Calcium-iron pyroxene. Formula CaFe(Si03)2 Silica 48'4,iron protoxide 29'4, lime 22'2 100. Color black. In crystals, and also lamellar massive. G. 3-5-3-58. Bxa A c axis ganese Man+ 48". is present in manganhedenbergite to 6 -5 p. c. Color grayish green. G. 3'55. =

=

=

=

=

Between

the two extremes, diopside and hedenbergite, there are numerous transitions to the formula Ca(Mg,Fe)Si2O6. As the amount of iron increases the color irom light to dark green to nearly black,the specific gravity increases from 3 -2 to the angle Bxa A c axis also from 36" to 48".

jonformmg langes

3-6,and

477

SILICATES

based in part upon coming under these two sub-species, varieties, of composition. peculiarities and black; sometimes to deep green color grayish green Salite (Sahlite), grayish and yellowishwhite; in crystals;also lamellar (parting||c (001)),and granularmassive; from with parting j|c (001), Sala in Sweden. Baikalite,a dark dingy green variety,in crystals, from Lake Baikal, in Siberia. in calcite, also forming loosely coherent to Coccolite is a granular variety,embedded taining compact aggregates; color varying from white to pale green to dark green, and then confrom KOKKOS, a grain. considerable iron; the latter the originalcoccolite. Named thin-foliated pyroxene, DIALLAGE. A lamellar or characterized by a fine lamellar 6 (010),and less often || structure and parting || a (100),with also parting |j c (001). Also a fibrous structure ||c axis. Twinning ||a (100),often polysynthetic; interlamination with Color grayish green to bright grass-green, and deep orthorhombic common. an pyroxene of surface a (100) often pearly, sometimes also brown. Luster metalloidal or green; exhibitingschiller and resembling bronzite,from the presence of microscopic inclusions of to 40"; 0 a +39 4; secondary origin. Bxa A c axis 1-681; y 0;024. H. In composition near G. 3'2-3'35. times diopside,but often containing alumina and somein considerable amount, then properly to be classed with the augites. Often changed Named from to amphibole, see smaragdite, and uralite,p. 490. difference, dta^Xayrj, of in allusion to the dissimilar planes of fracture. This is the characteristic pyroxene gabbro, and other related rocks. Omphacite. The granular to foliated pyroxenic constituent of the garnet-rock called Contains often interlaminated with amphibole (smaragdite); color grass-green. eclogite, The

followingare

structure, in part

on

=

=

-

=

=

=

A^Os.

some

3.

much

A SCHEFFERITE. iron. Color brown

manganese

pyroxene,

sometimes

also

containing

to black.

In crystals, often elongated sometimes tabular || also with p (101)prominent, more c (00_1), in the direction of the zone b (010) : p (101),rarelyprismatic,|| c axis. Twins, with a (100) massive. tw. Also crystalline, as Cleavage prismatic,very distinct. pi. very common.

also black .^Optically +. (iron-schefferite} iron-schefferite from.Pajsberg, Sweden, is black in in the same color and + 49" to 59" for different zones crystal. The c axis 69" 3'. It brown iron-schefferite (urbanite)from Langban, Sweden, has Z A c axis resembles garnet in appearance. Franklin Furnace, N. J. (but the zinc from is a manganese-zinc pyroxene Jeffersonite be due to impurity). In large,coarse crystalswith edges rounded and faces uneven. may Color greenishblack,on the exposed surface chocolate-brown. and iron. Stronglypleosodium, manganese Blanfordite. A pyroxene containingsome in the Central Provinces, with manganese chroic (rose-pinkto sky-blue). Found ores India. for the monoclinic magnesium pyroxene. Clinoenstatite has been suggested as the name Color

Bxa

yellowish brown

or

Z

A c axis has Z A

to

44"

=

reddish

brown;

25"'. The

=

=

II. Aluminous 4. AUGITE. Aluminous Composition chieflyCaMgSi2Oe with pyroxene. and occasionally also containingalkalies and then gradu(Mg,Fe)(Al,Fe)2SiO6, ating is also sometimes toward acmite. Titanium present. Here belong: a.

and

Color white or grayish. Contains alumina,with lime and magnesia, LEUC AUGITE. 3*19. Named from Xeu/cos, little or no iron. Looks like diopside. H. 6'5; G. =

=

white. b. FASSAITE.

Includes the pale to dark, sometimes or deep-green crystals, pistachioalso belong here. kinds of diallage and then resembling epidote. The aluminous from the localityin the Fassatal,Tyrol. Pyrgom is from irvpyu/jia, a tower. Includes the greenishor brownish black and black kinds,occurringmostly c. AUGITE. thick and stout, or tabular It is usually in short prismatic crystals, in eruptive rocks. twins (Figs.809, 810). Ferric iron is here present, in a relatively large a (100); often '= 0'022. +50" to 52". 0 a 1717; y amount, and the angle Bxa A c axis becomes green Named

||

=

"

from avyij, luster. kinds, which are then pleochroic. Named d. ALKALI- AUGITE. Here belong varieties of augite characterized by the presence of alkalies,especially soda; they approximate in composition and opticallyto acmite and (cf. 60",Fig.814),and are sometimes called aegirite-augite Fig.818, ajgirite (Bxa A c axis

TiO2 is present in

some

=

478 p.

MINERALOGY

DESCRIPTIVE

chieflyfrom

480). -Known etc.

Pyr.

Varying widely,owing

"

to

ent the wide variations in composition in the differoften and by insensible gradations. varieties,

3*75 Fusibility,

814

elseolite-syenite, phonolite,leu-

as rich in alkalies,

rocks

and

in

omphacite;

baikalite, diopside; 3 '5 in salite, and augite; 2 '5 in jeffersonite

3 in

hedenbergite. Varieties rich in iron afford a magnetic fused on charcoal,and in general globule when of iron. varies with the amount the fusibility Many ganese. varieties give with the fluxes reactions for manvarieties are unacted Most by acids. upon Characterized by monoclinic crystallization Diff. ing and the prismaticangle of 87" and 93", hence yieldnearly square prisms; these may be mistaken for scapoliteif terminal faces are wanting or indistinct (but scapolitefuses easilyB. B. with intumescence). The oblique parting (|| c (001), Fig. 811) often dull green to gray and also the common distinctive, colors. brown Amphibole differs in prismatic angle mon (55^" and 124|") and cleavage,and in having comwhich to fibrous varieties, columnar are rare with pyroxene. (See also p. 486.) The Micro. common rock-forming pyroxenes are distinguishedin thin sections by their high relief;usuallygreenish to olive tones of color; distinct system of interruptedcleavage-crackscrossingone another at nearly right general lack of pleoangles in sections _L c axis (Fig.812); high interference-colors; 35" to 50" and higher,for sections ||b (010). The lastchroism; large extinction-angle, named sections are easilyrecognizedby showing the highest interference colors; yielding the latter in no cleavage-cracks, opticalfiguresin convergent light and having parallel See also segirite, the direction of the vertical axis. p. 480. A zonal banding is common, the successive laminae sometimes differingin extinctionangle and pleochroism; also thje hour-glassstructure occasionallydistinct (Fig.815, from Lacroix). mineral in igneous rocks,being the Obs. Pyroxene is a very common Some rocks consist almost most important of the ferromagnesianminerals. in volcanic rocks but is It most entirelyof pyroxene. commonly occurs found also,but less abundantly, in connection with graniticrocks. It is mineral in crystalline limestone and dolomite,in serpentine and a common in forms large beds or veins,especially metamorphic schists; sometimes "

"

"

Archaean is

rocks.

It

occurs

also in meteorites.

The

pyroxene

of limestone

mostly white and light green or gray in color,fallingunder diopside other metamorphic rocks is (malacoh'te, salite, coccolite);that of most sometimes white or colorless, but usually green of different shades, from pale green to greenishblack, and occasionallyblack; that of serpentineis in fine crystals, sometimes but often of the foliated green kind called that of eruptiverocks is usually the black to greenishblack augite. diallage; In limestone the associations are often amphibole, scapolite, clase, vesuvianite,garnet, orthoand sometimes titanite, brown tourmaline,chlorite, apatite,phlogopite, talc,zircon, In eruptive rocks it spinel, rutile, etc.; and in other metamorphic rocks mostly the same. be in distinct embedded may form; it crystals,or in grains without external crystalline often occurs with similarly disseminated chrysolite(olivine), crystalsof orthoclase (sanidine),labradorite, leucite, amphibole, etc. etc.; also with a rhombic pyroxene, in basic eruptive Pyroxene,as an essential rock-making mineral,is especiallycommon rocks. Thus, as augite,with a triclinic feldspar (usuallylabradorite),magnetite, often in basalt, basaltic lavas and diabase; in andesite; also in trachyte; in peridotite chrysolite, and pikrite; with nephelite in phonolite. Further with elseolite, orthoclase,etc., in and augite-syenite; elaeohte-syenite and the also as diallagein gabbro; in many peridotites formed from them; as diopside (malacolite) serpentines in crystalline schists. In limburgite,augititeand pyroxenite,pyroxene spar is present as the prominent constituent, while feldit may is absent; also form rock masses alone nearly free from associated minerals. Diopside (alalite, in fine crystalson the Mussa mussite) occurs Alp in the Ala valley in Piedmont,Italy,associated with garnets (hessonite) and talc in veins traversingserpentine; in fine crystals at Traversella, Piedmont; at Zermatt in Switzerland; Schwarzenstein in the and elsewhere in Tyrol and in the Salzburg Alps; Reichenstein, Zillertal, Ober-Sulzbachtal,

480

MINERALOGY

DESCRIPTIVE

yellow;the yellowish.

brown, Z brownish brown With some

to

latter has X

deep

grass-green,

Y

lightergrass-green,

Z

lowish yel-

2" to 6", as in (Oil) and X A c axis (vom Rath, etc.)s orientation according to Brogger. Fig.818 shows the optical Fig.819.

authors

=

=

-

"

Ill

EssentiallyNaFe(SiO3)2 or Comp. iron Silica 52'0, sesquioxide34'6, soda iron is also present.

Na2O.Fe2O3.4Si02

"

13'4

=

=

Ferrous

100.

fuses at 2 to a lustrous black magnetic flame deep yellow; with the fluxes reacts for iron and sometimes Slightly manganese. acted upon by acids. Micro. ^Egiriteis characterized in thin sections by of green its grass-green color; strong pleochroism in tones in sections || and yellow; the small extinction-angle "(010). Distinguishedfrom common hornblende,with which green it might be confounded, by the fact that in such sections the cleavage is negthe direction of extinction lying near ative direction in hornblende is pos(X), while the same itive

Pyr.. etc.

"

B.B.

globule,coloring the

"

(Z). ^Egirite

Artif

Acmite be produced artificially can by fusing such together its constituent oxides but usually under of magnetite is formed. conditions only a glasscontainingcrystals in a pegmatite vein; at Rundemyr, The originalacmite occurs Obs. east of the littlelake called Rokebergskjern, in the parish of Eker, near Acmite foot long, Kongsberg, Norway. It is in slender crystals,sometimes a in feldsparand quartz. embedded in igneous rocks rich in soda and containingiron,commonly in occurs especially jEgirite rocks containingleucite or. nephelite;thus in aegirite-granite, and some nephelite-syenite, varieties of phonolite; often in such cases iron-ore grains are wanting in the rock, their placebeingtaken by aegirite crystals. In the sub-variety of phonolite 818 called tinguaite, the rock has often a deep greenish color due to the of minute abundance crystals of aegirite.Large crystalsare found in the pegmatite facies of nephelitein West syenites as Greenland, Southern Norway, the peninsula Kola in Russian Lapland, Ditro in "

.

"

Transylvania. Prominent American occurrences the following: Magnet Cove, Ark. (large crystals);Salem and N. J. Quincy, Mass.; Libertyville, (dike); Trans Pecos district in Texas; Black Hills,S. D.; Cripple Creek, Col.; Bearpaw Mts., Judith Mts. and the Crazy Mts. in Mon.; also vanadium-bearing from aegirites Libby,Mon., also at Montreal, Canada. Acmite is named from "KM, point, in allusion to the pointed extremities of the Mginte is from ^Egir,the Icelandic god of the sea. "

'

are

SPODUMENE.

Monoclinic.

crystals;

Triphane. Axes

a : b : c 1-1238 : 1 : 0*6355; 0 69" 40'. Twins: tw. pi.a (100). Crystalsprismatic(mm'" 110 A HO often flattened || a (100); the vertical planesstriated and =

=

93" 0'), furrowed;'crystals

sometimes

very

Cleavagem

lar,ge.Also massive,cleavable. (110)perfect. A lamellar structure

=

||a (100)sometimes

,

very

481

SILICATES

prominent,

a

separatinginto thin plates. Fracture

crystalthen

Brittle. H. cleavagesurfaces somewhat

to subconchoidal.

=

6'5-7.

G. Color

=

pearly. thystine yellowish green, emerald-green,yellow, ameStreak white. Transparent purple. Pleochroism to translucent. strong in deep Ax. varieties. pi. || Optically+ green 26". b (010). Bxa A c axis + Dispersion

on

uneven

vitreous, greenishwhite,grayishwhite, 3-13-3-20.

Luster

820

.

=

v, horizontal.

"

p

1-669.

j8

=

7

=

2 V

58".

=

a

1-651.

=

1-677.

yellow-greento emerald-green color; In small (" to 2 the latter variety is used as a gem. inches long) slender prismatic crystals,faces often has

Hiddenite

a

etched. is a clear lilac-colored variety found near Kunzite and also at Vanakarata, Pala,San Diego Co.,California, The unaltered material from Branch ville, Madagascar color. Used as a gem stone. Conn., shows the same .

Norwich,

Mass

Hiduenite

Comp. LiAl(SiO8)2or Li2O.Al2O3.4SiO2 100. Silica 64-5, alumina 27-4, lithia 8*4 Generally contains a little sodium; the variety hiddenite also chromium, to which the color may =

"

=

be due. B.B. swells up, imparts a purple-red color becomes white and opaque, Pyr., etc. to the flame (sometimes obscured by sodium), and fuses at 3 '5 to a clear or white (lithia) glass. Not acted upon by acids. Kunzite shows strong phosphorescence with an orangeelectric discharge,by ultra violet rays, X-rays, or pink color when excited by an oscillating "

radium

emanations. Characterized

varieties)as well as by its perfectparting ||a (100) (insome pearly luster than feldspar by prismatic cleavage; has a higher specificgravity and more Less fusible than amblygonite. or scapolite. Gives a red flame B.B. tions Alter. Spodumene undergoes very commonly alteration. First by the action of soluNaAl containing soda it is changed to a mixture of eucryptite,LiAlSiO4, and albite, SisOg. Later through the influence of potash salts the eucryptiteis changed to muscovite. is known This resultingmixture of albite and muscovite as cymatolite,having a wavy These alteration products are well shown in the specimens fibrous structure and silkyluster Conn. from Branch ville, An Artif artificial spodumene has been obtained together with other silicates by however, fusing together lithium carbonate, alumina and silica. This spodumene differs, from The the natural mineral in its opticalpropertiesand has been called ^-spodumene. into the /3modification on heating to 1000". natural mineral,or spodumene, is transformed in pegmatite veins,sometimes in crystalsof very great size. Obs. Spodumene occurs Crystalsfrom the Etta tin mine, S. D., with faces up to 40 feet in length have been reported. Occurs on the island of Uto, Sweden; at KillineyBay, Ireland;in small transparent crystals of a pale yellow in Brazil,province of Minas Geraes. Variously colored spodumene from Madagascar. In the United States,in graniteat Goshen, Mass.; also at Chesterfield, Chester, Huntington (formerlyNorwich), and Sterling,Mass.; at Windham, Me., with garnet and staurolite and at Peru, with beryl,triphylite, petalite. In Conn., at Branchville,the crystals in S. D. at the often of immense size; near Stony Point, Alexander Co., N. C. (hiddenite)', Etta tin mine in Pennington Co. Kunzite from Pala, Cal. Hiddenite is named for W. E. The name spodumene is from awodios, ash-colored. Diff.

"

"

.

"

.

"

Hidden Use.

and "

for Dr. G. F. Kunz. colored transparent varieties

Kunzite

The

JADEITE. Monoclinic.

are

used

as

gem

stones;

see

above.

471. Cleavage and opticalcharacters like with crystalline structure, sometimes Usually massive, granular, pyroxene. also obscurelycolumnar, fibrous foliated to closelycompact.

Axes,

see

p.

482

MINERALOGY

DESCRIPTIVE

at anglesof Cleavage: prismatic,

93" and

about

cult. 87"; also ||a (100)diffi-

6'5-7. G. 3-33-3-35. splintery.Extremely tough. Color of cleavage. apple-greento Luster subvitreous,pearly on surfaces greenishwhite, and nearly nearly emerald-green, bluish green, leek-green, Bxa A Optically+ white; sometimes white with spots of bright green. H.

Fracture

=

=

.

c

axis

30" to 40". 2 V to subtranslucent.

Comp. 25

-2,soda

15 -4

Streak

0=1-654.

Essentiallya metasilicate spodumene, NaAl(SiO3)2

"

to

alumina

72".

=

=

uncolored.

aluminium sponding correSilica 59*4,

and

of sodium

Na2O.Al2O3.4SiO2

or

lucent Trans-

=

100.

=

ing Chloromelanite is a dark green to nearly black kind of jadeite(hence the name), containformula. iron sesquioxideand not conforming exactlyto the above attacked by acids B.B. fuses readilyto a transparent blebby glass. Not Pyr.,etc. from saussurite. after fusion,and thus differing Obs. Occurs chieflyin eastern Asia, thus in the Mogoung district in Upper Burma, in a reddish clay; in Yungin a valley25 miles southwest of Meinkhoom, in rolled masses in Thibet. ever, Much of southern China; uncertaintyprevails,howprovince Yunnan, chang, since jadeiteand nephrite have usually been confused with to the exact as localities, also on the American each other. continent,in Mexico and South America ; May occur "

"

perhapsalso

in

Europe. highlyprized in

Jadeite has long been

the

in China, where East, especially

and

utensils of great varietyand beauty. early man, thus in the remains of the lake-dwellers of France, in Mexico, Greece,Egypt, and Asia Minor.

into ornaments

It is also found

with

it is worked the relics of

Switzerland,at various points in

A pyroxene, resemblingjadeitein structure and consistingof the molecules of jadeite, at the manganese mines of St. diopside,and acmite in nearly equal proportions,occurs Marcel, Italy. Use. As the material jade,is used as an ornamental See below. stone. JADE is a general term used to include various mineral substances of tough, compact texture and nearly white to dark green color used by earlyman for utensils and ornaments, and stillhighly valued in the East, especially It includes properly two in China. species a varietyof amphibole (p.489), either tremolite only; nephrite, with G. or actinolite, 2 '95-3-0. and jadeite, of the pyroxene and in composition a soda-spodumene, with group G. 3-3-3-35;easilyfusible. The jade of China belongs to both species, and so also that of the Swiss lake-habitations of Mexico. Of the two, however,the former, nephrite, is the more and makes the common jade (ax stone or Punamu stone) of the Maoris of New Zealand; also found in Alaska. The name jade is also sometimes looselyused to embrace other minerals of more less or similar characters, and which have been or might be similarlyused thus sillimanite, pectolite, serpentine;also vesuvianite, garnet. Bowenite is a jade-likevariety of serpentine. The "jade tenace" of de Saussure is now called saussurite. "

=

=

"

WOLLASTONITE.

Tabular

Monoclinic.

Axes

a

:

Spar

b

: c

=

1-0531

:

1

822

co, cr,

tabular

to

N.

0*9676; 0 110

A

540

A

Oil 001

A A A A

001 001

ct,

Diana,

:

mm"', hhf", gg't

110 540 Oil 101 301 101

=

=

=

=

=

=

=

84" 30'. 92" 79" 87" 40" 74" 45"

42'. 58'. 51'.

3'. 59'. 5'.

Y.

||a (100)or

c

Twins: tw. pi. a (100). Crystals commonly (001); also short prismatic. Usually cleavable massive

fibers parallelor reticulated;also compact. fibrous,

Cleavage: a (100)perfect;also c (001);t (101)less so. Fracture uneven, brittle. H. 4-5-5. G. 2-8-2-9. Luster vitreous,on cleavage surfaces pearly. Color white,inclining to gray, yellow,red, or brown. Streak white, =

=

bubtransparent to translucent.

Optically -.

Bxa

A

c

axis

=

+

32".

Dis-

483

SILICATES

persion p ft

v, inclined distinct.

"

1-633.

=

7

pi.||b (010).

Ax.

2E

70"; a

=

=

T621.

1*635.

=

CaSi03 metasilicate,

Calcium Comp. 48-3, 100. ""

or

CaO.SiO2

Silica 51*7, lime

=

=

When

wollastonite is heated above

1190" C. it develops a basal cleavage,becomes pseudobut probably monoclinic. This material has

hexagonal,opticallypositive,nearly uniaxial

been called pseudowollastonite. B.B. fuses quietly to a white, almost glassy globule. With hydrochloric Pyr., etc. from the presacid decomposed with separationof silica;most varieties effervesce slightly ence of calcite. Often phosphoresces. Micro. In thin sections wollastonite is colorless with a moderate relief and medium to the elongation of the is usually normal birefringence. The plane of the optic axes "

"

crystals. Wollastonite may be obtained artificially by heating a glassof the composition At higher temperatures the pseudowollastonitemodification 800" and 1000". is obtained. in granularlimestone,and in regionsof granite, Obs. Wollastonite is found especially a contact formation; it is very rare in eruptive rocks. It is often associated with a lime Artif

CaSiOs

"

.

to between

"

as

garnet, diopside,etc. Occurs in Hungary in the copper mines of Cziklowa in the Banat; at Pargas in Finland; stone; Harzburg in the Harz Mts., Germany; at Auerbach, Hesse, Germany, in granular limeat Vesuvius, rarelyin fine crystals;on the islands of Elba and Santorin. In the United States,in N. Y., at Willsborough ; Diana, Lewis Co.; Bonaparte Lake, In Pa., Bucks Co., 3m. In Canada, Lewis Co. west of Attleboro; in Cal.,at Crestmore. and Morin, Quebec, with apatite. at Grenville; at St. Jerome Named after the English chemist, W. H. Wollaston (1766-1828). Alamosite. Lead metasilicate,PbSiOs. Closely related to wollastonite in crystal In radiating fibrous aggregates. Monoclinic. forms. 6'5. Cleavage ||6 (010). G. at

=

H.

4'5.

=

Colorless

or

white.

Refractive

index about

T96.

Found

near

Alamos, Sonora,

Mexico. PECTOLITE.

Moneclinic.

Axes

a

:

b

: c

=

1-1140

:

1

:

0-9864; ft

84" 40'.

=

Commonly in close aggregationsof acicular crystals;elongated ||b axis, but rarelyterminated. Fibrous massive,radiated to stellate. and Brittle. H. 5. c (001)perfect. Fracture a uneven. (100) Cleavage: 2 '68-2 -78. Luster of the surface of fracture silky or subvitreous. G. to opaque. Color whitish or grayish. Subtranslucent Ax. pi. Optically+. and Bxa _L b (010); Bx0 nearly _L a (100). 2 V 1-61. 60". ft Silica 54-2, lime HNaCa2(SiO3)3 or H2O.Na2O.4CaO.6Si02 Comp. =

=

=

=

=

"

33-8, soda 9 -3,water

27

100.

=

classed with the hydrous speciesallied to the zeolites. Pectolite is sometimes In the closed tube yieldswater. B.B. fuses at 2 to a white enamel. composed Dein part by hydrochloricacid with separationof silica as a jelly. Often gives out lightwhen broken in the dark. A secondary mineral,occurring like the zeolites mostly in basic eruptiverocks, Obs. in cavities or seams; in Scotland near Found burgh; Edinoccasionallyin metamorphic rocks. at Kilsyth,Corstorphine Hill (walkerite); Island Skye. Also at Mt. Baldo and Mt. Monzoni in the Tyrol; at Niederkirchen,Bavaria (osmelite). and Great Notch, N. J.; Lehigh Co., Pa.; compact Occurs also at Bergen Hill,Paterson at Isle Royale, Lake Superior; at Magnet Cove, Ark., in elseqlite-syenite (manganpectolite with 4 p. c. MnO); compact, massive in Alaska, where used, like jade,for implements.

Pyr., etc.

-

"

Schizolite. Like manganpectolite, HNa(Ca,Mn)2(SiOs)3, but triclinic. In prismatic 5-5 '5. G. 3'0-3'1. Color lightred to brown. From crystals. Two cleavages. H. the nephelinesyeniteof Julianehaab, southern Greenland. Near pectolite, but contains zirconium. Rosenbuschite. Index, 1-65. From Norway. In nephelite-syenite-porphyry, Red Hill,Moultonboro, N. H. =

=

MINERALOGY

DESCRIPTIVE

484

niobate

zirconium-silicateand

A

Wohlerite.

crystals,yellow to

Indices,1700-1

brown.

726.

of Ca, Na, etc. Occurs in

prismatic,tabular

In

several elseolite-syenite^ on

In syenite from Red Hill,N. H. near Brevik, in Norway. islands of the Langesund fiord, also F, Ti, Ta. etc. A complex zirconuim-silieate of Mn, Ca, etc.,containing Lavenite. in the the island Laven Found on In yellow to brown prismaticcrystals. Index, 1750. in eheolite-syemte. elsewhere also .Langesund fiord,southern Norway;

Triclinic Section

7.

RHODONITE.

Triclinic. Axes 81" 39'. 44'- y

a

:

b

: c

1*07285

=

:

1

:

0-6213;

a

=

103"

18'; ]8

=

108"

=

tabular Crystalsusuallylargeand rough with rounded edges. Commonly 1|c (001);sometimes resemblingpyroxene in habit. Commonly massive, embedded grains. cleavable to compact; also in_ M (110)perfect;c (001)less perfect. Fracture conCleavage: m (110), 3-4G. 5-5-6-5. choidal to uneven; tough when compact. H. very Color somewhat light surfaces pearly. Luster vitreous; on cleavage 3-68. greenishor yellowish,when brownish red,flesh-red, rose-pink;sometimes =

=

impure;

often black outside from

Optically

translucent.

Comp.

.0

"

.

=

Streak

white.

Transparent

to

173.

Silica 45-9, metasilicate,MnSiOa or MnO.SiO2 ally and occasion100. Iron, calcium (inbustamite),

Manganese

"

exposure.

=

protoxide54-1 replacepart of the (in'fowlerite) =

manganese

zinc

manganese. 825

824

823

Franklin

db,

100

A

ac,

100 010 100

A

be, am,

A A

010 001 001 110

=

=

=

=

94" 72" 78" 48"

Furnace,

N.

J.

26'.

mM,

110

A

110

36*'.

en,

001

A

221

=

42i'.

ck, kn,

001

A

221

=

221

A

221

=

33'.

=

92" 28|'. 73" 52'. 62" 23'.

86"

5'.

B.B. blackens and fuses with slightintumescence at 2'5; with the fluxes Pyr., etc. fowlerite gives with soda on charcoal a reaction for zinc. gives reactions for manganese; Slightlyacted upon by acids. The calciferous varieties often effervesce from mechanical of calcium admixture carbonate. In powder, partly dissolves in hydrochloric acid, and the insoluble part becomes of a white color. Darkens to the air,and times someon exposure becomes nearly black. Diff. Characterized by its pink color; distinct cleavages; hardness; fusibility and "

"

reactions B.B. Occurs in Sweden at Langban, Wermland; in iron-ore beds, in broad cleavageplates,and also granularmassive,and at the Pajsberg iron mines near Filipstad(paisbergite) sometimes in small brilliant crystals;in the district of Ekaterinburg in the Ural Mts., massive like marble, whence it is obtained for ornamental with tetrahedrite at Kappurposes; nik and Rezbanya, Hungary; St. Marcel, Piedmont, containing Italy; Mexico (bustamite, CaO). In crystalsfrom Broken Hill,New South Wales. Occurs in Cummington, Mass.; on Osgood's farm, Blue Hill Bay, Me.; fowlerite(con-

manganese Obs.

"

485

SILICATES

tainingZnO) at Mine Hill,Franklin Furnace, and SterlingHill,near in fine crystals. in calcite and sometimes usually embedded

Ogdensburgh, N. J.,

Named from podov,a rose, in allusion to the color. is often altered chieflyby oxidation of the MnO Rhodonite (as in marceline,dyssnite); also by hydration (stratopeite, neotocite,etc.); further by introduction of CO2 (allagite,

photidte,etc.). Use.

Rhodonite

"

at

times is used

as

an

ornamental

stone.

In cleavage masses. triclinic, manganese-iron pyroxene. Indices, 175-1 H. -76. 5-5-6. G. 3'8. Color,amber to dark brown. Easily fusible to black Found near magnetic globule. Alters to skemmatite. Iva, Anderson Co., South Carolina. near Babingtonite. (Ca,Fe,Mn)SiO3with Fe2(SiO3)a. In small black tricliniccrystals, rhodonite in angle (axes on 5'5-6. 3'35-3'37. G. From Index, 172. p. 471). H. Arendal,Norway; at Herbornseelbach,Nassau, Germany; at Baveno, Italy. From Somerville and Athol, Mass.; in the zeolite depositsof Passaic Co., N. J. Hiortdahlite. ular Essentially(Na2,Ca)(Si,Zr)Oa,with also fluorine. In pale yellow tabOccurs sparingly on an island in the Langesund Index, 1'695. crystals(triclinic). fiord,southern Norway. A

Pyroxmangite.

=

=

=

A

Sobralite.

=

Optically+

triclinic pyroxene.

.

Colorless.

From

eulysiterock

at

Sodermanland, Sweden. 3.

Amphibole

Group

Orthorhombic,Monoclinic,Triclinic RSi03, with R Composition for the most part that of a metasilicate, Further often also containingaluminium Mn,Na2,K2,H2. Ca,Mg,Fe chiefly, and ferric iron,in part with alkalies as NaAl(Si03)2or NaFe(SiO3)2; perhaps =

ii

also

in

containingRR2SiOe. a.

Orthorhombic

Section a

(Mg,Fe)SiO3 (Mg,Fe)Si03 with (Mg,Fe)Al2Si06

Anthophyllite GEDRITE

0. Monoclinic

a

1

:

b

:

1

: c :

0-2938

/3 73" 58'

.

VARIETIES.

I. NONALUMINOUS

CaMg3(SiO3)4 Ca(Mg,Fe)3(SiO3)4 Nephrite,Asbestus,Smaragdite,etc. (Fe,Mg)SiO3 Cummingtonite Dannemorite (Fe,Mn,Mg)SiO3

1.

TREMOLITE

2.

ACTINOLITE

3.

RICHTERITE

FeSiO3

Grtinerite

II. ALUMINOUS 4.

:b :

Section

0-5511

Amphibole

0-5138

(K2,Na2Mg,Ca,Mn)4(SiO3)4

VARIETIES-

HORNBLENDE Edenite

Pargasiteand Common

Hornblende

ChieflyCa(Mg,Fe)3(SiO3)4with and (Mg,Fe)2(Al,Fe)4Si2Oi2 Na2Al2(SiO3)4

MINERALOGY

486

DESCRIPTIVE

Glaucophane

NaAl(Si03)2.(Fe,Mg)Si03 2NaFe(SiO3)2.FeSiO3 NaFe(Si03)2.FeSi03

Riebeckite Crocidolite Arfvedsonite

a

:

b

: c

0'5475

:

1

:

/3

0'2925

=

76" 10'

Na8(Ca,Mg)3(Fe,Mn)14(Al,Fe)2Si21045 0-5509

:

1

:

0*2378

=

73" 2'

Triclinic Section

7.

^Enigmatite. and imperfectl included under the triclinic section is the rare The only species known aenigmatite(cossyrite). of specieswhich, while falling GROUP embraces a number The AMPHIBOLE in the common related in form as shown in different systems, are yet closely in characters and 56" also chemical com54" to of position. optical prismaticcleavage ically As alreadynoted (seep. 471), the speciesof this group form chemallied Pyroxene Group, and between to that of the closely a series parallel i n form and other characters. is close them there a relationship crystalline is less The Amphibole Group, however, fullydeveloped, includingfewer show less varietyin form. and those known species, "

-"

and amphibole proper are the following: The chief distinctions between pyroxene 87" and 93"; with amphibole 56" and 124"; the prismatic Prismatic angle with pyroxene distinct in the latter. cleavagebeing much more With pyroxene, crystalsusuallyshort prismaticand often complex, structure of massive kinds mostly lamellar or granular; with amphibole, crystalschieflylong prismatic and simple,columnar and fibrous massive kinds the rule. The specific varieties is higher than of the like varieties gravityof most of the pyroxene of amphibole. In composition of corresponding kinds, magnesium is present in larger in amphibole (Ca : Mg 1 : 1 in diopside, 1 : 3 in tremolite) amount ; alkalies more play a prominent part in amphibole. frequently =

=

The

of the group, as regards opticalrelations of the prominent members of the exhibited i s the position ether-axes, by followingfigures(Cross); for the corresponding Fig. 797, p. 472, for a similar representation compare

the

members

I.

of the pyroxene

Anthophyllite.

group.

II. Glaucophane. V. Arfvedsonite.

a.

III.

Tremolite, etc.

VI.

Orthorhombic

IV.

Hornblende.

Riebeckite.

Section

ANTHOPHYLLITE.

Orthorhombic.

(mm"'

110

fibres often very

Axial ratio a : b 0*5137 : 1. Crystalsrare, habit prismatic 110 54" 23). Commonly lamellar, fibrous massive; or slender;in aggregationsof prisms. =

A

=

488

DESCRIPTIVE

MINERALOGY

prismatic;usuallyterminated by the low clinodome, r (Oil),sometimes by forms (as and then suggestingrhombohedral r and p (101)equallydeveloped fibres often like flax; Also columnar coarse or fine, or fibrous, of tourmaline). and or also coarse fine, usuallystrongly granularmassive, rarelylamellar; coherent,but sometimes friable. Cleavage: m (110) highly perfect;a (100),b (010)sometimes distinct. 5-6. G. Brittle. H. 2-9-3-4,varying to vitreous pearlyon cleavagefaces ; fibrous with the composition. black and white, through various shades varieties often silky. Color between also dark brown; rarelyyellow,pink, of green, incliningto blackish green; parent; rose-red. Streak uncolored, or paler than color. Sometimes nearly trans-

subconchoidal, uneven.

Fracture

=

=

Luster

usuallysubtranslucent to opaque. as described stronglymarked in all the deeplycolored varieties, Ax. pi. Optically rarely-f beyond. AbsorptionusuallyZ " Y " X. b (010), + 15" to 18" in most or Z A c axis on ||b (010). Extinction-angle 1" up to 37"; hence also Bxa A c axis 75" cases, but varyingfrom about to 72",etc. See Fig.832. Dispersionp " v. Axial anglesvariable;see beyond. Pleochroism

"

.

,

=

=

"

"

indices of refraction, birefringenceand extinction angles Opticalcharacters, particularly with change in composition,particularlywith the total amount of iron present. In generalthe indices and extinction angles increase with increase of iron content while the decreases. birefringence vary

In 'part a normal metasilicate of calcium and magnesium, Comp. and thus in generalanalogous to the RSi03,usuallywith iron,also manganese, The alkali metals,sodium and potassium,also present,and more pyroxenes. In part also aluminous,correspondingto commonly so than with pyroxene. the aluminous sometimes Titanium is present and also rarely pyroxenes. "

fluorine in small amount. The aluminium is in part present as NaAl(SiO3)2, but many amphiboles containing aluminium or ferriciron are basic than a normal metasilicate; more they may sometimes be n

m

explained as doubtful.

but the containing R(Al,Fe)2SiO6, The amphibole formulas are in many

nature

exact

double

cases

of the compound is often the corresponding ones for

832

pyroxene

kte

is

Thus, for most

833

tremolite and

Ca actinolite,

CaMgaSuOw, while diopsideis CaMgSi206, etc.

:

Mg(Fe)

=

1

3,and hence

tremo-

489

SILICATES

Rammelsberg has shown that the composition of most aluminous amphiboles may be expressed in the general form mRSiO3.nAl2O3; while Scharizer, modifying this view, proposes to regard the amphiboles as molecular compounds of Ca(Mg,Fe)3Si4Oi2 (actinolite), i

ii

in

for which he uses orthosilicate (R2,R)3R2Si3Oi2, name Breithaupt's syntagmatite, originallygiven to the Vesuvian hornblende. Penfield concludes that (1) amphibole is a metasilicate, (2) that fluorine and hydroxyl are isomorphous with the protoxidesand (3) that the presence of sesquioxidesis explained by their introduction into the molecule in the form of various bivalent radicals. The crystallographic positionhere adopted is that suggested by Tschermak, which best exhibits the relation between amphibole and_pyroxeme. Some authors retain the former position,according to which p (001),r (111),etc. Fig. 833 shows the corresponding opticalorientation. and

the

=

I.

=

Containinglittleor

Aluminium

no

TEEMOLITE.

Grammatite, nephrite in part. Calcium-magnesium Silica 577, magnesia 28*9,lime 13'4 amphibole. CaMg3(SiO4)3 Ferrous 100. iron,replacingthe magnesium, present only sparingly,up to 3 p. c. Colors white to dark gray. In distinct crystals, either long-bladedor short and stout.. In aggregates long and thin columnar,or fibrous;also compact 2'9-3'l. Sometimes parent transgranular massive (nephrite, below). G. and colorless. Optically b (010),or Z A on Extinction-angle axis 74" to 72". 2V +16" to 18",hence Bxa A c axis 80" to c 1.

Formula

=

=

=

"

.

=

88".

a

=

1-609.

=

(3

1-623.

=

7

=

-

=

-

1'635.

Tremolite was named by Pini from the Tremola Gothard. Winchite is the name given to a blue amphibole near of Central India.

valley on

the

south

side of the St.

tremolite from the manganese

mines

2. ACTINOLITE.

Calcium-magnesium-iron amphibole.Formula Ca(Mg,Fe)3 and In crystals, either shortxbright green grayish green. in or or long-bladed,as tremolite; columnar fibrous;granular massive. 3-3 '2. Sometimes G. transparent. The variety in long bright-green the crystals break easilyacross the prism. crystalsis called glassyactinolite; fibrous and radiated kinds are often called asbestiform The actinolite and (Si03)4.Color =

radiated

actinolite. Actinolite

owes

its green

Pleochroism distinct, the as increasing

color to the ferrous iron present. of iron increases,and hence

amount

Y yellow-green, X greenishyellow. darker;Z emerald-green, b (010), " X, Zillertal. Optically on Extinction-angle and 15" axis 75". 2V A " + c Bxa 78"; p v, a

the color becomes

AbsorptionZ Z

A c 1-611.

axis

(3

=

=

"

Y

"

.

=

1-627.

7

=

=

=

-

1-636.

atfinolite from a/cris, a ray, and XZ0os,stone, a translation of the German Name Strahlslein or radiated stone. changed to actinote by Haiiy, without reason. NEPHRITE. Jade in part. A tough, compact, fine-grainedtremolite (or actinolite). 2'96-3'l. G. (M5'5. breaking with a splintery fracture and glisteningluster. H. in diseases of the kidney, from ""e"/"p6s, Named from a supposed efficacy kidney. It varies to dark green (actinolite), iron protoxidebeing in color from white (tremolite) in the latter, The latter kind sometimes encloses distinct prismaticcrystalsof present up to 6 or 7 p. c. actinolite. A derivation from an originalpyroxenic mineral has been suggested in some from Mexico or Peru cases. Nephrite or jade was brought in the form of carved ornaments A similar stone comes from Eastern land after the discovery of America. Asia, New Zeasoon and Alaska. See jadeite, p. 481; jade,p. 482. is an amphibole occurringwith jadeitefrom Central Asia. Szechenyiite ASBESTUS. and other varieties of amphibole, exceptAsbestos. Tremolite,actinolite, ing the fibers of which are somethose containingmuch times alumina, pass into fibrous varieties, and easilyseparableby the fingers, and look like flax. These flexible, very long,fijie, kinds are called asbestus (from the Greek for incombustible) The colors vary from white to Named

=

.

=

490

MINEEALOGY

DESCRIPTIVE

The name amianthus is appliedusuallyto the finer and more silky green and wood-brown. or fibrous serpentine, containing called asbestus is chrysotile, that is popularly kinds. Much 12 to 14 p. c. of water. Byssoliteis a stiff fibrous variety. cork of interlaced fibers;and mountain leather is in thin flexible sheets,made Mountain in thicker pieces;both are so lightas to ftoat on water, and they are often hydrous, the same and gray to brown in wood is compact fibrous, color white to gray or yellowish.Mountain like wood. little a dry color,looking actinolite in composition but A thin-foliated variety of amphibole, near SMARAGDITE. common It has a lightgrass-green color,resembling much alumina. green some

carrying diallage. In

It below. see derived from pyroxene (diallage) by uralitization, cases many of the original retains much of the structure of the diallageand also often encloses remnants It forms, along with whitish or greenish saussurite,a rock called saussuritemineral. gabbro, the euphotide of the Alps. The originalmineral is from Corsica,and the rock is the verde di Corsica duro of the arts. URALITE. distinct,retain the Pyroxene altered to amphibole. The crystals,when form of the originalmineral, but have the cleavage of amphibole. The change usually the surface,transforming the outer layer into an aggregation of slender on commences (cf Fig. amphibole prisms,parallelin positionto each other and to the parent pyroxene of the change is complete the entire crystalis made up of a bundle 803, p. 473). When to pale or deep green, amphibole needles or fibers. The color varies from white (tremolite) In compositionuralite appears to conform nearly to actinolite, the latter the more common. The most also in opticalcharacters. prominent change in composition in passing from as is that correspondingto the difference existing the original between the two species pyroxene in calcium. in general,that is,an increase in the magnesium and decrease The change, .

of paramorphism, although usually so designated. Uralite is not strictly a case therefore, It has since been observed described by Rose in a rock from the Ural Mts. originally from many of "uralitizalocalities. The microscopicstudy of rocks has shown the process tion" authors'regard many and some to be very common, hornblendic rocks and schists to represent altered pyroxenic rocks on a largescale. CUMMINGTONITE. Amphibole-Anthophyllite. Iron-Magnesium Amphibole. Here belong certain varieties of amphibole resembling anthophyllite and essentially identical with it in composition,but optically From monoclinic. The Kongsberg, Norway; Greenland. in color; usually fibrous or fibre-lamellar, originalcummingtonite is gray to brown often was

radiated.

G. 3'l-3'32; from Cummington, Mass. DANNEMORITE. Iron-Manganese Amphibole. Color yellowishbrown to greenish gray. Columnar or fibrous,like tremolite and asbestus. Contains iron and manganese. From Juddite is a manganese Sweden. amphibole found at Kacharwahi, India. Iron- Amphibole. Asbestiform GRUNERITE. lamellar-fibrous. or Luster silky; color 3713. Formula brown; G. FeSiO3. =

=

3. RICHTERITE.

Sodium-Magnesium-Manganese Amphibole. (K2,Na2,M2;,

Ca,Mn)4(Si03)4. In elongatedcrystals, seldom terminated. 3 '09. G. Color brown, yellow, rose-red. Z A c axis Transparent to^ranslucent. + 17"-20"; /3 0'024. From 1-63; 7 a Pajsberg and Langban, Sweden. Characterized by the presence of manganese and alkalies in relatively largeamount. Imerinite is a soda-amphibole, related to soda-richterite from the province Imerina, Madagascar. Breislakite occurs in wool-like forms at Vesuvius and Capo di Bove, Italy. Color dark brown to black,pleochroism stronglymarked. Inferred to belong near richterite. =

=

=

-

=

II. Aluminous. 4.

ALUMINOUS

AMPHIBOLE.

Hornblende.

Contains

alumina

or

ferric

iron, and

usuallyboth,with ferrous iron (sometimes manganese), magnesium, calcium,and alkalies. The kinds here included range from the light-colored edemte containingbut littleiron,through the lightto dark green pargasite, to the dark-colored or black the color growing darker with increase hornblende, in amount of iron. Extinction-angle variable,from 0" to 37", see below. Pleochroism strong. AbsorptionusuallyZ " Y " X. EDENTTE.

Aluminous

Magnesium-Calcium Amphibole.

Color

white

to gray

and

pale

491

SILICATES

3'0-3'059. Resembles colorless; G. anthophylliteand tremolite. To this varietybelong various pale-colored localityat Edenville,N. Y. amphiboles, having less than 5 p. c. of iron oxides. is a varietyfrom the neighborhood of Lake Baikal,Siberia, Koksharovite named after the Russian mineralogist,von Koksharov. Soretite is an aluminous amphibole from the anorthite-diorite rocks of Koswinsky in the green,

and

also

Named

from

the

=

northern Ural Mts. COMMON Colors bright or dark green, and bluish green to HORNBLENDE, PARGASITE. 3'05-3'47. Pargasiteis usuallymade to include green and grayish black and black. G. bluish green blende hornkinds, occurring in stout lustrous crystals,or granular; and Common =

the greenishblack and black kinds, whether in stout crystalsor long-bladed, nar, columThe extinctionor massive granular. But no line can be drawn between them. fibrous, + 15" to 25" chiefly. Absorption Z " Y " X. angle on 6 (010),or Z A c axis at Pargas, Finland, in bluish green and grayish black crystals. Z A c Pargasiteoccurs 59". Pleochroism: Z greenish blue; Y axis + 18"; 0 a 1'64; y 0'019; 2V emerald-green; X greenishyellow. from basaltic and other igneous rocks vary someto black hornblendes The dark brown what 0" to + 10" chiefly; widely in opticalcharacters. The angle Z A c axis 0 1725; Z brown, Y 0'072 Pleochroism: but (maximum). a yellow,X yellow-green, y =

=

=

=

=

-

=

=

=

"

variable. from Traversella,Italy,is an iron amphibole with strong pleochroism;X Speziaite, Z 23". Y azure-blue,Z A c axis yellow-brown, green, The Kataforite 30" to 60"; absorption Y " Z " X; of Norway (Brogger)has Z A c axis arfvedsonite pleochroism: Z yellow,Z violet,X yellow-brown; it approximates toward (p.494). Lake Baikal, Siberia, is a Mts., near Kupfferite,from a graphite mine in the Tunkinsk deep green amphibole (aluminous) formerly referred to anthophyllite. Syntagmatiteis the black hornblende of Vesuvius. Bergamaskiteis an iron-amphibolecontainingalmost no magnesia. From Monte Altino, Province of Bergamo, Italy. Kaersutite is a titaniferpus amphibole from Kaersut, Umanaks fiord,North Greenland. Hastingsiteis an amphibole low in silicaand high in iron and soda, from the nephelitesyeniteof Dungannon, Hastings Co., Ontario. from Philipstad,Sweden, is an iron-magnesium amphibole showing unusual Philipstadite pleochroism. for the corresponding varieties of pyroxene, as see Essentiallythe same Pyr. p. 478. Diff. age, Distinguished from pyroxene (and tourmaline) by its distinct prismatic cleavcommon yieldinganglesof 56" and 124". Fibrous and columnar forms are much more =

=

=

=

=

"

"

than

with

pyroxene,

(see also or

pp.

Differs

bladed.

lamellar

478, 486). from

and

foliated forms

rare

Crystals often long, slender, the

fibrous

zeolites in not

with acids. Epidote has a peculiargreen gelatinizing and shows a different cleavage. color,is more fusible, In sections amphibole generally rock Micro. olive or brown, shows distinct colors, green, sometimes and is strongly pleochroic. Also recognized by its high relief;generallyrather high interference-colors; by the very perfectsystem of cleavage-crackscrossing 124" in sections _L c axis (Fig. at angles of 56" and 834). In sections ||b (010) (recognizedby yieldingno axial figurein convergent light,by and by having parallelcleavage-cracks,||c axis), showing the highestinterference-colors, hornblendes makes small angle (12"-15")with the the extinction-direction for common a from comwith c axis);further,this direction is positiveZ (different mon cleavage-cracks(i.e., and 813 cf. and 818). Figs. aegirite, pyroxene Artif Experiments on the artificialproduction of the amphiboles have shown that in generalthey are unstable at high temperatures and that their formation in igneous rocks unusual is due either to the rapid coolingof the magma, to the presence of water or to some In generalwhen the amphiboles are fused they are transformed conditions of pressure, etc. into the corresponding pyroxenes. Obs. only sparinglyin volcanic rocks but is found in many Amphibole occurs talline crysety, Tremolite,the magnesia-lime varilimestones, and graniticand schistose rocks. is especially in limestones, common particularly magnesian or dolomitic;actinolite (also in steatitic rocks and nephrite),the magnesia-lime-ironvariety,in the crystalline schists, in both igneous and metawith serpentine; and dark green and black hornblende,occurs "

"

.

"

492

MINERALOGY

DESCRIPTIVE

varieties of peridotite, in diorites and some syenites, morphic rocks. It is found in granites, schists. hornblende gneissesand the hornblende ot a dark greenish black consists of massive or amphibolite, Hornblende-rock, the hornblende, or actinotexture. Occasionally has and green granular a black color, or Hornblende-schist has the same in rock-masses, as at St. Francis,in Canada. occurs lite, It often contains a little but is schistose or slatyin structure. composition as amphibolite, needles. Granite and varieties of it the hornblende is in part in minute feldspar. In some constituent. it is This is diorite with and a common contain hornblende, often syenite it is usually present in small, forms of gneiss. In these cases also true of the corresponding often fibrous in structure; also as rough bladed crystals. irregular masses, Prominent foreignlocalities of amphibole are the following: Tremolite (grammatite) Gulsjo, in dolomite at Campolongo, Switzerland; also at Orawitza, Rezbanya, Hungary; schists of the Central and Eastern Actinolite in the crystalline Alps, Wermland, Sweden. Tyrol; at Zoblitz in Saxony; Arendal, Norway. especiallyat Greiner in the Zillertal, and elsewhere in Tyrol; in Savoie,France; also in the island Asbestus at Sterzing, Zillertal, Hornblende at Arendal, of Corsica. Pargasiteat Pargas, Finland; Saualpe in Carinthia. Kongsberg and Kargero, Norway; in Sweden and Finland; at Vesuvius; Aussig and Tepand utensils is widely Bohemia; etc. Nephrite,which in the form of jade" ornaments litz, the relics of earlyman distributed among (seejade,p. 482), is obtained at various points in Lun is that in the Karakash The most important source Central Asia. valley in the Kuen In New Mts., on the southern borders of Turkestan; also other localitiesin Central Asia. at Schwemmsal Zealand. near Leipzig; Nephrite has been found in Europe as a rolled mass in Swiss Lake habitations and similarlyelsewhere. at Thomaston; In the United States,in Me., black crystalsoccur pargasiteat PhippsFane. In Mass., and New burg. In Ver.,actinolite in the steatite quarriesof Windham tremolite at Lee; black crystalsat Chester; asbestus at Pelham; cummingtonite at Cummington. In Conn., in large flattened white crystalsand in bladed and fibrous forms In N. Y., Warwick, Orange Co.; near in dolomite,at Canaan. Eden ville;near (tremolite) Amity; at the Stirlingmines, Orange Co.; in short green crystalsat Gouverneur, St. Lawrence PitCo.; with pyroxene at Russell; a black varietyat Pierrepont; at Macomb; cairn; tremolite at Fine; in Rossie, 2 miles north of Oxbow; in large white crystalsat Hudsonite from Greenwood Furnace. Diana, Lewis Co.; asbestus near Cornwall, N. Y., formerlyclassed as a pyroxene has been shown to be an amphibole. In N. J.,tremolite or at Bryam, and other varieties of the speciesat Franklin and gray amphibole in good crystals Newton, radiated actinolite. In Pa.,actinolite at Mineral Hill,in Delaware Co. ; at Unionat Kennett, Chester Co. In Md., actinolite and asbestus at the Bare Hills in serpenvllle; tine; asbestus is mined at Pylesville, In Va., actinolite at Willis's Mt., in Harford Co. in Alaska. Buckingham Co.; asbestus at Barnet's Mills,Fauquier Co. Nephrite occurs In Canada, tremolite is abundant in the Laurentian at Calumet Falls,Litchlimestones, Pontiac Co., Quebec; also at Blythfield, field, Renfrew Co., and Dalhousie, Lanark Co. Black hornblende at various localities in Quebec and Ontario with pyroxene, apatite, Asbestus and mountain titanite, cork at Buckingham, Ottawa etc.,as in Renfrew Co. Co., Quebec; a bed of actinolite at St. Francis,Beauce Co.,Quebec; nephrite has been found in British Columbia and Northwest Territory. "

GLAUCOPHANE. near amphibole in form. Mpnoclinic;

Crystalsprismaticin habit,usually columnar to granular. commonly massive,fibrous, or Cleavage: m (110) perfect. Fracture conchoidal to uneven. Brittle. "L 6-6-5. G. 3-103-3-113. Luster vitreous to pearly. Color azure-blue, bluish black, grayish. Streak grayish blue. lavender-blue, Translucent. stronglymarked : Z sky-blueto ultramarine-blue, Y reddish or Plepchroism bluish violet, X yellowishgreen to colorless. Absorption Z " Y " X. cally OptiAx. pi.116 (010) Z A c axis + 4" to 6",rarelyhighervalues. 2V indistinct; =

=

.

45".

Comp. 9-9

Obs.

18

=

1-638.

T

=

=

1-638.

Essentially If Mg : Fe 2 : 1,the NaAl(SiO")s.(Fe,Mg)SiQ,. Silica 57'6,alumina 16'3,iron protoxide 77, requires: magnesia 8-5,

formula soda

=

.

1-621.

=

a

"

=

"

=

100. Occurs

as

the

hornblendic constituent

or icophane-schuts, also glaucophanite;

more

or

of certain crystallineschists,called less prominent in mica schists,am-

493

SILICATES

It is often associated with mica, garnet, diallageand First described from the island of Syra, one etc. omphacite, epidote and zoisite, of the the southern as on Cyclades; since shown to be rather widely distributed, slope of the Alps is a fibrous variety from the Island Rhodus Corsica,Japan, etc. Rhodusite (gastaldite) and Asskys river,Minassinsk, Siberia. Holmquistiteis a lithium-bearing varietyfrom the etc. gneiss,eclogites, phibolites,

,

Island of Uto. In the United of

California,as Glaucophane

States,glaucophane schists have been described Sulphur Bank, Lake Co.

from

the Coast

Ranges

at

is named

from

yXavKos, bluish green, and

to appear. ^atj/eo-tfm,

in composition between amphibole intermediate glaucophane and nearly related to the latter. Occurs in lath shaped crystals. being opticallymore riebeckite, in the crystalline Color blue. schists of the Coast Ranges of Strongly pleochroic. Found California. An

Crossite.

RIEBECKITE.

Monoclinic.

Axes

a

:

b

: c

=

0;5475:

1

:

0-2925; 0

=

76" 10'.

In

bedded em-

striated. Cleavage: prismatic(56") prismaticcrystals, longitudinally Luster black. vitreous. Color Pleochroism perfect. : very stronglymarked b axis)deep blue,X (nearly11 c axis)dark blue. Z green, Y ( Optically 4"-5" (=b?). Axial angle large. 0 small,X A c axis Extinction-angle =

"

.

=

=

1-687. in

Silica 50-5, iron sesquiEssentially2NaFe(Si03)2.FeSiO3 oxide 26-9, iron protoxide12-1, soda 10*5 It corresponds closelyto 100. the acmite (segirite) among pyroxenes.

Comp.

=

"

=

Originallydescribed from the graniteand syeniteof the island of Socotra in the in Ocean, 120 m. N. E. of Cape Guardafui. the eastern extremity of Africa; occurs often radiating and closelyresembling tourmaline; also in of prismatic crystals, groups lar granophyre blocks found at Ailsa Crag and at other points in Scotland and Ireland. A simiat Mynydd Also another in granuMawr, Carnarvonshire,Wales. amphihqleoccurs Found Greenland. at Narsarsuk. lite in Corsica. From A pegmatite at Quincy, Mass. so-called arfvedsonite from St. Peter's Dome, Pike's Peak region,Col.,occurringwith astroriebeckite. phylliteand zircon,is shown by Lacroix to be near Extinction-angleon 6, 3" to 4". A soda from Bababudan X A c axis amphibole, related to riebeckite, Hills, bababudanite. Mysore, India,has been named Obs.

"

Indian

=

Blue

CROCIDOLITE.

Asbestus.

and easily Fibrous,asbestus-like ; fibers long but delicate, separable. Also 56". H. 4. G. or 3-20-3-30. earthy. Cleavage: prismatic, Luster silky;dull. Color and streak lavender-blue or leek-green. Opaque. Fibers somewhat Z green, Y violet, X blue. elastic. Pleochroism: Optically b inclined 18" 20" to 2E with 95" on + c axis. (010) Extinction-angle massive

=

=

=

.

approx.

7

"

a

=

0'025.

in

Comp. 22-0,iron

NaFe(SiO3)2.FeSiO3 (nearly) 100. protoxide19'8,soda 8'6

=

"

Silica 49-6, iron

sesquioxide

=

Magnesium

calcium

and

replace part of the ferrous iron, and

hydrogen part of the

sodium. B.B. fuses easilywith intumescence to a black magnetic glass,coloringthe Pyr., etc. yellow (soda). With the fluxes gives reactions for iron. Unacted upon by acids. Obs. Occurs in South Africa,in Griqualand-West, north of the Orange river,in a "

flame

"

of quartzose schists called the Asbestos In a micaceous Mountains. porphyry near At Golling in Salzburg, Austria. In the United States,at Framont, in the Vosges Mts. Beacon Pole Hill,near Cumberland, R. I. Emerald Mine, Buckingham, and Perkin's Mill,

range

Templeton, Ottawa Abriachanite

Loch

Co., Ontario, Canada. earthy amorphous

is an Ness, Scotland.

structure.

Crocidolite

form

is named

occurring in the Abriachan KOOK'IS, woof, in allusion

from

near district,

to

its fibrous

494

MINERALOGY

DESCRIPTIVE

oxidation of the iron and infiltration The South African mineral is largelyaltered by both of silica, resultingin a compact siliceous stone of delicate fibrous structure, chatoyant color,popularlycalled tiger-eye(alsocat's-eye). Many luster,and bright yellow to brown to the final product; also varieties occur forming transitions from the originalblue mineral mineral has penetrated the quartz. the extent to which the original varieties depending upon

ARFVEDSONITE.

Axes

Monoclinic.

a

:

b

: c

=

0-5569

:

1

:

0*2978; 0

73" 2'.

=

terminated; Crystalslong prisms,often tabular ||b (010),but seldom distinctly Twins: in also prismatic those aggregates. of amphibole; near angles tw.

pi.a (100). Cleavage: prismatic,perfect; b (010) less perfect. Fracture

6. G. Brittle. H. thin scales deep green. splinters.Pleochroism =

vitreous.

Luster

3 -44-3 -45

=

Color

pure

uneven.

black;

in

Opaque except in thin gray. Y lavender, Z marked: greenishblue, deep strongly X palegreenishyellow. Absorption Z " Y " X; sections ||a (100) are deep Axial angle,large, a greenishblue, ||b (010)olive-green. Optically 14". b 1708. 1707. o n (010),with c axis 1'687. Extinction-angle 0 7 ferrous of and metasilicate A basic sodium, calcium, slightly Comp. iron chiefly. Streak

deep bluish

=

-

.

=

=

=

"

has been to be segirite;that from shown supposed arfvedsonite from Greenland Peak, Col.,has been referred to riebeckite. to a black magnetic globule; colors the B.B. fuses at 2 with intumescence Pyr., etc. Not acted flame" yellow (soda); with the fluxes gives reactions for iron and manganese. by acids. upon brownIn thin sections shows Micro. or or gray-green gray- violet colors; strongly pleochroicin blue and green tints;negative elongation? iron and and Obs. Arfvedsonite amphiboles of similar character, containing much as nephelite-syenite, soda,are constituents of certain igneous rocks which are rich in alkalies, certain porphyries,etc. Large and distinct crystalsare found only in the pegmatite veins in such rocks, as at Kangerdluarsuk, Narsarsuk, Greenland, where the associated minerals and also in the nephelite-syenites are eudialyte,feldspar,etc. Arfvedsonite occurs sodalite, of the Christiania related rocks the Kola on region in southern Norway; peninsula in The Russian Lapland; Dungannon Texas. lated retownship, Ontario; Trans Pecos district, in similar rocks at Montreal, brownish pleochroicamphiboles (cf.barkevikite) occur Canada; Red Hill, N. H.; Salem, Mass.; Magnet Cove, Ark.; Black Hills,S. D.; Square St. Peter's Dome, Col.,etc. Butte, Mon. Osannite from from an amphibole-gneiss at Cevadaes, Portugal, and Tschernichewite a arfvedsonite. magnetite bearing quartzitein the northern Ural Mts., are near BARKEVIKITE. An arfvedsonite In prismatic crysbut more basic. amphibole near tals. 3*428. Color deep velvet-black. Cleavage: prismatic (55" 44f')- G. ism Pleochromarked, colors brownish. Extinction-anglewith c axis on b (010) 12|". Occurs at the wohlerite localitynear Barkevik, on the Langesund fiord,and elsewhere in southern In largecrystalsat Lugar, Ayrshire, Scotland. Norway. The

Pike's

"

"

"

=

=

JEnigmatite. Cossyrite. Essentiallya titano-silicate of ferrous iron and sodium, but and ferric iron. containing also aluminium In prismatic triclinic crystals. Cleavage: 3 74-3 "80. prismatic,distinct (66"). G. Color black, ^nigmatite is from the sodalitesyemte of Tunugdliarfik and in minute Kangerdluarsuk, Greenland. Cossyrite occurs in the liparitelavas of the island Pantellaria crystalsembedded (ancient name Cossyra) ; also widespread in the rocks of East Africa. Rhonite is like senigmatitebut contains much less ferrous oxide and alkalies with increase in alumina, ferric oxide, etc. From basaltic =

rocks in the Rhon

district and

WEINBERGERITE. of

radiating fibers.

Madras, India.

elsewhere

in

Germany

Perhaps NaAlSiO4.3FeSiO3. Black

color.

From

a

and

Bohemia.

'

Orthorhombic. In sphericalaggregates meteoric iron at Codai Canal, Palni Hills,

496

MINERALOGY

DESCRIPTIVE

at Transparent berylsare found in Siberia,India and Brazil. In Siberia they occur Miask with topaz; in the mountains of Ekaterinburg; near and Shaitanka, near Mursinka A clear aquamarine crystalweighing 110'5 kg. with topaz, in E. Siberia. Adun-Chalon at Elba; Minas Geraes, Brazil. Beautiful crystalsalso occur found at Marambaya, was in Bohemia. in Saxony, and Schlackenwald Other localities the tin mines of Ehrenfriedersdorf the Mourne Aberdeen, Scotland Mts., Ireland; yellowish green at Rubislaw, near are in Sweden; Tamela and Broddbo in Finland; (davidsonite); Limoges in France; Finbo in in New Rabenstein South Wales. and Bodenmais Bavaria; Pink, Pfitsch-Joch,Tyrol; alkali-rich berylsare found in Madagascar. have been found in N. H., at Acworth In the United States, berylsof giganticdimensions

Bethel; at Grafton, and in Mass., at Royalston. In Me., at Albany; Norway; Hebron, a ca3sium beryl (Cs2O, 3*60 p. c.),associated with pollucite;in Paris, with black In Mass., at tourmaline; at Topsham, pale green or yellowish;at Stowe and Stoneham. and at the MidIn Conn., at Haddam, and at Chesterfield. Barre; at Goshen (goshenite), dletown and Portland feldsparquarries; at New Milford, of a clear golden yellow to dark Hill. In ya., amber and Chester; at Mineral In Pa., at Leiperville color; Branchville. at Amelia white. In N. C., in Alexander Court House, sometimes Co., near Stony Point, fine emeralds; in Mitchell Co.; Morganton, Burke In Ala., Cposa Co., and elsewhere. of Mt. Antero, beautiful aquamarines. Co., of a lightyellow color. In Col.,near the summit In S. D., in the Black Hills in largecrystals. Rose-pink crystals, often showing prominent pyramid faces,from San Diego Co., Cal.,also colorless and aquamarine. and

Use.

The

"

transparent mineral

is used

as

a

stone;

gem

see

above

under

Varieties.

Eudialyte. Essentially a metasilicate of Zr,Fe(Mn),Ca,Na, etc. In red to brown tabular or rhombohedral G. H. 2'9-3'0. 5-5'5. crystals;also massive. Optically 1'606. -J-. o" 1'611. From 6 Kangerdluarsuk, West Greenland, etc., with arfvedsonite and sodalite;at Lujaor on the Kola peninsula,Russian Lapland, in elseolite-syenite, there forming a main constituent of the rock-mass. Eucolite,from islands of the Langesund fiord in Norway, is similar (but optically ). Eudialyte and eucolite also occur at Magnet Cove, in Ark., of a rich crimson to peach-blossom red color,in feldspar,with elseolite and =

=

=

=

"

aegirite. H. Elpidite. Na2O.ZrO2.6SiO2.3H2O. 7. G. Color 2'54. Massive, fibrous. white to brick-red. Indices Southern Greenland. 1 '560-1 '574. Biaxial,+. ASTROLITE. with (Na,K)2Fe(Al,Fe)2(SiO3)5.H2O?.In globular forms radiating =

"

=

=

H.

structure.

Neumark,

near

The

G.

3'5.

=

Color

2'8.

=

Fusible, 3'5.

green.

Found

in

diabase

a

tuff

Germany.

following are

fiord

rare speciesof complex composition,all from the Langesund regionof southern Norway.

Catapleiite. H4(Na2)Ca)ZrSi3pii. In thin tabular hexagonal prisms. H. 6. G. Color lightyellow to yellowishbrown. Biaxial,+. Indices, 1 '591-1 '627. Natronor catapleiite, contains only sodium; color blue to gray and white; on heatsoda-catapleiite, ing the blue color disappears. Cappelenite. A boro-silicate of yttrium and barium. In greenish brown hexagonal crystals. =

=

2-8.

Melanocerite. A fluo-silicateof the cerium and yttrium metals and (also B, Ta, etc.). In brown to black tabular rhombohedral crystals.

Caryocerite. Near =4.

Tritomite. with

boron.

The

G.

=

Color

3'4.

dark

brown

to the to

last-named

two

nearly black.

species. Rhombohe-

Optically "

A

fluo-silicate of thorium, the cerium and yttrium metals In dark brown crystalsof acute triangularpyramidal form.

followingare

chiefly

melanocerite, containingThO2.

Steenstrupine (from Greenland) is allied H.

calcium

also from

the

.

and

calcium,

region:

same

Leucophanite. Na(BeF)Ca(SiO3)2. In glassygreenish tabular crystals(orthorhombicsphenoidal). H. =4. G. 2'96. Optically Indices, 1'571-1'598. =

-.

Meliphanite. low square

A

pyramids

Indices,1 '593-1

'612.

fluo-silicate of

beryllium,calcium,and

(tetragonal). Color yellow.

H.

=

sodium G.

5-5'5.

near =

leucophanite. In 3*01.

Optically

-

497

SILICATES

Ca2(OH,F)SiO3.

Custerite.

In fine granular masses. Monoclinic. Cleavages parallel prism, all making nearly 90" with each other. Twinning plane c (001), twin lamellae. H. =5. G. 2 -91. Color greenish gray. Transparent. Bxa nearlyperpendiculartoe (001). Indices,1 '58-1 '60. Difficultly Optically+. fusible. Decomposed by hydrochloricacid. Found in limestone contact zone at the Empire mine, Custer Co., Idaho. Monoclinic. In small twinned crystals. H. Didymolite. 2CaO.3Al2O3.9SiO2. 4-5. Color dark gray. 271. G. fusible. Insoluble. Found Opaque. Index 1 '5. Difficultly mineral in limestone from Tatarka River, Yenisei District,Siberia. as contact base showing in

and

to

=

=

=

Cordierite.

IOLITE.

Dichroite.

Orthorhombic. Axes a : b : c 0-5871 Twins: tw. pi.m (110),also d (130), both Habit short prismatic (mm 60" 50')(Fig.838). As embedded grains; also massive, compact. =

:

1

:

0;5585.

yieldingpseudo-hexagonalforms. 839

Cleavage: b (010) distinct; a(100)and c(001)indistinct. Crystals often show

a

lamellar structure

when ||c (001),especially altered. Brittle. 2*66.

slightly

Fracture H.

subconchoidal. 7-7 '5. 2-60G. vitreous. Color various

=

=

Luster shades

of

blue,lightor dark,

lucent. smoky blue. Transparent to transPleochroism strongly marked except in thin sections. Axial colors variable. Thus: Z

Bodenmais

(=

b

axis)dark

Berlin-blue.

Y

(

=

a

axis)lightBerlin-blue.

(

X

=

c

axis)

yellowishwhite. Y

X. Pleochroic halos common, often brightyellow; axis. Exhibits seen ||c idiophanousfigures.Optically Ax. pi.||a (100). Bx. J_ c (001). Dispersionfeeble, 2V 70" 23' v. p " Indices 1'534 to 1-599. from (also40" to 84"). variable,

Absorption Z

best

"

"

in sections

"

.

=

H2(Mg,Fe)4Al8Siio037or H2O.4(Mg,Fe)O.4Al2O3.10SiO2. 7 : 2, the percentage compositionis: Silica 49*4, alumina 100. Ferrous iron replaces 33'6, iron protoxide5*3, magnesia 10-2, water 1-5 part of the magnesium. Calcium is also present in small amount. Comp. If Mg

"

:

Fe

=

=

B.B. Pyr.,etc. Decomposed

loses transparency and

fuses at 5-5'5. Only partiallydecomposed by fusion with alkaline carbonates. Diff. Characterized by its vitreous luster, color and pleochroism; fusible on the edges unlike quartz; less hard than sapphire. Micro. ference-color Recognized in thin sections by lack of color; low refraction and low interit is very similar to quartz, but distinguishedby its biaxial character; in volcanic rocks commonly shows distinct crystaloutlines and a twinning of three individuals like aragonite. In the gneisses, of occurrence etc.,it is in formless grains,but the common of sillimanite needles, the pleochroichalos of a yellow color around small inclusions, especially inclusions, particularly zircons,and the constant tendency to alteration to micaceous pinite seen along cleavages, help to distinguishit. Obs. Occurs in granite,gneiss (cordierite-gneiss) hornblendic,chloritic and talcose , schist,and allied rocks,with quartz, orthoclase or albite, tourmaline,hornblende, andalusite,sillimanite, ous garnet, and sometimes beryl. Less commonly in or connected with ignemasses from the magma, rocks,thus formed directly as in andesite, etc.; also in ejected "

acids.

"

"

"

on

498

MINERALOGY

DESCRIPTIVE

(infragments of older rocks); further formed as a contact-mineral in connection with eruptive dikes,as in slates adjoininggranite. in Finland Occurs at Bodenmais, Bavaria, in granite,with pyrrhotite,etc.; Orijarvi, Tunaberg, in Sweden; from Switzerland; in colorless crystalsfrom Brazil; (steinheilite)-; Ceylon affords a transparent variety,the saphir d'eau of jewelers;from Ibity,Madagascar; Greenland.

from

Conn., associated with tourmaline in a graniticvein Conn. Litchfield, AtBrimfield,Mass.; at Richmond

In the United States,at Haddam, gneiss. In largealtered crystalsfrom N.

in

H.

I elite from 'lov, and (from dixpoos,two-colored), violet, X10os,stone; Dichroite after Cordier, the French geologist(1777-1861). dichroism; Cordierite, The Alteration. alteration of iolite takes place so readilyby ordinary exposure, that the mineral is most commonly found in an altered state, or enclosed in the altered iolite. be a simple hydration; or a removal of part of the protoxide bases by carThis change may bon dioxide; or the introduction of oxide of iron; or of alkalies, forming pinite and mica. The first step in the change consists in a division of the prisms of ioliteinto platesparallel to the base, and a pearly foliation of the surfaces of these plates;with a change of color to As the alteration proceeds, grayishgreen and greenishgray, and sometimes brownish gray. the foliation becomes more complete; afterward it may be lost. The mineral in this altered Named

from

its

condition has many and auralite) names : as hydrous iolite ( includingbonsdorffite from Abo, from Helsingfors;esmarkite and Finland; fahlunitefrom Falun, Sweden, also pyrargillite praseolitefrom near Brevik, Norway, also raumite from Raumo, Finland,and peplolite from from Ramsberg-, Sweden; chlorophyllite Unity, Me.; aspasioliteand polychroilitefrom Kragero. There are further alkaline kinds, as pinite,cataspilite, gigantolite, iberite, ing belongto the Mica Group. Use.

Iolite is sometimes

"

used

as

a

gem.

Jurupaite. H2(Ca,Mg)2Si2O7. Monoclinic? 275. 1-57. n Crestmore, Cal.

G.

=

Radiating fibrous.

White.

H

=

4

=

The

followingare

rare

lead,zinc,and barium

silicates:

In Barysilite. Pb3Si2O7. Rhombohedral. embedded with masses curved lamellar 3. Cleavage: basal. H. G. 611-6-55. Color white; tarnishing on From the Harstig mine, Pajsberg,and Langban, Sweden. exposure. Molybdophyllite. (Pb,Mg)SiO4.H2O. Hexagonal. In irregular foliated masses with 3-4. perfect basal cleavage. H. G. 47. Colorless to pale green, 1-81 co fusible. From Difficultly Langban, Sweden. structure.

=

=

=

=

=

Ganomalite.

Pb4(PbOH)2Ca4(Si2O7)3. In prismatic crystals (tetragonal);also

granular. H Langban, Sweden;

G.

=3 also

=574.

Colorless

to

gray.

Indices, 1'83-1'93.

sive mas-

From

Jakobsberg. Closelyrelated to ganomalite. Pb4(PbCl)2Ca4(Si2O7)3. Probably tetragonal.

Nasonite.

Massive,granularcleavable. H. =4. G. 5'4. White. Fusible. From Franklin^N. J. Margarosanite. Pb(Ca,Mn)2(SiO3)3. Triclinic. Slender prismatic crystalsand cleavable granular. Three cleavages, one perfect. Colorless and transparent with pearly lus2-5-3. G. 3-99. Easilyfusible. From Franklin,N. J.,and Langban, Sweden. Hardystonite. CasZnSisOr. Tetragonal. In granular masses. Three cleavages. =

=

H.

=

=

G.

3-4.

3'4.

=

Color white. From Franklin,N. J. Approximately (Pb,Ba,Ca)B2(SiO3)i2. Massive; coarselycrystalline.

Hydotekite. U.

=

5 -5-5.

G.

=

Color

3-81.

Barylite. Ba^SiAt ' "

in

I

'

;

at ii

Taramellite.

white

to

Langban,

From

Langban, Sweden.

colorless prismatic orthorhombic

Optically+.

ft

=

1-685.

.

crystals.

Occurs

with

Color

reddish brown. F"Und ln lime-

hedyphane

Sweden.

in

Ba4FeFe4Si10O31. Orthorhombic?

K^t

n.

pearly gray. of

groups

greasy?' LustTer

nlimestone crystalline r

In

^^

Fibrous. "** tO ^^

Candoglia Italy Roeblingite. ,H2CaSiO4).2(CaPbSO4).In dense, white,compact, crystallinemasses. 6. "

u.

=

6 433.

From

Franklin

Furnace

N. J.

499

SILICATES

III.

Orthosilicates.

R2SiO4

Salts of Orthosilicic Acid, H4SiO4; characterized by 1 : 1 for silicon to bases. The followinglist includes the more prominent groups silicates.

an

ratio of

oxygen among

the Ortho-

of basic orthosilicates are A number here included,which yieldwater ignition; upon less basic than also others which are normal more or but which are of a orthosilicate, because of their relationship to other normal necessityintroduced here in the classification, MICA GROUP is so closelyrelated to many salts. The Hydrous Silicates that (with also Talc,Kaolinite,and some others)it is described later with them.

Hexagonal. Nephelite Group. Isometric. Soda lite Group. Helvite Isometric-tetraheGroup. draL Garnet

Isometric. Group. Orthorhombic. Chrysolite Group. Tri-rhombohePhenacite Group.

Scapolite Group. Tetragonalpyramidal. Zircon Group. Tetragonal. Danburite OrthorhomGroup. bic. Datolite

Group.

Epidote Group.

Monoclinic. Monoclinic.

dral.

Nephelite Group.

Hexagonal i

Typical formula RAlSiO4 K^NaeA^C^ Nephelite Soda-nephelite(artif.)NaAlSi04 LiAlSiO4 Eucryptite Cancrinite Microsommite The

c

Kaliophilite

GROUP

are

0-8389

KAlSi04

H6Na6Ca(NaC03)2Al8(SiO4)9 (Na,K)ioCa4Ali2Sii2052SCl4

speciesof the NEPHELITE

=

2c

=

0'8448

2c

=

0'8367

and hexagonal in crystallization i

have

in part the typicalorthosilicate formula RAlSi04. From this formula artificial soda-nephelite, nephelite itself deviates somewhat, though an NaAlSiO4, conforms to it. The speciesCancrinite and Microsommite are related in form and also in composition,though in the latter respect somewhat to connect this group with the sodalite group complex. They serve

following. Elseolite.

Nepheline.

NEPHELITE.

0-83893. Hexagonal-hemimorphic (p. 101). Axis c In thick six- or twelve-sided prisms with plane or modified summits. Also massive compact, and in embedded thin grains; structure sometimes =

columnar.

Cleavage: Brittle.

H.

(110)distinct;c (001)imperfect. Fracture subconchoidal.

m

2-55-2-65. Luster vitreous to greasy; G. little a varieties. Colorless, white,or yellowish;also,when massive, dark green, greenishor bluish parent gray, brownish red and brick-red. Transto opaque. Indices: o" 1-538. Optically 1-542,e Var. 1. Nephelite. Glassy. Usually in small glassycrystalsor grains,transparent with vitreous luster, first found on Mte. Somma, Vesuvius. Characteristic particularly of

opalescentin

=

5'5-6.

=

some

=

"

.

"

"

=

MINERALOGY

DESCRIPTIVE

500

monly comcrystals,or more eruptive rocks and lavas. 2. Elceolite. In large coarse massive, with a greasy luster,and reddish, greenish,brownish or gray in color. rocks,syenite, inclusions. Characteristic of granularcrystalline clouded by minute Usually "

younger

etc.

This is the composition of the artificial mineral. NaAlSiO4. Comp. and also small Natural nephelitealways contains silica in varying excess to NaeK^AlgSigCV The approximates usually composition of potash. amounts "

Synthetic experiments,yieldingcrystalslike nephelitewith the composition NaAlSiO4, lead to the conclusion that a natural soda-nephelitewould be an orthosilicate with this formula, while the higher silica in the potash varieties may be explainedby the presence, and NaAlSi3O8 (albitein hexagonal modification). in molecular combination, of KAlSiO4 be more lite, simply explainedby consideringnormal nepheThe variation in composition may The other NaAlSiO4, to take up in solid solution silica or other silicate molecules. viz.,eucryptiteLiAlSiO4. and kaliophilite, speciesof the group are normal orthosilicates, B.B. fuses Pyr.?etc. Gelatinizes with acids. "

quietlyat

3 '5 to

a

colorless glass,coloring the flame

yellow.

with acids from scapoliteand feldspar,as Diff. Distinguishedby its gelatinizing Massive varieties have also from apatite,from which it differs too in its greater hardness. luster. a characteristic greasy Micro. Recognized in thin sections by its low refraction; very low interferencein crystals; faint negative extinction when colors,which scarcelyrise to gray; parallel uniaxial cross yieldedby basal sections in converging light. The negative character is best told by aid of the gypsum plate(seep. 266). Micro-chemical tests serve to distinguishnonof alkali feldspar;the section is treated with dilute from similar ones characteristic particles stained with which coats the nepheliteparticles, acid,and the resultant gelatinoussilica, "

"

cosine

other

dye. Nephelite is easilyprepared artificially by fusing its constituents together in the proper proportions. Obs. Nephelite is rather widely distributed (as shown by the microscopic study of rich in soda and at the of a magma rocks) in igneous rocks as the product of crystallization time low in silica (which last prevents the soda from being used up in the formation same of albite). It is thus an essential component of the nephelite-syenites and phonoliteswhere it is associated with alkali feldsparschiefly. It is also a constituent of more basic augitic rocks such as nephelinite,nephelite-basalts, theralite,etc., most of nephelite-tephrites, which are volcanic in origin. The variety elceolite is associated with the granular plutonic rocks, while the name nephelitewas originallyused for the fresh glassy crystalsof the modern lavas; the terms have in this sense orthoclase and relative significance the same as sanidine. elceolite. Modern usage, however,tends to drop the name The original in crystals in the older lavas of Mte. Somma, Vesuvius, with occurs nephelite mica, vesuvianite,etc.; at Capo di Bove, near Rome; in the basalt of Katzenbuckel, near Heidelberg,Germany; Aussig in Bohemia; Lobau in Saxony. Occurs also in massive forms or

Artif.

"

"

foyaite);Ditro,Hungary

(inthe rock ditroite) ; Pousac, France; Brazil; South Africa. Elaeolite occurs massive and crystallized at Litchfield, Me., with cancrinite;Salem, Mass.; Red Hill,N. H.; in the Ozark Bits.,near Magnet Cove, Ark.; elseolite-syenite is also found near Beemersville,northern N. J.; near Montreal, Canada; at Dungannon _

township,Ontario,in enormous at various points,as crystals. Nephelite rocks also occur the Transpecos district, North America, as in Texas; Pilot Butte, Texas; also in western Col. at Cripple Creek; in Mon., in the Crazy Mts., the Highwood, Bearpaw and Judith |Cts.;Black Hills in S. D.; Ice River, British Columbia. Named from i/e^eXrj, in allusion to its becoming cloudy when immersed nephelite a cloud, in strong acid; elceolite is from eXaiov, oil,in allusion to its greasy luster. Gieseckite is a pseudomorph after nephelite. It occurs in six-sided greenin Greenland ish luster; also at Diana in Lewis Co., N. Y. gray prisms of greasy Dysyntribitefrom Diana is similar to gieseckite, is also liebenerite, as from the valleyof Fleims, in Tyrol, Austria. See further FINITE under the MICA GROUP. Eucryptite. LiAlSi04. in

albite and

p.

181). G.

derived =

from

2-667.

In

symmetrically arranged crystals (hexagonal),embedded, at Branchville,Conn, (seeFig.488,

the alteration of spodumene Colorless or white.

501

SILICATES

Phacellite. Phacelite. In bundles of slender Facellite. Kaliophilite. KAlSiO4. acicular crystals(hexagonal), also in fine threads, cobweb-like. H. =6. G. 2*493Colorless. Occurs in ejectedmasses 2'602. at Mte. Somma, Vesuvius. =

CANCRINITE.

_Hexagonal. 25" 58'. Usually massive.

0111

=

Axis

c

=

Rarely

and

04224; in

1010

mp

1011

A

prismaticcrystalswith

a

=

64",ppf 1011

low terminal

A

pyramid.

H. 5-6. Cleavage: prismatic,m (1010) perfect;a (1120) less so. 2 -42-2 -5. Color white, gray, G. yellow, green, blue, reddish. Streak Luster subvitreous, uncolored. of a littlepearlyor greasy. Transparent to 1-524. 1-496. translucent. e co Optically =

=

=

-.

Comp.

=

H6Na6Ca(NaC03)2Al8(SiO4)9

"

Silica 387, carbon 9Si02.2C02 100. 17-8,water 3-9

or

3H2O.4Na2O.CaO.4Al2O3. 29-3, lime 4-0, soda

dioxide 6-3, alumina

=

=

In the closed tube gives water. B.B. loses color,and fuses (F. 2) with it readilyfrom to a white blebby glass,the very easy fusibility distinguishing Effervesces with hydrochloric acid, and forms a jellyon heating, but not

Pyr., etc. intumescence

nephelite.

=

"

before. Micro. Recognized in thin sections by its low refraction;quite high interferenceIts common association with nephelite,socialite, colors and negative uniaxial character. it from all other etc.,are valuable characteristics. Evolution of CO2 with acid distinguishes minerals except the carbonates,which show much higher interference-colors. Cancrinite has been prepared artificially Artif a mixture by heating under pressure of nepheliteand alumina and sodium carbonate; also by the treatment of sodium silicate, labradorite by sodium carbonate at high temperatures. and related Cancrinite occurs Obs. only in igneous rocks of the nephelite-syenite formed It is in part believed to be original, rock groups. i.e., directlyfrom the molten magma; of nepheliteby infiltrating in part held to be secondary and formed at the expense waters holding calcium carbonate in solution. Prominent localitiesare Miask in the Ilmen similarlyat Barkevik and other localities Mte.,Russia, in coarse-grainednephelite-syenite; the Langesund fiord in southern on Norway; in the parishof Knolajarvi in northern Finland of cancriniteand nephelite,it composes a mass (where, associated with orthoclase,segirite of Sarna and Alno in Sweden, syenite); at Ditro,Transylvania, etc.; in nephelite-syenite occasional accessory component of many and in Brazil; also in small amount as an phonoliticrocks at various localities. In the United States at Litchfield and West Gardiner, Me., with ela3oliteand blue sodaafter Count Cancrin, Russian Minister of Finance. lite. Named with nearly one-half the CO2 replaced by SO3 is found in an SULPHATIC CANCRINITE fringence Co., Col. Has lower refractive indices and' birealtered rock on Beaver Creek, Gunnison "

"

.

"

than

cancrinite.

In minute Near Microsommite. cancrinite;perhaps (Na,Et)i0Ca4Ali2Sii2O52SCl4). Vesuvius (Monte colorless prismatic crystals(hexagonal. See Fig. 30, p. 19). From 1-521. 1'529. 2'42-2'53. H. =6. G. co e Somma).

Davyne. 1-518.

e

=

Near

=

=

=

microsommite.

From

Mte.

Somma;

Laacher

See, Germany.

o"

=

1'521.

Sodalite Sodalite

Group.

Isometric

Na4(AlCl)Al2(SiO4)3

Haiiynite

(Na2,Ca)2(NaSO4.Al)Al2(Si04)3

Noselite

Na4(NaSO4.Al)Al2(Si04)3 Na4(NaS3.Al)Al2(SiO4)3

Lazurite

and perThe speciesof the Sodalite Group are isometric in crystallization haps In compositionthey are peculiar tetrahedral like the followinggroup. (likecancrinite of the precedinggroup) in containingradicals with Cl, S04 and S, which are elements usuallyabsent in the silicates. These are shown in the

MINERALOGY

DESCRIPTIVE

502

who shows that with the included be garnets in a broad close resemblance and in characterized by isometric crystallization a GROUP proper, p. 505. See further under the GARNET

suggestedby Brogger,

formulas written above in the form this group and the one followingmay group

composition.

The formulas and chloride

also often written

are

sulphide) (sulphate, "

as

if the

thus for

compound

consisted

of

a

cate sili-

3NaAlSiO4 + NaCl, sodalite,

etc. SODALITE.

form

Isometric, perhaps tetrahedral. Common

the

dodecahedron.

Twinsforminghexagonalprismsby elongationin the direction tw. pi.o (111), grains;in 406, p. 165). Also massive, in embedded of an octahedral axis (Fig. from elaeolite. formed concentric nodules resembling chalcedony, conchoidal to less distinct. Fracture or Cleavage: dodecahedral, more sometimes Luster vitreous, 2'14-2'30. G. 5-5-6. white; sometimes blue, yellowish, Color gray, greenish, Streak uncolored. lavender-blue,lightred. Transparent to translucent.

Brittle.

uneven.

H.

=

=

incliningto greasy. n

1-4827.

=

Comp.

Na4(AlCl)Al2(SiO4)3Silica 37'2, =

"

17

2C1) chlorine 7'3 1017, deduct (0 The formula may small part of the sodium. NaCl. =

=

Pyr.. etc. fuses with

"

In

the closed tube

intumescence,

at

=

alumina

31*6, soda

25'6,

Potassium replacesa also be written 3NaAlSiO4 + 100.

B.B. white and opaque. the blue varieties become colorless glass. Soluble in hydrochloric acid and a

3 '5-4,to

yieldsgelatinoussilicaupon evaporation. leucite and haiiyniteby chemical tests alone; Diff. Distinguishedfrom much analcite, dissolvingthe mineral in dilute nitric acid and testing for chlorine is the simplest and "

best. Micro. isotropiccharacter and Recognized in thin sections by its very low refraction, In uncovered rock sections lack of good cleavage; also,in most cases, by itslack of color. with a the minerals of this group be distinguishedfrom each other by covering them may of sodium sodalite crystals to evaporate slowly. With littlenitric acid which is allowed with noselite crystalsof both compounds chloride will form; with haiiynitecrystalsof gypsum; which after the addition of calcium chloride;lazurite will evolve hydrogen sulphide will blacken silver. Aftif. .Sodalite can be obtained by fusingnephelitewith sodium chloride;also by the It has been action of sodium carbonate and caustic soda upon muscovite at 500". duced proat temperatures below 700". also in various artificialmagmas Obs. Sodalite occurs and related rock only in igneous rocks of the nephelite-syenite of a magma rich in soda; also as a product associated groups, as a product of the crystallization with enclosed masses and bombs in the form of lava,as at ejectedwith such magmas Often associated Vesuvius. with nephelite(or elseolite), cancrinite and eudialyte. With sanidine it forms a sodalite-trachyte at Scarrupata in Ischia,Italy,in crystals. In Sicily, Val di Noto, with nepheliteand analcite. At Vesuvius,in bombs in white, Monte Somma on dodecahedral crystals;massive and of a gray color at the Kaiserstuhl and near translucent, A varietyfrom Monte Lake Laach, Germany. Somma num containing 2 per cent of molybdetrioxide has -been called molybdosodalite.At Ditro, Transylvania, in an elaeolitesyenite. In the foyaiteof southern Portugal. At Miask, in the Ilmen Mts., Russia; in the augite-syenite of the Langesund-fiordregion in Norway. Greenland Further in West in sodalite-syenite; the peninsulaof Kola, Russia. A blue massive variety occurs at Litchfield and West in the Occurs Gardiner,Me. theralite of the Crazy Mts., Mon., also at Square Butte, Highwood Mts., and in the BearMts., in tinguaite. Occurs also in the ela3olite-syenite of Brome, Brome paw Co., and of and Beloeil, Montreal province of Quebec; at Dungannon, Ontario, in large blue masses and in small palepink crystals. At KickingHorse Pass, Bristish Columbia. A sodalite containing Hackmanite. about 6 per cent of the molecule Na4[Al(NaS)]Al2 (biO4)3trom a rock called tawite from the Tawa valleyon the Kola peninsula,Lapland. "

"

"

.

^

V

apatite,titanite,zircon, and (microperthite?), + and probably uniaxial. Regarded by Brogger as optically metamorphism in limestone.

orthoclase scapolite plagioclase,

amount n

MINERALOGY

DESCRIPTIVE

504

mineral undetermined'

result of contact which see. Similar to sodalite, Micro. moisture; the variety from Chile Heated in the closed tube gives off some etc Pvr blue on cooling Fuses but the color of the mineral remains light, clows with a beetle-green acid and yieldsgelatiSoluble in hydrochloric nous white glass. to a intumescence with

a

_

"

easily(3)

evolves hydrogen sulphide. India,in the valleyof the Kokcha, a branch of the Oxus, Badakshan, Obs Baikal Siberia. Further, in at the south end of Lake Also miles above Firgamu. a few From at Monte Somma, Vesuvius, rare. masses In ejected Chile in the Andes of Ovalle.

evaporationand

silicaupon

in

Occurs

"

Siberia and Persia.

richlycolored varieties of lapislazuli are highly esteemed for costlyvases of mosaics; and when dered powThis has been replaced, constitutes the rich and durable paint called ultramarine. an important commercial product. ultramarine,now however, by artificial Use

The

"

in the manufacture and ornamental furniture; also employed

"",Helvite

Group.

Isometric-tetrahedral

(Mn,Fe)2(Mn2S)Be3(Si04)3 (Fe,Zn,Mn)2( (Zn,Fe)2S)Be3(Si04)3 Bi4(SiO4)3 (Al(OH,F,Cl)2)6Al2(SiO4)3

Helvite Danalite

Eulytite Zunyite

isometric-tetrahedral in includes several rare species, GROUP to related the of the SODALITE in and species composition crystallization which follows: GROUP the GARNET of to those also and GROUP HELVITE

The

HELVITE.

in tetrahedral

Isometric-tetrahedral. Commonly

crystals cal ; also in spheri-

masses.

in traces. Fracture uneven Brittle. to conchoidal. Luster vitreous, Color resinous. t o inclining and t o reddish brown. siskin-green, honey-yellow,inclining yellowishbrown,

Cleavage: octahedral

H.

=

G.

6-6*5.

=

Streak uncolored.

3'16-3'36.

Subtransparent.

n

=

1 739.

Pyroelectric.

(Be,Mn,Fe)7Si3Oi2S.This may be written (Mn,Fe)2(Mn2S)Be3 Comp. taking (SiO4)3 analogousto the Garnet Group, the bivalent group -Mn-S-Mn the placeof a bivalent element,R, and 3Be correspondingto 2A1, cf. p. 505. Composition also written 3(Be,Mn,Fe)2SiO4.(Mn,Fe)S. "

Fuses at 3 in R.F. with intumescence to a yellowish brown Pyr.,etc. bead, opaque With the fluxes givesthe manganese Soluble in hydroreaction. becoming darker in R.F. chloric acid,givinghydrogen sulphideand yieldinggelatinoussilicaupon evap9ration. Obs. Occurs at Schwarzenbergand Breitenbrunn, in Saxony; at Kapnik, Hungary; also in the pegmatite veins of the augite-syenite in the of the Langesund fiord,Norway; Ilmen Mts.,Russia,near Miask, in pegmatite. In the United States,with spessartite, at the mica mines near Amelia Court-House,Amelia Co.,Va.; etc. sion Named by Werner, in alluto its yellow color,from -Xios,the sun. Danalite. H. (Be,Fe,Zn,Mn)7Si3Oi2S. In octahedrons; usually massive. 5'5-6. G. 3-427. Color flesh-red to gray. Occurs in small grains in the Rockport granite, Cape Ann, Mass.; at the iron mine at Bartlett, N. H.; El Paso Co., Col. In England at "

"

=

=

Eulytite. Bi4Si3Oi2. Usually H. n

=

^

4'5.

2?'

in minute tetrahedral crystals;also in sphericalforms. G. 6'106. Color dark hair-brown to colorless. grayish, straw-yellow, or Found witn native bismuth near Schneeberg,Saxony; also at Johanngeorgen=

stadt, Germany,

m

crystalson

quartz.

505

SILICATES

Zunyite. "

minute

A

In highly basic orthosilicate of aluminium, (Al(OH,F,Cl)2)6Al2Si3Oi2. 2*875. From H. =7. G. the Zuni mine, near SilCo., and on Red Mountain, Ouray Co., Col.

transparent tetrahedrons.

verton, San Juan

4.

=

Garnet

Group.

3RO.R2O3.3Si02.

or II

II

R

H

III

III Ill

III

Al,Fe,Cr,Ti.

Ca,Mg,Fe,Mn.

=

Isometric

Garnet A.

GROSSULARITE

B.

PYROPE

C.

ALMANDITE

SPESSARTITE Schorlomite D.

E. ANDRADITE Ca3Al2(SiO4)3 Ca3Fe2(SiO4); Also Mg3Al2(Si04)3 (Ca,Mg)3Fe2(SiO4)3, Fe3Al2(SiO4)3 Ca3Fe2((Si,Ti)04)3 F. UVAROVITE Mn3Al2(SiO4)3 Ca3Cr2(Si04)3, Ca3(Fe,Ti)2((Si,Ti)O4)

includes a series of important sub-species GROUP included The GARNET in the normal class of under the same name. specific They all crystallize and trapezoalike in habit,the dodecahedron the isometric system and' are forms. hedron being the common They have also the same generalformula, intermediate and while the elements present differ widely, there are many and thus of the garnets include titanium,replacingsilicon, varieties. Some w hich connected with the rare are speciesschorlomite, probably also has they formula. the same general GROUP proper are the speciesof the Sodalite and llelvite characterized by isometric crystallization, and all are Thus the formula of the Garnet Group is chemical structure.

Closelyrelated to the GARNET Groups (pp. 501, 504). All are with orthosilicates,

similar

Hill

where Na4 and the R3R2(SiO4)3; to this Sodalite conforms if written Na4(AlCl)Al2(SiO4)3, for Noselite (Haliynite) if the presence bivalent radical A1C1 are equivalent to R3; similarly of the bivalent group is assumed. NaSO4-Al In the Helvite Group, which is characterized by the tetrahedral character of the species the chemical relation is less close but probably exists, (perhaps true also of the Sodalites), of Helvite (Mn,Fe)(Mn2S)Be3(SiO4)3,where the bivalent as exhibited by writingthe formula -S-Mn-Senters, and 3Be may be regarded as taking the place of 2A1. group GARNET.

Isometric. 841

The

dodecahedron

and

trapezohedron,n (211),the

842

common

843

simpleforms; also these in combination,or with the hexoctahedron s (321). Cubic and octahedral faces rare. Often in irregular embedded grains. Also

MINERALOGY

DESCRIPTIVE

506 coarse massive; granular,

Sometimes

thick and bent.

fine,and sometimes friable;lamellar,lamellae like nephrite. compact, cryptocrystalline rather distinct.

(110) sometimes

d

Parting:

or

Fracture

subconchoidal 846

845

844

to

granularmassive; very tough when G. 3-15-4-3,varying with the compact Color vitreous resinous. to red,brown, yellow,white, composition. Luster red and green, colors often bright. Streak white. black; some apple-green, double refraction, Often exhibits anomalous Transparent to subtranslucent. 429. Refractive index Art. see etc.), (alsotopazolite, grossularite especially with the composition. The different pure rather high,and varying directly indices. molecules have approximatelythe following sometimes Brittle,

uneven.

friable when

H. cryptocrystalline.

=

6'5-7'5.

=

Pyrope 1705, Grossularite 1-735,SpessartiteI'SOO,Almandite Andradite

1'830,Uvarovite

1'870,

1'895. II

III

orthosilicate having the generalformula R3R2(SiO4)3,or Comp. The bivalent element may be calcium,magnesium, ferrous 3RO.R203.3Si02. iron or manganese; the trivalent element, aluminium, ferric iron or chromium, is s ilicon also sometimes titanium. rarelytitanium;further, replacedby The different garnet molecules are isomorphous with each other although there are apparentlydefinite limits to their miscibility.The greatermajority willbe found to have two or three component molecules ; in the case, however, where three are present one is commonly in subordinate amount. The index of refraction and specific with the variation in composition. gravityvary directly Var. There are three prominent groups, and various subdivisions under each,many of these blendinginto each other. An

"

"

I. Aluminium A. B.

C. D.

II. Iron

Garnet,including

GROSSULARITE PYROPE ALMANDITE SPESSARTITE

Calcium- Aluminium

Garnet Aluminium Garnet MagnesiumIron- Aluminium Garnet Garnet Manganese- Aluminium

Garnet,including

E.

ANDRADITE

Calcium-Iron

Garnet

Ca3Fe2(SiO4)3

(1)Ordinary. (2)Magnesian. (3)Titaniferous. III.

Chromium F.

The

Ca3Al2(Si04)3 Mg3Al2(SiO4)3 Fe3Al2(SiO4)3 Mn3Al2(SiO4)3

(4)Yttriferous,

Garnet.

UVAROVITE

Calcium-Chromium

Garnet

Ca3Cr2(SiO4)3

Garnet is from the Latin granatus, meaning like a grain, and directlyfrom pomegranate, the seeds of which are small,numerous, and red, in allusion to the aspect oi the crystals. name

507

SILICATES

Essonite or Hessonite. Cinnamon-stone. CalciumFormula Silica 40 -0,alumina 3CaO.Al2O3.3Si02 227, Often 100. lime 37 '3 containingferrous iron replacingthe calcium,and ferric iron replacingaluminium, and hence graduatingtoward C and groups Color (a) colorless to white; (6) pale green; 3-53. E. G. (c) amberand honey-yellow; (d) wine-yellow,brownish yellow,cinnamon-brown; (e) of chromium. Often rose-red;rarely (/) emerald-greenfrom the presence anomalies shows optical (Art.429). GROSSULARITE. Garnet.

A.

aluminium

=

=

=

and was The originalgrossularite (wiluitein part) included the pale green from Siberia, for the gooseberry; G. 3-42-372. from the botanical name named Cinnamon-stone, included a cinnamon-colored essonite (more properly hessonite), variety from Ceylon, or the yellowand yellowishred kinds are usually there called hyacinth; but under this name because of less hardness than the true hyacinth from fjvauv,inferior, included; named kind from the Ala valley,Piedmont, Succinite is an amber-colored which it resembles. is brown. Italy. Romanzovite and yellow-brown garnets are not invariably Pale green, yellowish, grossularite;some Garnet, or (includingtopazolite,demantoid, etc.)belong to the group of Calcium-Iron Andradite. =

so

Precious garnet in part. Magnesium-aluminium Garnet. Silica 44-8, alumina 25*4, magnesia 29*8 3MgO.Al203.3Si02 100. Magnesia predominates,but calcium and iron are also present; the G. 3'51. Color deep red to originalpyrope also contained chromium. The nearly black. Often perfectlytransparent and then prized as a gem. PYROPE.

B.

Formula

=

=

=

name

pyrope

is from

TTUPCOTTOS, fire-like.

Rhodolite,of delicate shades of pale rose-red correspondsin composition to two parts of pyrope

and

and

purple, brilliant by reflected light, of almandite; from Macon Co.,

one

N. C.

Precious garnet in part. Common garnet Silica 36 -2, Formula 3FeO.Al203.3SiO2 Ferric iron replacesthe aluminium 100. also to a greater or less extent. replacesthe ferrous iron,and Magnesium cf. rhodolite above. Color fine G. 4-25. thus it graduatestoward pyrope, brownish in translucent subor red, deep red, transparent, preciousgarnet; Part of in black. to common common belongs garnet translucent, garnet; Almandine. C. ALMANDITE. Garnet. in part. Iron-aluminium alumina 20 '5,iron protoxide43 '3

=

=

=

Andradite. The Hence

called because Alabandic carbuncles of Pliny were so in use. almandine the name or almandite, now

cut

and polishedat Alabanda.

Spessartine.Manganese-aluminium Garnet. Formula Silica 36'4,alumina protoxide43'0 20'6,manganese to a greater or less extent, and iron replacesthe manganese Ferrous 100. Color dark hyacinth-red, 4-18. G. sometimes ferric iron also the aluminium. to brownish red. with a tingeof violet, D.

SPESSARTITE.

3MnO.Al2O3.3SiO2

=

=

=

Calcium-iron Common Garnet, etc. Garnet, Black Silica 35'5,iron sesquioxide31 -5,lime Formula 3CaO.Fe2O3.3Si02 Aluminium 100. 33*0 replacesthe ferric iron; ferrous iron,manganese Colors various: 375. G. and sometimes magnesium replacethe calcium. wine-, topaz- and greenishyellow,apple-greento emerald-green;brownish red,brownish yellow;grayishgreen, dark green; brown; grayishblack,black. E.

Garnet.

ANDRADITE.

=

=

=

and

Andradite after the Portuguese mineralogist, Named d'Andrada, who in 1800 described ing Allochroite. of the included subvarieties, named one Chemicallythere are the followvarieties:

MINERALOGY

DESCRIPTIVE

508

Garnet, in which the protoxidesare wholly or almost wholly and transparency of topaz, and also (a) Topazolite,having the color ! a grass-green Demantoid hexoctahedron. vicinal a often showing crystals sometimes green; used as a gem. (6)Colophonite, brilliant diamond-like luster, with variety emerald-green o in color resinous in luster, brown granularkind, brownish yellow to dark reddish a coarse after the resin (from colophony, (c) Melamte and usually with iridescent hues; named here included. but all black garnet is not dull or lustrous; either black] black, ueXas from some (d) Dark green garnet,not distinguishable Pyreneiteis grayishblack melanite. trials. chemical allochroite except by a (a) Rothoffite.The originalallochroite was Calcium-iron Garnet, Manganesian 2 of fine-grainedmassive brown and reddish color, brown of or manganesian iron-garnet to liver-brown. from Langban, Sweden, is similar,yellowish brown Rothoffite, structure. and dark, dusky green and black, are light iron-garnet of kinds manganesian Other common nace is a massive brownish yellow kind, from Franklin Furand often in crystals.Polyadelphite of magnesia. amount contains a large (6)Apfrom Sala,Sweden, J. N. Bredbergite, to lome (properlyhaplome) has its dodecahedral faces striated parallel the shorter diagonal, the cube; and as this form is simpler form was fundamental the that inferred whence Haiiy derived from airXoos, simple. Color of the original than the dodecahedron, he gave it a name and brownish also found yellowishgreen d ark unknown brown; locality) aplome (of in Siberia. at Schwarzenberg in Saxony, and on the Lena green hence 3. Titaniferous.Contains titanium and probably both TiO2 and Ti2O3; formula Color black. schorlomite. It thus graduates toward 3Ca6.(Fe,Ti,Al)2O3.3(Si,Ti)O2. Contains yttriain small amount; rare. Calcium-iron Garnet. 4. Yttriferous Calcium-iron

Simple

1

lime' Includes-

Calcium-chromium Garnet. Uwarowit. Ouvarovite. chromium lime Silica 30*6, sesquioxide Formula 3CaO.Cr203.3SiO2 35'9, in H. the 7 '5. chromium of the takes Aluminium 100. 33-5 place part. F.

UVAROVITE.

=

=

=

G.

3-41-3-52.

=

Color

emerald-green.

3 black glass; F. or varieties of garnet fuse easilyto a lightbrown Pyr. but uvarovite,the and grossularite; 3 '5 in andradite and pyrope; in almandite,spessartite, Andradite F. 6. and almandite fuse to a magnetic chrome-garnet,is almost infusible, Almost all kinds react for iron; globule. Reactions with the fluxes vary with the bases. in other varieties;a chromium and less marked reaction in spessartite, strong manganese Some varieties are partiallydecomposed by reaction in uvarovite,and in most pyrope. acids; all except uvarovite after ignitionbecome soluble in hydrochloricacid,and generally yieldgelatinoussilicaon evaporation. Decomposed on fusion with alkaline carbonates. Thus The density of garnets is largelydiminished by fusion. a Greenland garnet fell from 3'63 to 2'95. from 3'90 to 3'05 on fusion,and a Vilui grossularite Diff. Characterized by isometric crystallization, cahedrons usually in isolated crystals,dodeguished or trapezohedrons; massive forms rare, then usually granular. Also distinkinds the fusibility.Vesuvianite by hardness,vitreous luster,and in the common Fuses more easily,zircon and quartz are infusible;the specificgravity is higher than for tourmaline,from which it differs in form; it is much harder than sphalerite. Micro. Distinguishedin thin sections by its very high relief;lack of cleavage; isoof not readilytold from some tropiccharacter;usuallyshows a pale pink color; sometimes the spinels. Artif. While members of the garnet group their synthehave been formed artificially sis is difficult. Apparently they can be produced only under exact conditions of temperature and pressure that are difficultto reproduce. Natural garnets when fused break down into various other minerals. Obs. Grossularite is especiallycharacteristic of metamorphosed impure calcareous rocks,whether altered by local igneous or generalmetamorphic processes; it is thus commonly found in the contact zone of intruded igneous rocks and in the crystalline schists. Almandite is characteristic of the mica schists and metamorphic rocks containing alumina and iron; it occurs also in some igneous rocks as the result of later dynamic and metamorphic it forms with the varietyof amphibole called smaragdite the rock eclogite. processes; characteristic of such basic igneous rocks as are formed from magmas Pyrope is especially containing much magnesia and iron with littleor no alkalies, the peridotites, as dunites, etc.; also found in the serpentinesformed from these rocks; then often associated with spinel,chromite, etc. in graniticrocks,in quartzite, Spessartite occurs in whetstone schists (Belgium) ; it has been noted with topaz in lithophyses in rhyolite(Colorado). The black variety of andradite, is common in eruptiverocks,especially melanite, with nephelite, leucite, etc.

"

Most

=

=

"

*

"

"

"

thus

in

phonohtes,leucitophyres, : in nephelinites

such

cases

often titaniferous

or

associated

509

SILICATES

in zonal intergrowth;it also occurs as a product of Demantoid in serpentine. Uvarovite belongs occurs metamorphism. particularly also in granular limestone. with chromite in serpentine; it occurs Garnet crystalsoften contain inclusions of foreignmatter, but only in part due to alteration; epidote,quartz (Fig.486, p. 180); at times the garnet is a as, vesuvianite,calcite, mere shell,or perimorph,surrounding a nucleus of another species. A black garnet from Arendal, Norway, contains both calcite and epidote; Tvedestrand, Norway, are wholly calcite crystals from within,there being but a thin crust of garnet. Crystals dodecahedrons with a from East Woodstock, Me., are thin shell of cinnamon-stone enclosingcalcite;others from Raymond, Me., show successive layers of garnet and have been noted. calcite. Many such cases Garnets are often altered,thus to chlorite, serpentine; sometimes to limonite. Crystals of pyrope are even surrounded (kelyphiteof Schrauf) by a chloritic zone in Fig. 847. not homogeneous, as shown Among prominent foreign localitiesof garnets, besides the following GROSSthose already mentioned, are

with

a

titaniferous garnet, sometimes

contact

"

ULARITE:

the

Fine

Mussa-Alp

from

Ceylon; on with Piedmont, Italy, Zermatt, Switzerland;

cinnamon-stone comes in the Ala valleyin

and diopside; at at Kimito in Finland; honeypale yellow at Auerbach, Germany; brownish (romanzovite) yellow octahedrons in Elba; pale greenishfrom the banks of the Vilui in Siberia,in serpentine Cziklowa and Orawitza in the Banat, Hungary; with vesuwith vesuvianite; also from vianite in and wollastonite in ejected masses at Vesuvius; in white or colorless crystals Tellemark, in Norway; also dark brown at Mudgee, New South Wales; dark honey-yellow at Guadalcazar, and clear pink or rose-red dodecahedrons at Xalostoc, Morelos, Mexico, xalostocite and rosolite. called variously,landerite, In serpentine (from peridotite)near PYROPE: Meronitz and the valley of Krems, in Bohemia gings (used as a gem); at Zoblitz in Saxony; in the Vosges Mts.; in the diamond digin granite,gneiss,eclogite, of South Africa ("Cape rubies"). ALMANDITE: Common localitiesin Saxony, Silesia, etc.; at Eppenreuth near Hof, Bavaria; in large etc.,in many at Falun in Sweden; hyacinth-red or brown in the Zillertal, dodecahedrons Tyrol, Austria. in fine crystalsfrom Ceylon,Pegu, British India,Brazil,and Greenland. Precious garnet comes mont, From SPESSARTITE: Aschaffenburg in the Spessart, Bavaria; at St. Marcel, PiedItaly; near Chanteloube, Haute Vienne, France, etc. clinochlore

ANDRADITE:

The

beautiful green

demantoid

or

"Uralian

emerald"

occurs

in transparent

in the gold washings of Nizhni-Tagilskin the Ural greenishrolled pebbles,also in crystals, and at Morawitza at Schwarzenberg,Saxony; brown to green Mts.; green crystalsoccur Dognacska, Hungary; emerald-green at Dobschau, Hungary; in the Ala valley,Piedmont, at Italy,the yellow to greenishtopazolite.Allochroite, apple-green and yellowish,occurs also brown, at Vesuvius on Mte. Somma; Zermatt, Switzerland; black crystals(melanite), berg at Schwarzennear Bareges in the Hautes-Pyrenees,France, (pyreneite).Aplome occurs in Saxony, in brown to black crystals. Other localitiesare Tyrol, Austria; Pfitschtal, Found at SaraUVAROVITE: Langban, Sweden; Pitkaranta,Finland; Arendal, Norway. Bisersk,also in the vicinityof Kyshtymsk, Ural Mts., in chromic iron; at novskaya near Jordansmuhl, Silesia;Pic Posets near Venasque in the Pyrenees on chromite. In North America, in Me., beautiful crystals of cinnamon-stone (withvesuvianite)occur at Parsonsfield, In N. H., at Hanover, small Phippsburg,and Rumford, at Raymond. In Ver.,at New clear crystalsin gneiss; at Warren, cinnamon Fane, garnets; at Graf ton. in chlorite slate. In Mass., in gneissat Brookfield; in fine dark red or nearly black trapein mica zohedral crystalsat Russell,sometimes very large. In Conn., trapezohedrons, slate,at Reading and Monroe; dodecahedrons at Southbury and Roxbury; at Haddam, crystalsof spessartite. In N. Y., brown crystalsat Crown Point, Essex Co.; colophonite Essex Co.; in Middletown, Delaware as a largevein at Willsboro, Co.,largebrown crystals; a cinnamon variety at Amity. In N. J.,at Franklin,black,brown, yellow,red, and green In Pa., in Chester dodecahedral the Franklin Furnace garnets; also near (polyadelphite] in at Chester, brown; Co., at Pennsbury, fine dark brown crystals;near Knauertown; in Leiperville, Concord, on Green's Creek, resembling pyrope; red; at Mineral Hill,fine brown; at Avondale quarry, fine hessonite; uvarovite at Woods' chrome mine, Lancaster In Va., beautiful transparent spessartite, Co. used as a gem, at the mica mines at Amelia ings Court-House. In N. C., fine cinnamon-stone at Bakers ville;red garnets in the gold washof Burke, McDowell, and Alexander counties; rhodolite in Macon Co.; also mined near .

510

MINERALOGY

DESCRIPTIVE

"

and as In garnet-paper." Co., to be used as "emery," Warlich, Burke In Ark., at Magnet Cove, a titaniferous the peridotite of Ellis Co. crystals altered to chlorite occur at the schorlomite. melanite with Large dodecahedral at Nathrop, In fine spessartite crystals Mich. Lake Col., iron Mt. Superior, mine, Spurr crystals at Ruby Mt., Salida, Chaff ee Co., in lithophyses in rhyolite; in large dodecahedral In Ariz.,.yellow-green crystals in the Gila canon; the exterior altered to chlorite. pyrope in the western river M., fine pyrope the part of the territory. N. the Colorado on on In Cal., with with chrysolite and a chrome-pyroxene. Navajo reservation green copper Idria. Fine Co.; uvarovite, in crystals on chromite, at New Valley, El Dorado ore, Hope and Morgantown Ky., fine pyrope

in

in diameter in the mica occur schists at crystals of a rich red color and an inch or more of the Stickeen river, in Alaska. Wrangell, mouth dark In Canada, at Marmora, red; at Grenville, a cinnamon-stone; an emerald-green millerite and calcite; fine colorless to pale olivechrome-garnet, at Orford, Quebec, with brownish Co., Quebec, with white pyroxene, crystals, at Wakefield, Ottawa or honeygreen, dark red carrying chromium; yellow vesuvianite, etc., also others bright green garnet in the townships of Villeneuve at Hull, Quebec. (spessartite) and Templeton; Use. and The various colored used are transparent garnets as semiprecious gem Fort

"

At

s'ones.

times

the

Schorlomite.

mineral

black, with From Magnet

massive,

conchoidal

3*88.

Cove,

Partschinite. H.

=

6-5-7.

G.

=

used

is also

analogous

Probably

fracture in

Ark.;

as

to

an

abrasive.

3CaO.(Fe,Ti)2O3.3(Si,Ti)O2.

garnet, and

vitreous

nepheline-syenite

(Mn,Fe)3Al2Si3Oi2 like spessartite. 4-006. Color yellowish, reddish,

luster. Ice

on

In

H.

7"7 '5.

River, British

small

From

=

the

dull

Usually

G.

3'81"

=

Columbia.

crystals (monoclinic).

auriferous

sands

of Oldh-

pian, Transylvania. Same

Agricolite. globular forms.

as

From

for

eulytite, Bi4Si3Oi2, but

Johanngeorgenstadt,

Chrysolite

Monticellite

Group.

Chrysolite Hortonolite

(Fe,Mn)2SiO4

Tephroite

Mn2Si04

CHRYSOLITE

calcium, iron

twms

or

semi-

R2Si04.

Orthorhombic

Fe2SiO4

Knebelite

hat

globular

(Fe,Mg,Mn)2SiO4

Fayalite

with

In

GaMgSiO4 Mg2SiO4 (Mg,Fe)2SiO4

Forsterite

The

monoclinic.

Germany.

GROUP

includes

a

series .of orthosilicates

of magnesium

and

They all crystallize in the orthorhombic manganese. but little variation in axial ratio. The prismatic angle is about of the unit brachydome about 60"; corresponding to the latter observed. are The type species is chrysolite (or olivine),which

t^^ the

/"V

comparatively

m

Varylng Pr"Porti"ns rare

magnesium

and

and

iron

is hence silicates

system 50"

and

threefold contains

intermediate

512

MINERALOGY

DESCRIPTIVE

(a) in igneous Obs. Chrysolite(olivine)has two distinct methods of occurrence: of norite,basalt,diabase and gabbro, formed by the crystallization rocks, as peridotite, "

low in silica and

magmas

magnesia; from

rich in

accessory

an

852

component

in

such

rocks

853

rock constituent as in the dunites; until it is the mam increase in amount the olivine may also (6) as the product of metamorphism of certain sedimentaryrocks containingmagnesia In the dunites and peridotitesof igneous origin the in impure dolomites. and silica, as chrysoliteis commonly associated with chromite,spinel,pyrope, etc.,which are valuable from olivine. In the metamorphic indications also of the originof serpentinesderived rocks the above are wanting, and carbonates,as dolomite,breunnerite, magnesite, etc., rocks of this latter kind may the common also occur altered are associations;chrysolitic to

serpentine. Chrysolite also

in some embedded in grains,rarely crystals, meteoric irons. occurs Also present in meteoric stones, frequentlyin sphericalforms, or chondrules,sometimes made up of a multitude of grains with like (or unlike)opticalorientation enclosingglass between. Vesuvius in lava and on Monte Somma in Among the more prominent localities are: ejectedmasses, with augite,mica, etc. In Germany observed in the so called sanidine bombs at the Laacher of See; at Forstberg near May en in the Eifel and forming the mass "olivine bombs" Daun in the Dreiser Weiher near in the same region; at Sasbach in the Baden Kaiserstuhl, (hyalosiderite)In crystalsof gem-quality from Egypt. In Sweden, with ore-deposits, at Langban, Pajsberg,Persberg,etc. In serpentineat Snarum, Noras way, in largecrystals, themselves altered to the same mineral. Common in the volcanic rocks of Sicily, the Hawaiian Islands,the Azores, etc. In the United States,in Thetford and Norwich, Ver.,in boulders of coarselycrystallized the crystalsor masses several inches through. In olivine-gabbroof Waterville,in basalt, the White Mts., N. H.; at Webster, in Jackson Co., N. C., with serpentineand chromite; with chromite in Loudon Co., Va.; in Lancaster Co.,Pa. In small clear olive-greengrains with garnet at some In basalt in Canada, near points in Ariz, and N. M. Montreal, at Rougemont and Mounts Royal and Montarville, and in eruptive rocks at other points. Alteration of chrysolite often takes placethrough the oxidation of the iron; the mineral becomes brownish or reddish brown and iridescent. The end in leaving the process may cavity of the crystalfilledwith limonite or red oxide of iron. A very common kind of alteration is to the hydrous magnesium silicate, serpentine,with the partialremoval of the iron its separation in the form or of grains of magnetite, also as iron sesquioxide; this change has often taken place on a largescale. See further under serpentine, 573. p. Chrysolite is named from xpvris,gold,and Al0os. The from hyalosiderite, oaXos, and iron. glass, The chrysolithus o-iSrjpos, of Pliny was probably our topaz ; and his topaz .

our

chrysolite. The clear, fine

Use.

"

T^Y-*

Fr"m

exact chrysolite,

cleavable^G

green

r"ck

*the

varieties

are

of ?armeloite

used

as

Carmelo

composition undetermined.

h*

a

stone; usually caUed peridot. gem Bay, Cal.; a silicate resembling an Has been noted as a pseudomorph

Bohemia. Mittelgebirge'

Orthorhombic,foliated

and

513

SILICATES

The p.

510.

of the ChrysoliteGroup axial ratios of the other members The speciesare brieflycharacterized as follows:

are

given in the table

on

Occurs in colorless to gray crystalson Mte. Somma, vius; VesuCaMgSiO4. Mt. stone on Monzoni, Tyrol, Italy; in crystalsor grains in lime(batrachite) 3'03-3'25. at Magnet Cove, Ark. G. Optically Indices,1 '651-1 '668. In embedded Glaucochroite. CaMnSiO4. prismatic crystals. Crystal constants and those of ChrysoliteGroup. Found Color, delicate bluish green. opticalpropertiesnear at Franklin 3 '4. G. Furnace, N. J. H. =6. Forsterite. Mg2SiO4. Occurs in white crystalsat Vesuvius; in greenish or yellowish 3'21-3'33. G. 1'659. embedded Optically +. grains at Bolton, Mass, (boltonite). ft In Hortonolite. Occurs at (Fe,Mg,Mn)2SiO4. rough dark-colored crystalsor masses. the iron mine of Monroe, Orange Co., N. Y. ; Iron Mine Hill,Cumberland, R. I. G. 3'91. Optically Indices, 1768-1 '803. the Mourne Mts., Ireland; the Azores; the Yellowstone Fayalite. Fe2SiO4. From From Cuddia Mida, Island of Pantelleria, Park; Rockport, Mass., etc. Italy. Crystals and massive, brown G. 4'1 Optically to black on Indices,1 '824-1 '874. exposure. variety found at Sodermanland, Sweden. Manganfayalite is a manganese 4-1. Knebelite. G. (Fe,Mn)2SiO4. From Dannemora, and elsewhere in Sweden. in the From with Hill and also zinc, varietyroeppetite. Sterling Tephroite. MnoSiO4; Franklin Furnace, N. J.; also from Sweden; from Benderneer, New Color South Wales. flesh-red to ash-gray. G. 41. Index about T80. Optically Monticellite. in masses

=

-.

=

=

=

=

-.

=

"

.

=

=

"

.

Phenacite

Group.

Willemite Troostite

Zn2SiO4

Phenacite

Be2SiO4

Tri-rhombohedral

R2Si04.

rr' 64" 30'

0-6775

63"

0-6611

c

(Zn,Mn)2SiO4 24'

includes the above orthosilicates of zinc (manGROUP PHENACITE ganese) class of the and beryllium. Both belong to the tri-rhombohedral rhombotrigonaldivision of the hexagonal system, and have nearlythe same hedral angle. The rare speciestrimerite,MnSiO4.BeSiO4, which is pseudois probably to be regarded as connectingthis group with hexagonal (triclinic) the precedingChrysoliteGroup. The

The

followingrare

Dioptase

speciesare

related: rr' 54" 5' 56" 17' 53" 49'

Tri-rhombohedral

H2CuSiO4

H7(MnCl)Mn4(SiO4)4 Pyrosmalite H7( (Fe,Mn)Cl)(Fe,Mn)4(SiO4)4 Friedelite

c

0'5342 0'5624 0'5308

These in the above axial ratios; to each other in form, as shown speciesare very near They are also they further approximate to the speciesof the Phenacite Group proper. and themselves in composition,since they are all acid orthosilicates, closelyrelated among in the latter have the general formula H2RSiO4 H8R4(SiO4)4,where (e.g.for Friedelite) form the place of one hydrogen atom is taken by the univalent radical (MnCl). =

WILLEMITE.

Axis c 0*6775; rr' (1011) A (IlOl) 64" 30'; eer (0112) A (1012) 36" 47'. In hexagonal prisms,sometimes long and slender,again short and stout; rarelyshowing subordinate faces distributed accordingto the phenacite type. Also massive and in disseminated grains;fibrous. N. J.-;a (1120)easy, N. J. Cleavage: c (0001) easy, Moresnet; difficult, 3 -89-4 -18. Luster Brittle. H. 5'5. G. Fracture conchoidal to uneven. Tri-rhombohedral.

=

=

=

=

=

MINERALOGY

DESCRIPTIVE

514

Color white or greenishyellow,when purest; rather weak. vitreo-resinous, often dark brown flesh-red, grayishwhite, yellowishbrownapple-green,

Figs.854-857, New

=

Jersey,

e

impure. Streak uncolored.

when "o

856

855

854

1-693.

Comp.

Zinc

"

oxide 73*0

100.

=

Transparent

to

Optically+

opaque.

.

1712.

=

e

x (3121). (0112),s (1123),u (2ll3),

Silica 27-0, zinc Zn2Si04 or 2ZnO.Si02 orthosilicate, Manganese often replacesa considerable part of the zinc =

and iron is also present (introostite),

in small amount.

in the forcepsglows and fuses with difficulty to a white enamel; the Jersey fuse from 3 '5 to 4. The powdered mineral on charcoal in R.F. givesa coating,yellow while hot and white on cooling,which, moistened with solution of With soda the coating is more cobalt,and treated in O.F., is colored bright green. readily Soluble in hydrochloricacid and yieldsgelatinoussilica upon obtained. evaporation. Obs. From Altenberg near Aix-la-Chapelle. Moresnet, Belgium; at Stolberg,near From In N. J. Musartut, Greenland; Mindouli, French Congo; Kristiania,Norway. at Mine Hill,Franklin Furnace, and at SterlingHill,two miles distant. Occurs with zincite and franklinite, varying in color from white to pale honey-yellowand lightgreen to dark sometimes Rare at the Merritt in largereddish crystals(troostite). ash-grayand flesh-red; mine, Socorro Co., N. M.; also at the Sedalia mine, Salida,Col. Named by Levy after William I.,Kinfc of the Netherlands.

Pyr.,etc.

B.B.

"

varieties from

New

"

Use.

"

An

ore

of zinc.

PHENACITE.

Tri-rhombohedral.

Axis

c

=

0-6611; rr' (1011) A

Crystalscommonly rhombohedral 858

Miask.

in

(1101) 63" 24'. habit,often lenticular in form, the =

859

Florissant. Col.

prismswanting; also prismatic, sometimes terminated of the third series, x (seefurther, pp. 110-112).

860

Mt.

Antero, Col.,Pfd.

by the rhombohedron

515

SILICATES

(1120) distinct;r (1011) imperfect. Fracture conchoidal. 2-97-3-00. G. Luster vitreous. Colorless; also brown. Transparent to subtranslucent brightwine-yellow,pale rose-red; 1'6697. co 1'6540; e Optically+ Be2SiO4 or 2BeO.SiO2 Silica 54*45, Berylliumorthosilicate, Comp. gluCleavage:

Brittle.

H.

=

a

7 '5-8.

=

=

=

.

=

"

cina 45-55

100.

=

Alone

"

unaltered;

with

borax

soda

affords

fuses with extreme slowness,unless a white enamel; with more, intuinfusible. Dull blue with cobalt solution. and becomes mesces Occurs at the emerald and chrysoberylmine of Takovaya, 85 versts east of EkaObs. terinburg, Ural Mts.; also in the Ilmen in the Framont Mts., near Miask, Russia; near Vosges Mts.; Kragero, Norway; at the Cerro del Mercado, Durango, Mexico; crystals from San Miguel di Piracicaba,Minas Geraes, Brazil. In Col.,on amazon-stone, at Topaz Butte, near 16 miles from Pike's Peak; Florissant, also on quartz and beryl at Mt. Antero, Chaffee county. Occurs at Chatham, N. H. in allusion to its having been mistaken from Named for quartz. a deceiver, (j""va",

Pyr., etc. pulverized,to

remains

transparent glass. With

a

"

Trimerite. (Mn,Ca)2SiO4.Be2SiO4. In thick tabular prismatic crystals, pseudoand angle. H. 6-7. in form G. 3 '474. Color salmon-pink to hexagonal (triclinic) From the Harstig Indices,1715-1 725. nearly colorless in small crystals. Optically". mine, Wermland, Sweden. =

JDioptase. H2CuSiO4

or

H2O.CuO.SiO2.

=

Commonly

in

prismatic crystals(ssr0221 Cleavage: r (lOTl)perfect.

Also in crystalline aggregates; massive. H. 5. conchoidal to uneven. G. Fracture vitreous. Color emerald-green. Opti3 '28-3 '35. Luster cally 1-707. 1-654. +. e co in druses of well-defined crystalson Occurs quartz, in a compact limestone west of the hill occupying seams of Altyn-Tiibe in the Kirghiz Steppe, Russia; in the gold washings at several points in Siberia; atRezbanya, A

=84"

2021

33$') "

=

copper

leagues east

In fine crystals at the of Comba, in the French

the copper Metcalfe and

near

Plancheite.

Mine

other

Mindouli, two

Congo State. Also Co., and from Clifton,Graham Florence,Ariz. H2Cu7(Cu.OH)8(SiO3)i2. Fibrous, often

mines

at

quartz with

Copiapo, Chile, on

From

ores.

861

=

=

Hungary.

=

of

Found associated with dioptase,etc.,at Mindouli, 3'4. mammillary. Blue color. G, French Congo. Friedelite. H7(MnCl)Mn4Si4Oi6. Crystalscommonly tabular \\c (0001); also massive, the manganese Color rose-red. From H. 3'07. 4-5. G. cleavable to closelycompact. of Adervielle,vallee du Louron, Hautes mine Pyrenees, France; from Sjo mine, Wermland, Sweden; from Franklin Furnace, N. J. Crystals thick hexagonal prisms or H7((Fe,Mn)Cl)(Fe,Mn)4Si4Oi6. Pyrosmalite. 3*06-3'19. Color blackish green to 4-4'5. G. tabular; also massive, foliated. H. land in Wermpale liver-brown or gray. Index about 1'66. From the iron mines of Nordmark and at Dannemora, Sweden. =

=

=

=

Scapolite Group. Meionite Wernerite

c c

=

Tetragonal-pyramidal

0-4393

Mizzonite, Dipyre

c

=

=

=

0-4384

Marialite

c

=

0-4424 0-4417

in the pyramidalclass of speciesof the SCAPOLITE GROUP crystallize axial ratio. They are white or the tetragonalsystem with nearly the same grayish white in color, except when impure, and then rarelyof dark color. The

516

MINERALOGY

DESCRIPTIVE

Hardness aluminium

5-6*5; G.

=

in

sodium

and

calcium

with

composition they are silicates of varying amounts; chlorine is also traces. Iron, magnesia, potash are not In

2-5-2-8.

=

only in present, sometimes of inclusions or of alteration. Carbon dioxide and present unless by reason sulphur trioxide have been noted in certain analyses. It has been suggested often

that these radicals enter

into the

composition in

the

same

manner

as

the

chlorine. are analogousto the Feldsparsin that they form a series Scapolites of silica increasing with gradualvariation in composition,the amount the increase of the alkali, soda, being40 p. c. in meionite and 64 p. c. in marialso in the amount of chlorine alite. A correspondingincrease is observed is also in Furthermore there a gradual present. change specific gravity,in and in resistance to acids, the strengthof the double refraction, from the easily which is only slightly 2-72, to marialite, decomposed meionite,with G.

The

with

a

=

attacked

has G. be composition may compounds, viz.:

has shown that the variation in Tschermak of two fundamental end explainedby the assumption

and

2-63.

=

Meionite

Ca4Al6Si6025

Me

Marialite

NaiAlgSigC^Cl

Ma

By the isomorphous combination of these compounds the compositionof the speciesmentioned above may be explained;no sharp line can, however, be drawn between them. the series is characterized by the decrease in the strength of the double Optically tion in passing from meionite to marialite. Thus (Lacroix)for meionite " e for typicalwernerite 0'03-0-02; for dipyre 0'015. =

"

The

more

0'036' '

tetragonalspecies melilite and

angle. The

refrac-

gehleniteare

near

the

in Sca*polites

vesuvianite is also related.

common

MEIONITE.

0-43925. In prismatic crystals(Fig.201,"p.86), Tetragonal. Axis c glassyor milky white; also in crystalline grainsand massive. Cleavage: a (100)rather perfect, somewhat m less Fracture con(110) so. =

either clear and

choidal. Brittle. H. 5-5-6 to white. Transparentto

G.

=

-.

=

co

1-597; e

Comp. hme

25' 1

=

2-70-2-74.

Luster

vitreous.

translucent;often cracked within.

1-560.

=

Ca4Al6Si6025or4CaO.3Al2O3.6Si02 Silica 40-5, alumina

"

less Color-

Opticallv

=

34-4,

100.

=

The

varieties included here from nearly pure meionite to those consisting:of range and marialite in the ratio of 3 : Me 3 : 1. No : Ma 1, i.e., sharp line can be drawn between meionite and the following s pecies. Obs. Occurs in small crystals in cavities,usually in limestone blocks, on Monte bomma Vesuvius. Also in ejectedmasses at the Laacher See,Germany. A mineral in rneiomte

=

"

h"^11 "\neiSu basal cleavagehas been

m

WERNERITE.

*h"lBlack Foi"est, Germany,

COMMON

is like meionite

except for

a

SCAPOLITE.

Tetragonal-pyramidal. Axis

c

=

0-4384.

Crystals prismatic, usuallycoarse, with f the

which

called pseudomeionite.

pyramidal class sometimes

uneven

shown

faces and often large. The in the development of the

517

SILICATES

faces

(311) and

z

(131). Also massive,granular,or with

zx

sometimes

appearance;

eer, rr',

101

A

111

A 111

mr,

110

A

111

A

311

zz'", 311

a

faint fibrous

columnar. Oil

=

32" 59'.

=

43" 45'.

=

=

58" 12'. 29" 43'.

tinct, Cleavage: a (100) and m (110) rather disbut interrupted.Fracture subconchoidal. Brittle.

H.

=

5-6.

G.

=

2-66-273.

Luster

to resinous; pearly externally, inclining cross-fracture surface cleavage and Color white, gray, bluish,greenish, vitreous. and reddish, usually light;streak uncolored. 1-570. Transparent to faintlysubtranslucent. Optically", co 1-549. e Intermediate between meionite and marialite and correspondComp. ing

vitreous

to

=

=

"

of these in a ratio 3 : 1 to 1 : 2. combination to a molecular The silica varies from 46 to 54 p.c., and as its amount increases the soda and chlorine with silicafrom 54 p. c. to 60 p. c. are classed with also increase. Scapolites mizzonite;they correspond to Me : Ma from 1 : 2 to 1 : 3 and upwards. The percentage compositionfor a common compound is as follows: Me

:

Ma

3

:

1

SiO2 46*10

A12O3 30'48

CaO

Na2O

19'10

3'54

Cl 1 -01 =100*23

fuses easilywith intumescence to a white blebby glassgivinga strong flame color. Imperfectly decomposed by hydrochloric acid. Diff Characterized by its square form and prismatic cleavage (90"): resembles the cleavagesurface; feldsparwhen massive, but has a characteristic fibrous appearance on it is also more fusible,and has a higher specificgravity; also distinguishedby fusibility from with intumescence (which see, p. 478). pyroxene Micro. Recognized in thin sections by its low refraction;lack of color; rather high interference-colors reaching the yellows and reds of the firstorder,sections showing which of basal sections extinguishparallelto the cleavage; by the distinct negative axial cross which show the cleavage-crackscrossingat rightangles.

Pyr., etc.

"

B.B.

sodium

"

.

"

in metamorphic rocks, crystalline Occurs gneisses,amphibolites and schists, its junction with the associated graniticor abundantly in granular limestone near in beds of magnetite accompanying limestone. allied rocks; sometimes It is often associated with a light-colored amphibole, garnet, and also with apatite,titanite, pyroxene, associate than pyroxene, but in some has resulted zircon; amphibole is a less common cases from the alteration of pyroxene. Scapolitehas been^sjjownalso to be frequently. a ponent comof basic igneous rocks, especiallythose rich in plaglOuLiuLj much uiwitaining lime; it is regarded as a secondary product through a certain kind of.alteration. The scapolites of mica, more are easily altered; pseudormorphs rarely other minerals, are mon. comObs.

"

most

Prominent

localities are at Pargas, Finland, where it occurs in limestone; Arendal in with magnetite in limestone. Malsjo in Wermland, Sweden, where it occurs The pale blue or gray scapolitefrom Passauite is from Obernzell,near Passau, in Bavaria. Lake in Ver., at MarlBaikal, Siberia,is called glaucolite.In the United States,occurs In Mass., at Bolton; at Chelmsford. In N. Y. in Orange Co., Essex borough, massive. In N. J.,at Co., Lewis Co.; Grasse Lake, Jefferson Co.; at Gouverneur, in limestone. In Pa., at the Elizabeth mine, French Franklin and Newton. Creek, Chester Co. In Canada, at Calumet Island,massive; at Grenville;.Templeton; Wakefield,Ottawa at several points. Co.; at Bedford and Bathurst, Ont : Scapoliterocks occur Mizzonite. Here included are scapoliteswith 54 to 57 p. c. SiO2,correspondDipyre. ing

Norway, and

from molecular combination a in clear crystalsin ejectedmasses

Me

Ma Mte.

Me 1:3. : Ma Mizzonite Vesuvius. in elongated square prisms, often slender,sometimes large and coarse, in Dipyre occurs limestone and crystalline way; schists,chieflyfrom the Pyrenees; also in diorite at Bamle, Norless Saint-Nazaire,France; Algeria. Couseranite from the Pyrenees is a more or altered form of dipyre. to

occurs

on

:

=

1

:

2

Somma,

to

=

MINERALOGY

DESCRIPTIVE

Theoretically Na4Al3Si9O24Cl, see

Marialite actual

iinerkl correspondsto

Me

:

Ma

=

1

:

4.

516. p. It occurs

1-541-1- 554. The basalt tuff,at Pianura,

Indices, in

a

Naples.

near

In small (Ca,Na,)3Al2(SiO4)3. Sarcolite. Color flesh-red. Indices,1 '640-1 '656. 2-932.

crystals.H. tetragonal From

Monte

Somma,

G. 6. Vesuvius. =

=

2-545-

MELILITE.

0-4548. Usually in short square prisms (a (100)) Tetragonal. Axis c tables. in tetragonal also octagonalprisms (a,m (110)), or to Fracture conchoidal indistinct. Cleavage: c (001) distinct;a (100) Luster 2-9-3-10. vitreous, incliningto G. 5. Brittle. H. uneven. Pleochroism resinous. Color white, pale yellow,greenish,reddish, brown. anomalies. exhibits optical cally Optidistinct in yellow varieties. Sometimes =

=

=

co

-.

=

1-634.

"

=

1-629.

for melilite. Perhaps R12R4Si9036 or Na2(Ca,Mg)i1(Al,Fe)4(Si04)9 the Fe 1 Al : 1, : percentage compositionis: If Ca : Mg 8:3, and lime 31-3,magnesia 8'4,soda 4'3 11-2, Silica 37-7,alumina 7'1,iron sesquioxide Potassium is also present. 100.

Comp.

"

=

=

=

tures be explained as isomorphous mixcan group composition of the melilite-gehlenite 3CaO.Al2O3.3SiO2 or soda-sarcolite 3Na2O.Al2O3. three compounds, sarcolite, The last is noted in 2CaO.Al2O3.SiO2. 3SiO2; dkermanite, 8CaO.4MgO.9SiO2; velardeiiite, Mexico. from Velardena the in mining district, amount gehlenite large formed Melilite has been artificially by fusing together its constituent Artif. in slagsand has been produced in various artificialmagmas. It is found oxides. B.B. fuses at 3 to a yellowish or greenishglass. With the fluxes reacts for Pyr.,etc. acid and yieldsgelatinoussilica upon evaporation. iron. Soluble in hydrochloric ence-colors, Micro. Distinguishedin thin sections by its moderate refraction;very low interfershowing often the "ultra blue" (Capo di Bove); parallelextinction;negative ture" "peg struccharacter; usual development in tables parallelto the base and very common the basal planes due to parallelrod-like inclusions penetrating the crystal from inward: this,however, is not always easilyseen. Melilite is a component of certain igneous rocks formed from magmas Obs. very low and In in silica, rather deficient in alkalies, containing considerable lime and alumina. in the place of the more melilite appears to crystallize acid plagioclase. such cases Melilite of yellow and brownish colors is found at Capo di Bove, near Rome, in leucitophyre with nephelite,augite,hornblende; at Vesuvius in dull yellow crystals(somervillite) in certain basic eruptiverocks,as the melilite-basalts of Hochbohl not uncommon Owen near in Wurttemberg, of the Swabian also in the Alp, of Gorlitz,the Erzgebirge, Germany; nephelitebasalts of the Hegau, of Oahu, Hawaiian Islands,etc.; perovskite is a common associate. Occurs as chief constituent of rock on Beaver mon Creek, Gunnison Co., Col. Comin furnace slags. Melilite is named from nf"\t, honey, in allusion to the color. Humboldtilite occurs in cavernous blocks on Monte Somma, Vesuvius,with greenishmica, also apatite,augite; the crystalsare often rather large,and covered with a calcareous coating; less common in transparent lustrous crystalswith nephelite,sarcolite, etc., in an augiticrock. Zurlite is impure humboldtilite. Deeckeite is a pseudomorph after melilite with the composition (H,K,Na)2(Mg,Ca)(Al,Fe)2(Si2O6)5.9H2O, found in a melilite basalt from the Kaiserstuhl,Baden, Germany. Cebollite. H2Ca5Al""Si3Oi6. Orthorhombic H. =5. G. 2'96. Color (?). Fibrous. white to greenish gray. Indices,1 '59-1 '63. Fusible at 5. Soluble in acids. Found as alteration product of melilite near an Cebolla Creek, Gunnison Co., Col. Gehlenite. Ca3Al2Si2Oi0. Crystals usually short square 0-4001. prisms. Axis c 2 -9-3 '07. Different shades of grayish to liver-brown. From Mount ygreen Monzoni, the Fassatal, m in Tyrol, Austria. From Velardena mining district, Mexico. FUGGERITE Correspondsto a member of the gehlenite-akermaniteseries,3 ak : 10 geh. The

of the

"

"

"

"

',

=

=

^

=

From

Monzonite

of

Monzonital,Tyrol,Austria.

520

DESCRIPTIVE

MINERALOGY

Micro. Recognizedin thin sections by its high refraction producing a very strong * and relief and its extremely low birefringence; also in generalby its color,pleochroism, of the low birefringence, account uniaxial negativecharacter; the latter, on being difficult it from epidote, The low birefringence, with however, aids in distinguishing to determine. be confounded. which at times it may the ancient ejectionsof Vesuvius first found and Obs. Vesuvianite was the among It commonly its name. occurs as dolomitic blocks of Monte contact a Somma, whence with lime garnet mineral from the alteration of impure limestones,then usuallyassociated diopside,wollastonite;also epidote; also in serpentine,chlorite (grossularite), phlogopite, schist,gneissand related rocks. Prominent localitiesare Vesuvius; the Albani Mts.; in Switzerland at Zermatt, etc.; "

"

in the Fassatal,Austria; valley,in Piedmont, Italy; Mt. Monzoni near Eger in Bohemia Dognaczka, Hungary; Haslau (egeran); near Jordansmiihl,Silesia;on the Vilui river,near Lake Baikal,Siberia (sometimes called wiluite the same like the grossulargarnet from or region); Achmatovsk, Ural Mts.; in viluite, Christiansand; at Morelos, Mexico. Norway; at Arendal, colophonite" ; at Egg, near In North In N. H., at America, in Me. at Phippsburg and Rumford; at Sandford. Warren with cinnamon-stone. In N. Y., near In Lewis Amity. In N. J.,at Newton. and Clark Co., Mon. San Carlos in Inyo Co.; at Crestmore, Riverside Co. In Cal. near In Canada, at Calumet Pontiac Co.; at Grenville in calcite;at Templeton, Falls,Litchfield, Ottawa Co., Quebec. A lavender-colored variety,known as mangan-vesuvianite comes from near Black Lake, Quebec. is a closelycompact variety of an Californite color from olive-greento a grass-green Fresno and Tulare Cos., Cal. Siskiyou, the Mussa

at

Alp

Orawitza

in the Ala

and

"

Zircon

Group.

Zircon Thorite

.

Tetragonal

ZrSi04

c

=

Q'6404

ThSiO4

c

=

0-6402

This group includes the orthosilicates of zirconium and thorium, both alike in tetragonalcrystallization, axial ratio and crystalline habit. .These speciesare sometimes regarded as oxides and then included in the RUTILE GROUP (p.425), to which they approximate closelyin form. A similar form belongs also to the and to the phosphate,Xenotime; further, tantalate, Tapiolite, compound groups consisting of crystals of Xenotime and Zircon in parallel positionare not uncommon (Fig.462, p. 173) .

ZIRCON.

Tetragonal. Axis

871

c

ee',101 ee",101 pp', 111

A

Oil

A A

101 111

uu'

A

331

331

0-64037.

=

=

44" 50'

=

65"

=

16'. 56" 40"'. 83" 9' 872

mp

110

A

111

mu,

110

A

331

xx",

311

A

311

ax,

100

A

311

=

=

=

=

47" 20" 32" 31"

50'. 12"' 57'.

43'.

873

Frequentlyminerals which,like vesuvianite, melilite and zoisite, ing are doubly refractof extremely low and possibly(where they are positivefor one birefringence color

but

521

SILICATES

Twins:

pi.e (101),geniculatedtwins like rutile (Fig.412, p. 166). forms pyramidal. Also in irregular square prisms,sometimes

tw.

Commonly in and grains.

876

875

877 c

'Pi

Colorado

Cleavage: m

(110)imperfect;p (111)less distinct.

Fracture conchoidal. G. 4-68-470 but varyingwidelyto 4 '2 most common, and 4 '86. Luster adamantine. pale yellowish, Colorless, grayish,yellowish reddish brownish Streak uncolored. brown. yellow, Transparent to green, subtranslucent and opaque. Optically+. Birefringence high, co 1-9239, e 1*9682,Ceylon. Sometimes abnormally biaxial. H.

Brittle.

7*5.

=

=

=

=

Hyacinth is the orange, reddish and brownish transparent kind used for gems. Jargon name given to the colorless jor smoky zircons of Ceylon, in allusion to the fact that in luster,they are while resembling the diamond comparativelyworthless;thence came is

a

the

zircon.

name

Silica 32-8, zirconia Zr02.SiO2 littleiron (Fe2O3)is usuallypresent.

Comp.

ZrSi04

"

or

=

67-2

=

100.

A

Infusible; the colorless varieties

are unaltered,the red become colorless, made varieties glow and increase in density white; some by ignition. Not perceptiblyacted upon by salt of phosphorus. In powder decomposed fused with soda on the platinum wire,and if the product is dissolved in dilute hydrowhen chloric tested with turmeric color characteristic of zirconia when acid it gives the orange acted upon Not by acids except in fine powder with concentrated sulphuric acid. paper. and bisulphates. Decomposed by fusion with alkaline carbonates Diff. Characterized by the prevailingsquare pyramid or square prism;also by its the diamond is optically adamantine hardness,high specific gravity,and infusibility; luster,

Pyr., etc.

"

while dark-colored

varieties

are

"

isotropic. Recognized in thin sections by its very high relief;very high interferenceapproach white of the higher order except in very thin sections; positive It is distinguishedfrom cassiterite and rutile only by its lack of color, uniaxial character. the 1-itteralso in many and from cases by method of occurrence. has been prepared artificially Zircon oxide with quartz Artif by heating zirconium Micro.

"

colors,which

"

.

in gaseous Obs.

silicon fluoride.

A common constituent of igneous rocks,especiallythose of the more accessory and particularlythe kinds derived from magmas containing much feldspathicgroups It is one of the earliest minerals to crystallize from a etc. soda, as granite,syenite,diorite, but in pegmatitic facies often in Is generallypresent in minute crystals, coolingmagma. rarely elsewhere,as in granular limestone, large and well-formed crystals. Occurs more in iron-ore beds. in chloritic and other schists;gneiss; sometimes Crystals are common found in volcanic rocks,probably in part as inclusions Sometimes auriferous sands. most "

acid

derived from older rocks. is so Zircon in distinct crystals

common

negative for another),do not show a blue,at times an intense Berlin blue,which

but

scale and

is known

as

the "ultra blue."

in the

pegmatitic forms

of the

nephelite-syenite

crossed nicols but a curious gray color between is quite distinct from the other blues of the color

522

etc.)that this rock there and (with segirite,

Norway

of southern augite-syenite

and

MINERALOGY

DESCRIPTIVE

where else-

zircon-syenite." been called a has sometimes in alluvial sands in Ceylon; in the gold regions of the Ural Mts.; in Norway, at Found and in veins in the augite-syenite Laurvik, at Arendal, in the iron mines, at Fredriksyarn, of the Langesund fiord;Pfitschtal, Tyrol,Austria; in Germany in lava at Niedermendig in "

the Eifel,red crystals;from Madagascar; from Minas Geraes, Brazil. In North America, in Me., at Litchfield;in N. Y., in Moriah, Essex Co., cinnamonand titantite; the outlet of Two at Ponds, Orange Co., with scapolite, near pyroxene red; Co.. in the town of Hammond; Amity; in St. Lawrence Warwick, chocolate-brown,near in the gold sands of In Pa., near Reading. In N. C., abundant at Rossie,Fine, Pitcairn. In Col.,with astroBurke, McDowell, Polk, Rutherford, Henderson, and other counties. In CaL, in auri phyllite, etc.,in the Pike's Peak region in El Paso Co.; at Cheyenne Mt. ferous gravels.

Canada, at Grenville,Argenteuil Co.; Co.,Quebec; in Renfrew Co., sometimes

In

Ottawa

in

Templeton and adjoining townships in large; in North Burgess,Lanark Co. frequently as a gem stone; also as a

very

Zircon in its transparent varieties serves Use. of the incandescent of zirconium oxide used in the manufacture "

source

mantles.

gas

is related but contains uranium, yttrium and Malacon is an altered zircon. Cyrtolite other rare elements. Naegite is apparently zircon with yttrium, niobium-tantalum,thorium, and uranium oxides. brown.

Occurs H.

=

in

spheroidalaggregates

7'5.

G.

Takoyama,

near

Mino, Japan.

Color green, gray

4'1.

=

Thorium Thorite. silicate, ThSiO4, like zircon in form; usually hydrated, black in 4 '5-5; also orange-yellow and- with G. color,and then with G. 5 '19-5 -40 (orangite). the Brevik From region and Arendal, Norway. Auerlite. Like zircon in form; supposed to be a silico-phosphate of thorium. son Hender=

Co.,N.

=

C.

Orthorhombic.

Danburite-Topaz Group. Danburite

CaB2(Si04)2 [Al(F,OH)2]AlSiO4 (A10)AlSiO4

Topaz Andalusite

J

RR2(Si04)2or (RO)RSi04

b

Al2SiO5 Al2Si05

Cyanite a

:

b

: c

0-8994

1

:

:

:

b

c

=

G'5444

:

b

c

=

0-5285

c

=

:

b

: c

=

: a

or

Sillimanite

a a

a

:

f

0'5070 0'9861

Orthorhombic Triclinic 90" 5J',ft

-

07090;

=

a

:b

a

101" 2'

=

0-4807 0-4770 0-4749 0-7025

0-970

=

7

105"

=

:

1

44J'.

DANBURITE.

Orthorhombic.

Axes

a

:

mm'", II',

878

b

: c

=_0'5444: 1

110

A

110

=

120

A

120

=

:

0-4807.

57" 8'. 85" 8'.

dd', 101 ww', 041

A

101

A

041

=

=

82" 53' 3'.' 125"

Habit embedded

prismatic, resemblingtopaz. Also in indistinct and disseminated masses. crystals, Cleavage: c (001) very indistinct. Fracture uneven

in

to subconchoidal. Brittle. H. 3-02. Color pale wine-yellowto dark

Streak

white. .

1-632. i

28-4

G.

2*97-

=

Luster vitreous to brilliant. Transparent to

crystal surfaces

on

translucent. =

7-7-25.

colorless, yellowish white,

wine-yellow,yellowish brown.

greasy, a

=

or

ft

=

1-634.

7

=

CaO.B2O3.2SiO2

=

Optically

-

1-636. Silica 48'8, boron

2V

=

88"

trioxide

523

SILICATES

B.B. fuses at 3'5 to a colorless glass,and imparts a green color to the O. F. Pyr., etc. attacked for the solution (boron). Not decomposed by hydrochloricacid,but sufficiently When to give the reaction of boric acid with turmeric paper. previouslyignitedgelatinizes with hydrochloricacid. Phosphoresces on heating,giving a reddish light. Occurs Obs. at Danbury, Conn., with microcline and oligoclasein dolomite. At Russell,N. Y., in fine crystals. On the Piz Valatscha, the northern spur of Mt. Skopi south of Dissentis in eastern Switzerland, in slender prismatic crystalsand elsewhere in In crystalsfrom Takachio, Hinga, and from Obira,Bungo, Japan. From Switzerland. Mt. Bity and Maharitra, Madagascar. This doubtful BARSOWITE. in the Ural Mts., is species,occurring with blue corundum authors classed with danburite; composition CaAl2Si2Q8 like anorthite. by some "

"

TOPAZ.

Orthorhombic.

Axes

a

b

:

879

110 120 201 043 021

A A

1TO 120

A

201 043

A

021

A

55" 43'.

=

89" 49'. 122"

1'. 64" 55'.

=

:

yy',041 ci, 001

041

^cu, 001

A A

223 111

001

A

221

124"

=

or c

882

Ural

41'.

34" 14'. 45" 35'. 63" 54'.

=

=

"=

Crystalscommonly prismatic, m (110) predominating; or I (120)and the form then a nearly square prism resembling andalusite. Faces in the prismaticzone often vertically and often showing striated, vicinal planes. Also firm columnar; Cleavage:

047698.

uu', 111 uu'", 111 oo', 221

A

Til

A

111

A

221

=

oo'"

A

221

=

221

=

78"

=

39"

105"

20'. 0'. 7'.

49"

37*'.

87" 18'.

=

granular,coarse

:

Durango A

co,

1

881

Japan

=

=

0-52854

=

880

Brazil

mm'", II, dd', XX', //',

: c

883

884

fine.

(001) highly perfect.

Fracture subconchoidal to uneven. Brittle. H. 8. G. 3 -4-3 -6. Luster vitreous. Color straw-yellow, wine=

=

Ural

yellow,white, grayish,greenish, bluish,

Japan

reddish.

Streak uncolored. parent Transto subtranslucent. Optically+. Axial angles variable. 2V 49" to 66". =

For Var.

D

a

=

1-62936

ft

=

1 "63077

Ax.

pi.||6 (010). Bx J_ Brazil: indices,

c

(001).

Refractive 7

=

1 '63747

.'.

2V

=

49" 31'

Ordinary. In prismatic crystalsusually colorless or pale yellow, less often pale blue,pink, etc. The yellow of the Brazilian crystalsis changed by heating to a pale rose-pink. Often contains inclusions of liquidCCV Physalite,or pyrophysalite,is a coarse nearly opaque variety, from Finbo, Sweden; intumesces when from ""waXis, bubble,and heated, hence its name irvp, fire. Pycnite has a columnar,very Rose made out that 'the cleavage was the same, and compact structure. "

524

MINERALOGY

DESCRIPTIVE

probablythe

the form

same;

Des

and

Cloizeaux

that the opticalcharacters

showed

were

those of topaz.

and then [A1(F,OH)]2 (AlF)2SiO4;usuallycontaining hydroxyl Silica 32 '6,alumina 55 '4, former 522. The requires on SiO4 or as given p. 100. 87 deduct (O fluorine 207 2F) 1087,

Comp.

"

=

=

=

in the closed tube, with potassium bisulphategives B.B. infusible. Fused Pyr.,etc. gives a the characteristicfluorine reactions. With cobalt solution the pulverizedmineral attacked by sulphuricacid. A variety of topaz from fine blue on heating. Only partially a pink or red hue, resembling the Balas ruby. Brazil,when heated,assumes Diff. Characterized by its prismaticcrystalswith angles of 56" (124") or 87" (93"); yieldsfluorine B.B. also by the perfectbasal cleavage;hardness; infusibility; Artif. by heating a mixture of silica and aluminium Topaz has been made artificially fluoride and then ignitingthis mixture in silicon fluoride gas. in the highly acid igneous rocks of the granitefamily, Obs. especially Topaz occurs where it appears to be the result of fumarole in veins and cavities, as graniteand rhyolite, sometimes also in the surrounding schists, of the magma; action after the crystallization In these occurrences often accompanied by fluorgneisses, etc.,as a result of such action. tourmaline. in tin-bearingpegmatites. Topaz alters tie,cassiterite, Frequently occurs of muscovite. aesilyinto a compact mass Fine topaz comes from Russia from the Ural Mts., from Alabashka, in the region of Ekaterinburg; from Miask in the Ilmen Mts.; also the gold-washingson the River Sanarka in Govt. Orenburg; in Nerchinsk,beyond Lake Baikal,in the Adun-Chalon Mts., etc.; in the provinceof Minas Geraes,Brazil,at Ouro Preto and Villa Rica, of deep yellow color;in and Germany at the tin mines of Zinnwald Ehrenfriedersdorf,and smaller crystalsat and Altenberg;sky-blue crystalsin Cairngorm, Aberdeenshire,Scotland; Schneckenstein the Mourne in crystalsof mountains, Ireland; on the island of Elba. Physaliteoccurs great size,at Fossum, Norway; Finbo, Sweden. Pycniteis from the tin mine of Altenberg in Saxony; also of Schlackenwald, at Durango, Mexico, Zinnwald, etc. Fine crystalsoccur with tin ore; at San Luis Potosi in rhyolite. Mt. Bischoff, Tasmania, with tin ores; in New South Wales. In Japan in pegmatite from Otani-yama, Province similarly of Omi, Kioto. near In the United States,in Me., at Stoneham, in albitic granite. In Conn., at Trumbull, with fluorite; at Willimantic. In N. C., at Crowder's In Col.,in fine crystals Mountain. colorlessor pale blue from the Pike's Peak region; at Nathrop, Chaff ee Co., in wine-colored in lithophyses in rhyolite;similarly crystalswith spessartite in the rhyoliteof Chalk Mt. In Texas in fine crystalsat Streeter. In Utah, in fine transparent colorless crystalswith quartz and sanidine in the rhyoliteof the Thomas Range, 40 miles north of Sevier Lake. In Col. in Ramona Co. The name topaz is from ro-n-a^os, island in the Red an Sea, as stated by Pliny. But "

"

"

"

the topaz of by Pliny and Use.

"

Pliny was earlier

As

a

gem

not the true

writers,as well

"

topaz,as it yieldedto the file." Topaz was included as under the name by many later, chrysolite.

stone.

ANDALUSITE.

Orthorhombic. 885

Axes

a

:

b

: c

0-9861

=

886

:

1

:

070245.

mm'",

110

A

110

89" 12'.

88'

Oil

A

Oil

70"

10'.

Usually in coarse prismaticforms, the in form. prisms nearly square Massive, imperfectly columnar; sometimes radiated and granular.

Cleavage:

m

sometimes (110)distinct, a (100) less perfect;

perfect (Brazil); b

Fracture uneven, sub(010) in traces. conchoidal. Brittle. H. 7-5. 3'16 G -3 '20. Luster vitreous;often weak. Color whitish, rose-red,flesh-red, violet, pearl-gray,reddish brown, olive-green. =

=

525

SILICATES

Streak uncolored. chroism strong in Sections normal to

Transparent

to opaque, Pleousually sub translucent. colored varieties. some Absorption strong, X " Y " Z. an optic axis are idiophanous or show the polarizationbrushes Ax. pi. distinctly(p. 288). Optically 85". T632. ||b (010). Bx J_ c (001). 2V a "

.

=

=

887

0

1*638.

=

7

=

1-643.

Var. Made is a variety in stout crystals Chiastolite, or having the axis and angles of a different color from the rest, of carbonaceous owing to a regular arrangement impurities and hence exhibitinga colored cross, or through the interior, in a transverse tesselated appearance section. a Fig. 888 shows sections of a crystal. Viridine is a green taining variety coniron and manganese from near many. some Darmstadt, Ger"

100

"

Comp. Silica

Al2SiO5

"

36-8, alumina

sometimes

present,

as

=

(A1O)AlSiO4 63*2 in

or

100.

Al2O3.SiO2

Manganese manganandalusite. =

*z

=

is

B.B. infusible. With cobalt solution gives a color after ignition. Not composed decomposed by acids. Defusion with caustic alkalies and alkaline carbonates. on Diff. Characterized by the nearly square prism, plepchroism,hardness, infusibility; B.B. reaction for alumina Micro. Distinguished in thin sections by its high relief;low interference-colors, which are only slightlyabove those of quartz; negative biaxial character; negative extension of the crystals(difffrom sillimanite) ; rather distinct prismatic cleavage and the constant from pyroxenes, which have also greater birefringence); parallelextinction .(diff. also these are by its characteristic arrangement of impurities when present (Fig.888). The pleochroism, which is often lacking,is,when present, strong and characteristic.

Pyr., etc.

"

blue

"

"

.

888

Most Obs. common in argillaceousschist,or other scnists imperfectlycrystalline; with serpentine. The also in gneiss,mica schist and related rocks; rarely in connection varietychiastolite is commonly a contact mineral in clay-slates, e.g., adjoininggraniticdikes. associated with sillimanite with parallelaxes. Sometimes in Spain, in Andalusia; in Austria in the Tyrol, Lisens Alp; in Saxony, at BraunsFound In Brazil,province of Minas dorf ; Bavaria, at Wunsiedel, etc. Geraes, in fine crystalsand rolled pebbles. Remarkable crystalsof chiastolite from Mt. Howden, near as Bimbowrie, South Australia. N. H., White Mtn. In North America, in Me., at Standish. Notch; Mass., at Westford; Lancaster, both varieties;Sterling,chiastolite. Conn., at Litchfield and Washington. largecrystals;Upper Providence. Co., near Leiperville, Pa., in Delaware from The made Named is from the Latin Andalusia, the first localitynoted. name macula, a spot. Chiastolite is from X"*O"TOS, arranged diagonally,and hence from chi, the Greek for the letter X. name Use. When clear and transparent may stone. serve as a gem "

"

Guarinite. In minute 2(K,Na)2O.8CaO.5(Al,Fe,Ce)2O3.10SiO2. Orthorhombic. thin H. 6'5. G. 2 -9-3-3. tables,flattened ||b (010),nearly tetragonal in form. Color sulphur-yellow,honey-yellow. Pleochroic,canary-yellow to colorless. Found in a grayish Axial ratio and opticalproperties agree closely with trachyte on Mte. Somma, Vesuvius. those of danburite. =

=

DESCRIPTIVE

526

MINERALOGY

Fibrolite.

SILLIMANITE.

110 A 110 88" 15', mm'" 0'970 : 1. in rounded. and striated Commonly faces 230 hh' 230 A in close often parallel terminated; n ot g roups, long slender crystals distinctly passinginto fibrous and columnar massive forms; sometimes radiating. H. 6-7. G. uneven. Cleavage: b (010) very perfect. Fracture Color subadamantine. hair-brown, Luster vitreous,approaching 3-23-3-24. grayishbrown, grayish white, grayish green, pale olive-green.Streak unsometimes distinct. Pleochroism translucent. colored. Transparent to

Axes a : b 69". Prismatic

Orthorhombic. =

=

=

=

Optically+. Dispersionp a

1-638.

=

Comp. 63'2

Double refraction strong. Ax. pi. ||b Axial angle and indices variable. " v.

0 "

1-642.

=

Al2SiO5

=

7

=

(010). 2V

=

Bx

=

c (001). (approx.).

J_

20"

1*653.

Silica 36'8, alumina

(A10)AlSi04, like andalusite.

100.

=

silicates. Both andalusite and Sillimanite is the most stable of the three aluminium when heated. into sillimanite converted strongly are cyanite Same andalusite. as Pyr. Characterized by its fibrous or columnar Diff. form; perfectcleavage; infusibility; reaction for alumina. In thin sections recognized by its form, usually with transverse Micro. fractures; parallel extinction;high interference-colors. Artif. Sillimanite has been made, artificially by fusing its oxides together. Both heated. andalusite and cyaniteare converted into sillimanite when strongly Obs. Often present in the quartz of gneissesand sometimes granitesin very slender, minute prisms commonly aggregated together and sometimes intergrown with andalusite; with corundum. ioliteis also a common associate;rarelyas a contact mineral; often occurs Observed in many in Bohemia; at Fassa in Tyrol, Austria thus near Moldau localities, (bucholziie) (fibrolite} ; in the Carnatic,India, with corundum ; at Bodenmais, Bavaria; Freiberg,Saxony; in France,near Pontgibaud and other points in Auvergne; forms rolled in the diamantiferous sands of Minas masses Geraes, Brazil. In the United States,in Mass., at Worcester. In Conn.; near Norwich, with zircon, monazite and corundum; In N. Y., at Yorktown, Westchester at Willimantic. Co.; in Monroe, Orange Co., (monrolite). In Pa., at Chester on the Delaware, near Queensbury in N. C. forge; in Delaware Co.; Del., at Brandy wine Springs. With corundum Named from the fibrous massive variety; sillimanite. after Prof. Benjamin fibrolite Silliman of New Haven (1779-1864). "

"

"

"

"

worthite probably belong Bamlite,xenolite,

CYANITE.

Kyanite.

to

the sillimanite;

Disthene.

Triclinic. Axes a : b : c 0-8994 105" 44i'. ac, 100 A 001 78"

90" 5|',0 101" 2', : 1 : 07090; a 86" 45'. 30'; be,010 A 001 Usuallyin longbladed crystals, rarelyterminated. Also coarselybladed columnar to subfibrous. Cleavage: a (100)very perfect; b (010)lessperfect ; also H. 5-7 the c parting11 (001). -25; least, 4-5, on a (100) | caxis; 6-7 on a (100) ||edge a (100)/c (001); 7 on b (010). G. 3-56-3-67. Luster vitreous to pearly. Color blue,white; blue along the center of the blades or crystalswith white margins; also gray, black. green, =

7

=

last is altered.

=

=

=

889 ",

^

=

=

=

Streak

uncolored. Translucent to chroism transparent. Pleodistinct in colored varieties. Optically Ax. pi.nearly 1 a (100) and inclined to edge a/b on about a 30", and about 7i" on 6 (010),cf. Fig. 889. 2V 82". 1-717. 1722. B a 1'729. 7 "

.

=

=

=

=

H

MINERALOGY

DESCRIPTIVE

528 G. Color

=5-5-5.

fracture.

=

2-9-3-0. Luster white; sometimes

vitreous,rarelysubresinous

grayish,pale

rarelydirty olive-greenor

green,

a

on

surface of

yellow,red,or

honey-yellow.Streak

white.

thystine, ame-

Trans-

891

890

Bergen Hill

rarelyopaque parent to translucent; 1-625.

|8

1-653.

=

7

=

white.

2V

Optically

-.

=

74".

a

1*669. 893

Andreasberg

Bergen Hill

of varied habit,usually with a greenishtinge. Ordinary. In glassycrystals 64" 47, prismaticand clinodome zones g., 110 A 110 vary but little/e. 66" 37',etc. White opaque 2. Compact massive. cream-colored,pink; while Oil A Oil From the Lake Superiorregion. breakingwith the surface of porcelainor Wedge wood ware. 3. Betryoidal;Botryolite.Radiated columnar, having a botryoidalsurface,and containing but opticallyidentical. water than the crystals, more Var.

1.

"

anglesin

The

the

=

=

Comp.

A

"

HCaBSiO5

or

basic

orthosilicate

of

boron

H20.2CaO.B2O3.2SiO2; this

Silica 37-6,boron

may trioxide 21-8,lime 35-0,water

calcium; empirically Ca(BOH)Si04

and be 5'6

written =

=

100.

In the closed tube givesoff much B.B. fuses at 2 with intumescence water. Pyr.,etc. clear glass,coloringthe flame bright green. Gelatinizes with hydrochloricacid. Diff. Characterized by its glassy,greenish,complex crystals; easy fusibilityand "

to

a

"

green

flame B. B.

Datolite is found chieflyas a secondary mineral in veins and cavities in basic Obs. eruptive rocks, often associated with calcite,prehnite and various zeolites;sometimes associated with danburite; also in gneiss,diorite, and serpentine; in metallic veins; sometimes in beds of iron ore. Found in Scotland, in trap, at the Kilpatrick Hills,etc.; in a bed of magnetite at Arendal in Norway (botryolite) ; at Uto in Sweden; at Andreasberg, Germany, in diabase and in veins of silver ores; in Rhenish Bavaria (the humboMtite) ; at the Seisser Alp,Tyrol,Austria,and at Theiss,near Claussen,Hungary; in geodes in amygda"

529

SILICATES

loid; in Italy,in graniteat Baveno Catini in Tuscany. at Monte In the United States Rocky Hill quarry, In N. Westfield,Mass.

not

Lago Maggiore,at Toggiana in Modena,

near

with

uncommon

the

diabase

of Conn,

and

in serpentine,

Mass.

Thus

at

Hartford, Conn.; at Middlefield Falls and Roaring Brook, Conn.; J.,at Bergen Hill and Great Notch in splendidcrystals;at Paterand the opaque Both crystals in the Lake Superiorregion. compact variety, of a massive daTeurdai, to divide,alluding to the granular structure

the

son, Passaic Co. from Named

variety. (Ca,Fe)3(BO)2(SiO4)2. Crystals often tabular || H. 3'38. 5. G. Color black,blackish brown. Stoko and other islands,in the Langesund fiord,Norway. Index about Found T68. on In prismatic crystals. Cleavage ||6 (010) Euclase. HBeAlSiO5 or Be(AlOH)SiO4. Luster vitreous. Colorless to pale green 7*5. 3'05-3'10. G. blue. or perfect. H. From 1'655. erous Brazil,in the province of Minas Geraes; in the aurif0 Optically +. Ural Mts., near sands of the Orenburg district, southern the river Sanarka; in the Bavaria. Glossglocknerregion of the Austrian Alps; from Epprechtstein,Fichtelgebirge, Gadolinite. Be2FeY2Si2Oi0 or Be2Fe(YO)2(SiO4)2. Crystals,often prismatic, rough Fracture and conchoidal or commonly in masses. Cleavage none. splintery. coarse; 4'24-4 '29 (isotropic Brittle. 6'5-7. H. G. 4'0-4'5;normally 4'36-4 '47 (anisotropic), Color black,greenishblack, and amorphous from alteration). Luster vitreous to greasy. Falun and Ytterby, Sweden; Hittero,Norway; also brown. From also in Llano Co., near and rough crystals, sometimes Texas, in nodular masses up to 40 or 60 pounds in weight. Crystals from Kumak, East Greenland. The gadolinite-earths (partlyreplaced by the oxides of cerium, yttrium earths or and lanthanum didymium) form a complex group which contains considerable erbium, less definite character. elements (ytterbium,scandium, etc.)of more also several new or A and the yttrium metals chiefly. Massive; amorYttrialite. silicate of thorium phous. 4-575. Color on the fresh fracture olive-green, G. changing to orange-yellow Associated with the gadoliniteof Llano Co., Texas. surface. on Rowlandite. An occurring massive with gadoliniteof Llano Co., yttrium silicate, Texas; color drab-green. An Thalenite. yttrium silicate. In tabular or prismatic monoclinic crystals. H. 174. in Sweden Found at Osterby in Dale4'2. Color flesh-red. /3 6*5. G. c

Homilite. (Ca,Fe)3B2Si2Oi0 or (001); anglesnear those of datolite.

=

=

=

=

=

=

=

"

"

=

=

=

=

carlia and

at

Askagen

Color Found

of

=

grayish green in pegmatite

Mackintoshite.

Llano

silicateof the yttrium metals, (Sc,Y)2Si2O7. Orthorhombic. 6-7. G. cleavage. H. large tapering crystals.Prismatic

A

Thortveitite. groups

in Wermland.

to white in Iveland

altered.

when

Usually

translucent.

In radiating =

3*57.

fusible. Difficultly

parish,Satersdalen,Norway. Massive.

Silicate of uranium, thorium, cerium, etc.

Color

black.

Co., Texas.

ii

a.

=

R2(ROH)R2(SiO4)3

or

in

in

ii

ii

R

Ca,Fe;

in

in

ii

in

HR^R3Si3O13 Basic Orthosilicates,

Monoclinic

and

Orthorhombic

Epidote Group.

R

=

in

Al,Fe,Mn,Ce, etc.

Section

Orthorhombic

a

Zoisite

Ca2(AlOH)Al2(SiO4)3 j8. Monoclinic

0'6196

Allanite

Ca2(AlOH)(Al,Mn)2(SiO4)3 (Ca,Fe)2(A10H)(Al,Ce,Fe)2 (SiO4)3

0'3429

Section

mCa2(AlOH)Al2(SiO4)3 Piedmontite

1

1-8036

64" 37'

1-6100

1-8326

64" 39'

1*5509

1-7691

64" 59'

MINERALOGY

DESCRIPTIVE

530

includes the

GROUP

EPIDOTE

The

speciesagree

monoclinic

complex orthosilicates. The the orthprhombic species

above

closelyin form.

them

To

corresponding to

zoisite is also related in angle,its prismaticzone have: Thus we clinic orthodomes, etc. 34'. 63" Epidote 110 110 A Zoisite mm'", =

uu',

.

There

021

021

A

=

68" 54'.

cr,

001

A

101

=

mm',

110

A

110

=

the

63"

mono-

42'.

70"

4',etc.

position be, however, a monoclinic calcium compound, having the comwith ordinary and strictly isomorphous but monoclinic of zoisite,

to

seems

epidote;it is called dinozoisite. ZOISITE.

Axes

Orthorhombic.

J

a

:

b

: c

=

0'6196

:

1

:

0-34295. ^

mm'", dd',

110

A

HO

101

A

101

=

63" 34'.

=

57" 56'.

jf, Oil oo'",111

A

Oil

A

111

=

37" 52'.

=

33" 24'.

and seldom Crystalsprismatic,deeply striated or furrowed vertically, Also massive; columnar to compact. terminated. distinctly to subconchoidal. uneven b (010) very perfect. Fracture Cleavage: the cleavageLuster on 3-25-3-37. vitreous; G. 6-6 -5. H. Brittle. brown, greenish Color yellowish white, grayish gray, face,b (010),pearly. Streak uncolored. rose-red. to apple-green;also peach-blossom-red gray, =

=

Transparent i

to subtranslucent.

Pleochroism strong in (010);also ||c (001). Bx Axial angle variable even

0

=

1-703.

7

=

Ax. pi.usually||b pink varieties. Optically+. _L a (100). Dispersionstrong, p " v; also p " v. 1-700. 0"-60". in the same a crystal. 2V =

1*706.

1. Ordinary. Colors gray Var. prismaticor columnar forms; also in "

=

to

white and brown; also green. Usually in indistinct 3'226-3'381. Unionite is a G.

fibrous aggregates. Thulite. Fragile;

=

pleochroism strong. 3. Compact, zoisite. 2. Rose-red or very pure saussurite of the mineral material known as Includes the essential part of most massive. which has arisen from the alteration of feldspar. in saussurite-gabbro), (e.g., Silica 397, alumina HCa2Al3Si3013 or 4CaO.3Al2O3.6SiO2.H2O Comp. alumina is sometimes The 100. replaced 33-7,lime 24-6,water 2*0 mula. general forby iron,thus graduating toward epidote,which has the same =

"

=

Not posed decomB.B. swells up and fuses at 3-3'5 to a white blebby mass. Pyr., etc. Gives off water with hydrochloricacid. by acids;when previouslyignitedgelatinizes when stronglyignited. Diff. with intumescence; reCharacterized sembles by the columnar structure; fusibility some amphibole. Micro. Distinguishedin thin sections by its high relief and very low interferencecolors;lack of color and biaxial character. From epidote it is distinguishedby its lack of color and low birefringence;from vesuvianite by its color and biaxial character. Thin sections frequentlyshow the "ultra blue" (p.520) between crossed nicols. Obs. in those crystalline Occurs especially schists which have been formed by the dynamic metamorphism of basic igneous rocks containingplagioclaserich in lime. Commonly of the amphiboles (actinolite, one accompanies some smaragdite,glaucophane, etc.); thus in amphibolite, glaucophane schist,eclogite;often associated with corundum. The original zoisite is that of the eclogite of the Saualpe in Carinthia (saualpite] Other localitiesare: Kauris in Salzburg; Sterzing,etc.,in Tyrol, Austria; the Fichtelgebirgein Bavaria; Marschendorf in Moravia; Saastal in Switzerland; the island of Syra, one of the Cyclades,in glaucophane schist. In crystalsfrom Chester, Mass.. Thulite occurs at Kleppan in Tellemarken,Norway, and at Traversella in Piedmont, Italy. "

"

"

"

.

531

SILICATES

Pistacite.

EPIDOTE.

Axes

Monoclinic.

a

:

b

: c

mm'

110

A

110

=

ca,

001

A

100

=

ce,

001

A

101

=

cr,

001

A

101

=

ar'.

100

A

101

=

"

109" 64" 34" 63" 51"

1-5787

:

1

:

1-8036;0_= 64" 37'.

56'. 37'. 43'.

d,

001

A

201

=

co,

001

A

Oil

=

en,

001

A

111

42'.

an"', 100 rm"', 111

A A

111 111

41'.

894

=

=

=

89" 58" 75" 69" 70"

26' 28' 11' 2'

29'

897

tw. lamellae. Crystals often as embedded pi.a (100)common, b at terminated and the ortho-axis one .extremityonly; usuallyprismatic|| in the into acicular the faces a zone (100)/c (001) deeply passing forms; of various striated. Also fibrous,divergent or parallel; granular,particles rock-masses. sometimes fine granular,and forming sizes, Brittle. Cleavage: c (001)perfect;a (100)imperfect. Fracture uneven. H. Luster vitreous; on c (001)inclining to pearly 6-7. 3-25-3-5. G. Color pistachio-green resinous. or or yellowishgreen to brownish green, greenishblack, and black; sometimes clear red and yellow; also gray and grayish white, rarelycolorless. Streak uncolored, grayish. Transparent to generallysubtranslucent. opaque: Pleochroism strong : vibrations 11Z green, Y brown and stronglyabsorbed, Z " Y " X in X yellow. Absorption usuallyY " Z " X] but sometimes in rocks. Often the variety of epidote common exhibits idiophano-usfigures; best in sections normal to an opticaxis,but often to be observed if flattened in natural Crystals(Sulzbach),especially ||r(101). (See p. 288.) Optically-. 2" 56'. Ax. pi. ||b (010). Bx.a.r A c axis Z J_ a (100) nearly. Dispersioninclined, Hence feeble,p " v. strongly marked; of the axes 1'754. 1-729. Axial anglelarge, a /3 7

Twins:

tw.

=

=

-

=

=

-

=

=

1-768. Var. yellowish Epidotehas ordinarilya peculiar green But (pistachio)color, seldom found in other minerals. black on one this color passes into dark and lightshades side and brown the other; red,yellow and colorless on "

"

varieties also

occur.

shade, as described, the )istachio tint rarely Ordinary. Color green of some absent, (d) "corza is epidotesand (c) Granular massive, (a) In crystals, (b) Fibrous, is from the gold washings in Transylvania. The Arendal, Norway, epidote (Arendalite) Delmostly in dark green crystals;that of Bourg d'Oisans,Dauphine, France, (Thallite, Var.

1.

532

MINERALOGY

DESCRIPTIVE

green phiniteOisanite)in yellowish crystalsfrom the auriferous sands from Achmatovsk, Ural Mts.

sometimes crystals, of A

varietyfrom

Puschkinite includes is ordinary epiAchmatite dote

transparent.

Ekaterinburg, Ural

Mts.

Garda,

Hoste

Island,Terra

del

Fuego,

is colorless and resembles zoisite. 2. The Bucklandite from Achmatovsk, Ural Mts., described by Hermann, is black with and differs from ordinary epidote in having the crystalsnearlysymmetrical a tingeof green, 3 '51. G. and not, like other epidote,lengthened in the direction of the ortho-axis. and Carmine-red to straw-yellow,strongly pleochroic; deep crimson 3. Withamite. From 3 '137; in small radiated Glencoe, in groups. 6-6'5; G. straw-yellow. H. but contains littleMnO. referred to piedmontite, Sometimes Scotland. Argyleshire, is a chromium-bearing epidotefrom Tawman, Kachin Hills, Upper Burma. 4. Tawmanite =

=

=

Deep

color and

green

Comp.

the ratio or H2O.4CaQ.3(Al"Fe8)2O8.6SiO2, HCa*(Al,Fe)8Si"Oi8 position: to iron varies commonly from 6 : 1 to 3 : 2. Percentagecom-

"

of aluminium

Al

For

:

strong pleochroism,emerald-green to brightyellow.

Fe

=

3 : 1 SiO2

37'87,A12O3 24'13,Fe2O3 12'60,CaO

23'51, H2O

1'89

=

100

Clinozoisite is an epidote without iron,having the composition of zoisite;fouqueiteis is supposed to contain in Ceylon. Picroepidote from an anorthite-gneiss probably the same Mg in place of Ca. tumescence In the closed tube gives water on strong ignition. B.B. fuses with inPyr., etc. black mass which is generallymagnetic. Reacts at 3-3 '5 to a dark brown or for manganese for iron and sometimes with the fluxes. Partiallydecomposed by hydrochloric with acid. Decomposed on fusion acid,but when previouslyignited,gelatinizes "

with

alkaline carbonates. often by its peculiaryellowishgreen Characterized (pistachio)color ; readily fusible and yieldsa magnetic globuleB.B. Prismatic forms often longitudinally striated, but they have not the angle,cleavageor brittleness of tremolite;tourmaline has no distinct is less fusible (incommon cleavage, forms) and usuallyshows its hexagonal form. Micro. Recognized in thin sections by its high refraction;strong interference-colors risinginto those of the third order in ordinarysections;decided color and strikingpleochroism; also by the fact that the plane of the optic axes lies transverselyto the elongationof the crystals. Obs. Epidote is commonly formed by the metamorphism (both local igneous and of generaldynamic character)of impure calcareous sedimentary rocks or igneous rocks containing much lime. It thus often occurs in gneissicrocks, mica schist,amphibole schist, sandstones and limestones altered by neighboring igneous serpentine;so also in quartzites, rocks. Often accompanies beds of magnetite or hematite in such rocks. Has also been found in granite(Maryland), and regarded as an originalmineral. It is often associated with quartz, feldspar, It someetc. times actinolite, axinite,chlorite, forms with quartz an epidote rock, called epidosite.A similar rock exists at Melbourne in Canada. A gneissoidrock consistingof flesh-colored orthoclase,quartz and epidotefrom the Unaka Mts. (N. C. and Tenn.) has been called unakyte. Beautiful crystallizations from Bourg d'Oisans,Dauphine, France; the Ala valley come and in Piedmont, Italy; Elba; Zermatt, Switzerland; Zillertal in Tyrol, Traversella, Austria; also in fine crystalsfrom the Knappenwand in the Untersulzbachtal,Pinzgau, Austria,associated with asbestus,adularia,apatite,titanite, scheelite;further at Striegau, Silesia;Zoptau, Moravia; Arendal, Norway; the Achmatovsk mine near Zlatoust, Ural Mts. In North America,occurs in N. H., at Franconia and Warren. In Mass., at Hadlyme and Chester in crystalsin gneiss; at Athol, in syenitic gneiss,in fine crystals; Newbury, limestoneIn Conn., at Haddam, in largesplendid crystals. In N. Y., near Amity; Diff

"

.

"

"

Sr

Monroe, Orange Co.; Warwick, pale yellowish green, with titanite and pyroxene. In C., at Hampton's, Yancey Co.; White's mill,Gaston Co.; Franklin, Macon Co.; in crystalsand crystalline in quartz at White Plains, masses In Mich., in the Alexander Co. Lake Superior region, at many of the mines. Crystals from Seven Devils mining district, Idaho; from Riverside, Cal.; from Sulzer,Prince of Wales Island, Alaska. Epidote was named by Haiiy, from the Greek e7ri5o"m,increase,translated by him, N.

((

qui

a

recu

the accroissement,"

base of the prism (rhomboidal prism) having one side from TriaraKux, the pistachio-nut, Pistacite, refers to the color. Similar in an8le to ordinary epidote,but contains 5 to 15 ?ie"d?10n?ite' p. c. Mn2O3. than

-

o'5.

un

the other.

G.

=

3'404.

Color

reddish

brown

and

reddish

black.

Pleochroism

strong.

533

SILICATES

Ax. pi. ||b (010). Bxa.r A c axis Optically +. + 82" 34', 173. 3". Occurs with manganese at St. Marcel, Pied0 mont, ores Italy. In crystallineschists on lie de Groix, France; in glaucophane-schist in Japan. Occasionally in quartz porphyry, as in the antique red porphyry of Egypt, also that of

Absorption X

X

caxis

A

Y

"

=

Mountain,

South

Z.

"

6" to

-

=

=

-

Pa.

Belongs in Epidote Group containing, PbO, MnO, CaO, SrO, MgO, Crystals which are very small and lath shaped show characteristic A12O3, Fe2O3, Mn2Os. H. red. 6-7. G. 4'0. Found epidote habit and closelyrelated angles. Brownish at Franklin, N. J. Hancockite.

=

=

Orthite.

ALLANITE.

Monoclinic.

Axes,

p. 529.

In

lar angle near epidote. Crystals often tabulong and slender to acicular prismaticby elongation 11axis b. and in embedded Also massive grains. observed. Cleavage: a (100) and c (001) in traces; also m (110) sometimes also

11a (100);

Fracture

uneven

to

cent

subconchoidal.

or

submetallic,pitchy

Luster

Pleochroism

opaque.

Brittle.

H.

Color

brown

resinous.

or

strong:

Z

brown.

greenish

.

Allanite.

Var.-^ or

plates. Color

The black

original mineral brownish

or

from

was

black.

G.

3-0-4-2.

yellow, Y reddish brown, (010). Bxa A caxis 32J" Also isotropicand amorphous

1*682.

=

=

Subtranslu-

pi. ||b

Ax.

"

to black.

brownish

Optically j8 Birefringencevariable. approx. by alteration analogous to gadolinite. X

G.

5-5-6.

=

=

East

Greenland,

3'50-3'95.

=

in

tabular

Bucklandite

crystals

is anhydrous

allanite in small black crystals from a magnetite mine near Arendal, Norway. Bagrationin black of Achmatovsk occurs (epidote). crystalswhich are like the bucklandite Orthite included, in its originaluse, the slender or acicular prismatic crystals,containing But these graduate into massive Falun, Sweden. some forms, and water, from Finbo, near

ite

orthites

some

anhydrous,

are

or

nearly

as

so

as

most

allanite.

The

name

is from

6p66s

straight. ii

Comp.

in

ii

epidote HRR3Si3Oi3

Like

"

H20.4R0.3R203.6Si02

or

with

R

m

Ca

=

Fe, and

and

R.

of the

those

amounts

=

Al,Fe, the cerium metals Ce, Di, La, and in smaller considerable Some varieties contain yttrium group.

water, but probably by alteration. closed tube, and all kinds yield a swells up 2 '5) to a dark, (F. for iron. the fluxes reacts Most varieties gelatinizewith blebby, magnetic glass. With hydrochloric acid, but if previously ignited are not decomposed by acid. Obs. Occurs in albitic and common feldspathicgranite,gneiss,syenite,zircon syenite, stone in Greenland; Thus Sweden; Striegau, Silesia. Also in white limeporphyry. Norway; of magnetic iron. Rather the Bergstrasse,Germany; often in mines at Auerbach on as

Pyr.,

small

etc.

varieties

Some

"

amount

on

give much

strong ignition. B.B.

in1 the

water

fuses

easily and

=

"

common

as

an

constituent

accessory

tonalite of Mt. inclosed Sometimes

the

Adamello, as

a

in many the

rocks, as in andesite, diorite,dacite,rhyolite, scapolite rocks of Odegaarden, Norway, etc. in crystalsof the isomorphous species, epidote. From

Austria,

nucleus

Madagascar. with sanidine, sodalite, nephelite,hornblende, etc. at the Laacher See, Germany (bucklandite). In Mass., at the Bolton In N. Y., Moriah, Essex Co., with magnetite and quarry. In N. J., at Franklin Furnace with feldspar and magapatite; at Monroe, Orange Co. netite. In Pa., at South Mountain, near Bethlehem, in large crystals;at East Bradford; in Amherst In Va., in large masses Eckhardt's Co.; near Co., abundant. furnace, Berks also in Bedford, Nelson, and Amelia counties. In N. C., at many points. At the Devil's At

Vesuvius

Similarly

Head

in

in ejected masses trachytic ejected masses

Mt., Douglas Co., Col.

In Texas

in Llano

Co.

MINERALOGY

DESCRIPTIVE

534 AXINITE.

Triclinic. Axes T

a

b

:

: c

=

04921

:

1

:

0-4797;

a

82" 54',ft

=

91"

=

52',

131" 32'.

=

901

900

ftoa

M

am,

aM, as,

Bethlehem, P;

Poloma

Dauphine" 100 A 100 A 100 A

110 110 201

=

=

=

15" 34'. 28" 55'. 21" 37'.

Mr,

110

A

111

mr,

110

A

ras,

110

A

111 201

=

=

=

45" 15'. 64" 22'. 27" 57'.

Crystalsusuallybroad and acute-edged,but varied in habit, Also masgranular. 6'5-' conchoidal. Brittle. H. Fracture b distinct. Cleavage: (010) Color 3-271-3-294. Luster G. plum-blue, clove-brown, highly glassy. and pearl-gray; also honey-yellow,greenish yellow. Streak uncoloi Ax. pi. Pleochroism strong. Optically Transparent to subtranslucent. 65"-70". 2V Axial variable. and Bxa approximately J_ x (111). angles 1-68 (approx.).Pyroelectric 0 (p.307). with catcium and A boro-silicate of aluminium varying Comp.

lamellae often curved; sometimes sive,lamellar,

=

=

"

.

=

=

"

Calcium of iron and manganese. (SiOJs. R Formula, RyR^ in largeexcess, again in smaller amount and manganese sometimes chiefly, gen. prominent; iron is present in small quantity,also magnesium and basic hydro-

amounts

=

B.B. fuses readilywith intumescence, imparts a pale green color to the Pyr., etc. O.F.,and fuses at 2 to a dark green to black glass;with borax in O.F. givesan amethystine bead (manganese), which in R.F. becomes yellow (iron). Fused with a mixture of bisulphate of potash and fluorite on the platinum loop colors the flame green (boricacid) Not acid. decomposed by acids,but when previously with hydrochloric ignited,gelatinizes Obs. Axinite occurs in clove-brown crystals;near Bourg d'Oisans in Dauphine, France; at Andreasberg, Harz Mts., Germany; Striegau,Silesia;on Mt. Skopi, in eastern Switzerland;Elba; at the silver mines of Kongsberg, Norway; Nordmark, Sweden; near Miask in the Ural Mts.; in Cornwall,England,of a dark color,at the Botallack mine near St. Just,etc. From Obira,Japan. In the United States, at Phippsburg,Me.; Franklin Furnace, N. J.,honey-yellow;at Bethlehem,Pa.; in Cal. at Bonsall,San Diego Co., at Riverside,Riverside Co., and at Consumers Co. Mine, Amador "

.

"

Named

from

an a^lvij,

axe, in allusion to the form

of the crystals.

PREHNITE.

Axes a Orthprhombic-hemimorphic.

Distinct individual crystals rare; mm7" prismatic,

(110)A

(HO)

=

:

b

: c

=

0-8401

:

1

:

0-5549.

usuallytabular ||c (001); sometimes 80" 4'; againacute pyramidal. Commonly

MINERALOGY

DESCRIPTIVE

536

Group

Humite

:b

a

Prolectite

1-0803

Monoclmic [Mg(F,OH)]2Mg[SiO4]i?

:

1

:

T8861

90C

1

:

3-1447

90C

Chondrodite Monoclmic [Mg(F,OH)]2Mg3[Si04]2

1-0863

[Mg(F,OH)]2Mg5[Si04]3 Orthorhombic

1-0802

6

Humite

c

4-4033

Clinohumite T0803

[Mg(F,OH)]2Mg7[SiO4]4 Monoclinic

:

1

:

5'6588

90C

talline specieshere included form a remarkable series both as regards crysthey have sensibly form and chemical composition. In crystallization almost exactly are ratio for the lateral axes, while the vertical axes the same 3:5:7:9 (see also below). Furthermore, in the ratio of the numbers though one speciesis orthorhombic,the others monoclinic,they here also does not sensibly since the axial angle0 in the latter cases correspondclosely,

The

90".

differ from

(alsoSjogren),the composition,as shown by Penfield and Howe of the univalent g in which each orthosilicates basic speciesare atoms while the Mg present are in the rati"^; (MgF) or (MgOH) enters, is theoretical only, 1 -i Prolectite for The compositiongiven 3 : 5 : 7. its In physr be that which would crystallization. expected from characters these speciesare very similar,and several of them may o"|ij in pa even intercrystallized localityand together at the same In

three

lamellae. The

%

.

The speciesof the group in angle to chrysoliteand approximate closely axial ratios may be compared as follows: Prolectite

a

Chondrodite.

a

Humite

b

Clinohumite

a

Chrysolite

b

Chrysoberyl

b

CHONDRODITE

HUMITE

"

chrysoi

CLINOHUMITE.

"

Axial ratios as given above. Habit varied, Figs. 902 to 910. Twins the twinningplanesinclined 60",also 30",to c (001)in the brachycommon, dome or clinodome zone, hence the axes crossingat angles near 60"; often and repeated as trillings

twins,with

(001)as

c

lamellae (cf. polysynthetic Fig.609, p. 299). Also of the three speciesare often twinned

as

plane. Two

tw.

together.

Cleavage: c (001)sometimes

distinct.

Fracture subconchoidal to uneven. Luster vitreous to resinous. Color white,lightyellow,honey-yellowto chestnut-brown and garnet- or hyacinthred. Pleochroism sometimes distinct. Optically.+ Brittle.

H.

6-6-5.

=

G.

3-1-3-2.

=

.

Chondrodite.

Bx0 A

c

Somma.

axis

Absorption X

=

A

c

axis

=

X

"

+

25"

Z

"

52'

Y.

Ax. Optically +. pi. and Bxa J_ b (010). Brewster; 28" 56' Kafveltorp;30" approx., Mte.

0'031. 1-619; 7 2V 80". a Humite. Ax. pi. ||c (001). Bx J_ a (100). 0 Clinohumite. Ax. pi. and Bxa _L b (010). Bx0

Brewster.

0

=

=

-

2V

=

76".

0

=

1-670.

=

7

-

a

=

1'643.

=

0'038.

A

c

axis

7 =

a

-

+

=

0'035.

11"-12"; 7^"

approx.,

537

SILICATES

903 904

Figs.902, 903, Chondrodite,Brewster, N. Y.

Chondrodite,Sweden

906 907 905

Projection

103

on

(001)

Projection

Figs.905, 906, Chondrodite,Mte.

on

(Olb)

Somma

Humite, Sweden 910

908

Projection

Humite, Vesuvius

Clinohumite,Brewster

on

Clinohumite,Mte.

(010)

Somma

with related formulas Basic fluosilicates of magnesium as shown in the table above. and iron Hydroxyl replacespart of the fluorine, often takes the placeof magnesium.

Comp.

"

varieties blacken and B.B. infusible;some Pyr., etc. potassium bisulphate in the closed tube gives a reaction "

a reaction for iron. fluoride.

Gelatinizes with

acids.

Heated

with

then burn

white. Fused with With the fluxes sulphuric acid gives off silicon for fluorine.

538

MINERALOGY

DESCRIPTIVE

in the ejected at Vesuvius -Chondrodite, humite, and elinohumite all occur Somma. associated Monte found are They on limestone of both or feldspathic type masses magnetite, spinel,vesuvianite,calcite,etc.; also less with chrysolite, biotite,pyroxene, is the rarest and often with sanidine,meionite, nephelite. Of the three species,humite together in the same They seldom all occur elinohumite of most frequent occurrence. and elinohumite) appear of the species (as humite together. and only rarely two mass, of humite, and parallel intergrowthswith crystals Occasionallyelinohumite interpenetrates chrysolitehave also been observed. at Mte. Somma, Vesuvius,as above noted; at Pargas, Finland,honeyChondrodite occurs yellow in limestone; at Kafveltorp,Nya-Kopparberg,Sweden, associated with chalcopyrite, galena,sphalerite. At Brewster, N. Y., at the Tilly Foster magnetic iron mine in deep of "chondrodite" points where the occurrence garnet-redcrystals.Also probably at numerous Obs.

reported.

has been

mine near at the Ladu Sweden, with magnetite in crysFilipstadt, also occurs talline with elinohumite in Andalusia, Spain. Also in limestone In crystalline limestone. Noted large,coarse, partlyaltered crystalsat the TillyFoster iron-mine at Brewster, N. Y. Humite

at

Franklin

J.

N.

Furnace,

Somma and in Andalusia; in crystallinelimestone near at Mte. Clinohumite occurs but highly modified crystals. Lake Baikal in East Siberia;at Brewster, N. Y., in rare called titanolivine)from Ala Hydroclinohumite is a titaniferous variety (originally

Valley,Piedmont, Italy. Prolectite is from other

Kq mine, Nordmark, Sweden;

the

very

rare;

imperfectlyknown.

have been noted, chieflyin crystalline localities of "chondrodite" limestone; most of them are probably to be referred to the specieschondrodite, but the drodite" is yet to be proved. At Brewster largequantitiesof massive "choncases identityin many and from its extensive associated with magnetite, enstatite,ripidolite, occur alteration serpentinehas been formed on a large scale. The granular mineral is common in limestone in Sussex Co., N. J.,and Orange Co., N. Y., associated with spinel,and occasionally and Also in Mass., at Chelmsford, with scapolite; corundum. with pyroxene In Canada, in limestone at St. Jerome, Grenville, etc., at South Lee, in limestone. abundant. The name chondrodite is from xwSpos, a grain, alluding to the granular structure. is from Sir Abraham Humite Hume. Numerous

Leucophcenicite. Mn5(MnOH)2(SiO4)3, similar to the humite type In striated crystalselongated parallel Monoclinic. Massive. to ortho-axis. G. Color lightpurplishred. From 3'8. Fusible. Franklin, N. J.

of H.

formula. =

5*5-6.

=

.

Lievrite.

ILVAITE.

Orthorhombic.

Axes

mm'", as',

oil

Yenite. a

:

Commonly Columnar

b

A lIO A 120

110 120

in

: c =

=

:

1

:

0*4427. rr'

101

A

101

oo', 111

A

Til

=

=

67" 11'. 62" 33'.

striated. prisms,with prismaticfaces vertically

compact

or

0'6665

=

67" 22'. 73" 45'.

massive.

Cleavage: 6(010), c(001) rather distinct.

Fracture

uneven.

Brittle. H. Luster submetallic. 5-5-6. G. 3'99-4'05. Color iron-black or dark grayishblack. Streak black,inclining to green or brown. Opaque. =

Comp. ^

4SiO2

H2O.CaO.4FeO.Fe2O3. CaFe2(FeOH) (SiO4)2 or sesquioxide19 -6, iron protoxide35 -2, 2-2 100. 137, water replace part Manganese may =

lime of the ferrous iron.

Pyr.,etc.

=

-

-

Silica 29 -3,iron =

B.B. fuses quietlyat 2'5 to a black magnetic bead. With the fluxes reacts Some varieties give also a reaction for manganese. Gelatinizes with hydrochloric acid. Obs. Found on Elba in dolomite;on Mt. Mulatto near Predazzo, Tyrol, Austria,in granite; Schneeberg, In crystals from Siorarsiut,South Saxony; Fossum, in Norway. Lrreenland. Reported as formerlyfound at Cumberland, R. I.; also at Milk Row quarry,

lor

iron.

"

"

539

SILICATES

In fine

Somerville,Mass.

the Latin

Ilvaite from

name

crystalsfrom South Mountain of the island (Elba).

Dewalquite. A vanadio-silicate of aluminium In prismatic crystals resembling ilvaite. H.

Ardennite.

arsenic.

about

Index

yellowishbrown.

to

mine, Owyhee Co.,Idaho.

Found

179.

and =

Salm

at

Named

also containing manganese; 6-7. G. 3*620. low YelChateau in the Ardennes, =

Belgium. Langbanite.

RhomManganese silicate with ferrous antimonate; formula doubtful. In iron-black bohedral-tetartohedral. 6'5. hexagonal prismatic crystals. H. From Luster metallic. G. 4'918. Langban, Sweden. =

=

lead silicates. See also p. 498. In minute prismatic crystals; often in H. =5. G. =6'19. Color dark reddish brown; black sheaf -like forms; also massive. the surface. From southern Chile; Langban and Jakobsberg, Sweden; Bena Padru, on near Ozieri,Sardinia. Melanotekite. 3PbO.2Fe2O3.3SiO2 or (Fe4O8)Pb8(SiO4)s. Orthorhombic; prismatic. G. Luster 573. metallic to greasy. 6'5. Color black to Massive; cleavable. H. with native lead at Langban, Sweden. Occurs Also in crystalsresembling blackish gray. kentrolite at Hillsboro,N. M. The

followingare

rare

Probably 3PbO.2Mn2O3.3SiO2.

Kentrolite.

=

=

In small H2Be4Si?O9 or H2O.4BeO.2SiO2. Orthorhombic-hemimorphic. G. 6-7. 2'59-2'60. Colorless to pale yellow. prismatic crystals. H. in feldspathicveins,often with other beryllium T603. Usually occurs Optically 0 minerals as a result of the alteration of beryl. At the quarries of Barbin near Nantes, France; Pisek, Bohemia; Irkutka Mt., Altai Mts., Russia; Ireland, Southern Norway; Cornwall, England; Mt. Antero, Chaff ee Co.,Col.,with phenacite; Amelia Court-House, Va.; Oxford Co., Me. Bertrandite.

tabular

or

=

=

=

"

.

Smithsonite.

CALAMINE.

Hemimorphite.

Orthorhombic-hemimorphic. mm'", ss', "', ee', w', w'",

110

A

101

101

A

101

301 Oil 031

A

301 Oil

121

A

A

A

031 121

Axes

a

:

b

07834

: c

76"

9'. 62" 46'.

=

=

122"

=

:

1

:

04778.

912

913

41'.

51" 5'. 110" 12'. 78" 26'.

=

=

=

matic; Crystalsoften tabular ||b (010);also prisstriated. Usually faces 6 vertically implanted and showing one extremity only. ing Often grouped in sheaf -like forms and formdrusy surfaces in cavities. Also stalacfibrous titic, mammillary, botryoidal,and forms; massive and granular. Cleavage: m (110)perfect;s(101) less so; c

(001)in

traces.

Fracture

uneven

to

subconchoidal.

Brittle.

H.

=

4-5-5,

Luster 3 -40-3 -50. latter when vitreous; c (001) crystallized.G. sometimes with a delicate Color adamantine. sometimes white; subpearly, parent TransStreak white. bluish or greenishshade; also yellowishto brown. 1*617. 1-614. 46". 2V to translucent. a (3 Optically+.

the

=

7

=

Strongly pyroelectric.

1-636.

H2ZnSiO5 or zinc oxide 67 -5,water 7-5

Comp.

(ZnOH)2SiO3

"

=

100.

The

or

water

H2O.2ZnO.SiO2 goes

off

only

Silica 25-0, at a red heat; =

at 340" C.

unchanged Pyr., etc.

=

=

=

"

B.B. almost In the closed tube decrepitates, whitens, and givesoff water. On charcoal with soda gives a coating which is yellow while hot,and

infusible (F. =6).

MINERALOGY

DESCRIPTIVE

540

and heated in O.F., this coatingassumes cooling Moistened with cobalt solution, on blue. Gelatinizes with acids mineral itself becomes bright green color,but the ignited

white a

ignited. previously

when

even

.

,,..,.

.,,

Characterized by its mfusibihty; reaction for zinc; gelatimzation with smithsonite (which effervesces with acid),also prehnite. some

f)iQ Resembles

.,

acids.

beds in or usually found associated in veins and smithsonite are Calamine iron and lead. of Thus at Aix-lazinc, sulphides accompanying rocks stratifiedcalcareous in Belgium; Rezbanya, Raibel and Bleiberg,in Carinthia; Moresnet Chapelle Germany; at Alston At Roughten Gill,in Cumberland; Moor, white; and Schemnitz, Hungary. Matlock, in Derbyshire; Leadhill,Scotland; at Nerchinsk, m eastern Siberia. From Obs.

"

near

Santa Eulalia,Chihuahua, Mexico. Ogdensburg, N. J.,in fine clear crystalat SterlingHill,near line In the United States occurs and Phenixville lead mines; at Friedensville. In Pa., at the Perkiomen masses. With the zinc depositsof southwestern in Va., at Austin's mines in Wythe Co. Abundant and massive calamine. Crystals especiallyabout Granby, both as crystallized

Missouri, At the Emma mine, Leadville,Col; from Organ Mts., N. M.; Elkhorn Mts., Mon. Cottonwood Canon, Utah. ruption The name Calamine (with Galmei of the Germans) is commonly supposed to be a corof Cadmia. Agricola says it is from calamus, a reed,in allusion to the slender in the cadmia fornacum. common forms (stalactitic) from

Use.

An

"

of zinc.

ore

H.

G.

5'5.

=

Stokesite.

G.

3'2.

=

3'33.

=

Monoclinic-clinohedral (see Figs. 352, 353, p. 138). white to amethystine. Index, 1 '67. From Franklin,N. J.

H2CaZnSiO5.

Clinohedrite.

Colorless

or

Orthorhombic.

Perhaps H^aSnSisOn.

"

Colorless.

0

=

From

1*61.

Prismatic cleavage. Cliff,St. Just, Cornwall.

Roscommon

H.

6.

=

In radiated and stellated tufts. G. 2'935. Color Carpholite. H4MnAlsSi2O10. 1*63. Occurs at the tin mines of Schlaggenwald, to wax-yellow. Biaxial, 0 Bohemia; Wippra, in the Harz Mts., on quartz, etc. In prismatic orthorhombic Lawsonite. H4CaAl2Si2Oio. crystals;mm'", 110 A 110 Luster vitreous to greasy. 3*09. 67" 16'. G. Colorless, pale blue to grayish blue. 1'669. Occurs in crystalline schists of the Tiburn Optically-f-. /3 peninsula, Marin Caledonia. Co., Gal.; also in the schists of Pontgibaud, France, and New Hibschite. Same as for lawsonitc, H4CaAl2Si2Oio. In minute isometric crystals, usually octahedrons. H. 3'0. 6. G. Colorless or pale yellow. Refractive index, 1 '67. Infusible. From the phonolite of Marienberg, Bohemia. Associated with melanite. Cerite. A silicateof the cerium with water. metals chiefly, Crystals rare; commonly Color between clove-brown 5'5. 4*86. G. and massive; granular. H. cherry-red to gray. Indices,1 '83-1 '93. Occurs at Bastnas, near Riddarhyttan,Sweden. Toernebohmite. A silicateof the cerium metals, chiefly, R3(OH)(SiO4)2. Monoclinic? Color,green to olive. /3 1'81. Biaxial,+. Strong dispersion,P " v. Pleochroic, rose to blue-green. From Sweden. Bastnas, near Riddarhytta.n, Beckelite. Ca3(Ce,La,Di)4Si3O15.Isometric Crystalssmall,often microscopic. Cubic 5. G. 4*1. cleavage. H. Color yellow. Infusible. Occurs with nepheline syenite rocks near Mariupol, Russia. =

straw-

=

"

.

=

=

=

=

=

=

=

=

=

=

A basic silicatechieflyof the cerium Hellandite. Monoclinic. Prismatic habit. H. 5*5.

calcium. Found in

=

pegmatite near

metals, aluminium,manganese G.

37.

=

Color

and Fusible.

brown.

Kragero, Norway.

Bazzite.

A silicateof scandium with other rare earth metals, iron and a littlesoda. In minute Hexagonal. prisms,often barrel shaped. H. 6*5. 2'8. G. Color azureTransparent in small individuals. Optically-. Refractive indices,co 1'626. =

=

=

e

i rb05.

=

Strongly dichroic,

co

=

pale greenishyellow, e at Baveno, Italy.

=

azure-blue.

Infusible.

soluble In-

ordinaryacids. Found ANGARALITE In thin 2(Ca,Mg)0.5(Al,Fe)2O.,.6SiO2. m

U.

-

2-b2.

Color

tabular hexagonal(?)crystals. carbonaceous In contact impurities. Uniaxial,+. of zone part of Yenisei District, Siberia.

black

limestone,southern

from

TOURMALINE.

Axis Rhombohedral-hemimorphic._ c

cr, 0001 co, 0001

A

A

lOll 0221

=

=

27" 20'.

45" 57'.

rr'

1011

A

oilA oof,

1101

20*1

=

"

=

0-4477. 4fi" W

im'

39^1

# %\ %i,l|i^ 1} I4626" gj/ A

Q^91

AA"

T

541

SILICATES

Crystals usually prismatic in habit, often slender to acicular;rarely the prism nearlywanting. Prismatic faces stronglystriated verflattened, 914

916

515

917

918

ma

and tically,

the crystalshence often much rounded to cross-section of the prism three-sided (m, Fig.921),sixsided (a),or nine-sided (m and a). Crystalscommonly monly comhemimorphic. Sometimes isolated,but more

barrel-shaped.The 921

in

or

Sometimes or sive masparallel radiatinggroups. also coarse or compact; columnar, fine,parallel divergent. Cleavage: a (1120) r (1011) difficult. Fracture sub,

conchoidal to

Brittle and

often rather friable. vitreous to resinous. Colur black, brownish black, bluish black, most blue,green, red, and sometimes of rich common; and green shades; rarelywhite or colorless;some specimens red internally externally; and others red at one extremity,and green, blue or black at the other; the zonal arrangement of different colors widely various both as parent Transto the colors and to crystallographic directions. Streak uncolored. H.

=

7-7-5.

uneven.

G.

=

2-98-3-20.

Luster

to opaque.

axial colors varying in deep-colored Stronglydichroic, especially varieties; for mit widely. Absorption co much strongerthan for e, thus sections 11c axis transin the tourmaline sensiblythe extraordinaryray only,and hence their use (e.g., light. Exhibits idiophanousfigures tongs (p.243) ) for givingpolarized OO2. Indices: rather high,co e (p.288). Optically Birefringence 1-6222 colorless blue1-6193 er 1-6366, 1*6435, variety; o"r =. coy ey "

"

.

=

=

=

=

542

MINERALOGY

DESCRIPTIVE

abnormally biaxial. stronglypyroelectric. Sometimes

green.

electric by

Becomes

also friction;

the most common, In crystalsas above described; black much Var. Ordinary. (a) Rubellite; the red, sometimes transparent; the Siberian is mostly violet-red (siberite), the Brazilian rose-red; that of Chesterfield and Goshen, Mass., pale rose-red and opaque; or (6) Indicolite, indigolite;the blue, that of Paris,Me., fine ruby-red and transparent. from the indigo-bluecolor, (c)Brazilian Sapphire (in either pale or bluish black; named jewelry); Berlin-blue and transparent, (d) Brazilian Emerald, Chrysolite(or.Peridot)of less Brazil; green and transparent, (e)Peridot of Ceylon; honey-yellow. (/)Achroite; color(g) Aphrizite; black tourmaline, from Kragero, Norway. tourmaline, from Elba, somewhat Resembles columnar. common and black; coarse hornblende, (h) Columnar resinous fracture,and is without distinct cleavage or anything like a fibrous but has a more "

in the texture; it often has the appearance

appearance

on

a

broken

surface of

some

kinds of

soft coal.

aluminium, with also either or prominent. A generalformula may be written as HgAlaCB.OH^Si^ip (Penfieldand Foote) in which the hyrogen be replacedby the alkalies and also the bivalent elements, Mg,Fe,Ca. may Fluorine is commonly present in small amounts. Comp. magnesium, "

A

complex

iron

silicate of boron

and

the alkali metals

The varieties based upon composition fall into three prominent groups, between which there are many gradations: 1. ALKALI TOURMALINE. Contains sodium or lithium, or both; also potassium. G. 3-0-3-1. Color red to green; also colorless. From pegmatites. 2. IRON TOURMALINE. G. 3-1-3-2. Color usually deep black. Accessory mineral in siliceous igneous rocks and in mica schists, etc. 3. MAGNESIUM TOURMALINE. G. 3-0-3'09. Usually yellow-brown to brownish limestone or dolomite. black; also colorless. From A chromium tourmaline also occurs. G. 3*120. Color dark green. The magnesia varieties fuse rather easilyto a white blebby glass or slag; Pyr., etc. the iron-magnesia varieties fuse with a strong heat to a blebby slagor enamel; the iron varieties fuse with difficulty, only on the edges; the iron-magnesia-lithia or, in some, varieties fuse on the edges,and often with great difficulty, and some are infusible;the lithia varieties are infusible. With the fluxes many varieties give reactions for iron and manganese. Fused with a mixture of potassium bisulphate and fluor-spargives a distinct reaction for boric acid. Not decomposed by acids. Crystals, especiallyof the lightercolored varieties,show strong pyroelectricity. =

=

=

=

"

Diff.

Characterized by its crystallization, prismatic forms usual, which are three-, nine-sided,and often with rhombohedral nar terminations; massive forms with columstructure;also by absence of cleavage(unlikeamphibole and epidote); in the common black kinds by the coal-like fracture; by hardness; by difficultfusibility (common kinds),

six-,

"

or

compared

with

garnet and

vesuvianite.

The boron test is conclusive. thin sections by its somewhat high relief;rather erence~colors'ne"gativeuniaxial character;decided colors in ordinary lightin u"nugin which basal i sections often exhibit zonal structure. a Also, especially, by its remarkable the direction of crystalelongationis _]_to the -bsorption when vibration-planeof the lower nicol; this with its lack of cleavagedistinguishes it from biotite and amphibole, which alone among rock-making minerals show similar strong absorption. Ubs. found in graniteand gneissesas a result of fumarole Commonly action or of legalizinggases m the fluid magma, especiallyin the pegmatite veins associated with icn rocks; at the periphery of such masses altered limestones,gneisses, or in the schists, or !tc.,immediately adjoiningthem. It marks especiallythe boundaries of graniticmasses, its associate minerals are those characteristic of such quartz, albite, occurrences; microcline muscovite etc. The varietyin granular limestone or dolomite is commonly Micro.

in Readily distinguished

"

"

vn,

tne

bluish-black

e

d

variety sometimes associated with the brown tin ores; with lithium variety is often associated with lepidolite. Red or green varieties, in the Ural Mts- Elba; Campolongo in Tessin, Switzer-" *he Province Minas from Geraes, Brazil; yellow and brown

kat?F mburg Pp"n-CUrQnear ^lr?:XOny; A" "

"netles br?Tn "romEibenstock,Saxony; the Snarum and dal'0N".rway; Kragero, Norway; i

crystais"ccur

in c""n

Zillertal, Tyrol, Austria; at pale yellowish brown at different iocaiities-

MINERALOGY

DESCRIPTIVE

544

Figs.397, p. 164; 439, 440, 441, p. 170). (230)rare, also in repeatedtwins (cf. flattened and ||b axis; often with rough surfaces. Crystalscommonly prismatic Fracture b ut interrupted;m (110)m traces. Cleavage: b (010)distinct, y

ing Subvitreous,inclin3 '65-3 77. G. 7-7-5. Brittle. H. and brownish to brown yellowish black, Color dark reddish to resinous. Streak uncolored to grayish. Translucent to nearly or quite opaque. brown. distinct : Z ( c axis)hyacinth-red Pleochroism

subconchoidal.

=

=

=

yellowishred; or Z gold-yellow, Ax. +. Y lightyellowto colorless. Optically x 88" 2V (appi. ||a (100). Bx _L c (001). 1*746. 1741. 1-736. ft 7 prox.). a to

**"*"

Y

blood-red,X,

=

I

MI

\

=

=

/

Comp.

=

HFeAl5Si2Oi3, which

"

may

be

ten writ-

H2O.2Fe0.5Al2O3. or (A10)4(AlOH)Fe(SiO4)2 4SiO2

010

010

"x

=

Silica 26*3, alumina 2'0

15-8,water

100.

=

55

'9,iron protoxide

Magnesium

replaces littleof the ferrous iron part of the aluminium. a

ganese) (alsomaniron;ferric

from Nordmark, Sweden, contains manlarge amounts. B.B. infusible, excepting the manganesian \g Pyr., etc. variety, which fuses easily to a black magnetic glass. " With the fluxes gives reactions for iron, and sometimes Z for manganese. decomposed by sulphuricacid. Imperfectly Diff. Characterized by the obtuse prism (unlikeandalusite,which is nearly square); by the frequency of twinning forms; by hardness and infusibility. Micro. Under the microscope,sections show a decided color (yellowto red or brown) and strong pleochroism (yellow and red); also characterized by strong refraction (high rather brightinterference-colors, parallelextinction and biaxial character (generally relief), positivein the direction of elongation). Easily distinguishedfrom rutile (p. 427) by its

Nordmarkite

/\

in

ganese

"

"

"

biaxial character and

lower interference-colors.

Usually found in crystallineschists,as mica schist,argillaceousschist,and gneiss,as a result of regionalor contact metamorphism; often associated with garnet, silliaceous Sometimes encloses symmetricallyarranged carbonmanite, cyanite, and tourmaline. impuritieslike andalusite (p.524) Other impuritiesare also often present, especially sometimes silica, up to 30 to 40 p. c.; also garnet, mica, and perhaps magnetite, brookite. Occurs with cyanitein paragoniteschist, at Mt. Campione, Switzerland; in the Zillertal, Tyrol,Austria; Goldenstein in Moravia; Aschaffenburg,Bavaria; in largetwin crystalsin the mica schists of Brittany and Scotland. In the province of Minas Geraes, Brazil. Abundant In throughout the mica schists of New England. In Me., at Windham. N. H., brown at Franconia; at Lisbon; on the shores of Mink Pond, loose in the soil. In in fine crystals. In Conn., at Bolton, Vernon, etc.; Southbury with Mass., at Chesterfield, black crystals. In N. C., near son garnets; at Litchfield, Franklin, Macon Co.; also in Madiand Clay counties. In Ga., in Fannin Co., loose in the soil in fine crystals. In large crystalsfrom Ducktown, Tenn. Obs.

"

.

Named Use.

from

(rravpos,

a

cross.

is cut for a gem. a transparent stone Occasionally In fibrous to columnar Kornerupine. Near MgAl2SiO6. aggregates, resembling sillimamte. H. 6'5. G. 3'273 kornerupine;3'341 prismatine. Colorless to white, or brown. Biaxial, Indices,1 '669-1 '682. at Fiskernas on the west coast of Greenland. Kornerupineoccurs Prismatine is from Waldheim, Saxony. Found in large,clear crystalsof a sea-green color and gem quality "

=

=

-.

trom

near Betroka, Madagascar. Sapphirine. Mg6Ali2Si2O27. In indistinct tabular crystals. Usually in disseminated grains, or aggregationsof grains. H. 7'5. G. 3'42-3'48. Color pale to dark blue or green. Biaxial, Indices, 1705-1711. From Greenland. Fiskernas, southwestern Occurs near Betroka,Madagascar. From St. Urbain, Quebec. =

=

-.

r\

A basic .p^didierite.

Orthornombic.

silicate of aluminium,ferric iron,magnesium, ferrous iron,etc. In elongated crystals. Two 3'0. Color bluish green. cleavages. G. =

545

SILICATES

/3

Found

Strongly pleochroic.

1-64.

=

in

pegmatite

Andrahomana

at

in

southern

Madagascar. Serendibite. thetic

10(Ca,Mg)O.5Al2p3.B2O3.6SiO2.In irregular grains showing polysyn-

twinning;

triclinic. H. monoclinic or Refractive Infusible. index, 17.

probably

marked.

Pleochroism

6*7.

=

G.

From

Color

3*4.

=

Gangapitiya

blue. Am-

near

bakotte, Ceylon. of calcium

A fluosilicate Silicomagnesipfluorite.

Si2O7Fi0.

Radiating fibrous in spherical forms. From Fusible. lightgreenish or bluish. Lupikko,

and

H.

magnesium, G.

2'5.

=

=

perhaps, H2Ca4Mg3 Color ash-gray,

2'9.

Pitkaranta, Finland.

near

silicate of calcium with aluminium and a little iron of uncertain sition. compoIn small tabular crystals. Colorless. Orthorhombic. G. 3'09. Transparent. Infusible. with microsommite Optically +. Decomposed by sulphuric acid. Found on Nocera limestone near and Sarno, Campagna, Italy. Grothine.

A

=

Luigite. A basic silicate containing ferrous oxide, lime, magnesia, Acts in a tuff found to violet. at cement as a Color, brown Amorphous. Portal, Uganda. ALOISIITE.

soda.

Found

Opaque.

G.

H. 3'5-4. Amorphous. ore near Vares, Bosnia.

Hi6Fe8Mn2Si3O29.

POCHITE. brown.

=

in iron

=

370.

Color

and Fort

reddish

SILICATES B.

Section The

Chiefly Hydrous

of this second

SILICATES

that is,those which

contain

Species

section include

the true hydrous compounds, of crystallization, like the zeolites;also the

water

There also included certain are hydrous amorphous species,as the clays,etc. which, while they yieldwater upon species as the Micas, Talc, Kaolinite orthosiliwithout doubt to be taken as acid or basic metasilicates, are ignition, is close to other true Their etc. relation,however, so hydrous species cates, here than to have placed them natural to include them that it appears more other acid and basic salts. Finally, some in the preceding chapter with and about chemical constitution the part referred here whose species are much doubt. still The divisions there is the water present played by nized recog"

"

are

as

follows: I. 1.

Introductory II.

1.

Mica

Group. III.

2.

Division

Zeolite

Subdivision.

2.

Zeolites

Division

Mica

Clintonite

Serpentine and

3.

Group. Talc

Chlorite

Group

Division

Chiefly Silicates of Magnesium. IV.

Kaolin

Chiefly Silicates of Aluminium; of the

Division for the most

part belonging to the

group

clays. V.

Concluding

Division

Species not included in the preceding divisions;chieflysilicates of the etc. heavy metals, iron, manganese,

546

MINERALOGY

DESCRIPTIVE

Division

I. Zeolite 1.

Subdivision

Introductory

Okenite, etc.,while not strictly Of the specieshere included,several,as Apophyllite, of occurrence. Pectolite ZEOLITES, are closelyrelated to them in composition and method "here. classed sometimes also Prehnite are and 483) (p.534) (p. radiated and Inesite. H2(Mn,Ca)6Si6Oi9.3H2O. Crystalssmall,prismatic;also fibrous, to flesh-red. Occurs at the manganese 3'029. Color rose6. G. spherulitic.H. Rhodotilite is the same mines near species from the Harstig mine, Dillenburg,Germany. From Jakobsberg and Langban, Sweden ; Villa Corona, Durango, Mexico. Pajsberg,Sweden. G.= Hillebrandite. 5'5. Ca2SiO4.H2O. 27. Orthorhombic; radiating fibrous. H. in contact Refractive index Fusible with difficulty.Found 1*61. Color white. zone Mexico. between limestone and diorite in the Velardena mining district, Crestmoreite. H. 3. Compact. Color, snow-white. Probably 4H2CaSiO4.3H2O. An alteration product of Wilkeite. From G. 2'2. T59. Crestmore, Riverside Co., ft =

=

=

=

=

=

=

2CaSiO6.H2O.

Riversideite.

G.

In

fibrous veinlets.

compact

Indices,1 "59-1 '60. Easily fusible. Ganophyllite. 7MnO.Al2O3.8SiO2.6H2O. 2-64.

=

micaceous. From

Color

brown.

H.

G.

4~4'5.

=

=

3. Silky luster. H. Crestmore, Riverside Co., Cal. In short prismatic crystals; also foliated, 2'84. Biaxial, Indices,17Q5-1730. =

From

-.

the

Harstig mine, near Pajsberg,Sweden. Lotrite. 3(Ca,Mg)O.2(Al,Fe)2O3.4SiO2.2H2O. 7'5. G.= grains and leaves. One cleavage. H.

in an aggregate of small Color green. Refractive index, chlorite schist in the valley of the Lotru, Transylvania. =

1'67.

Found

in small

in

veins

a

Massive,

3'2.

Okenite. H2CaSi2O6.H2O. 4'5-5. G. Commonly fibrous;also compact. H. 2'282 '36. Color white,with a shade of yellow or blue. Occurs Biaxial, in Index, 1'556. basalt or related eruptiverocks; as in the Faroe Islands; Iceland; Disko, Niorkornat, etc., =

.

=

"

.

Greenland; Poona, Gyrolite.

India.

From

Crestmore,Riverside Co., Cal.

H2Ca2Si3O9.H2O.

lamellar-radiate

in

Rhombohedral-tetartohedral.

Optically

structure. stilbite, laumontite,etc.; in

-.

co

=

1'56.

In

From

the

white concretions, Isle of Skye, with

India, etc. With apophylliteof New Almaden, California; Scotia. Found also at various placesin Bohemia; from Scotland and the Faroe Islands;Sao Paulo, Brazil. Reyeritefrom Greenland is similar to gyrolite. Zeophylliteis similar specieswhich may a be identical with In spherical gyrolite. Rhombohedral. forms with radiating foliated structure. Perfect basal cleavage. H. 3. G. 2*8. Color white, 1'56. From various localitiesin Bohemia u and elsewhere. also Nova

=

=

=

APOPHYLLITE.

Tetragonal. Axis 926

c

=

1 -2515. 927

ay, 100 A cp, 001 A

310 111

18" 26'. 60" 32'.

in scluare /"it Taried'

-)or by

o

and

p

928

929

op,

100

A

111

pp',

111

A

Til

52" 0'. 76" 0'.

Prisms (" (100))usuallyshort and terminated by (111),and then resemblinga cube or cubo-octahedron;

547

SILICATES

also acute

pyramidal (p (111))with or without c and a; less often thin tabular c often rough; a brightbut IIc. less vertically or striated; p more Also massive and lamellar;rarelyconcentric radiated. uneven. Fracture uneven. Cleavage: c (001) highly perfect;m (110) less so. 4-5-5. Brittle. H. 2-3-2-4. G. Luster of c pearly; of other faces vitreous. Color white,or grayish;occasionally with a greenish,yellowish, or rose-red tint,flesh-red. Transparent; rarelynearly opaque. Birefringence Often shows anomalous low; usually+, also opticalcharacters (Art. 429, Fig.617). Indices,1-535-1-537. Silica H7KCa4(SiO3)8.4fH20 or K20.8Ca0.16SiO2.16H20 Comp. lime 16*1 A small water 100. of fluorine 537, 25-0, potash 5-2, amount replacespart of the oxygen. Faces

=

=

"

.

"

=

=

The

formula

above

differs but

part of the basic hydrogen.

The

littlefrom H2CaSi2O6.H2O,in which potassium replaces form often accepted, H2(Ca,K)Si2O6.H2O,corresponds

less well with the analyses. In the closed tube exfoliates, Pyr., etc. whitens,and yieldswater, which reacts acid. B.B. colors the flame violet (potash),and fuses to a white vesicular enamel. exfoliates, F. 1*5. Decomposed by hydrochloricacid,with separationof slimy silica. Diff. Characterized by its tetragonalform, the square prism and pyramid the common habits; by the perfectbasal cleavage and pearly luster on this surface. Obs. Occurs commonly as a secondary mineral in basalt and related rocks,with various also datolite,pectolite, zeolites, calcite;also occasionallyin cavities in granite, at Poonah, gneiss,etc. Greenland, Iceland,the Faroe Islands,and British India,especially afford fine specimens of apophyllitein amygdaloidal basalt or diabase. Occurs also at Andreasberg, Harz Mts., Germany, of a delicate pink; Radautal in the Harz Mts.; at Orawitza, Hungary, with wollastonite; Uto, Sweden; on the Seisser Alp in Tyrol, Austria; Guanajuato, Mexico, often of a beautiful pink upon amethyst. In the United States,large crystalsoccur at Bergen Hill,Paterson, West Paterson, and Great Notch, N. J.; in Pa., at the French Creek mines, Chester Co.; at the Cliff, Phoenix and other mines, Lake Superior region; Table Mt. near Golden, Col.; in Cal., at the mercury mines of.New Almaden often stained brown by bitumen; also from Nova Scotia at Cape Blomidon, and other points. Named by Haiiy in allusion to its tendency to exfoliate under the blowpipe, from airb and (f"v\\oi", a leaf. Its whitish pearly aspect, resembling the eye of a fish after boiling, gave rise to the earlier name from ixOvs, Ichthyophthalmite, fish,6"f"da\iJi6s, eye, "

=

"

"

2.

The

Zeolites

ZEOLITES form a family of well-defined hydrous silicates, lated closelyreother in composition, in conditions of formation,and hence in mode of occurrence. They are often with rightspoken of as analogous to with sodium and the Feldspars,like which they are all silicatesof aluminium also rarelybarium and strontium; magnesium, iron,etc.,are calcium chiefly, absent position or present only through impurity or alteration. Further, the comin a number of cases correspondsto that of a hydratedfeldspar;while fusion and slow recrystallization of them of result in the formation from some aiiorthite (CaAl2Si2Og) or a calcium-albite (CaA^SieOie)as shown by Doelter. The Zeolites do riot, lization, however, form a singlegroup of speciesrelated in crystalof independent groups like the Feldspars,but include a number these are widely diverse in form and distinct in composition; chief among rhombohedral CHABAZITE the monoclinic PHILLIPSITE the GROUP; GROUP, A transition in GROUP. and the orthorhombic (and monoclinic) NATROLITE less wellcertain end compounds has been more or composition between these with cium established in certain cases, but, unlike the Feldspars, speciescalanother and an increase in alkali does not and sodium seem to replace one necessarily go with an increase in silica. to each

548

MINERALOGY

DESCRIPTIVE

hydrous silicatesthey are characterized by inferior hardness, sponding gravityis also lower than with correfrom 3-5 to 5-5, and the specific chiefly to these ters; charac2 -4. to 2 -0 Corresponding chiefly anhydrous species, of them' with gelathey are rather readilydecomposed by acids,many the to the family(from name B.B., which gives tinization. The intumescence and \iBos, stone)is characteristicof a largepart of the species. to boil, fefi", commonly in The Zeolites are all secondary minerals,occurringmost quently cavities and veins in basic igneous rocks,as basalt,diabase, etc.; less freand lime soda in the the In these cases etc. in granite, part gneiss,, sodalite, have been chieflyyieldedby the feldspar;the soda also by elseolite, the of often The different are e tc. family ciated assospecies etc. ; potashby leucite, included with and also with pectolite apophyllite(sometimes together; calcite. of the zeolites Many the zeolites), datolite, prehniteand, further, have been produced synthetically by various hydrochemical reactions. In spar generalthey appear to have been formed in nature by reactions upon the feldminerals. or feldspathoid Like other

Ptilolite.

Here Ca R delicate tufts.

RAl2SiioO24.5H2O.

:

=

K2

Na2

:

6

=

2

:

In short

1 approx.

:

Colorless,white.

Biaxial,+. Indices, bluish chalcedony in cavities in a vesicular augite-andesite 1 '480-1 '485. Occurs upon a found in fragments in the conglomerate beds of Green and Table mountains, Jefferson Co., and from Silver Cliff, Custer Co., Col.,also from Elba and Iceland. capillaryneedles,aggregated

Mordenite.

in

where R 3RAl2Si10p24.20H;.O,

-

in habit and

crystalsresembling heulandite concretions with pinkish. Occurs

fibrous

H.

structure.

=

K2

angles; also =

:

Na2

:

Ca

1

=

3-4.

Stilbite some

v"

Axes

a

:

1.

In

minute

=

Morden, King's Co., Nova Hoodoo near Mt., on the ridgeforming the divide between Clark's Fork of the Yellowstone river. Also from Seiseralpe, Tyrol, Austria and the

Monoclinic.

:

hemisphericalor reniform G. 215. Color white, yellowish or Scotia,in trap; also in western Wyoming

near

HEULANDITE.

1

:

in small

and Faroe

the East Fork Islands.

authors.

b

: c

0-4035

=

mm'",

110

A

1TO

ct,

001

A

201

:

1

:

0-4293; 0

88"

=

34J'.

=

43" 56'.

cs, 001

A

201

=

66"

=

63" 40'.

ex, 001

A

021

=

40" 38|'

0'.

Crystalssometimes flattened 11b (010),the surface of pearly luster (Fig.930; also Fig.21, p. 12); form often suggestiveof the orthorhombic system, since the angles cs and ct differ but little. Also in globularforms; granular.

"

\ t

Cleavage:b (010)perfect.

Fracture subconchoidal to uneven. H. 3-5-4. 2-18-2-22. G. Luster of 6 strong pearly; of other faces vitreous. Color various shades of wmte, passing into red, and brown. Streak white. gray Transparent to subtranslucent. Ax. pi. and Optically+. Bxa _L b (010). Ax. pi.and Bx0 for some localities nearly ||c also for others nearly_L c in white light. Bx0 A c axis + 57J" angle variable,from 0" to 92"; usually 2Er 52". 1-498. a Brittle.

=

=

=

Axial

=

P

=

1-^:99.

Comp.

"

7

=

H4CaAl2(Si03)6.3H20 or

alumina 16'8,lime 9'2,water

14'8

Strontia is usuaUy present, sometimes

Pyr.

"

As with

=

1-505.

stilbite, p. 551.

5H2O.CaO.Al2O3.6SiO2 100.

=

up

to 3 '6 p.

c.

=

Silica 59'2,

549

SILICATES

in basaltic rocks,associated with chabazite, occurs principally stilbite zeolites;also in gneiss,and occasionallyin metalliferous veins. from Berufiord, finest specimens of this speciescome The and elsewhere in Iceland; also in railroad cuttingsin the Bhor the Faroe Islands; in British India, near Bombay; Also occurs in the Kilpatrick Hills,near and Thul Ghats. Glasgow; on the Island of Skye; Fassatal,Tyrol, Austria; Andreasberg, Harz Mts., Germany; Viesch and elsewhere, Obs.

Heulandite

"

other

and

Switzerland. In the United

States,in diabase at Bergen Hill,West Paterson and Great Notch, N. J.; Superior; with haydenite at Jones's Falls near Baltimore (beauAt Peter's Point, Nova Scotia; also at Cape Blomidon, and other points. montite),Md. after the English mineralogicalcollector, H. Heuland, whose Named cabinet was the basis of the classical work (1837) of Levy. Brewsterite. H4(Sr,Ba,Ca)Al2(SiO3)6.3H2O. In prismaticcrystals. H. =5. G. 2-45. Color white, incliningto yellow and gray. Biaxial,+. Index, 1*45. From Strontian in Argyleshire,Scotland; near Freiburg in Breisgau, Germany. like heulandite,H4CaAl2(SiO3)6.3H2O. Crystals monoclinic, Epistilbite. Probably uniformly twins; habit prismatic. In radiated sphericalaggregations; also granular. Color white. 2-25. G. Biaxial,-. Indices,1 '502-1 '512. Occurs with scolecite at the, garet Berufiord,Iceland; the Faroe Islands; Poona, India; in small reddish crystals,at MarNova ville, Scotia,etc. Reissite is from Santorin Island. north

on

of Lake

shore

=

=

Wellsite

53" 27' 55" 37' 55" 10' 50" 50'

Phillipsite Harmotome

Stilbite

while crystallizing in the monoclinic system, are remarkable species, pseudo-symmetry exhibited by their twinned forms. Certain of these twins are pseudo-orthorhombic, others pseudo-tetragonal and more plex comtwins even pseudo-isometric. The

above

for the

Fresenius has shown that the speciesof this group may be regarded as forming a series, in which the ratio of RO : A12O3 is constant (= 1 : 1),and that of SiO2 : H2O also chiefly The 1:1. end compounds assumed by him are: Here

R

Ca,

and

=

K2

R2Al4Si4O16.6H2O. RAl2Si6Oi6.6H2O; Ba in harmotome, stilbite,

Ca

and chiefly,in phillipsite

are

present; also in smaller

amounts

regarded as a hydrated calcium albite, as a hydrated anorthite. Pratt that the anorthite and Foote, however, show mula end probably has the forcompound more The RAl2Si2O ;.2H2O (orthis doubled) formulas given beyond are those corresponding reliable analyses of certain typical to

while in wellsite Ba, Na2, Sr2. The firstof the above compounds

be

may

second

the

931

932

.

occurrences.

RAl2Si3Oio.3H2O with R

Wellsite. Ba

K2 in small :

=

3

:

1

amount.

:

3;

Sr

and

Na

Ca : also present =

Percentage composition:

SiO2 42-9, A12O3 24-3,BaO6'6, CaO 7'3,K2O 6' 1,H2O 12-8 100. Monoclinic (axesabove) ; =

in

complex twins, analogous to those of and harmotome phillipsite (Figs.931, 932). 4-4'5. Brittle. No G. Luster vitreous. Colorless to 2'278-2'366. cleavage. H. Bx _L b (010). Birefringenceweak. white. Optically +. Occurs at the Buck Creek (Cullakanee)corundum mine in Clay Co., N. C.; in isolated associated with crystalsattached to feldspar,also to hornblende and corundum; intimately Also found at Kurzy near chabazite. Simferopol,Crimea, Russia. =

=

MINERALOGY

DESCRIPTIVE

550 PHILLIPSITE.

Monoclinic. 110 100

mm"'

a/,

Axes A A

HO 101

b

:

a =

=

: c

07095

=

:

1

:

1-2563; ft

60" 42'. 34" 23'.

001

A

ee',Oil

A

cm,

55" 37'.

=

110 Oil

=

=

60" 50'. 92" 4'.

but often Crystals uniformly penetration-twins, orthorhombic forms. Twins or tetragonal simulating tw. but with c rarely, simple(1) pi. (001) sometimes, and then cruciform so that diagonalparts on b (010) ||edge belong together,hence a fourfold striation, be often observed on b. (2)Double twins, b/m, may the simple twins just noted united with e (Oil) as tw. pi., and, since ee' varies but little from 90", the result is a prism, terminated nearly square by what appear to be pyramidal faces each with a

933

.

from the medial line. also Fig. 400, p. 164. Figs. 452-454, p. 172; but striations striated often sometimes as Faces 6 (010) just noted, finely with and in general not so distinct as absent harmotome; also m (110) or striated ||edge b/m. Crystalseither isolated, grouped in tufts or spheres, radiated within and bristled with anglesat surface. Brittle. Cleavage: c (001),6 (010),rather distinct. Fracture uneven. Luster vitreous. Color white, sometimes 2-2. G. 4-4-5. reddish. H. Ax. pi. and Bx0 Translucent to opaque. Streak uncolored. Optically+. J_ b (010) The ax. pi.liesin the obtuse angleof the a-c axes, and is usually inclined to a axis about 15" to 20",or 75" to 70" to the normal to c (001) The 71"-84". however, is variable. 2Ha.r Indices,1-48-1-57. position, In is the formula some cases Silica Comp. (K2,Ca)Al2Si4Oi2.4H2O 16-5 100. Ca Here : K2 48-8,alumina 207, lime 7-6, potash 6-4, water series of striations away

double See

=

=

.

.

=

=

"

=

=

2:1.

B.B. crumbles and fuses at 3 to a white enamel. Gelatinizes with hydrochloric acid. Obs. In translucent crystalsin basalt,at the Giant's Causeway. Ireland;at Capo di the lavas of Mte. Somma, Bove, near Rome; Aci Castello and elsewhere in Sicily;among

Pyr.,etc.

"

"

Vesuvius; in Germany at Stempel, near Marburg; Annerod, near Giessen; in the Kaiserat Salesl, stuhl,with faujasite, Bohemia; in the ancient lavas of the Puy-de-D6me, France; from Richmond, Victoria. found near Pseudophillipsite, Rome, Italy,differs from phillipsite only in the manner in which it loses water on heating. HARMOTOME.

Monoclinic. 55" 10'.

Axes

a

:

b

: c

=

0*7031

:

1

:

1-2310; ft

=

934

Crystals uniformlycruciform penetration-twinswith c (001) as tw. pi; either (1) simpletwins (Fig.934) or (2) united

with tw. pi.e (Oil). These double as fourlings twins often have the aspect of a square prism with diagonal pyramid, the latter with characteristic feather-like striations from the medial line. Also in more complex groups

analogousto those

of

Cleavage:b (010) easy,

phillipsite. c (001) less so.

Fracture G. 2-442-50. Luster vitreous. Color into white; passing gray, yellow, red or brown. Streak white. Subtransparent to uneven

to subconchoidal. Brittle. H.

=

4-5.

=

translucent,

MINERALOGY

DESCRIPTIVE

552

G.

=

prismatic crystals.

slender

In

Monoclinic. Flokite. H8(Ca,Na2)Al2Si9026.2H20. 5. to (100) and (010). H. Perfect cleavages parallel intumescence. Fuses with '474. '472-1 1 Indices,

Colorless and 2 -10. From Iceland. =

parent. trans-

In pyramidal crystals, pseudo-tetragonal. Gismondite. Perhaps CaAl2Si2O8.4H2O. Biaxial. Colorless or white, bluish white, grayish,reddish. 2-265. G. 4'5 at Capo di Bove, Mt. near of Rome, Albano, in the Occurs leucitophyre 1-539. Index near Zermatt, Switzerland; Schlauroth near and elsewhere,etc.; on the Gorner glacier, etc. Bohemia, in Gorlitz Silesia;Salesl, H

-.

=

=

Caporcianite.

Leonhardite.

LAUMONTITE.

68" 46'. M451 : 1 : 0-5906; 0 Axes a : b : c Monoclinic. form the prism m (mm'" 110 A 110 tw. pi.a (100). Common Twins56" 55'). Also termination (ce 001 A 201 with oblique 93" 440 e, 201 a nd divergent. columnar, radiating Cleavage: 6 (010)and m (110)very perfect;a (100)imperfect. Fracture Luster vitreous, 2-25-2-36. G. 3 -5-4. Not very brittle. H. uneven. Color of faces the white, passing into cleavage. to pearly upon inclining uncolored. Streak lucent; Transparent to transyellow or gray, sometimes red. on Optically exposure. becoming opaque and usuallypulverulent + 65" to 70". Dispersionlarge, p " v; Ax. pi.||b (010). Bxa A c axis 1-513. 1'524. 1*525. 52" 24'. a 0 7 inclined,slight.2Er Silica 4H2O.CaO.Al2O3.4SiO2 H4CaAl2Si4Oi4.2H20 =. 51% Comp. =

=

=

=

=

=

"

.

=

=

=

=

=

=

"

217, lime 11-9,water

alumina Var.

and the

15-3

=

100.

is a laumontite which has lost part of its water (to one molecule), from the serpentrue of caporcianite.Schneiderite is laumontite is probably tine Catini,Italy,which has undergone alteration through the action of magnesian

Leonhardite

"

same

of Monte

solutions.

Pyr., etc.

"

B.B.

swells up

and

fuses at 2'5-3

to

a

white enamel.

Gelatinizes

with

acid. hydrochloric Occurs in the cavities of basalt and similar eruptive rocks; also in porphyry syenite,and occasionallyin veins traversingclay slate with calcite. Its principal localitiesare the Faroe Islands; Disko in Greenland; in Bohemia, at Eule in Switzerland; Baveno, Italy; Nagyag, Transylvania; the in clay slate; St. Gothard near Glasgow, Scotland; the Hebrides, and Fassatal,Tyrol,Austria; the Kilpatrickhills, the north of Ireland. In India,in the Deccan trap area, at Poona, etc. Peter's Point, Nova Scotia,affords fine specimens of this species. Found at PhippsAbundant in many placesin the copper veins of Lake Superior in trap, and on burg, Me. Isle Royale; on north shore of Lake du Lac. Superior,between Pigeon Bay and Fond Found also at Bergen Hill,N. J.; at the TillyFoster iron mine, Brewster, N. Y. Obs.

"

and

Laubanite.

snow-white.

CaaAUSuOu.GHjjO. Occurs

upon

Resembles

in basalt phillipsite

Chabazite

Group.

4'5-5. stilbite. H. Lauban, Silesia. =

Color

c

Gmelinite

(Ca,Na2)Al2Si4012.6H20 85" 14' 68" 8' (Na2Ca)Al2Si4Oi2.6H20

07345

Levynite

CaAl2Si3Oi0.5H20

0'8357

The

2'23.

=

Rhombohedral rr'.

Chabazite

G.

at

73" 56'

1;0860 or

fc

=

1*1017

fc

=

1-1143

Chabazite Group includes these three rhombohedral species. The rhombohedrons have different angles,but, as shown in the axial

fundamental

ratios above, they are closelyrelated,since,taking the rhombohedron Chabazite as_ the basis,that of Gmelinite has the symbol (2023) and

of of

Levynite(3034). The

variation in composition often observed

in the firsttwo

specieshas led

to the rather

553

SILICATES

plausiblehypothesisthat they compounds

to be viewed

are

isomorphousmixtures

as

(Ca,Na2)Al2Si2O8.4H2O,

of the

feldspar-like

(Ca,Na2)Al2Si6Oi6.8H2O.

CHABAZITE.

Rhombohedral.

Axis

c

1-0860;0001

=

936

A

1011

51"

=

25f.

937

938

Phacolite

Twins:

(1) tw. axis c axis, penetration-twinscommon. (2) Tw. pi. rhombohedron Form r(1011); contact-twins, rare. commonly the simple 85" 14');also r and varying littlein angle from a cube (rrf1101 A 1101 54" 47'). Also in complex twins. e (0112),(eef Also amorphous. Brittle. H. Cleavage: r (1011) rather distinct. Fracture uneven. 4-5. G. 2-08-2-16. Luster vitreous. Color white, flesh-red;streak uncolored. Transparent to translucent. Optically ; also + (Andreasberg, also haydenite). Birefringencelow. The interference-figure usually confused; .sometimes distinctlybiaxial;basal sections then divided into sharply defined sectors with different opticalorientation. These anomalous conditioned by the variation opticalcharacters probablysecondaryand chiefly =

'

=

=

=

"

in the amount

of water

present.

Mean

refractive index 1-5.

Var. 1. Ordinary. The most form is the fundamental common rhombohedron, in which the angle is so near 90" that the crystals for cubes. at first mistaken were Acadialite, from Nova Scotia (Acadia of the French of 18th century),is a reddish chabazite; sometimes nearly colorless. Haydenite is a yellowishvarietyin small crystalsfrom Jones's Falls,near 2. Phacolite is a colorless variety occurring in twins of hexagonal form Baltimore, Md. (Fig.938), and lenticular in shape (whence the name, from 0a/c6s, a bean)',the original from Here was Leipa in Bohemia. belongs also herschelite (seebachite)from Richmond, Victoria; the composite twins of great variety and beauty. Probably also the original herschelite from Sicily. It occurs in flat, almost tabular,hexagonal prisms with rounded terminations divided into six sectors. "

Somewhat

is often ratio of (Ca,Na2,K2): Al is nearly constant (= 1 : 1),but of A12 : Si varies from 1 : 3 to 1 : 5 ; the water also increases with the increase in silica. The composition usuallycorresponds to (Ca,Na2)Al2Si4Oi2.6H2O, which, if calcium alone is 100. If present, requires:Silica 47 -4,alumina 20'2, lime 11-1,water 21 -3 Ca : Nao 1:1, the percentage compositionis: Silica 47*2, alumina 20*0, lime 5-5,soda 6-1,water 21-2 100.

Comp.

noted

"

even

among

uncertain,since

specimens

from

a

the

rather same

wide

variation

locality.The

=

=

=

Potassium is present amount, also sometimes, barium and strontium. Streng of the explainsthe supposed facts most satisfactorily by the hypothesis that the members noted above. are as isomorphous mixtures analogous to the feldspars, group B.B. intumesces and fuses to a blebby glass,nearly opaque. Pyr., etc. Decomposed by hydrochloricacid,with separationof slimy silica. in small

"

MINERALOGY

DESCRIPTIVE

554 Diff

form (resemblinga cube). It is harder than by rhombohedral and fluonte in cleavage; fuses B.B. calcite unlike with effervesce acid;

"Characterized

calcite and does not unlike analcite. with intumescence m schist, gneiss, syenite, mica Occurs mostly in basaltic rocks,and occasionally Obs. associated with hornblendic schist. Occurs at the Faroe Islands,Greenland, and Iceland, "

at Oberstem, with harmotome, at Aussig in Bohemia; in Germany stilbite; and shire, RenfrewAnnerod, near Giessen; at the Giant's Causeway, Antrim, Ireland, at Richmond, near Melbourne, Australia (phacolite) In of etc. Isle Skye, Scotland;

chlorite and and

at

etc

Hill and West Paterson, In the United States,in syeniteat Somerville,Mass.; at Bergen In Nova Md. Scotia,wine (haydenite). Falls Baltimore, Jones's near N. J.,in crystals;at associated with heulandite,analcite and calcite, yellow or flesh-red (thelast the acadialite), Two Islands,Wasson's Bluff,etc. Neck, Swan's Five at Creek, Digby Islands, of a stone. chabazite is from x"*/3"^os, an ancient name The name

GMELINITE.

Rhombohedral.

Axis

c

=

0*7345.

Crystals usually hexagonal

in

aspect; sometimes

940

939

(0111) smaller

p

habit r(1011),_and

than

hedral; rr' 10_11A rp

c

1011

A

0111

=

rhombo68" 8', 37" 44'. 1101

=

(1010)

Cleavage: m (0001)sometimes

easy;

ture distinct. Frac4*5. Brittle. H. uneven. Luster vitreous. 2-04-2-17. =

G.

=

Colorless,yellowishwhite, greenish white, reddish white, fleshred. Transparent to translucent.

Optically positive,also negative. often disturbed, and basal low. Interference-figure Birefringence very into sections analogousto chabazite. Mean tive refracsections divided optically index, 1'47.

Comp.

In

"

part (Na2,Ca)Al2Si40i2.6H2O. If sodium 19-9,soda 12-1,water 21-1

this requires:Silica 46-9,alumina

alone =

100.

is present See also

p. 552. B.B. fuses easily(F. 2'5-3) to a white enamel. Decomposed by hydrochloric acid with separationof silica. Obs. Occurs in flesh-red crystalsin amygdaloidal rocks at Montecchio Maggiore, Italy;at Andreasberg,Germany; in Transylvania; Antrim, Ireland; Talisker in Isle of Skye, in largecolorless crystals. In Australia at Flinders,Victoria. In the United States in fine white crystalsat Bergen Hill,Great Notch and Paterson, N. J. At Cape Blomidon, Nova Scotia (ledererite) Islands and Five Islands. ; also at Two Gmelinite after Prof. Gmelin Named of Tubingen (1792-1860).

Pyr.,etc.

=

"

"

In rhombohedral G. 4-4'5. 2'09-2'lG. Levynite. CaAl2Si3Oi0.5H.,p. crystals.H. at GlenColorless, T50. Found white, grayish,reddish, yellowish. Optically co and at Island Magee, Antrim, Ireland; at Dalsnypen, Faroe arm Islands, in Iceland; in East Greenland; in the basalt of Table Mountain near Golden, Col. Offretite. A potash zeolite, related to the speciesof the chabazite group. In basalt =

=

=

"

.

of Mont

Simiouse,France.

ANALCITE.

Analcime.

Isometric. Usually in trapezohedrons; also cubes with faces n (211); again the cubic faces replacedby a vicinal trisoctahedron. Sometimes in composite groups about a singlecrystalas nucleus (Fig.389, p. 161). -Also massive granular;compact with concentric structure.

SILICATES

Cleavage: cubic, in

555

Fracture subconchoidal. Brittle. H. vitreous. Colorless,white; occasionally or reddish white. greenish, yellowish, grayish, Transparentto nearlyopaque. weak Often shows double refraction, 942 is apparently conwhich nected with loss of water and consequent change in molecular G.

5-5 -5.

=

2-22-2-29.

(Art.429).

structure

Comp.

Na

"

n

traces.

=

Luster

1-4874.

=

AlSi2O6 H2 O

=

Silica Na20.Al2O3.4Si02.2H2O 54.5, alumina 23-2, soda 14-1, =

water

8-2

100.

=

Analyses show

always

a

varying

silica and water above It has amounts requiredby formula. that a molecule containing the acid H2Si2O6 is present in soild solution in been assumed small amounts. in the closed tube. Yields water B.B. fuses at 2'5 to a colorless glass. Pyr., etc. Gelatinizes with hydrochloricacid. Diff. Characterized by trapezohedralform, but is softer than garnet, and yieldswater to a clear glass fuses without intumescence B.B., unlike leucite (which is also infusible); From leucite and spdalite unlike chabazite. surely distinguishedonly by chemical tests, of much absence of chlorine in the nitric-acid test (seesodalite, i.e., potash p. 502),absence and abundance of soda in the solution, anol evolution of much water from the powder in a closed glasstube below a red heat. Micro. Recognized in thin sections by its very low relief and isotropiccharacter; anomalies. often shows optical Occurs Obs. also prehnite,calcite, frequentlywith other zeolites., etc.,in cavities and in basic igneousrocks,as basalt,diabase,etc.: also in granite,gneiss, etc. seams Recently to be also a rather widespread component shown of the groundmass of various basic igneous rocks, at times being the only alkali-alumina silicate present, as in the so-called analcite-basalts. Has been held in such cases to be a primary mineral produced by the of a magma crystallization containingconsiderable soda and .water vapor held under pressure. excess

of

"

"

"

"

The Cyclopean Islands,near afford pellucidcrystals;also the Fassatal Catania,Sicily, Tyrol, Austria; other localities are, in Scotland, in the KilpatrickHills; Co. Antrim, etc.,in Ireland; the Faroe Islands; Iceland; near Aussig,Bohemia; at Arendal, Norway, in beds of iron ore; at Andreasberg, in the Harz Mts., Germany, in silver mines. In the United States,occurs at Bergen Hill and West Paterson, N. J.; in gneiss near and Yonkers, Westchester Co., N. Y.; abundant in fine crystalswith prehnite,datolite, in the Lake Superior region; at Table Mt. near Golden, Col.,with other zeolites. calcite, Nova Scotia affords fine specimens. is from The analcime electric power name avaXms, weak, and alludes to its weak The correct derivative is analcite, when heated or rubbed. as here adopted for the species. in

Faujasite. Perhaps 1'48. curs OcH. =5. 1'923. In isometric octahedrons. G. Colorless,white, n with augitein the limburgiteof Sasbach in the Kaiserstuhl,Baden, Germany, etc. =

=

Edingtonite. Perhaps BaAl2Si3Oio.3H2O. Crystals pyramidal in habit (orthorhombic, H. 2*694. 4-4 -5. G. White, grayishwhite,pink. pseudo-tetragonal);also massive. land, Glasgow, ScotOptically Indices, 1*538-1 '554. Occurs in the KilpatrickHills,near From with harmotome. Bohlet,Sweden. =

=

"

.

Natrolite

Group.

Orthorhombic

Monoclinic

and a

0*9785

Natrolite

a

Scolecite Mesolite

Ca(A10H)2(SiO3)3.2H2O (Na2Al2Si3O10.2H2O

[2[CaAl2Si3Oio.3H2O]

0-9764

0-3536 c

0-3434

89"

18'

556

MINERALOGY

DESCRIPTIVE

m GROUP agree closelyin angle,though varying The three speciesof the NATROLITE ; fecolecite is usually,also rarely monoclmic system; Natrolite is orthorhombic crystalline monoclmic and tnto be both Mesolite seems monoclinic,perhaps also in part triclinic; all these to common are species. clinic. Fibrous,radiatingor divergentgroups Natrolite,with the empiricalformula The Natrolite Group includes the sodium silicate, also Mesolite CaAlaSigOio.SHaO; Scolecite, calcium silicate, Na2Al2Si3Oi0.2H2O; the ,

\mNa2

Al2Si3Oio.2H2O nCaAl2Si3Oio.3H2O.

.

correspondingto

these and

between

intermediate NATROLITE.

Axes

Orthorhombic.*

a

:

b

c

0-9785

=

944

943

:

1

:

0*3536.

mm"',

110

A

1TO

=

88'

mo,

110

A

111

=

63

oo

111

A

111

oo'

111

A

111

11'.

37" 38'. 36" 47"'.

Crystalsprismatic,usuallyvery slender to acicular; frequentlydivergent,or in stellate Also fibrous,radiating, massive,granular, groups. or

compact.

fect, Cleavage: m (110) perfect;b (010)imperture perhaps only a plane of parting. FracH.

uneven.

="

G.

5-5'5.

=

2'20-2'25.

sometimes to pearly, inclining vitreous, to varieties. Color fibrous or grayish, in colorless; ish, yellowwhite, especially Ax. pi. || reddish to red. Optically+. Transparent to translucent. T482. 1'480. T493. 63". a 6 (010). Bx ft _L c (001). 2V 7 Luster

=

=

=

=

Ordinary. Commonly either (") in groups of slender colorless prismatic crystals, gent varying but littlein angle from square prisms, often acicular,or (6) in fibrous divervitreous in luster, or but slightly pearly (theseradiated forms often or radiated masses, resemble those of thomsonite and pectolite) ; often also (c)solid amygdules, usuallyradiated Galactite is silky in luster within; (d) rarely compact massive. fibrous,and somewhat in colorless needles from southern Scotland. ordinarilynatrolite, which have been given to the natrolite names brevicite, are Bergmannite, spreustein, the Langesund fiord,in the "Brevik" of southern Norway, on from the augite-syenite and from fibrous,massive, and in long prismatic crystallizations, region,where it occurs, in part from sodalite. Iron-natrolite white to red in color. Derived in part from elaeolite, is a dark green opaque the Brevik region; the or amorphous, from variety,either crystalline Var.

"

iron is due to inclusions.

Na2Al2Si3Oio.2H20 or Na2O.Al203.3Si02.2H20 100. 26-8,NasO 16-3,water 9-5

Comp.

"

=

Silica 474, alumina

=

In the closed tube whitens and becomes B.B. fuses quietlyat 2 opaque. colorless glass. Fusible in the flame of an ordinary wax candle. Gelatinizes with acids. Diff. and Distinguishedfrom aragonite and pectoliteby its easy fusibility gelatinization with acid. Obs. Occurs in cavities in amygdaloidal basalt,and other related igneous rocks; in granite, sometimes in seams mia; gneiss,and syenite. Found at Aussig and Teplitz in Bohein Auvergne, France; Fassatal,Tyrol,Austria; Kapnik, Hungary. in fine crystals In red amygdules (crocalite) in amygdaloid of Ireland,Scotland and Tyrol; the amygdaloid of and at Glen Farg (fargite) in Fifeshire. in the Common Bishopton, Scotland (galactite) of the Langesund fiord, From augite-syenite various localnear ities Brevik, southern Norway. in Greenland. In North America, in the trap of Nova Scotia; at Bergen Hill and West Paterson,N. J.; at Copper Falls, Lake Superior;from benitoite locality, San Benito Co., Cal. Named Mesotype by Haiiy, from Me"n"s, middle, and TVTTOS, type, because the form of the crystal in his view a square prism intermediate between the forms of stilbite was

Pyr.,etc.

to

"

a

"

"

"

"

*

In

rare

cases

the crystalsseem

to be monoclinic.

557

SILICATES

of Klaproth, is from natron, soda; it alludes to the presence of and analcite. Natrolite, also the name or soda-mesotype,in contrast with scolecite, lime-mesotype.

soda,

whence

SCOLECITE.

Monoclinic. Axes a : b : c 0-9764 89" 18'. : 1 : 0*3434; /3 88" 37%'),twins showing a Crystalsslender prismatic(mm'" 110 A 110 feather-like striation on b '(010),divergingupward; also as penetration-twins. Also massive, fibrous and radiated,and in Crystals in divergent groups. nodules. =

=

=

G. 5-5-5. 2-16-2-4. Luster Cleavage: m (110)nearlyperfect. H. when fibrous. to vitreous,or silky Transparent subtranslucent. Optically 15"-16". Ax. pi. and Bx0 J_ b (010). Bxa A c axis 2V 36" (approx.). =

=

"

.

=

a

1-512.

-

|8

=

1-519.

1'519.

=

7

CaAl2Si3O10.3H2O 26-0,lime 14-3,water 13*8

Comp.

=

"

CaO.Al2O3.3SiO2.3H20

or

=

Silica 45'9, alumina

100.

=

B.B. sometimes curls up like a worm from o-KuXqg,a (whence the name and not scolesite or scolezite)', which gives scolecite, other varieties intumesce but and all fuse at 2-2*2 to a white blebby enamel. Gelatinizes with acids like natrolite. slightly, Obs. Occurs in the Berufiord,Iceland; in Scotland in amygdaloid at Staffa Island and in Isle of Skye, at Talisker; near in Eisenach,Saxony; in Auvergne, France; common fine crystallizations In crystals in the Deccan from Karsanantrap area, in British India. In the United Golden near guit-Kakait,Greenland. States,in Col. at Table Mountain In Canada, at Black Lake, Megantic Co., Quebec. in cavities in basalt.

Pyr., etc.

"

worm,

"

Mesolite. Intermediate between natrolite and scolecite (see p. 556). In acicular and 2 -29. White or colorless. Indices, capillarycrystals;delicate divergent tufts,etc. G. In amygdaloidal basalt at numerous 1 '505-1 '506. points. Crystals from Faroe Islands to be triclinic, is name pseudomonoclinic through twinning. Pseudomesolite given appear Carlton Peak, Minn., like mesolite except for its opticalcharacters. to a zeolite from Gonnardite. (Ca,Na2)2Al2Si5Oi5.5"H2O. In spherules with radiating structure. G. 2-25-2-35. From basalt of Gignat, Puy-de-D6me, France. =

=

THOMSONITE.

Orthorhombic. Axes Distinct crystals rare;

a

:

b

: c

=

0-9932

:

1

:

1-0066.

89" 37'. Commonly prisms,mm'" 110 A ,110 radiated;in radiated sphericalconcretions;also closely

columnar, compact. Cleavage:

structure

in

=

6 (010)perfect;a (100) less so; c (001) in traces. Fracture H. Brittle. 5-5*5. G. 2-3-2-4. Luster subconchoidal. uneven less varieties or pearly. Snow-white; reddish,green; impure vitreous,more brown. Streak uncolored. Transparent to translucent. Pyroelectric.Optically Ax. + pi.11c (001). Bx J_ 6 (010). Dispersionp " v strong. 2V 1-497. 1-503. 1'525. 54" (approx.). a ft 7 to

=

=

=

.

=

=

=

less rectangularin outline, 1. Ordinary, (a) In regularcrystals, or usually more (c) Radiated prismatic in habit. (6) Prisms slender,often vesicular to radiated, fibrous, (d) Sphericalconcretions,consistingof radiated fibers or slender crystals. Also massive, granular to impalpable, and white to reddish brown, less often green as in Unionite. The sphericalmassive forms also radiated with several centers and of varying colors, sas. hence of much beauty when polished. Ozarkite is a white massive thomsonite from ArkanVar.

"

Comp.

(Na2,Ca)Al2Si2O8.2JH20or (Na2,Ca)O.Al2O3.2SiO2.2iH20.The

"

Ca varies from 3 : 1 to 1 : 1. If Ca compositionrequires:SiO2 37'0,A12O3 31-4,CaO ratio of Na2 100.

:

:

Na^

=

3:1

12'9,NaaO

the percentage 4-8,H20 13'9 =

MINERALOGY

DESCRIPTIVE

558

with

fuses

B.B. Pyr., etc. hydrochloricacid.

intumescence

at 2 to

a

white

enamel.

Gelatinizes

with

not to a clear glass. but fuses to an opaque, Resembles natrolite, some with in cavities in lava in amygdaloidal igneous rocks, sometimes Found Kilpatrick,Scotland; in the lavas of near elseoliteas a result of its alteration. Occurs many Vesuvius; in basalt at the Pflasterkaute in Saxe Weimar, GerMte Somma (comptonite) , '

Diff. Obs.

"

in

Bohemia,

in

Brevik, Norway; the Monzoni, Fassatal, Tyrol,

Sicily;near phonolite;the Cyclopeanislands,

Faroe' straw-yellow);at Islands; Iceland (carphostilbite,

Mt.

In the United States,at West Scotia. Paterson, N. J.; Occurs at Peter's Point, Nova in the Ozark Mts,, Ark.; in the amygdaloid of Grand Marais, Magnet Cove (ozarkite) the water-worn pebblesresembling agate, in part green (lintonLake Superior,which yields Golden, Col. ite); in the basalt of Table Mt. near An alteration product of thomsonite HYDROTHOMSONITE. (H2,Na2)Ca)Al2Si2O8.5H2O. at

or

Tschakwa

scolecite from

Batum

near

the Black

on

Sea.

In radiating fibrous and soda. zeolite containing lime Arduinite. From Val dei Zuccanti,Venetia,Italy. Color red. 2-26. G.

aggregates.

A

=

In (Ca,Na2)O.2Al2O3.3SiO2,4H2O. T533. Elongated |[Y.

Echellite.

H. 5. White. ft Northern Ontario. =

=

radiating,fibrous,spheroidal masses. Sextant Portage, Abitibi River,

From

In minute crystals, as for stilbite. Orthorhombic. only the to both vertical pinacoids. Colorless to yellow. Cleavages parallel Easily perpendicular to c (001). Optically-. G. =2*16. Occurs as a crust on calcite from Schwarzenberg, Saxony. Stellerite. CaAl2Si7Oi8.7H2O. Orthorhombic. Crystals tabular parallelto b (010). 3 '5-4. to b (010), imperfectparallelto a (100) and c (001). H. Cleavage perfectparallel mander 2*12. G. Indices,1 '48-1 '50. Found in cavity in a diabase tuff,Copper Island,Com-

Epidesmine.

Comp.

same

three pinacoidsshowing. Bxa 1 '50. Index fusible with intumescence. =

=

=

Islands. Erionite.

Orthorhombic.

H2CaK2Na2Al2Si6Oi7.5H2O.

In

aggregates of

slender

very

1'997. White. Occurs in cavities in rhyolitefrom Durkee, resemblingwool. G. fibers, Oregon. Bavenite. Fibrous-radiated of prismatic Ca3Al2(SiO3)6.H2O. Monoclinic. groups 2*7. G. Color white. 5'5. 1'58. Occurs in pegcrystals. One cleavage. H. 0 matitic druses in the graniteof Baveno, Italy. of the Bityite. A hydrous silicate of calcium and aluminium, with small amounts alkalies. Pseudo-hexagonal. In minute hexagonal plateswhich in polarizedlight show division into six biaxial sectors. 5*5. G. dices In3*0. Cleavage parallelto base. H. 1 '62-1 '64. Found crusts in pegmatite veins at Maharitra, Madagascar. as crystal 4'5-6. G. 2'263. Hydronephelite. HNa2Al3Si3Oi2.3H2O. Massive, radiated. H. Color white; also dark gray. to be a Index, 1'50. From Me.; said however Litchfield, mixture of natrolite, and diaspore. Ranite from the Langesund fiord, hydrargillite Norway, =

=

=

=

=

=

=

=

is similar.

II. Mica

Division

The speciesembraced under this Division fall into three groups: 1, the MICA GROUP, includingthe Micas proper; 2, the CLINTONITE GROUP, or the Brittle Micas; 3, the CHLORITE GROUP. Supplementary to these are the

Vermiculites, hydrated compounds, chieflyresults of the alteration of one

some

of the micas. All of the above

specieshave the characteristic micaceous structure,that is,they have highlyperfectbasal cleavageand yieldeasilythin laminae. They belong to the monoclinic system, but the positionof the bisectrix in general deviates but littlefrom the normal to the plane of cleavage;all of them show the basal section plane anglesof 60" or 120",marking the relative on position of the chief zones of forms present, and givingthem the of hexappearance

560

MINERALOGY

DESCRIPTIVE

belong those kinds for which the opticaxial plane is normal to b (010),the to planeof symmetry (Fig.945) ; in the second class the axial plane is parallel the fix to The crystallothe plane of symmetry. percussionfigureserves faces are wanting. A second series of graphicorientation when crystalline be more or less distinctly developed lines at rightanglesto those mentioned may the so-called elastic forming dull of surface, on an pressurea point by pressure and shows branches three often is sometimes only, more this six-rayed, figure; sometimes only two are developed. In Fig.945 the positionof the pressureis indicated by the broken lines. These lines are connected with glidingfigure 67" to the plane of cleavage (seebeyond). planesinclined some also the The micas of lepidolite, firstclass include : Muscovite,paragonite, some

varieties of biotite called anomite. Zinnwaldite class embraces:

rare

and most biotite,including lepidomelaneand phlogopite. and in most orthosilithe micas are silicates, cases Chemicallyconsidered, with potassium and hydrogen, also often magnesium, cates, of aluminium rubidium ferrous iron,and in certain cases ferric iron,sodium, lithium (rarely and caesium);further, Fluorine chromium. is rarely,barium, manganese, in is Other titanium also sometimes a nd some prominent species, present. elements (boron,etc.)may be present in traces. All micas yieldwater upon in consequence of the hydrogen (orhydroxyl)which they contain. ignition The

second

MUSCOVITE.

Monoclinic. Twins common

Common

Axes

Mica. a

b

: c

Potash =

Mica.

0*57735

:

1

:

3-3128; /3

=

89" 54'.

tw. pi. a plane in the zone accordingto the mica-law: cM 001 A 221 normal to c (001) the crystals often united by c. Crystals rhombic or hexagonal in outline with plane angles of 60" or 120". Habit less rough and tabular,passing into taperingforms with planes more or striated vicinal forms strongly Folia often very small horizontally; common. and aggregated in stellate, and scaly plumose,or globularforms; or in scales, and compact massive. massive; also cryptocrystalline Cleavage: basal,eminent. Also planesof secondarycleavageas shown in the percussion-figure (seepp. 559 and 189); natural plateshence often yield "

cM,

001

CM,

001

MM', MM',

221 HI

A A

221 111

=

A A

221 111

=

=

=

85" 81" 59" 59"

36'. 30'. 48'.

16"'.

stripsor

thin fibers less distinct in directions inclined 60" to this. Inin L laminae flexible and elastic when bent, very tough, harsh to the touch, passing into kinds which are less elastic and have a more less or unctuous or talc-likefeel. in symmetry Etching-figures on c (001) monoclinic narrow

||axis b, and

,

(rig.495, p. 190). ."~~'

^*' ^' ^ '76-3. Luster vitreous to more or less pearly or i Colorless, gray, brown, hair-brown, pale green, and violet,yellow, olive-green, rarelyrose-red. Streak uncolored. lucent. Transparent to transT*

=

Iky. dark

Pleochroism usuallyfeeble;distinct in "eyond). X ,

some deep-coloredvarieties (see Absorption in the direction normal to the cleavageplane (vibraaj strong,much more so than transversely 11X) ; hence a (vibrations

"

'i

561

SILICATES

in the first direction though crystalunless thin is nearly or quite opaque translucent through the prism. Optically Ax. pi. J_ b (010) and nearly 1" (behind)to a normal to c (001). J_ c (001). Bxa (= X) inclined about Dispersionp " v. 2V variable,usuallyabout 40", but diminishingin kinds 1*561. T590. T594. ft (phengite)relatively high in silica, a 7 "

.

--

=

"

Ordinary Muscovite.

=

In

often tabular ||c (001), crystalsas above described, striated;the basal plane often rough unless as commonly in plates without distinct outline,except as developed by cleavage. More developed by pressure (seeabove) ; the platessometimes very large,but passing into fine In normal scales arranged in plumose or other forms. muscovite "he thin laminae spring back with force when or less harsh to the touch, unless very bent, the scales are more small, and a pearly luster is seldom prominent. 2. DAMOURITE. and most Including margarodite,gilbertite, HYDROhydro-muscovite, in general. Folia less elastic;luster somewhat MICA pearly or silkyand feel unctuous like The scales are usuallysmall and it passes talc. into forms which are fine scaly or fibrous, and finally into the compact crypto-crystalline kinds called oncosine,including as sericite, much pinite. Often derived by alteration of cyanite,topaz, corundum, etc. Although that damourite and the allied varieties often spoken of as hydrous micas, it does not appear water than ordinary muscovite; they may, necessarilycontain more however, give it off more readily. named, was the talc-like mica of Mt. Greiner in the Zillertal, Margarodite,as originally Tyrol,Austria; granularto scalyin structure,luster pearly,color grayishwhite. Gilbertite in whitish,silkyforms from the tin mine of St. Austell,Cornwall. Sericite is a fine occurs scalymuscovite united in fibrous aggregates and characterized by its silkyluster (hencethe from O-T/PIKOS,silky}. name Var.

1.

"

also taperingwith vertical faces rough and

For the most and potaspart an orthosilicate of aluminium Comp. sium in H K the 2 this becomes common : 1, (H,K)AlSiO4. If,as kinds, : Silica 45-2,alumina 38*5,potash H2KAl3(SiO4)3 2H2O.K2O.3Al2O3.6SiO2 "

=

=

4-5

11-8,water

=

=

100.

of silica (47 to 49 p. c.)than correspondsto a normal Some kinds give a larger amount and orthosilicate, they have been called phengite. As shown by Clarke,these acid musbe most covites and can simply regarded as molecular mixtures of H^KA^SiO^s H2KAl3(Si308)3. Iron is usuallypresent in small amount only. Barium is rarelypresent, as in oellacherite. is also present in fuchsitefrom Chromium G. 2'88-2*99. Schwarzenstein, Zillertal, Tyrol, and elsewhere. B.B. whitens In the closed tube gives water. and fuses on the thin edges Pyr.,etc. 5'7) to a gray or yellow glass. With fluxes givesreactions for iron and sometimes (F. Not decomposed by acids. Decomposed on fusion with rarely chromium.* manganese, =

"

=

alkaline carbonates. Diff. Distinguishedin normal perfectbasal cleavageand micaceous "

kinds

from

all but

the speciesof this division by the

.

structure,the pale color separates it from most

flexible and elastic than the laminae are more the brittle micas and the chlorites.

those of phlogopiteand stillmore

biotite;

than those of

In thin sections recognized by want of color and by the perfectcleavage Micro. shown by fine lines (asin Fig.951, p. 564) in sections _1_c (001),in a direction parallelto c. sections show a peculiarmottled surface By reflected lightunder the microscope the same rather high,hence interference-colors bright. with satin-like luster;birefringence of the micas. It is an essential constituent of is the most Muscovite Obs. common of certain common varieties mica schist and related rocks,and is a prominent component of graniteand gneiss; also found at times in fragmental rocks and limestones;in volcanic and appears rocks it is rare only as a secondary product. The largestand best developed with graniticintrusions, either directly in the pegmatite dikes associated crystalsoccur in enormous platesfrom cuttingthe graniteor in its vicinity. Often in such occurrences "

"

which

the

mica

or

"isinglass"of

commerce

is obtained.

It is then

often associated with

orthoclase,quartz, albite;also apatite,tourmaline,garnet, beryl,columbite, crystallized speciescharacteristic of graniticveins. Further, muscovite often the of garnet, tourmaline, also quartz in thin plates between encloses flattened crystals tions sheets;further not infrequentlymagnetite in dendrite-like forms followingin part the direcof the percussion-figure. etc.,and other mineral

MINERALOGY

DESCRIPTIVE

562

Abiihl in the Sulzbachtal,Austrian Tyrol; with are: localities, Some of the best known Tyrol; Soboth, Styria; St. Gothard, Binnental, and adularia; Rothenkopf in the Zillertal, Mts., Ireland; Cornwall; Uto, Falun, Sweden; Skutelsewhere in Switzerland; Mourne and the East Indies. Obtained in largeplatesfrom Greenland terud,and Bamble, Norway. of Paris; at Buckfield,in fine crystals. In N. H., at Mica in the town In Me., at Mount In In Mass., at Chesterfield;South Royalston; at Goshen, rose-red. Acworth, Graf ton. the Middletown at w ith at feldspar at Litchfield, cyanite; quarry; at Monroe; Conn., In N. Y., near with albite, Warwick; Edenetc.; New Milford. Haddam; at Branch ville, In Pa., at Pennsbury, Chester Co.; at Unionville,Delaware Co., and at ville;Edwards. In Va., at Amelia In Md., at Jones's Falls,Baltimore. Middletown. Court-Hquse. In at many N. C., extensivelymined places in the western part of the state; the chief mines The mica in Mitchell,Yancey, Jackson and Macon Cos.; crystalsfrom Lincoln Co. are uranrare mines have also afforded many species,as columbite,samarskite,hatchettolite, Co. In S. C., there are also muscovite in Alexander deposits; inite,etc.; in good crystals also in Ga. and Ala. Mica mines have also been

in the Black Hills,S. D.; in Wash., extent to some worked Rockford, Spokane Co.; in Col. The important states for the production of mica are North Carolina,New Hampshire, Idaho, South Dakota, Virginia,Alabama, New York,

at

Connecticut. Muscovite

from

is named

Muscoviticum

Vitrum

or

Muscovy-glass,formerly a popular

of the mineral. As an insulatingmaterial in electrical apparatus; as a non-inflammable Use. material for furnace doors,etc.; in a finelydivided form as a non-conductor and fireproofing material; mixed with oil as a lubricant,etc. name

"

parent trans-

of heat

A generalterm Finite. used to include a large number of alteration-products especially In composialso spodumene, nephelite,scapolite, iolite, feldsparand other minerals. tion and potassium corresponding more less a hydrous silicateof aluminium essentially or closelyto muscovite, of which it is probably to be regarded as a massive, compact variety, of clay and other substances. lows: folCharacters usuallyvery impure from the admixture as Amorphous; granularto cryptocrystalline.Rarely a submicaceous cleavage. H. 2'5-3'5. Luster 2'6-2'85. G. Color grayish white, grayish green, peafeeble,waxy. reddish. dull to opaque. The Translucent of brownish, followingare some green, green, the minerals also classed as pinite:gigantolite, gieseckite (seep. 500),liebenerite, dysyntribite, killinite. rosite,polyargite, par ophite, wilsonite, Agalmatolite(pagodite)is like ordinary massive pinitein its amorphous compact texture, luster,and other physical characters,but contains more which may be from free silica, quartz or feldsparas impurity. The Chinese has H. 2785-2'815. Colors 2-2'5; G. usually grayish,grayish green, brownish, yellowish. Named from aja\na, an image; pagoditeis from pagoda, the Chinese carving the soft stone into miniature pagodas, images, etc. Part of the so-called agalmatoliteof China is true pinitein composition, another part is compact pyrophyllite, and stillanother steatite (seethese species). A sodium Paragonite. mica, corresponding to muscorite in composition; formula, HaNaAlsCSiCMs. In fine pearly scales; also compact. G. 278-2-90. Index, 1'60. Color yellowish, of the rock at Monte'Campione near grayish,greenish;constitutes the mass Faido in Canton Tessin,Switzerland, containingcyanite and staurolite;called paragoniteschist. Occurs associated with tourmaline and corundum at Unionville,Delaware Co., Pa. with an iridescent silver color and pearly luster. a mica Hallerite, ing Perhaps a lithium-bearparagonite. Found at Mesores,near Autun, France. of

=

=

=

=

=

BADDECKITE, an iron mica related near Baddeck, Nova Scotia.

to muscovite.

In small scales with

From

LEPIDOLITE.

a

copper-red color.

LithiaMica.

In aggregates of short

twins

sometimes

or

prisms,often with rounded terminal faces. Crystals trillings accordingto the mica law. Also in cleavable

plates,but commonly massive

scaly-granular, coarse

Cleavage: basal,highly eminent. Color

pearly

Translucent

Optically ,

p

d' *nd =

T

1'5975.

Ax.

pi.usually" 33*'"ellow to normal

-.

"

=

2-5-4.

or

fine. G. 2 -8-2 -9. =

Luster

rose-red,violet-gray or lilac, yellowish,grayishwhite, white.

in Si17oJf ou iZ irom

H.

b to

(010);rarely||6. c

Bxa (X)

563

SILICATES

Comp. The

In

"

R3Al(SiO3)3or KLi[Al(OH,F)2]Al(Si03)3. part a metasilicate, hydroxyl is variable.

ratio of fluorine and

molecule is representedby 3Li2O.2K2O. suggested that the puro lepidolite mixtures of this and the muscovite that most lepidolites are molecule. In the closed tube gives water and reaction for fluorine. B.B. fuses with Pyr., etc. at 2-2 '5 to a white or grayish glasssometimes intumescence magnetic, coloringthe flame of fusion (lithia) With the fluxes some varieties give reactions purplishred at the moment Attacked but not completelydecomposed by acids. After fusion, for iron and manganese. acid. with hydrochloric gelatinizes in graniticveins; often associated with in graniteand gneiss,especially Occurs Obs. also with amblygonite, spodumene, cassiterite, ated associetc.; sometimes lithia-tourmaline; in parallel with muscovite position. Found TJto in Sweden; Penig,Saxony; Rozena (orRozna), Moravia; Madagascar, near in the western In the United States,common etc. part of Me., in Hebron, Auburn, Paris, and Haddam Neck, Conn.; with rubellite near Mass.; Middletown etc.; at Chesterfield, San Diego, Cal. after the earlier German from XeTm, scale, name ing alludNamed lepidolite Schuppenstein, of the massive to the scaly structure varietyof Rozena. of lithium compounds. As a source Use. mineral occurring in rounded is a micaceous also COOKEITE aggregationson rubellite, An alteration of lepidolite or tourmaline. with lepidolite, tourmaline,etc.,at Hebron, Me. Composition Li[Al(OH)2l3(SiO3)2. biotite. Color pale violet,yellow to An iron-lithia mica in form Zinnwaldite. near and Altenberg, Germany; similarlyin CornOccurs at Zinnwald wall, brown and dark gray. England. From Narsarsuk, Greenland, and the York region,Alaska. is a lithium is a related lithium mica from Rockport, Mass. Polylithionite Cryophyllite is an alkalie mica containinglithium from mica from Kangerdluarsuk, Greenland. Irvingite near Wausau, Wis. A Manandonite. basic boro-silicate of lithium and aluminium, H24Li4Ali4B4Si6O53. of hexagonal plates. Perfect In lamellar aggregates or mammillary crusts Micaceous. able. Axial angle small and variLuster basal cleavage. Color white. pearly. Optically+. in pegmatite at Anby acids. Found Easilyfusible giving red flame. Unattacked River, Madagascar. tandrokomby, near the Manandona It has been

3Al2O3.8F.12SiO2 and "

.

"

"

BIOTITE.

Monoclinic; pseudo-rhombohedral.Axes

a

:

b

: c

=

0-57735

:

1

:

3

-2743;

90". Habit tabular or short prismatic;the pyramidal faces often repeatedin in symcombination. .Crystalsoften apparently rhombohedral metry oscillatory sibly since r (101)and z (132),z' (132),which are inclined to c (001)at sento which these the same together;further,the zones angle,often occur faces belong are inclined 120" to each other,hence the hexagonal outline of basal sections. Twins, according to the mica law, tw. pi. a plane in the sometimes in massive _L c (001) Often in disseminated scales, prismaticzone

0

=

.

aggregationsof cleavable scales. 960

948

M

co,

001 A

112

cM,

001

c/*,

001

221 111

A A

73" 1'. 85" 38'. 81" 19'.

cr,

001

cz,

001 221

MM',

A A A

T01 132 221

=

=

=

0'. 80" 0'. 80" 59" 48*'.

MINERALOGY

DESCRIPTIVE

564

in the percussion-figure;

planesof separationshown Cleavage: basal,highlyperfect; f (135) shown also gliding-planes /" (205),

in the

pressure-figure forms (Fig.489, (001)and yieldingpseudo-crystalline less Luster or 27-3-1. splendent,and more G. 2-5-3. p. 188). H. when submetallic lateral black; pearly on a cleavage surface,and sometimes and shining. Colors usuallygreen to black, surfaces vitreous when smooth in thin laminae, and sometimes even often deep black in thick crystals, brown or unless the lamina? are very thin;such thin lamina? green, blood-red, white. dark to Streak brown; also rarely transmitted paleyellow light; by ,

66" to

inclined about

c

=

=

uncolored.

Transparent

Pleochroism Hence sections

to opaque.

strong; absorption Y

Z

=

X

nearly,for

much

stronger.

and ||c (001)dark green or brown to opaque; those J_ c lighter for red vibrations or vibrations for 11c, paleyellow,green deep brown or green about microscopicinclusions. Pleochroic halos often noted, particularly J_ c. b dent Ax. pi.usually|| (010), rarely_L b. Bxa (=X) nearlycoinciOptically but inclined about half a degree, sometimes with the normal to c (001), Axial angleusuallyvery small,and often the reverse. to the front,sometimes 0*04 to 0-06. a high,y sensibly uniaxial;also up to 50". Birefringence In most an orthosilicate, chieflyranging between (H,K)2 cases Comp. "

.

"

=

"

Of these the second and (H,K)2(Mg,Fe)2Al2(SiO4)3. (Mg,Fe)4(Al,Fe)2(Si04)4 of iron varies biotite. The amount be to said typical represent may widely. formula

Var. Biotite is divided into two classes by Tschermak: Ax. pi. J_ 6 (010). Of these I. MEROXENE. Axial plane ||6 (010). II. ANOMITE. includes nearly all ordinary biotite, while anomite two kinds, meroxene is,so far as yet the typicallocalitiesbeing Greenwood observed,of restricted occurrence, Furnace, Orange is a name Co., N. Y., and Lake Baikal in East Siberia. Meroxene earlygiven to the Vesu"

vian biotite.

Anomite

is from

aw^tos,

contrary to law.

kinds of biotite containing much iron. are Haughtoniteand Siderophyllite Manganophylliteis a manganesian biotite. Occurs in aggregationsof thin scales. Color bronze- to copper-red. Streak pale red. From mont, Pajsberg and Langban, Sweden; PiedItaly. In the closed tube givesa littlewater. Some varieties give the reaction for Pyr.,etc. fluorine in the open tube; some kinds give littleor no reaction for iron with the fluxes, while others for iron. B. B. give strong reactions whitens and fuses on the thin edges. Completely decomposed by sulphuric acid,leaving the silicain "

thin scales.

DM. Distinguishedby itsdark green to brown black color and micaceous structure, usually nearly uniaxial. Micro. Recognized in thin sections by 'its brown (or green) color; strong pleochroism and "

and

"

^

to the elongation(unlike strong absorption parallel

"by ,.

them

from

^ro

tourmaline). Sections |c (001) are non-pleochroic, less distinct hexagonal commonly exhibit more or outlines and yielda negativesensiblyuniaxial figure. Sections _|_c are stronglypleochroicand are marked fine parallel, cleavagelines (Fig.951); they also have and nearly parallelextinction, show high polarizationcolors; by reflected lightthey exhibit sheen which is veiT characteristic and aids in distinguishing

u01' Vvha1tered

is "^i~V?iotitr an,imP"rtant constituent those formed

of many different kinds of igneous rocks, from magmas containing considerable potash and magnesia non in certain varieties of granites, syenite,diorite, etc.,of the massive granular type; i rhyohte trachyte,and andesite among the lavas;in minettes, It etc. kersantites, also as the product of metamorphic action in a variety of rocks. It is not infre-

illy

.curs

565

SILICATES

in parallel for example,forming the positionwith muscovite, the latter, portionsof plateshaving a nucleus of biotite. of the prominent localities of crystallized biotite are as follows: Vesuvius,comSome mon Monte on particularlyin ejected limestone masses Somma, with augite,chrysolite, The crystalsare sometimes nearly colorless or yellow and then nephelite,humite, etc. in the Fassatal and usually complex in form; also dark green to black; Mt. Monzoni in Hungary; in GerTyrol, Austria; Rezbanya and Morawitza Schwarzenstein,Zillertal, many at Schelingen and other points in the Kaiserstuhl and the Laacher See; on the west side of Lake Ilmen near Miask, Russia. in granite, gneiss,etc.; but notable States ordinary biotite is common In the United It occurs with muscovite localitiesof distinct crystalsare not numerous. (which see) as a of the pegmatite veins in the New or less prominent constituent more England States;also From Pennsylvania, Virginia,North Carolina. Greenwood, Orange Co., N. Y. Siderois from the Pike's Peak region,Col. phyllite

quentlyassociated

outer

altered biotite from

An

CASWELLITE.

Franklin

Furnace,N.

J.

PHLOGOPITE.

Monoclinic.

In form and anglesnear biotite. Crystalsprismatic, tapering; largeand coarse; in scales and plates. Thin laminae tough and elastic. H. Cleavage: basal,highlyeminent. Luster pearly, 278-2-85. often submetallic on cleavagesurface. 2-5-3. G. Color yellowishbrown to brownish red, with often something of a copper-like also pale brownish yellow,green, white,colorless. Often exhibits reflection; asterism in transmitted light,due to regularlyarranged inclusions. Pleochroism distinct in colored varieties: Z brownish red, Y brownish green, X Optically-. Ax. pi. ||b (010). Bxa yellow. Absorption Z " Y " X. nearly _!_ c (001). Axial angle small but variable even in the same specimen, from 0" to 50". Dispersionp " v. The axial angle appears to increase with from 1-541-1-638. of iron. Indices variable, the amount A near mica, biotite,but containing little iron; magnesium Comp. in is all the micas,and in most cases fluorine. Typipotassium prominent as

often

=

=

"

i

cal

phlogopiteis R3Mg3Al(SiO4)3,where

i

R

=

H,K,MgF.

of crystalline limestone or dolomite. It with pyroxene, land; amphibole, serpentine,etc. Thus as at Pargas, Finin St. Lawrence Co. and Jefferson Co., N. Y.; Franklin,N. J.; also Burgess, Ontario, and elsewhere in Canada. in allusion to the color. from "/"Xoyco7r6s, Named fire-like, when The asterism of phlogopite,seen is viewed through a thin sheet,is a candle-flame a common character,particularlyprominent in the kinds from northern New York and to be due to minute acicular inclusions, It has been shown rutile or tourmaline, Canada. producing a distinct sixarranged chieflyin the direction of the rays of the pressure-figure, givinga secondary star,usually rayed star: also parallelto the lines of the percussion-figure, less prominent than the other. Obs.

is often

"

Phlogopiteis especiallycharacteristic

associated

Taeniolite. Essentiallya potassium-magnesium silicate. Monoclinic, belongingto the elastic. H. 2 '5-3. Perfect basal cleavage. Folia somewhat G. mica group. 2 "9. Fusible. Colorless. From Narsarsuk, southern Greenland. =

=

of ferric iron Lepidomelane. Near biotite,but characterized By the large amount Annite from Cape Ann, Mass., From Langesund fiord,Norway; Haddam, Conn. 3. G. belongs here. In small six-sided tables,or an aggregate of minute scales. H. 3 '0-3 -2. Color black, with occasionallya leek-greenreflection. St. Marcel, Piedmont, Italy. Color copper-red. mica from Alurgite. A manganese Index, 1'59. Mariposite may belong here.

present.

=

=

Roscoelite.

A

has in which vanadium vanadium a muscovite mica; essentially 2'92-2'94. G. In minute scales;structure micaceous.

replaced the aluminium.

=

partly Color

MINERALOGY

DESCRIPTIVE

566

Occurs brown. Indices,1 '610-1 704. clove-brown to greenish Co. and elsewhere,El Dorado Granite Creek, Placerville,

gold mine

at

Monoclinic

called the Brittle Micas. They minerals here included are sometimes but are form and optical properties, the micas in cleavage,crystalline by the brittleness of the laminae, and chemicallyby their physically

The near

are

Group.

Clintonite

2.

in Cal. at the

marked basic character. proper to the In several respectsthey form a transition from the micas and of aluminium silicate basic is a chlorites. Margarite,or calcium mica, iron aluminium ferrous and of silicate calcium, while Chloritoid is a basic (withmagnesium), like the chlorites.

MARGARITE.

Rarely in distinct crystals.Usually in intersectingor aggregatedlaminae;sometimes massive, with a scalystructure. G. 3 -5-4*5. Cleavage: basal,perfect. Laminae rather brittle. H. Color faces vitreous. Luster of base pearly,of lateral grayish, 2-99-3-08. subtranslucent. reddish white, pink,yellowish. Translucent, Ax. pi.J_ b (010). Bxa approximatelyJ_ c (001),but varying Optically X A c axis + 6^". Dispersion more widely than the ordinary micas. from 76" to 128" in air. Refractive index ft =1-64Axial anglelarge, p " v. Monoclinic.

=

=

"

.

=

1-65.

Comp. 4'5

H2CaAl4Si2Oi2

"

=

Silica 30'2, alumina

51

'3, lime

14'0, water

100.

=

in the closed tube. B.B. whitens and fuses on the edges. Yields water etc. Pyr., Slowly and imperfectlydecomposed by boilinghydrochloricacid. Obs. Associated commonly with corundum, and in many cases obviously formed directlyfrom it; thus at the emery depositsof Gumuch-dagh in Asia Minor, the islands Naxos, Nicaria,etc. Occurs in chlorite of Mt. Greiner,Sterzing,Tyrol. In the United mine at Chester,Mass.; at Unionville,Chester States at the emery dum Co., Pa.; with corunin Madison Co. and elsewhere in N. C.; at Gainesville, Hall Co., Ga.; at Dudley ville, "

"

Ala. Named

Margarite from

.

SEYBERTITE.

fj.apyapiTt]s,

Clintonite.

Monoclinic,near

pearl.

Brandisite.

biotite in form.

Also

foliated

massive; sometimes

lamellar,radiate.

Cleavage:basal,perfect.

Structure

Laminae brittle. micaceous. foliated, mica. H. with 4-5. G. 3-3-1. pressure-figures, Luster pearly submetallic. Color reddish brown, yellowish,copper-red. Streak uncolored, or slightly yellowishor grayish. Pleochroism rather feeble. Ax. pi. J_ 6 (010) seybertite; Optically \\b brandisite. Bxa nearly J_ c (001). Axial anglesvariable, but not large, a 1-657. 1*646. ft 7 Percussion-

and

as

=

=

"

.

=

=

=

1 '658. !" The Amity seybertite ated is in reddish brown to copper-redbrittle foli(dintonite} the surfaces of the folia often marked masses; with equilateral triangleslike some and chlorite. Axial angle 3"-13".

y**"

mica

2. Brandisite

from the Fassatal,Tyrol, is in hexagonal prisms of a yellowish (disterrite) "lor to reddish gray; H. Ax. 5 of base; of sides, 6-6-5. pi. || (010). Axial angle 15"-30". Some of it pseudomorphous, after fassaite. ,

^T^en ffT?m"m b

=

568

DESCRIPTIVE

MINERALOGY

tical; though it is not certain that they are idenclassed with chloritoid, Ottreliteis generally in small, oblong, the composition H2(Fe,Mn)Al2Si2O9.It occurs to have it seems laceous less hexagonal in form and gray to black in color; in argilor shiningscales or plates,more borders of Luxemburg, and from the Ardennes, France, the schist near Ottrez,on and Belgium; also near Venasquite is Serravezza,Tuscany, Italy; Tintagel in Cornwall. France. is from the from and Phyllite from in the Teule, Finistere, Pyrenees, Venasque

England.

schists of New

3.

Chlorite

Group.

Monoclinic

The CHLORITE from the fact that a largepart of the takes its name GROUP with silicates minerals included in it are characterize^by the green color common in which ferrous iron is prominent. The speciesare in many respects in the monoclinic related to the micas. They crystallize closely system, but in part with distinct monoclinic symmetry, in part with rhombohedral try, symmeuniaxial opticalcharacter. with corresponding The plane anglesof the base are also 60" or 120", marking the mutual inclinations of the chief zones of forms. The mica-like basal cleavageis prominent in distinctly crystallized forms, but the laminae are tough and comparativelyinelastic. Percussion and be obtained with the micas and have the as pressure-figures may orientation. The same in general monoclinic in etching-figuresare symmetry, in part also asymmetric,suggestinga reference to the triclinic

system.

Chemicallyconsidered the chlorites are silicatesof aluminium with ferrous Ferric iron may magnesium and chemicallycombined water. be the aluminium in small amount present replacing chromium enters similarly ; in some forms,which are then usuallyof a pink instead of the more common color. Manganese replacesthe ferrous iron in a few cases. green Calcium and alkalies characteristicof allthe true micas are conspicuouslyabsent, or present only in small amount. The only distinctly crystallized speciesof the Chlorite Group are Clinochlore and Penninite. These seem to have the same composition,but while the former is monoclinic in form and habit,the latter is pseudo-rhombohedral and usuallyuniaxial. Prochlorite (including and Corundosome ripidolite) also occur in distinct cleavagemasses. philite Besides the speciesnamed there are other kinds less distinct in ring form, occurin scales, also fibrous to massive or earthy; they are often of more or less undetermined composition, but in many rence, cases, because of their extensive occurof considerable geological importance. These latter forms occur as secondary minerals resulting from the alteration especially of ferro-magnesian such silicates, as biotite, pyroxene, amphibole; also garnet, vesuvianite, tc. I hey are often accompanied by other secondary minerals,as serpentine, hmonite, calcite, etc., especiallyin the altered forms of basic iron and

"

"

rocks. The

" .

rock-makingchloritesare recognizedin thin sections by their characteristic thin leaves, scales or fibers, sometimes aggregatedinto greenish color;pleochroism; extinction parallel to the

in appearance irulites;by their

cleavage (unlikechoritoid and ottrelite); low reliefand extremely low interference-color which frequently exhibit the " ultra-blue." By this latter char?r

they

are

resemble and

readilydistinguished from the micas, which which they are frequently associated.

with

they strongly

569

SILICATES

Ripidolitein part.

CLINOCHLORE.

Monoclinic.

Axes

a

:

b

: c

=

0-57735

952

/

:

1

:

2-2772;0

=

89" 40'.

953

954

m"

Pfitsch

Zillertal

Wchwarzenstem

Crystalsusuallyhexagonal in form, often tabular ||c (001). Plane angles 60" or 120",and since closely similar anglesare found in the zones which the are separated by 60", symmetry 955 approximatesto that of the rhombohedral system. Twins: Mica (1) law, tw. pi._L c (001) in the zone

of the basal section

001

=

112; sometimes

contact-twins with c as composition 60" or a multipleof 60" in azimuth with reference to the other; also in threefold twins. (2) Penninite law, tw. pi. c, contact-twins also united by c (Fig. 954); here corresponding faces differ 180" in position. Massive, coarse scaly granular to fine granularand earthy. cmo

A

face,the

Cleavage:

part revolved

one

(001) highly perfect. Laminae flexible Achmatovsk and slightlyelastic. Percussion-figure orientated with the micas 2-2*5. as pressure-figures (p. 559). H. G. 2-65-2-78. of Luster pearly. Color cleavage-face somewhat to to deep grass-green yellowish and white; olive-green; pale green also rose-red. Streak Transparent to greenish white to uncolored. translucent. Pleochroism not strong,for green varieties usuallyX green, Z Ax. pi.in most cases yellow. Opticallyusually +. ||6 (010). Bxa inclined 2" 30'. Dispersomewhat to the normal to c (001), sion forward; for Achmatovsk Axial anglesvariable,even in the same v. times 0"-90"; somecrystal, p " sensiblyuniaxial. Birefringencelow. Indices approximately; a c

but

and

tough,

=

=

=

1-585.

0

1-586.

=

7

=

1-596.

Ordinary; green clinochlore,passing into bluish green; (a) in crystals,as described,usually with distinct monoclinic symmetry; (6)foliated;(c)massive. Contains usuallylittleor no iron. Color white,pale green, yellowish; Leuchtenbergiie. Var.

1.

"

often

resembles talc. From Kotschubeite. Contains in habit. Color rose-red.

Zlatoust in the Ural Mts. near oxide. several per cent of chromium Crystals rhombohedral From the southern Ural Mts. Pajsberg, Manganiferous. Manganchlorite. A chlorite from the Harstig mine near Sweden, is peculiarin containing2 -3 p. c. MnO.

Comp.

Normally H8Mg5Al2Si3Oi8

"

=

4H2O.5MgO.Al2O3.3SiO2

13-0 32-5, alumina 18-4, magnesia 36-1, water the and small the same replacesa magnesia, part of sometimes chromium replacesthe aluminium.

=

100.

Ferrous

iron

is true of manganese

=

Silica

usually rarely;

culty B.B. in the platinum forceps whitens and fuses with diffigrayish black glass. With borax, a clear glass colored by iron, and sometimes In sulphuricacid wholly decomposed. chromium. tinctly Micro. In thin sections color and pleochroism; discharacterized by pale green biaxial and usually +.

Pyr., etc. on

the

"

"

Yields water.

edges

to

a

MINERALOGY

DESCRIPTIVE

570

in connection with

talcose chloritic'and

rocks

schists and

or

iswasSffislfii ^^u^Tys: Orr-nrs

ssr "

tine;

Marienberg, Saxony;

u

Zoptau, Moravia.

serpen-

A manganesian

vanety

occurs

and plates; also Unionville large crystals ^niStherilJteddStates, Westchester, Pa., part changed Y, Brewster, mine and Tex^, fat magnetic

at

in

at

the

Pa

N.

at

iron

to

in

tine; serpen-

near' Lowell, Ver., in crystals. Pennine.

PENNINITE.

Apparentlyrhombohedral

but

in form

and pseudo-rhombohedral strictly

thick L"^abitCr'hombohedral: sometimes

tabular with c (001) prominent, also in again steep rhombohedral; hedral taperingsix-sided pyramids. Rhombostriated. faces often horizontally in crested often groups. Crystals of an Also massive, consisting gation aggreof scales;also compact cryptocrystalline. Cleavage: c (001) highly perfect. flexible. Laminae Percussion-figure with clinochlore Zermatt Texas and pressure-figure as but less easy to obtain; not elastic. 2-6-2-85. Luster H. 2-2-5. G. of cleavage-surface pearly; of lateral to olive-green; emeraldbrilliant. Color and sometimes vitreous, plates also violet,pink, rose-red,grayish red; occasionally yellowishand silverwhite. distinct: to subtranslucent. Pleochroism usually ||c Transparent in adjaboth sometimes and cent (001)green; _L c yellow. Optically+, also sometimes lamina of the same b ut crystal.Usually sensiblyuniaxial, section. biaxial (occasionally 2E distinctly 61") and both in the same Sometimes while the border is biaxial with 2E a uniaxial nucleus 36",the latter probablyto be referred to clinochlore. Indices 1-576 and 1-579. =

=

"

,

=

=

Var.

Penninite,as first named, included

1.

"

a

green

chlorite crystallized

from

the

Penninine Alps. Kammererite.

In hexagonal forms bounded by steep six-sided pyramids. Color Lake from kermes-red; peach-blossom-red. Pleochroism Itkul, distinct. Optically Bisersk,Perm, Russia; + Texas, Pa. Uniaxial or biaxial with axial angle up to 20". Rhofrom Lake dophyllitefrom Texas, Pa.,and rhodochrome Itkul belong here. Pseudophiteis compact massive, without cleavage,and resembles serpentine. "

Comp.

the Essentially

"

same

as

H8(Mg,Fe)5Al2Si3Oi8. clinochlore,

In the closed tube yields water. cultly B.B. exfoliates somewhat and is diffifusible. With the fluxes all varieties give reactions for iron,and many varieties react for chromium. Partially decomposed by hydrochloricand completely by sulphuric acid. Micro. In thin sections shows pale green color and pleochroism ; usually nearly

Pyr., etc.

"

"

uniaxial, "

Obs.

.

Occurs with serpentine in the region of Zermatt, Valais, Switzerland, near Rosa, especiallyin the moraines of the Findelen glacier;crystalsfrom Zermatt are sometimes 2 in. long and H in. thick; also at the foot of the Simplon Pass, Switzerland; at Ala, Piedmont, Italy,with clinochlore; in Tyrol, Austria; at Taberg at Schwarzenstein in Wermland, Sweden; at Snarum, Norway, greenishand foliated. Kammererite is found at the localitiesalreadymentioned; also near Miask in the Ural Mts.; at Haroldswick in Unst, Shetland Isles. In large crystals enclosed in the talc in crevices of the chromite from Kraubat, Styria. Abundant at Texas, Lancaster Co., Pa., along with clmochlore,some Also in clinochlore, crystalsbeing embedded the reverse. or Mt.

"

571

SILICATES

in N. C., with chromite at Culsagee, Macon From Washington, Cal. PROCHLORITE.

Co.; Webster, Jackson

Co.;

and other points.

Ripidolitein part.

In six-sided tables or prisms,the side planes stronglyfurMonoclinic. rowed and dull. Crystals often implanted by their sides,and in divergent

fan-shaped,vermicular,or spheroidal. Also in largefolia. Massive,

groups,

foliated,or granular. H.

G.

Translucent to opaque; transparent only in cleavagesurface feeblypearly. Color green, grassblackish green; the axis by transmitted lightsomeacross green, olive-green, times red. Streak uncolored or not elastic. greenish. Laminae flexible, Pleochroism distinct. Optically+ in most cases. Bx inclined to the normal 2". Axial anglesmall,often nearlyuniaxial;again 2E to c (001) some 23"30". Dispersionp " v. Lower in silicon than clinochlore, and with ferrous iron usuComp. ally, but not always,in largeamount. 1-2.

=

thin folia.

very

=

278-2-96.

Luster

of

=

"

Like other chloritesin modes Obs. of occurrence. Occasionallyformed from amphibole. in implanted crystals, Sometimes at St. Gothard, Switzerland, as enveloping often adularia,etc.; Mt. Greiner in the Zillertal, Tyrol, Austria; Rauris in Salzburg,Austria; "

Traversella in Piedmont, Italy; at Mts. Sept Lacs and St. Cristophe in Dauphine, France; Also massive in Cornwall, England, in tin veins; at Arendal in Norway; Styria,Bohemia. In Scotland at various Salberg and Dannemora, Sweden; Dognacska, Hungary. points. In the United States,near Washington, D. C.; on Castle Mt., Batesville, Va., a massive form resembling soapstone, color grayish green, feel greasy; Steele's mine, Montgomery at the Culsagee mine, in broad platesof a dark Co., N. C.; also with corundum in the small amount color and fine scaly; it differsfrom ordinaryprochlorite of ferrous green iron. in

Corundophilite. A chlorite occurring in deep green 1'583. brittle;contains but 24 p. c. SiO2. /3

more

laminae resembling clinochlore but Occurs with corundum at Chester,

=

Mass.

H4(Mg,Fe)2Al2SiO9. Silica 21'4 p. c. In hexagonal plates,foliated, resembling 271. talc from the Tyrol. H. 2-5-3. G. Color apple-green. Luster cleavage face. Optically+, sensiblyuniaxial. Occurs with diasporeat Chester,

AMESITE.

the green

pearly on

=

=

Mass.

SHERIDANITE.

A

chlorite from

Sheridan

Co., Wy., containingonly littleiron.

Besides the chlorites already described OTHER CHLORITES. which occur usuallyin distinct crystalsor plates,there are, as noted on p. 568, forms varying from fine scalyto In some fibrous and earthy, which are cases prominent in rocks. they may belong to the speciesbefore described,but frequently the want of sufficient pure material has left their These chlorites are commonly characterized by their green composition in doubt. color, distinct pleochroism and low birefringence(p. 568). been follow, ng are The which have names given particularlyto the chlorites filling in basic igneous rocks : aphrosiderite, cavities or seams euraldiabantite, delessite, epichlorite,

ite,chlorophceite, pycnochlorite. hullite,

followingare other related minerals. Moravite. 2FeO.2(Al,Fe)oO3.7SiO2.2H2O. In lamellar,scaly and granular forms with Fuses 3"5. G. 2'4. iron-black. Color cleavage. H. difficultly. perfect basal of Gobitschau Found at iron mines near Sternberg,Moravia. Cronstedite. Occurs tapering in hexagonal pyramids; also 4FeO.2Fe2O3.3SiO2.4H2O. in diverging groups; amorphous. Cleavage: basal,highly perfect. Thin laminae elastic. Color coal-black to brownish G. 3 '34-3 '35. black; by transmitted lightin thin scales From 1*80. Pfibram in Bohemia; also in emerald-green. Streak dark olive-green. /3 Cornwall, England. Massive; an aggregation of minute pearly Thuringite. 8FeO.4(Al,Fe)2O3.6SiO2.9H2O. From 1*63. near scales. Color olive-greento pistachio-green./3 Saalfeld,in ThurinHarper's gia; Hot Springs,Ark., etc.; from the metamorphic rocks on the Potomac, near The

=

=

=

=

=

MINERALOGY

DESCRIPTIVE

572

given

Ferry (owenite). Stilpnochloranis name

In

Sternberg,Moravia.

Gobitschau, near Brunsvigite.

to

an

yellowto

alteration product of thuringitefrom bronze-red scales.

and In cryptocrystalline 9(Fe,Mg)O.2Al2O3.6SiO2.8H2O.

radiated aggregates. Under sometimes forming spherical 1-2. outline. Color olive-green to yellow-green. H. Harz in the Germany. Radautal Mts., the gabbro of the

microscope

G.

=

3U

=

foliated

folia show Occurs in

masses

hexagonal cavities in

of the Chlorite Group. A member Griffithite. 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2.7H2O. Fusible to magnetic slag. Pleochroic,pale yel2 '31. G. low, 1. H. dark green. in amygdaloidal cavities in a Indices 1 '48-1 '57. Occurs brown-green. olive-green, basalt from Cahuenga Pass, Griffith Park, Los Angeles, Cal. Color

=

=

CHAMOSITE. with H. about

Contains

3; G.

=

iron

(FeO)

with

but

Occurs

little MgO. to black.

From

3-3'4; color greenishgray

compact

Chamoson,

or

oolitic St.

near

Maurice, in the Valais,Switzerland. ing. Stilpnomelane. An iron silicate. In foliated plates; also fibrous,or as a velvety coatOccurs at Obergrund and elsewhere Color black, greenish black. 2 '77-2 '96. G. from the Sterling Chalcodite, in Silesia; Weilburg, Nassau, Germany. also hi Moravia; near and calcite,is the same Iron mine, in Antwerp, Jefferson Co., N. Y., coating hematite mineral in velvety coating of mica-like scales with a bronze color. A silicate of ferric and ferrous iron,intermediate of Chlorite Group. Minguetite. A member 2'86. Color blackish between green. stilpnomelane and lepidomelane. G. Fuses to a black magblack. Optically netic Strongly pleochroic,lightyellowto opaque Minguet mine, near enamel. Segre, Decomposed by hydrochloricacid. From Maine-et-Loire,France. crystals. Color dark Strigovite. H4Fe2(Al,Fe)2Si2Oii.In aggregations of minute the minerals in cavities in the granite of Striegauin Occurs as a fine coating over green. =

=

"

.

Silesia.

Rumpfite. fine scales.

of very Probably a variety of clinochlore. Massive; granular, consisting Occurs with talc near St. Michael and elsewhere in greenish white.

Color

Styria. In rough hexagonal prisms. Micaceous Spodiophyllite.(Na2,K2)2(Mg,Fe)3(Fe,Al)2(SiO3)8. 3-3'2. brittle. H. G. 2 '6. Color cleavage. Laminae ash-jgray. Fusible. From Narsarsuk, southern Greenland. =

APPENDIX

TO

THE

MICA

=

DIVISION.

"

VERMICULITES.

The

VERMICULITE GROUP includes a number of micaceous cates, minerals, all hydrated siliin part closelyrelated to the chlorites, but varying somewhat widely in composition. They are alteration-products chieflyof the micas,biotite, phlogopite, etc.,and retain the micaceous more or less perfectly cleavage,and of ten-show the negative opticalcharacter and small axial angle of the original less indefinite species.-Many of them are of a more or chemical nature, and the composition varies,with that of the originalmineral and with the degree of alteration. The laminae in generalare soft,pliable, and inelastic;the luster pearly or bronze-like, and the color varies from white to yellow;and brown. Heated to 100"-110" dried over or sulphuricacid most of the vermiculites lose considerable water, up to 10 p. c., which is probablyhygroscopic;at 300" another portion is often given off; and at a red heat a somewhat is expelled. Connected largeramount with the loss of water ignitionis the upon common physical character of exfoliation; of the kinds especiallyshow some this to a marked degree,slowly opening out, when heated gradually,into long worm-like threads. Ihis character has given the name to the group, from the Latin vermiculari, to breed worms. Ihe minerals included can hardly rank as distinct species and only their names be can here:

given

Jefferisite, vermiculite, culsageeite, kerrite, lennilite, hallite, vaalite, philadelphite,

macomte, dudleyite, pyrosclerite.

HI.

The borne

Serpentine and

Talc

Division

leadingspeciesbelonginghere,Serpentineand Talc,are closelyrelated of the Mica Division preceding,as noted beyond. in part amorphous, are included with them. silicates,

Chlorite Group other magnesium

SILICATES

573

,

SERPENTINE.

Monoclinic. In distinct crystals, but only as pseudomorphs. Sometimes folia rarelyseparable;also delicately foliated, the fibers often easily fibrous, and either flexible or brittle. Usuallymassive,but separable, microscopically also fine granularto impalpableor cryptocrystalline finelyfibrous and felted, ; in structure but often by compensation nearlyisotropic; slaty. Crystalline amorphous. Cleavage b (010),sometimes distinct;also prismatic(50")in chrysotile. Fracture usually conchoidal or splintery.Feel smooth, sometimes greasy. H. fibrous varieties 2-2-2-3; 2-5-4, rarely 5-5. G. 2-50-2-65; some 2-36-2-55. Luster subresinous to retinalite, greasy, pearly,earthy;resin-like, Color leek-green, or wax-like;usuallyfeeble. blackish green; oil-and siskinyellow; none bright;sometimes nearlywhite. green; brownish red, brownish On exposure, often becoming yellowishgray. Streak white,slightly shining. =

=

Translucent to opaque. feeble. Optically Pleochroism perhaps also + in chrysotile.Double refraction weak. Ax. pi. |a (100). Bx (X) J_ 6 (010)the cleavagesurface; Z || often large;2V 20" to 90". elongationof fibers. Biaxial, anglevariable, Indices variable,from 1*490-1' 571. -

,

=

in strucMany unsustained specieshave been made out of serpentine,differing ture (massive,slaty,foliated, fibrous), or, as supposed, in chemical composition;and these in part, stand as varieties, others based on variations in texture,etc. along with some now, A. IN CRYSTALS PSEUDOMORPHS. The most have the form of chrysolite. common Other kinds are pseudomorphs after pyroxene, amphibole, spinel,chondrodite,garnet, less phlogopite,etc. Bastite or Schiller Spar is enstatite (hypersthene) altered more or completely to serpentine. See p. 474. B. MASSIVE. 1. Ordinary massive, (a) Precious or Noble Serpentineis of a rich oilin thick pieces. when color, of pale or dark shades, and translucent even green The former has a (b) Common Serpentineis of dark shades of color,and sub translucent. hardness of 2*5-3; the latter often of 4 or beyond, owing to impurities. Resinous. Retinalite. resin-like Massive, honey-yellow to light oil-green,waxy or Var.

"

"

luster. Bowenite (NephriteBowen) Massive, of very fine granulartexture,and much resembles 2 '594nephrite,and was long so called. It is apple-greenor greenishwhite in color; G. R. I..; also a similar kind 2*787; and it has the unusual hardness 5 "5-6. From Smithfield, .

=

from

New Zealand. Ricolite is a banded variety with a fine green color from Mexico. thin lamellar in structure, separatinginto translucent folia. C. LAMELLAR. Antigorite, H. 2-5; G. 2*622; color brownish green by reflected light;feel smooth, but not greasy. =

From D.

G.

=

N.

J.

=

Antigorio valley,Piedmont, Italy. THIN FOLIATED. Marmolite, thin foliated; the laminae brittle but From 2*41; colors greenishwhite, bluish white to pale asparagus-green.

separable. Hoboken,

E. FIBROUS. Chrysotile. Delicately fibrous,the fibers usually flexible and easily yellow separating; luster silky,or silkymetallic; color greenishwhite, green, olive-green, of in serpentine. It includes most and brownish; G. Often constitutes seams 2 -219. is popularly called asbestus of what the silky amianthus of serpentine rocks and much (asbestos). Cf. p. 489. and often not easilysepaPicrolite, columnar, but fibers or columns not easilyflexible, rable, or affordingonly a splinteryfracture; color dark green to mountain-green, gray, from Bare Hills, Baltimorite is picrolite brown. from Taberg, Sweden. The original was =

Md.

and specific gravity. In is like serpentine except in regard to its solubility of radiatingfibers from near Dillenburg,Nassau. It frequently F. SERPENTINE ROCKS. Serpentine often constitutes rock-masses. mixed with more less of dolomite,magnesite, or calcite, making a rock of clouded or occurs or ophicalcite. veined with white or pale green, called verd antique,ophiolite, green, sometimes mottled with red, or has something of the aspect of a red Serpentine rock is sometimes Radiotine

sphericalaggregates

574

MINERALOGY

DESCRIPTIVE

of oxide of iron. pentine reddish portionscontainingan unusual amount Any serrock cut into slabs and polishedis called serpentinemarble. Microscopicexamination has established the fact that serpentinein rock-masses has been and many apparently homogeneous serpentines largelyproduced by the alteration of chrysolite, In other cases it has resulted from the mineral. show more or less of this original or amphibole. Sections of the serpentine derived from chrysolite alteration of pyroxene of a net (Fig.958) ; the lines marked often show a peculiarstructure, like the meshes by grainsof magnetite also follow the originalcracks and cleavage directions of the chrysolite (Fig.959, a). The serpentinefrom amphibole and pyroxene commonly shows an analogous structure; the iron particlesfollowingthe former cleavthe nature of the originalmineral 968 can age lines. Hence often be inferred. Cf. Fig. 959, a, b, c (Pirsson).

porphyry; the

A magnesium silicate, H4Mg3Si209 Comp. Silica 44.1, magnesia or 3MgO.2SiO2.2H20 Iron protoxide often 100. 43-0, water 12-9 replacesa small part of the magnesium ; nickel "

=

=

in small

is sometimes amount present. is chiefly expelledat a red heat.

water

The

In the closed tube yieldswater. B. B. Pyr., etc. iron reaction. Gives usually an posed Decomedges with difficulty.F. ==6. chrysotilethe silica is left in fine by hydrochloric and sulphuricacids. From -"-

fuses

the

on

fibers. Diff. Characterized by softness, absence of cleavage and feeble waxy or oily luster; low specific gravity; by yieldingmuch water B.B. Micro. Readilyrecognizedin thin sections by its greenish or yellowish green color; low relief and aggregate polarizationdue to its fibrous structure. When the fibers are the interference-colors are not very low, but the confused aggregates may parallel, show "

"

..Mife

"lMii$ \M

a,

Serpentinederived

from

i

chrysolite; 6, from amphibole; c, from

pyroxene

the "ultra blue" or even be isotropic.The constant association with other magnesia bearing minerals like chrysolite, hornblende,etc.,is also characteristic. The presence pyroxene, oi lines of iron oxide particles noted above (Fig.959) is characteristic. as Obs. Serpentine is always a secondary mineral resulting,as noted from the "

above, containingmagnesia, particularly chrysolite, amphibole or pyroxene. frequently torms largerock-masses, then being derived from the alteration of peridotites dumtes and other basic rocks of igneous origin; also of and amphibolites, or pyroxene chrysoliterocks of metamorphic origin. In the first case it is usually accompanied by spinel,garnet, chromite and sometimes nickel ores; in the second case nates by various carbosuch as dolomite, magnesite, breunnerite, etc. Crystalsof serpentine,pseudomorphous after monticellite, in the Fassatal Tyrol occur Austria. A variety containingsoda from the Zillertal, Tyrol, is called nemaphyllite Near Miask at Lake Aushkul,Barsovka, Ekaterinburg,and elsewhere in Russia; in Norway, Fine precious from Falun and Gulsjo in Sweden, the serpentinescome ?vT M?' of alteration

of silicates

iL

in Aberdeenshire, w^lF^lAn Pnei^b0^od Scotland;the ofQPorts"y England; Corsica, Siberia,

Lizard

in Cornwall,

Saxony, etc.

Isle'Precious serpentine. Al?erlf^e'' Roxbnrv0^ Roxbury, etc. In Mass, fine ataVDef '

m

Newburyport.

In R.

I,

at

In

Ver,

Newport;

at New Fane, bowenite at Smith-

MINERALOGY

DESCRIPTIVE

576

rightanglesto this direction;brownish to blackish ties Streak usuallywhite; of dark green variegreen and reddish when impure. translucent. to Optically tive negalighterthan the color. Subtransparent Indices Ax. pi.11a (100). Bx _L c (001). Axial anglesmall,variable. and

less translucent

approx.;

1'539.

=

a

at

0

1-589.

=

=

7

1'589.

having a greasy feel, usuallyeasilyseparated, Foliated,Talc. Consists of folia, 2'55-278. presentingordinarilylightgreen, greenishwhite, and white colors. G. and brownish Coarse grayish gray granular, green, Steatite a. or Soapstone. Massive, 6. Fine granuor less impure. lar Pot-stone is ordinary soapstone, more l-2'5. in color;H. and soft enough to be used as chalk; as the French chalk,which is cryptocrystalline, or talc. An impure slaty talc,harder than c. Indurated milk-white with a pearlyluster, Var.

"

=

and

=

ordinary talc. Pseudomorphous. a. Fibrous, fine to 6. Rensselaerite, having the form of pyroxene

altered from northern New

coarse,

from

and tremohte. enstatite York and Canada.

acid metasilicate of magnesium, H2Mg3(SiO3)4 or H2O. The water goes 100. 4*8 63 -5,magnesia 317, water Silica 3MgO.4Si02 off only at a red heat. Nickel is sometimes present in small amount.

Comp.

An

"

=

=

varieties yieldwater. In the closed tube B.B., when intenselyignited,most Pyr.,etc. the thin edges to a and fuses with difficulty on In the platinum forcepswhitens,exfoliates, white enamel. assumes on ignitiona pale red color. Not Moistened with cobalt solution, decomposed by acids. Rensselaerite is decomposed by concentrated sulphuric acid. "

foliated structure; Characterized softness,soapy feel; common by extreme is flexiblebut inelastic. Yields water only on intense ignition. Obs. Talc or steatite is a very common mineral,and in the latter form constitutes extensive beds in some regions. It is often associated with serpentine,talcose or chloritic and dolomite,and frequentlycontains crystalsof dolomite,breunnerite,also asbesschist, Diff.

"

pearlyluster;it "

tus, actinolite, tourmaline,magnetite. Steatite is the material of many which the most common are pseudomorphs, among those after pyroxene, and spinel. The magnesian minerals are hornblende,mica, scapolite, those which commonly afford steatite by alteration; while those like scapoliteand nephelite, which contain soda and no magnesia, most frequently yield pinite-likepseudomorphs. There also steatitic pseudomorphs after quartz, dolomite,topaz, chiastolite, are staurolite, cyanite,garnet, vesuvianite, chrysolite, gehlenite. Talc in the fibrous form is pseudomorph after enstatite and tremolite. Apple-greentalc occurs at Mt. Greiner in the Zillertal, Tyrol, Austria; in the Valais and St. Gothard in Switzerland; in Cornwall,England, near Lizard Point, with serpentine; the Shetland islands. In North in Me., at Dexter. In Ver., at Bridgewater, America, foliated talc occurs handsome In Mass., at Middlefield,Windsor, Blantalc,with dolomite; Newfane. green In R. I.,at Smithfield, Andover, and Chester. delicate green and white in a crystalfprd, line limestone. In N. Y., at Edwards, St. Lawrence ciated assoCo., a fine fibrous talc (agalite) with pink tremolite;on Staten Island. In N. J., Sparta. In Pa., at Texas, in South Mountain, ten miles south of Carlisle;at Chestnut Nottingham,Unionville; Hill, the Schuylkill, on talc and also soapstone, the latter quarried extensively. In Md., at Cooptown, of green, blue, and rose colors. In N. C., at Webster, Jackson portant Co. The imstates for the productionof talc and soapstone are New and Virginia. York, Vermont In Canada, in the townships Bolton, Button,and Potton, Quebec, with steatite in beds of Cambrian

age;

in

the

township of Elzevir,Hastings Co.,Ontario,an impure grayishvariety

Archaean rocks. Use. In the form hearth stones,furnace in

of soapstone used the

"

linings, etc.;

for wash

tubs, sinks,table tops, switchboards, burners,tailors' chalk, slate pencils, fillerin papers, as a lubricant,in toilet powders,

tips of

gas

etc" 3rnaments' etc" ; Powdered form in the G^?M"is aPPa.rentlyvarietyof talc,differing its m

as

a

%

solubility in

acids.

SEPIOLITE.

Gava

amount

of water

present and

in

valley,Italy.

Meerschaum.

Compact, with rarely fibrous.

From

H.

smooth

a =

2-2-5.

feel,and fine earthy texture, or clay-like;also G. 2. Impressible by the nail. In dry =

577

SILICATES

floats

Color

grayish white, white, or with a faint yellowish 1-55. or Biaxial,". Opaque. /3 Silica 60-8, magnesia H4Mg2Si3O10 or Comp. 2H2O.2MgO.3SiO2 12-1 100. Some 27-1, water analyses show more water, which is probably nickel may to be regarded as hygroscopic. Copper and replace part of the magnesium. masses

reddish

water.

on

tinge,bluish green.

=

"

=

=

In

the closed tube water and a fuse with difficultyon

yields first hygroscopic moisture, and at a higher temperature B.B. smell. varieties blacken, then burn some the thin edges. With cobalt solution a pink color on white, and by hydrochloric acid with separation of silica. ignition. Decomposed in Asia Minor, in masses in stratified earthy or alluvial deposits at the Obs. Occurs in Moravia; in Morocco, called in French Pierre de plains of Eskihi sher; at Hrubschitz beds. Savon de Maroc; at Vallecas in Spain, in extensive A fibrous mineral, having the composition of sepiolite, in Utah. occurs is German The meerschaum word for sea-froth,and alludes to its lightness and color. the bone of which is light and porous. Sepioliteis from "rr}Tria, cuttle-fish, Pyr.,

etc.

"

much

gives

burnt

"

hydrous

A

Connarite.

G.

Color

2'459-2'619.

=

nickel silicate,perhaps H^N^SisOio. In small fragile grains. From yellowish green. Rottis, in Saxon Voigtland.

Spadaite. Perhaps 5MgO.6SiOa.4H2O. Rome. Capo di Bove, near

Massive, amorphous.

Color

reddish.

From

Piotine.

SAPONITE.

In nodules, or filling cavities. Soft, like butter or cheese,but Luster 2 '24" 2 '30. Color white, yellowish, drying. G. greasy. adhere reddish. Does to the not grayish green, bluish, tongue. A and but the hydrous silicate of magnesium aluminium; Comp. material is amorphous and probably always impure, and hence analyses give Contains 19-26 results. uniform SiO2 40-45 no p. c., A12O3 5-10 p. c., MgO

Massive.

brittle

on

=

"

p. c.,

H20

p. c.; also

19-21

Fe2O3, FeO, etc.

B.B. gives out water very readily and blackens; thin splinters fuse with Pyr., etc. by sulphuric acid. difficultyon the edge. Decomposed in cavities in basalt,diabase, etc.; also with serpentine. Thus at Lizard Occurs Obs. Point, Cornwall, in veins in serpentine; at various localities in Scotland, etc. Saponite is from sapo, soap; and piotine from TTIOT^S, fat. "

"

Composition

LASSALLITE. masses.

Tech,

G.

=

1.5.

From

perhaps 3MgO.2Al2p3.12SiO2.8H2O.

the antimony

mine

at Miramont

and

In

at Can

snow-white

Pey

near

fibrous Arles-sur-

France.

and A silicate of iron, magnesium potassium. Earthy or in minute cavities in amygdaloid at Mte. Baldo Index, 1 '63. From Very soft. Color green. near Verona, Italy. and Glauconite. Amorphous, Essentially a hydrous silicate of iron and potassium. Color resembling earthy chlorite; either in cavities in rocks, or loosely granular massive. abundant in the in rocks of nearly all geological ages; Occurs dull green. Index, 1'61. constituting 75 to 90 p. c. of the whole. "green sand," of the Chalk formation, sometimes A manganese shores. the continental sediments Found glauconear abundantly in ocean nite from the Marsjat forest,Ural Mts., has been called marsjatskite. Greenalite is a green hydrated ferrous silicate found as granules in the cherty rock associated with iron ores of the Resembles Minn. Mesabi glauconitebut contains no potash. district, Celadonite.

scales.

In Corresponds approximately to K2q.l2(Fe,Mg)O.Al2O3.13SiO2.5H2O. Color grayish yellow. From 2*408. Taberg in Wermcrystallinescales. G. land, Sweden, with garnet, diopside, etc. Pholidolite.

minute

=

MINERALOGY

DESCRIPTIVE

578

IV.

KAOLIN

DIVISION

Kaolin.

KAOLINITE.

hexagonal scales or plates or either a clay-like mass, Usually constituting

Monoclinic; in thin rhombic, rhomboidal with

anglesof 60" and

120".

compact, friable or mealy. 2-6-2-63. 2-2-5. G. inelastic. H. Cleavage:basal,perfect.Flexible, Color dull to earthy. white,grayish Luster of plates, pearly;of mass, pearly sometimes brownish,bluish or reddish. Scales transparent white, yellowish, and plastic. to translucent;usuallyunctuous pi. inclined Bx0 _L b (010). Bxa and ax. negative. Opticallybiaxial, 20" to normal to c (001). Axial anglelarge,approx. 90". 0 behind some =

=

=

1-482. In crystalline Kaolinite. scales,pure white and with a satin luster in the less impure scales but more or kaolin,in part in crystalline Ordinary. Common includingthe compact lithomarge. Var.

1.

"

2.

mass.

Comp. water

Silica 46.5, alumina 39.5, H4Al2Si209,or 2H2O.Al203.2SiO2 The water goes off at a high temperature, above 330". 100. =

"

14-0

=

B.B. infusible. Gives a blue color on ignitionwith cobalt Yields water. Insoluble in acids. sembles ReDiff. Characterized by unctuous, soapy feel and the alumina reaction B.B. under the microscope. infusorial earth,but readilydistinguished Obs. Ordinary kaolin is a result of the decomposition of aluminous minerals, especially the feldsparof graniticand gneissoidrocks and porphyries. In some regions where these rocks have decomposed on a largescale,the resultingclay remains in vast beds of less mixed with oxide of iron from with free quartz, and sometimes or kaolin,usuallymore in connection with of the other minerals present. Pure kaolinite in scales often occurs some tion, iron ores of the Coal formation. It sometimes forms extensive beds in the Tertiary formaAlso met with accompanying as near or Richmond, Va. diaspore and emery corundum. Occurs in the coal formation in Belgium; Schlan in Bohemia; in argillaceous schist at Lodeve, Dept. of H6rault, France; as kaolin at Diendorf (Bodenmais) in Bavaria; at Schemnitz, Hungary; with fluoriteat Zinnwald, Germany. Yrieix,near Limoges, France, of kaolin in Europe (a discovery of 1765) ; it affords material for the is the best locality famous Sevres porcelainmanufactory. Large quantitiesof clay (kaolin)are found in Cornwall and West Devon, England. In the United States,kaolin occurs at Newcastle and Wilmington, Del.; at various localitiesin the limonite regionof Ver. (atBrandon, etc.), sonville, Mass., Delaware Co., Pa.; JackIn crystalplates Ala.; near Webster, N. C.; Edgefield,S. C.; near Augusta, Ga. from National Belle mine, Silverton, Col. From Lawrence Co., Ind. The name Kaolin is a corruptionof the Chinese Raiding, meaning high-ridge, the name of a hill near Jauchau Fu, where the material is obtained. Use. The finer, of porcelain,china,etc.; in the grades used in the manufacture purer form of clay in pottery, stoneware, bricks,etc.

Pyr.,etc.

"

solution. "

"

"

Pholerite. from

the coal

Near mines

but kaolinite, Fins,Dept.

of

some

of

analyses give

15 p.

c.

water.

The

originalwas

France. 'Allier,

Faratsihite. (Al,Fe)2O?.2SiO2.2H2O. Intermediate kaolinite and between chloropal. In microscopichexagonal plates. Soft. Monoclinic. 2. G. Color pale yellow. Index a littlehigher than that of kaolinite. Difficultly fusible. Decomposed by hydrochloric acid. From Faratsiho, Madagascar. =

HALLOYSITE.

Massive.

Clay-likeor earthy. Hardly plastic.H. 1-2. G. 2-0-2-20. Luster waxy, to dull. Color white,grayish, greenish,yellowish,

Fracture conchoidal. somewhat pearly,or

=

=

579

SILICATES

bluish,reddish.

sometimes Translucent to opaque, becoming translucent increase of one-fifth in weight. in transparent water, with an

even

or

Var. in luster and opaque massive. Ordinary. Earthy or waxy Galapectiteis halloysiteof Angleur,Belgium. Pseudosteatite is an impure variety,dark green in color,with H. 2'25. G. 2'469. Indianaite is a white porcelainclay from Lawrence Co.,Indiana, where it occurs with allophane in beds four to ten feet thick. Smectite is greenish,and in certain states of humidity appears transparent and almost gelatinous;it is from Conde, near Houdan, France. Bole, in part, may belong here; that is those colored,unctuous clays containingmore less iron oxide,which also have about 24 p. c. of water; the iron gives them a brownish, or Here yellowishor reddish color; but they may be mixtures. belongs Bergseife(mountainsoap). "

=

=

A silicate of aluminium like kaolinite, but amor(Al2O3.2SiO2) phous and containingmore is somewhat uncertain, but the water; the amount formula is probably to be taken as H4Al2Si2O9.H2O or 2H2O.Al2O3.2SiO2.H2O Silica 43-5, alumina 36 -9,water 100. 19 -6

Comp.

"

=

=

Yields water. Pyr., etc. Decomposed by acids. "

Obs.

B.B.

infusible.

A

fine blue

on

tion. ignitionwith cobalt solu-

Occurs often in veins or beds of ore, as a secondary product; also in granite aluminous minerals. rocks,being derived from the decomposition of some A clay-like TERMIERITE. of uncertain composition from substance resembling halloysite the antimony mines of Miramont, France. and

"

other

Newtonite. Found Sneed's on

HgA^Si^On-H^O. Creek

BATCHELORITE. Tasmania.

In

soft white compact masses Co., Ark. part of Newton

in the northern

Al2O3.2SiO2.H2O.

A

green

foliated mineral

resembling kaolin.

from

Mt.

Lyell mine,

A Cimolite. hydrous silicate of aluminium, 2Al2O3.9SiO2.6H2O. Amorphous clayColor white, grayishwhite, reddish. 2' 18-2*30. From like,or chalky. Very soft. G. the island of Argentiera (Kimolos of the Greeks). Montmorillonite. Probably H2Al2SLiOi2.nH2O. Massive, clay-like. Very soft and tender. Luster feeble. and bluish ; also pistachio-green. Color white or grayishto rose-red, Unctuous. is paler Montmorillonite,from Montmorillon, France, is rose-red. Confolensite rose-red;from Confolens, Dept. of Charente at St. Jean-de-Cole,near Thiyiers. is a clay from the basalt of Stolpen,Germany. Stolpenite Saponite of Nickl"s is a white, plastic,soap-likeclay from the granite from which issues one of the hot springs of Plombieres,France, called Soap Spring; it was named smegmatite by Naumann. =

PYROPHYLLITE.

Monoclinic?

Foliated,radiated lamellar or somewhat fibrous;also granular latter the sometimes compact cryptocrystalline; slaty. not elastic. Feel greasy. Laminae Cleavage: basal,eminent. flexible, 1-2. H. G. 2 -8-2 -9. Luster of folia pearly; of massive kinds dull and glistening.Color white,apple-green, grayishand brownish green, yellowish to ocher-yellow, Optically grayish white. Subtransparent to opaque. Bx _L cleavage. Ax. anglelarge, Mean to 108". index,1*58. to

or

=

=

"

.

(1) Foliated,and often radiated,closelyresembling talc in color,feel,luster and (2) Compact massive, white, grayish and greenish,somewhat pact resembling comThis compact variety includes part of what has gone under French chalk. or steatite, the name of agalmatolite,from China; it is used for slate-pencils, and is sometimes called pencil-stone. Var.

"

structure.

Comp. water

5'0

H2Al2(SiO3)4or

"

H2O.Al2O3.4SiO2

=

Silica 667, alumina

Yields water, but only at a high temperature. Pyr., etc. the edges. The radiated varieties exfoliate on difficulty "

with

28*3,

100.

=

B.B. whitens, and fuses in fan-like forms, swelling

MINERALOGY

DESCRIPTIVE

580

with cobalt solution and Moistened of the assay volume times the original by sulphuric acid, and Partiallydecomposed heated gives a deep blue color (alumina). carbonates. alkaline with fusion completelyon by the reaction for alumina with cobalt talc,but distinguished Resembles some UD

to

many

Diff.

"

Obs

Compact

"

near

of

base

is the material or pyrophyllite of cyanite. Occurs

varietyis often the gangue Ottrez, Luxemburg; Ouro

some

in the Ural

schistose rocks.

Mts.;

at

The

ated foli-

Westana, Sweden;

Preto, Brazil.

Mt., Mecklenburg Co., N. C.; in Lincoln Co., Ga., on Graves Mt. for making slate-pencils and The compact kind, at Deep River, N. C., is extensivelyused or pagodite of China, often used for ornamental resembles the so-called agalmatolite Cottonstone in stellate aggregations Chesterfield Dist., S. C., with lazulite and cyanite; in white

Also

in

carvings. USe.

the

For

"

same

purposes

as

talc,which

see.

ALLOPHANE.

usuallythin,with a mammillary surface, Amorphous. In incrustations, stalactitic. sometimes Occasionallyalmost pulverulent. hyalite-like; conchoidal and Fracture shining,to earthy. Very brittle. imperfectly Luster vitreous to subresinous;brightand waxy 1-85-1-89. H. 3. G. internally.Color pale sky-blue,sometimes greenishto deep green, brown, 1*49. Translucent, n yellowor colorless. Streak uncolored. Silica 23'8, alumina aluminium Al2Si05.5H20 silicate, Hydrous Comp. water of 100. Some analysesgive 6 equivalents 40-5,water 35-7

and

=

=

=

=

"

=

=

Silica 22-2,alumina

not

40'0

100.

=

often present. The coloringmatter of the blue variety is due to traces substances intermediate between allophane and chrysocolla(mixtures) The green variety is colored by malachite, and the yellowish and

Impuritiesare and of chrysocolla, are

37-8,water

uncommon.

brown

by iron. in the closed tube. B.B. but is infusible. Yields much water crumbles Pyr.,etc. Gives a blue color on ignitionwith cobalt solution. Gelatinizes with hydrochloricacid. Obs. cate silialuminous Allophane is regarded as a result of the decomposition of some (feldspar, etc.);and it often occurs incrustingfissures or cavities in mines, especially "

"

those of copper and limonite, and even in beds of coal. Named from aXXos, other, and ^aiveadai, to appear, in allusion to its change of appearance under the blowpipe. Melite.

H. 2(Al,Fe)2O3.SiO2.8H2O. In imperfectprisms. Stalactitic, 3. massive. Infusible. From Thuringia. Saalfield, Collyrite.2Al2O3.SiO2.9H2O. A clay-likemineral, white, with a glimmering luster, and adheringto the tongue. G. 2-2 -15. greasy feel, From Ezquerra in the Pyrenees. SchrStterite. 8Al2O3.3SiO2.30H2O. Resembles in like gum allophane; sometimes H. 3-3 -5. G. 1-95-2 -05. Color pale green or yellowish. From appearance. Dollinin Styria; at the Falls of Little River, on the Sand Mt., ger mountain, near Freienstein, Cherokee Co., Ala. =

Color bluish brown.

2-2.

=

=

The

=

are minerals following clay-like

Cenosite. I^Ca^Er^CSi^n. From Hittero, Norway;

Nordmark,

Britholite. In

A

or

mineral

substances:

Orthorhombic.

G.

=

Sinopite,smectite,catlinite.

Color

3'38.

yellowishbrown.

Sweden.

complex silicateand phosphate of the cerium metals and calcium. agonal. Hexcrystals. H. 5'5. G. 4-4. brown. From Color nepheline

minute

"

=

=

syenite region of Julianehaab, South Greenland. Erikite. Compositionuncertain;

essentiallya silicate and phosphate of the cerium rthorhombic. In prismatic crystals. H. 5'5. G. 3'5. Color light yellow-brown to dark gray-brown. From in South Greenland. nepheline-syenite Plazolite 3CaO Isometric. In minute dodecahedrons. b5. G. =3-13. Colorless to lightyellow, n 171. From Cal. =

=

Al20A2(Si02,C02).2H20. =

Crestmore,

581

SILICATES

Thaumasite. H. in traces.

CaSiO3.CaCO3.CaSO4.15H2O. 3'5.

=

G.

=

1-877.

Color

Massive, compact, crystalline.Cleavage white.

Uniaxial,o-. co

=

1'507,

=

"

Occurs cavities and crevices at the Bjelkemine, near filling Areskuta, Jemtland, at first soft but hardens to the air. Also in fibrous crystalline on masses exposure Co., Utah. erson, N. J.; from Beaver

Spurrite. H.

=

and

2Ca2SiO4.CaCO3.

Color pale gray, ft diorite in Velardena mining 5.

=

=

+

In aggregates MnSiO3.2Mn2(OH)AsO3. of thin folia. Hexagonal. cleavage. Color nearly black, red by transmitted light. Optically

From

Langban,

Sweden.

A

In compact hydrated calcium borosilicate,8CaO.5B2O3.6SiO2.6H2O. 4'5. G. Color white. 2'7-2'9. Fusible. resembling unglazed porcelain. H. borax depositsin Mohave desert,16 miles N. E. of Daggett, San Bernardino Co.,

Bakerite. masses

From

1*96.

=

masses.

limestone

Basal

3-4. n

.

between

zone

3-81-3-90.

Dixenite. =

granular cleavable

CaO.2UO3.2'SiO2.GH2O.In radiated aggregations; massive, Color yellow. Biaxial,-. Indices, 1'650-1'670. From the at Wolsendorf,Bavaria; Mitchell Co., Kupferberg, Silesia. Uranotil occurs

G.

granite of

H.

In

contact

at Pat-

Uranotil.

Uranophane. fibrous.

Probably monoclinic. Infusible. .From Mexico. district, T67.

1'468.

Sweden;

=

=

Cal. CHRYSOCOLLA.

often opal-like enamel-like in texture; earthy. Inor Cryptocrystalline; Sometimes seams. botryoidal. In microscopicacicular crustingor filling from Mackay, Idaho. crystals Rather sectile; Fracture conchoidal. translucent varieties brittle. H. 2-2*238. Luster 2-4. G. vitreous,shining,earthy. Color mountaininto bluish passing sky-blueand turquois-blue;brown to black green, green, when Crystals impure. Streak,when pure, white. Translucent to opaque. from Idaho w 1-46; e 1-57; weakly pleochroic, Uniaxial,+; gave: e co colorless, paleblue-green. True to correspond to CuSiO3.2H2O chrysocollaappears Comp. Silica 34-3,copper oxide 45 -2,water 20 -5 100, the water being double that of dioptase. =

=

=

=

=

=

=

"

=

also alumina, black oxide of Composition varies much through impurities; free silica, and be present; the color coniron oxide of oxide of sequently (orlimonite) manganese may copper, It has been suggested that the and black. varies from bluish green to brown is not definite but that it is usuallyin the form of a mineral composition of most chrysocolla gel with copper oxide,silica and water occurring in varying proportionsaccording to the conditions of formation. B.B. decrepitates, colors the In the closed tube blackens and yieldswater. Pyr.,etc. flame emerald-green, but is infusible. With the fluxes gives the reactions for copper. With soda and charcoal a globule of metallic copper. Decomposed by acids without "

gelatinization. Obs. Accompanies

in the upper other copper part of veins. ores, occurringespecially in copper mines in Cornwall, England; Hungary; Siberia;Saxony; South Australia; Chile,etc. In the United States,similarlyat the Schuyler'smines, N. J.; at Morgantown, Pa.; at In crystalsfrom the Clifton mines, Graham mine, Utah. Co., 'inGila Co., Ariz.; Emma Mackay, Idaho. of a material used the name Chrysocollais from XPV(TOS, gold,and KO\\"X,glue,and was is often applied now in solderinggold. The name to borax, which is so employed. "

Found

Use.

"

Chrysocolla may

serve

as

a

minor

ore

of copper.

Shattuckite. 2CuSiO3.H2O. Compact, granular, fibrous. at Indices, 1 '73-1 '80. Pleochroic,dark to light blue. Found Ariz.,forming pseudomorphs after malachite.

3-8. Color blue. G. Shattuck mine, Bisbee, =

Color pale blue to nearly white; Bisbeeite. CuSiO3.H2O. Orthorhombic, fibrous. of fibers positive. Indices 1-59 to 1-65. Pleochroic,very pale green to pale mine at Bisbee, Ariz.,resultingfrom the hydrationof Found at Shattuck olive-brown.

Elongation

shattuckite.

582

MINERALOGY

DESCRIPTIVE

CHLOROPAL.

earthy. massive, with an opal-like appearance; the second a conchoidal G. 1727-1-870, earthy varieties, and Color pistachio-green. yellow greenish Ceylon. 2-105,

Compact H.

2-5^-5.

=

specimen;

=

conchoidal

Fragile. Fracture Opaque to subtranslucent. the to Adheres feebly tongue. earthy.

and

splintery

to

characters,and was named from the Hungarian Chloropalhas the above-mentioned occurringat Unghwar. and greenish,with an unctuous is pale straw-yellow or canary-yellow, Nontronite feel; flattens and grows lumpy under the pestle,and is polished by friction; from Nontron, Pinguite is siskin- and oil-green,extremely soft,like ftewDept. of Dordogne, France. with a slightlyresinous luster,not adhering to the tongue; from Wolkenstein made soap, has a grass-green color (whence the name), and occurs Graminite in Saxony. at Menzenberg,in the Siebengebirge,Germany; in thin fibrous seams, or as delicate lamellaB. Var.

"

mineral

A hydrated silicate of ferric iron, perhaps with the general Comp. Silica 41-9, iron sesquiformula Fe2O3.3SiO2.5H2O or HeF^CSiO^a^I^O "

=

oxide 37 -2,water The

20*9

=

is present in

Alumina

100.

varieties.

some

and

The silica both vary much. mixed with Hungarian chloropal occurs of its analyses. opal,and graduates into it,and this accounts for the high silica of some Obs. Localities mentioned also at Meenser above. Chloropal occurs Steinbergnear On Gottingen, Germany; pinguite at Sternberg,Moravia. Lehigh Mt., Pa., south of in connection with iron deposits. From Palmetto Allentown, occurs Mts., Esmeralda Co., water

"

Nev.

HCBFERITE.

An

iron silicate near

chloropal. Color

Miillerite. Zamboniniie. Fe2Si3O9.2H2O. Color yellowishgreen. 2-0. Infusible.

G.

=

Hisingerite.

A

Massive.

are following hydrous

radiated

masses

the

mines

nontronite.

Soft.

From

2'5-3'0.

=

From

Morencite. A hydrated ferric silicate of brownish yellow. From Morenci, Ariz.

The

Kfitz, Bohemia.

Resembles

Nontron, Dordogne, France. of uncertain hydrated ferric silicate, composition. Amorphous,

Fracture conchoidal. H. =3. G. brownish black. Streak yellowish brown. Langban, etc.,Norway; from Greenland.

Bementite.

From

green.

Luster

greasy.

Color

Riddarhyttan, Tunaberg,

uncertain

composition.

pact. com-

black

to

Sweden;

Fibrous.

Color

silicates.

manganese

HeMn^SiO^. Orthorhombic. resembling pyrophyllite. G. of Franklin

Cleavages ||to =

three pinacoids. In soft Color pale grayish yellow. From

2 "981.

Furnace,N. J. Monoclinic(?).In thin tabular crystals. Good cleavage. H. G. 2-46. Color brown. 1 "62-1 -63. Opaque. Indices, From Langban, Sweden. Agnolite. H2Mn3(SiO3)4.H2O. Name given to the manganese silicate occurring as part of the material from Schemnitz,Hungary, known as manganocalcite. Triclinic. In zinc

.

Mn*Si8O28.7H2O. EcJr"P^e=4.

T

=

radiatingfibrous Orientite. 77" 776.

masses.

Color

flesh-red to

H.

^I7" ^ From opaq;f 1795.

=

Onente

H-

G. Province,Cuba.

3.

=

Monoclinic. PprS?tdh^10n?te' 3"z*LMn)9|iO*-H*". cleavage. H= 4-5-5.

Perfect basal 1 76.

-

G.

crepitates

and

=

3*91.

=

3'0.

Radiating prismatic.

4-"-5.

=

G.

=5.

Ca4Mn4(SiO4)5.4H2O. Orthorhombic. ""

y

rose.

Optically+. In acute

"

Brown to 1758.

pyramidal crystals.

Color,bright pink

then fuses readily. Soluble in acids.

to reddish brown. From Franklin, N. J.

A of manganese, 1}ydrojf ran,??;"*6' sjjicate of needle-like ~

radiating groups G

magnesium and zinc,8RO.3SiO2.2H2O. crystals. Colorless and transparent. From Franklin, N.

In -^T^-Qi %""?*** iMn0-3SKV3H20. olor brown. From the ~

stalactitic and

Harstigmine near and iron,of "?!]"* ?ica11 "[ allv dee"rivedefrnm alteration of rhodonite. Amorphous. and manSanese

liverTbro^n

=

reniform Pajsberg,Sweden.

In J.

shapes.

doubtful composition, usuColor black to dark brown

MINERALOGY

DESCRIPTIVE

584

||c (001); also prismatic.Sometimes

flattened

massive, compact;

rarely

1$} in f*l 11\ T*

in greenoI vite Cleavage- m (110)rather distinct;a (100), (112)imperfect; to due often (221) twinning Parting less so. easy 1177 n (111)easy, t (111) to adamantine resinous. Luster 3 -4-3 -56. G. 5-5'5. lamellae. H. Streak black. and white, slightly Color brown, gray, yellow,green, rose-red reddish in greenovite.Transparent to opaque. but distinct in deep-colored kinds: Pleochroism in generalrather feeble, colorless. Z red with tinge of yellow;.7, yellow,often greenish;X, nearly =

=

Bx A c axis Ax. pi.||b (010). Bx nearly J_ x (102),i.e., Optically+ axial o f the the hence and peculiarity large, " v very + 51". Dispersionp 27". a in white, light. Axial angles variable. 2V interference-figure =

.

=

1-900.

ft

1-907.

=

7

=

=

2-034.

to black, the originalbeing thus colored,also Ordinary, (a) Titanite; brown from a^v, a wedge)',of lightshades, as (named subtranslucent. (6) Sphene or opaque yellow. Liguriteis an appleetc.,and often translucent;the originalwas yellow,greenish, subkind. Lederite is brown, opaque, or greenish a Semeline) green sphene. Spinthere(or translucent,of the form in Fig. 960. of rutile and ilmemte, not Titanomorphiteis a white mostly granular alteration-product in certain crystalline rocks; here also belongs most leucoxene (see p. 418). uncommon ganese; owing to the presence of a littlemanManganesian; Greenovite. Red or rose-colored, in Narukot, India. from St. Marcel, Piedmont, Italy; from Jothvad eucolite-titanite. Here belong grothite, alshedite, Containingyttrium or cerium.

Var.

"

CaTiSiO5 Comp. 100. 28*6 lime 40-8, "

=

and also

or

CaO.TiO2.Si02

Iron is

yttrium in

some

present in

=

Silica 30-6, titanium

varying amounts, sometimes

dioxide ganese man-

kinds.

varieties change color,becoming yellow, and fuse at 3 with B.B. some Pyr., etc. intumescence,to a yellow,brown or black glass. With borax they afford a clear yellowish if the solution be concentrated green glass. Imperfectly soluble in heated hydrochloricacid; and With salt of phosphorus in R. F. a fine violet color. along with tin,it assumes gives a violet bead; varieties containing much iron require to be treated with the flux on charcoal with metallic tin. Completely decomposed by sulphuricand hydrofluoricacids. Diff. Characterized by its obliquecrystallization, a wedge-shaped form by common; resinous (oradamantine) luster;hardness less than that of staurolite and greater than that of sphalerite. The reaction for titanium is distinctive, but less so in varieties containing "

"

much

iron.

Micro.

Distinguishedin thin sections by its acute-angledform, often lozenge-shaped; generallypale brown tone; very high relief and remarkable birefringence, causing the section to show white of the higher order; by its biaxial character (showing many lemniscate curves); and by its great dispersion, which produces colored hyperbolas. Artif. Titanite is apparently produced artificially only with difficulty.It has been obtained by fusingtogether silicaand titanic oxide with calcium chloride. Obs. Titanite,as an accessory component, is widespread as a rock forming mineral, though confined mostly to the acidic feldspathicigneous rocks; it is much more common in the plutonicgranular types than in the volcanic forms. Thus it is found in the more basic hornblende granites, and is especiallycommon and characteristic syenites,and diorites, in the nephelite-syenites. It occurs in also in the metamorphic rocks and especially the schists, It gneisses, etc.,rich in magnesia and iron and in certain granular limestones. is also found in beds of iron ore; commonly associated minerals are amphibole, pyroxene, chlorite, scapolite, zircon,apatite,etc. In cavities in gneiss and granite,it often accompanies adularia, smoky quartz, apatite,chlorite, etc. Occurs at various points in the Grisons,Switzerland, associated with feldspar and chlorite;Tavetsch; Binnental;in the St. Gothard region; Zermatt in the Valais ; Maderanertal in Uri; also elsewhere in the Alps; in Dauphine (spinthere), France; in Italy at Ala (hgunte) and at St. Marcel, in Piedmont; at Schwarzenstein and Rothenkopf in the Tyro1' z"Ptau, Moravia; near Tavistock, England; near Tremadoc, in /uif r' XT JNorth Wales; from Kragero and in titanic iron at Arendal, Norway; with magnetite at "

its

"

"

i

TITANO-SILICATES,

585

TITANATES

Achmatovsk, Ural

Sweden;

Mts. found among volcanic rocks, Occasionally the Rhine. Andernach on In Mass., in gneiss,in the east part of Lee; at In Me., in fine crystalsat Sandford. and In N. Y., at Roger's Rock Bolton with pyroxene scapolitein limestone. Lake on in small brown crystals;at Gouverneur, in black crystalsin granular George, abundant limestone; in Diana near Natural Bridge, Lewis Co., in largedark brown crystals, among

Nordmark,

as

at Lake

(semeline) and

Laach

at

Iredell Co., yellowishwhite with sunstone; also Buncombe Statesville, Co., Alexander Co., other points. in Quebec at Grenyille, Occurs in Canada ArgenteuilCo.; also Buckingham, Templeton, Co.; in Ontario at North Burgess, honey-yellow;near Eganville, Wakefield,Hull, Ottawa Renfrew Co., in very large dark brown crystalswith apatite,amphibole, zircon. Molengraaffite. A titano-silicateof lime and soda. Monoclinic (?). In imperfectprismatic From crystals.Cleavage (100)perfect. Color yellow-brown. Indices, 173-177. in Pilandsberg,near a rock, "lujaurite," Rustenberg, Transvaal. A titano-silicate of calcium, aluminium, ferric iron, and Keilhauite. the yttrium 6'5. titanite in habit and angles. H. G. metals. 3'52-377. Color Crystalsnear From brownish black. near Arendal, Norway. A titano-silicate of the cerium Tscheffkinite. metals, iron, etc., but an alteration less heterogeneous, and the composition of the originalmineral is very or product, more G. 5-5'5. 4'508-4'549. Color velvet-black. uncertain. Massive, amorphous. H. in the Ural Mts. Also from South India, Kanjamalai Hill, From mountains the Ilmen Salem district. An isolated mass weighing 20 Ibs. has been found on Hat Creek,near Massie's Mills,Nelson Co., Va.; also found, south of this point,in Bedford Co. and

=

=

=

=

H, Na, K, and R Fe, Mn chiefly, Astrophyllite.Probably R4R4Ti(SiO4)4with R In elongated crystals;also in thin stripsor blades; includingalso Fe2O3. Orthorhombic. in stellate groups. sometimes Cleavage: 6 (010) perfect like mica, but laminae brittle. H. 3 '3-3 '4. Luster submetallic,pearly. Color bronze-yellowto gold-yellow. G. 3. Indices,1 '678-1733. Optically+. Occurs on the small islands in the Langesund fiord,near Brevik, Norway, in elseolitein feldspar,with catapleiite, black mica, etc. segirite, Similarlyat syenite, embedded Also with arfvedsonite and zircon at St. Kangerdluarsuk and Narsarsuk, Greenland. Peter's Dome, Pike's Peak, El Paso Co., Col. =

=

=

Johnstrupite.A fluorine.

and

Index,

1 -646.

Rinkite,also Narsarsukite.

tabular

silicateof the cerium metals, calcium prismatic monoclinic crystals. G.

and

In

From

Mosandrite.

In

=

Barkevik, Norway.

near

Near near

A

sodium with titanium chiefly, Color brownish green.

3 '29.

=

in form Johnstrupite is Johnstrupite, from

and

composition and from the

Greenland.

""

highly acidic titano-silicate of ferric

crystals.Fine prismaticcleavage.

H.

=7.

same

region.

f""

iron

G.

=

and sodium. Tetragonal. Color honey-yellow, 27. In pegmatite at Fusible.

T55. or ocher-yellow. weathering brownish gray Narsarsuk, southern Greenland. Neptunite. A titano-silicate of iron (manganese) and the alkali metals. In prismatic black. 3 '23. Color 5-6. G. Streak, cinnamon-brown. monoclinic crystals.H. at Narsarsuk and elsewhere, Mean Pleochroic,yellow to deep-red. Found index, 170. called southern Greenland, and at the benitoite localityin San Benito Co., Cal. (originally w

on

=

=

=

carlosite) .

In crystals Hexagonal, trigonal(ditrigonal-bipyramidal) Benitojte. BaTiSi3O9. 3'6. Color sapphire-blueto lightblue and 6'2-6'5. G .= with p(1011) prominent. H. 177. Fusible colorless. Transparent. Strongly dichroic,deep blue to colorless, co of the San Benito the headwaters Found at 3. associated with neptuniteand natrolite near River in San Benito Co., Cal. In minute wedge-shaped crystals. Leucosphenite. Na4Ba(TiO)2(Si2O5)5. Monoclinic. 1'66. Color white. 3'0. G. Difficultlyfusible. 6'5. /8 Distinct cleavage. H. From Narsarsuk, southern Greenland. .

=

=

=

=

=

considerable zirconia.

Nao(TiO)2Si2O7. Contains

Lorenzenite. acicular

crystals.Distinct cleavage.

minute From

MINERALOGY

DESCRIPTIVE

586

H.

Narsarsuk, southern Greenland. Joaquinite. A titano-silicate of calcium Associated

yellow.

with benitoite from

6.

=

and Benito

San

G.

iron.

=

3 -4.

In Orthorhombic. 1 '78. Fusible.

/3about

Orthorhombic.

Color, honey-

Co., Cal.

Perofskite.

PEROVSKITE.

Crystalsin general(Ural Mts., Zermatt, Isometric or pseudo-isometric. Switzerland) cubic in habit and often highly modified, but the faces often to the edges and apparCubic faces striated parallel ently in reniform Also individuals. if of pyritohedral penetration-twins, showing small cubes. masses subconchoidal. to uneven Cleavage: cubic, rather perfect. Fracture mantine. metallic-adato adamantine Luster 4-017-4-039. G. 5*5. Brittle. H. reddish brown, Color pale yellow,honey-yellow,orange-yellow,

distributed. irregularly

as

=

=

Streak colorless, Usually grayish. Transparent to opaque. double refraction. Mean index, about 2*38. exhibits anomalous however, conforms to the isometric system; optically, Geometricallyconsidered,perovskite oped molecular structure (alsoas develit is uniformly biaxial and usuallypositive. The Cf. Art. 429. to correspond to Orthorhombic symmetry. by etching)seems Titanium dioxide 58-9, lime 41-1 Calcium titanate,CaTiO3 Comp.

grayishblack.

=

"

=

Iron is

100.

present in small

replacingthe calcium.

amount

charcoal infusible. With salt of phosphorus in O.F. dissolves easily, giving a greenishbead while hot, which becomes colorless on cooling; in tirely Enand on coolingassumes R.F. the bead changes to grayish green, a violet-blue color. decomposed by boilingsulphuricacid. associated with chlorite, and magnetic iron in chlorite Obs. Occurs in small crystals, Zlatoust,in the Ural Mts.; at Schelingen in the Kaiserstuhl, slate,at Achmatovsk, near Germany, in granularlimestone; in the valley of Zermatt, Switzerland,near the Findelen Pfitsch and in Tyrol, Austria; various Pfunders glacier;at Wildkreuzjoch, between noted in microscopic octahedral crystalsas a rock localities, Piedmont, Italy. Sometimes also in serpentine(alteredperidotite) constituent; thus in nephelite-and melilite-basalts; at Syracuse, N. Y.; in igneous rocks,Beaver Creek, Gunnison Co., Col.

Pyr.,etc.

"

In the

forcepsand

on

"

In black isometric crystals. From Knopite. Near perovskitebut contains cerium. Alno, Sweden. Dysanalyte. A titano-niobate of calcium and iron,like perovskitewith lime replaced to some extent In cubic crystals. by iron,etc. Pseudo-isometric,probably Orthorhombic. the granular limestone of Vogtsburg, Kaiserstuhl,Baden, GerColor, iron-black. From many. Has previouslybeen called perovskite,but is in fact intermediate between the titanate,perovskite,and the niobates,pyrochlore and koppite. From Mte. Somma,

Vesuvius. A related mineral,which

has also long passed as perovskite,occurs It is in octahedrons Cove, Ark. or black or brownish black in color and submetallic in luster. See also the allied titanate, mentioned bixbyite, on p. 425.

brookite,rutile,etc.,at Magnet

with magnetite, cubo-octahedrons,

Geikielite.

Magnesium iron titanate,(Mg,Fe)TiO3. Hexagonal, rhombohedral. ally UsuroUed pebbles. H. =6. G. 4. Color bluish or brownish black. high. From Ceylon. Delorenzite. A titanate of iron,uranium and yttrium of uncertain composition. Orthorhombi Prismatic habit. Color black. Resinous in pegmatite at luster. Found Graveggia,Val Vigezzo,Piedmont, Italy. Yttrocrasite. A hydrous titanate of the yttrium earths and thorium. Orthorhombic. G4-8. Black color with pitchy to resinous luster. Infusible. **"_? 5'5~6; Found in Burnet Co., three miles east of Barringer Hill,Texas. massive, Index, very

as

=

=

Brannerite.

Essentially (UO,TiO,UO2)TiO3. greenish brown"

Basin

Idh

H"

=

4'5"

G"

"

Prismatic crystalsor granular. Blank. 4'5-5'4F"und in gold placers,Stanley

NIOBATES,

Oxygen 3.

and

The Niobates metatantalic

NIOBATES,

587

TANTALATES

Salts

TANTALATES

(Columbates)and Tantalates and acid, RNb2O6 RTa^A;

are

salts of metaniobic chiefly part Pyroniobates, of the species, which are

also in

R2Nb2O7, etc. Titanium is prominent in a number hence intermediate between the niobates and titanates. Niobium and tantalum also enter into the compositionof a few rare as lavensilicates, wohlerite, ite,etc. The

followinggroups

The

isometric

be mentioned: may PYROCHLORE GROUP, includingpyrochlore,microlite, etc. The tetragonal FERGUSONITE GROUP, including fergusoniteand sipylite. The orthorhombic COLUMBITE GROUP, includingcolumbite and tantalite. Also the orthorhombic SAMARSKITE samarskGROUP, includingyttrotantalite, ite,and annerodite. The speciesbelonging in this class are for the most part rare, and are hence but briefly described. PYROCHLORE.

Isometric.

Commonly in octanedrons;also in grains. sometimes distinct. Fracture conchoidal. Brittle. Cleavage octahedral, H. 4 -2-4 -36. 5-5-5. Luster vitreous or resinous, G. the latter on fracture surfaces. Color brown, dark reddish or blackish brown. Streak light Subtranslucent to opaque, brown, yellowishbrown. Chiefly a niobate of the cerium metals, calcium and other Comp. bases,with also titanium,thorium,fluorine. Probably essentially a metaniobate with a titanate, RNb2O6.R(Ti,Th)03; fluorine is also present. :

=

=

"

Obs. at Fredriksvarn and Laurvik, Norway; Occurs in elseolite-syenite the island on Lovo, oppositeBrevik, and at several pointsin the Langesund fiord;near Miask in the Ural Mts. Named from -n-vp,fire,and x^wpos, green, because B.B. it becomes yellowish green. A variety of pyrochlore from near Wausau, Wis., has been called marignadte. Neotantalite. that of tantalite. Composition near Isometric, in octahedrons. H. 5-6. 5'2. G. Color clear yellow. Refractive index, 1*9. with Found kaolin at Colettes and Echassieres,Dept. PAllier,France, "

=

=

ii

ii

In small octahedrons. H. Isometric. 5-5. Chalcolamprite. RNb2OeF2.RSiO3. G. 3 '8. Color dark gray-brown. Crystal faces show a copper-red metallic iridescence. Occurs sparinglyat Narsarsuk, South Greenland. Endeiolite is a similar mineral from the same composition with the substitution of the hydroxyl localitysupposed to have the same =

=

group

for the fluorine.

Koppite. Essentially a minute

dodecahedrons. in limestone.

brown

embedded

A

Hatchettolite. a

at

(100) and the mica

m

=

tantalo-niobate

(311). G.

mines

pyroniobate of cerium, calcium, etc., near pyrochlore. In From 4'45-4'56. G. Schelingen,Kaiserstuhl,Germany,

477-4-90. of Mitchell Co., N. =

of uranium, near pyrochlore. In octahedrons with Color yellowish brown. Occurs with samarskite, C.; from Mesa Grande, Cal.

In octahedrons. G. 5 24. of uranium, etc. Isometric. Antsirabe, on Samiresy Hill,Madagascar. Microlite. bium, Essentiallya calcium pyrotantalate,CauTa2O7, but containing also nioIsometric. Habit fluorine and hedral; octaa variety of bases in small amount. H. 5'5. G. crystalsoften very small and highly modified. 5'485-5'562; T94. From 6*13 Virginia. Color pale yellow to brown, rarely hyacinth-red, n Mass., in albite;Branchville,Conn.; Rumford, Me.; Uto, Sweden; GreenChesterfield, Samiresite.

A

niobate

=

Color golden-yellow. From

=

=

=

MINERALOGY

DESCRIPTIVE

588

Courtat Amelia at the mica mines Also in fine crystals up to 1 in. in diameter House, Amelia Co., Va. PYRRHITE. Probably a niobate related to pyrochlore,and perhaps identical with From Alabashka, near Mursinka orange-yellowoctahedrons. microlite. Occurs in minute in the Ural Mts.; from Mte. Somma, Vesuvius. land.

5'5.

=

G.

of

niobate

A

RISORITE. H.

In

4-18.

=

yttrium

the

pegmatite

at

Isotropic. Color

metals.

yellow-brown.

Risor, Norway.

Tyrite. Bragite

FERGUSONITE.

Axis Tetragonal-pyramidal.

c

Crystals pyramidal

T4643.

=

or

matic pris-

in habit.

subconchoidal. Brittle. H. Fracture (111) in traces. nally 5-5-6. G. 5-8, diminishingto 4 -3 when largelyhydrated. Luster exterColor brownvitreous and submetallic. ish dull,on the fracture brilliantly Streak pale brown. Subtransblack; in thin scales pale liver-brown.

Cleavage:

=

s

=

Index, 2-19.

lucent to opaque.

(and tantalate)of yttrium with Essentiallya metaniobate Comp. also iron,calcium,etc. in amounts; uranium, varying cerium, etc., erbium, "

formula

General

in

in

R(Nb,Ta)O4 with

R

=

Y,Er,Ce.

in considerable amount, but probably not an Water is usually present and sometimes increases. gravity falls as the amount originalconstituent;the specific From Obs. Cape Farewell in Greenland, in quartz; also at Ytterby and Kararfvet, From Sweden. near Beforona, Madagascar; South Africa; Australia; Ceylon; Takathe island of on Mino, Japan. Tyrite is associated with euxenite at Hampemyr yama, Tromo, and Helle on the mainland, Norway; bragiteis from Helle,Naresto, etc.,Norway. Found in the United States,at Rockport, Mass., in granite; in the Brindletown gold Burke Co., N. C., in gold washings; with zircon in Anderson district, Co., S. C.; at the gadolinitelocalityin Llano Co., Texas, in considerable quantity. Sipylite. A niobate of erbium chiefly,also the cerium metals, etc., near fergusonite in form. 4 '89. G. Color Rarely in octahedral crystals. Usually in irregularmasses. brownish black to brownish orange. Occurs sparinglywith allanite in Amherst Co., Va. "

=

COLUMBITE-TANTALITE.

Orthorhombic. yy'", mm'", gg', cfc, cq,

Axes

a

:

b

: c

0'8285

=

:

1

:

0'8898.

A

2lO

=

45"

ce,

001

A

021

=

60" 40'.

110

A

110

=

79" 17'.

ao,

100

A

111

=

51" 16'.

130

A

130

=

43" 50'.

cu,

001

A

133

=

43" 48'.

001

A

103

=

19" 42'.

uu',

133

A

133

=

29" 57'.

001

A

023

=

30" 41'.

uu"'

133

A

133

=

79" 54'.

210

0'.

,

Twins: tw. pi.e (021)common, usually contact-twins,heart-shaped(Fig. 385, p. 160),also penetration-twins; further tw. pi.q (023)rare (Fig.434, p. 169). Crystalsshort prismatic, often rectangular prisms with the three pinacoids

prominent; also thin tabular ||a (100);the pyramids often but slightly developed,sometimes,however,acutelyterminated by u (133)alone. Also in largegroups of parallel and massive. crystals, Cleavage:a (100)rather distinct; 6 (010)less so. Fracture subconchoidal to uneven. Brittle. H. 6. G. 5 -3-7 -3,varying with the composition (see below). Luster submetallic, often very brilliant, sub-resinous. Color iron-black, grayish and brownish black,opaque; and rarelyreddish brown =

=

Streak dark

translucent;frequentlyiridescent. 2-26.

".=

0

2-20.

=

7

=

589

TANTALATES

NIOBATES,

red to black.

Optically4-

2-34. 968

967

Middletown

Black

969

Greenland

Hills

Niobate and tantalate of iron and manganese, Comp. (Fe,Mn)(Nb, Ta)206,passingby insensible gradationsfrom normal COLUMBITE, the nearly The iron and pure niobate,to normal TANTALITE, the nearlypure tantalate. also and Tin in small amount. widely. vary tungsten are present manganese The Niobium percentage composition for FeNb2O6 pentbxide 82-7, iron Tantalum protoxide17 '3 100; for FeTa^Oe pentoxide86-1,iron protoxide "

=

=

13-9 In

100.

=

some

=

manganocolumbite varieties,

or

the iron is largelyreplacedby manganotantalite,

manganese.

The shown

connection between the specificgravity and in the followingtable: G.

Greenland

Acworth, Limoges

N.

H.

5 '36 5'65

Bodenmais

(Dianite)

Haddam

G.

Ta2O5

Bodenmais Haddam Bodenmais Haddam

5 '92 6'05

27-1

6 '06 613

35-4 31-5

Tantalite

7-03

65-6

TaaOe 3 '3

574

15'8 13 '8 13'4

5'85

lO'O

570

the percentage of -metallic acids

is

30-4

Diff. Distinguished (from black tourmaline, etc.) by orthorhombic crystallization, rectangularforms common; high specific gravity; submetallic luster,often with iridescent surface; cleavage much less distinct than for wolframite. For B.B. With salt of phosphorus dissolves alone unaltered. Pyr., etc. tantalite, coal slowly,givingan iron glass,which in R.F. is pale yellowon cooling;treated with tin on charit becomes Decomposed on fusion with potassium bisulphatein the platinum green. with dilute hydrochloric acid a yellowsolution and a heavy spoon, and gives on treatment white powder, which, on addition of metallic zinc,assumes a smalt-blue color; on dilution with water the blue color soon disappears. Columbite,when decomposed by fusion with caustic potash, and treated with hydrochloricand sulphuricacids,gives,on the addition of zinc,a blue color more lastingthan with tantalite. Partiallydecomposed when the powdered mineral is evaporated to dryness with concentrated sulphuricacid,its color is changed to acid and metallic zinc it white, lightgray, or yellow, and when boiled with hydrochloric givesa beautiful blue. Obs. Columbite at Rabenstein and Bodenmais, Bavaria, in granite; Tamoccurs mela, in Finland; Chanteloube,near Limoges, France, in pegmatitewith tantalite;near of the Sanarka Miask, in the Ilmen Mts., Russia, with samarskite; in the gold-washings region in the Ural Mts.; in Greenland,in cryolite, at Ivigtut (or Evigtok), in brilliant crystals. In crystalsfrom Ampangabe and Ambatofotsikely,Madagascar. in granite;also at StoneIn the United States,in Me., at Standish,in splendent crystals ham with cassiterite, In N. H., at Acworth, at the etc.,manganotantalitefrom Rumford. in a granite mica mine. In Mass., at Chesterfield;Northfield. In Conn., at Haddam, Fairfield Co., in a vein of albitic granite,in large vein; near Middletown; at Branch ville, "

"

"

590

MINERALOGY

DESCRIPTIVE

translucent crystals(manganocolumbite} also in minute crystalsand aggregatesof crystals, with chrysoberyl.In Pa., Mineral Hill,Delaware In N. Y., at Greenfield, spodumene. upon In Va., Amelia Co. Co., in fine splendent crystalswith microlite,monazite, etc. of Mitchell Co. In Col., on microcline at In N. C., with samarskite at the mica mines In S. D. in the Black Hills region, the Pike's Peak region; Turkey Creek, Jefferson Co. Fresno In Cal.,King's Creek district, Co., from Rinc.on and in the graniteveins. common Pala. from manganotantalite with petalite,lepidolite, Mangantantalite (Nordenskiold)from Uto, Sweden, occurs region in etc. Manganotantalite(Arzruni)is from gold-washingsin the Sanarka microlite, Australia. West the Ural Mts.; from Pilbarra district, in Finland,in Tammela, at Harkasaari near Torro; in Kimito, Massive tantalite occurs at Katiala,with lepidolite, at Kaidasuo, and in Kuprtane line, tourmaat Skogbole; in Somero and Finbo; in France, at Chanteloube Falun, at Broddbo and beryl; in Sweden, near near Limoges, in pegmatite. In the United States,in Yancey Co., N. C.; Coosa Co.,Ala.; Canon near City, Col. also in the Black Hills,S. D.; in largemasses Source of tantalum used in making filaments for incandescent electric lights. Use. hedrons. Tapiolite. Fe(Ta,Nb)aO6. Like tantalite,but occurring in square tetragonal octaTapioliteshows close similarities with the minerals of the Rutile Group, in From Color pure black. the Kulmala 7'496. authors place it. G. which some farm, In twin crystalsfrom Topsham, Me. Mossite,a niobium tapiolite. Tammela, Finland. Found at Berg near Skogboliteand ixiolite are twinned varieties of tapioMoss, Norway. lite. ,

"

=

Stibiotantalite. Orthorhombic, hemimorphic in direction of a (Sbp)2(Ta,Nb)2Oe. axis. Polysynthetictwinning parallelto a (100). Cleavage a 5*5. (perfect). H. 6'0-7'4 (varyingwith composition). /S. 2'40-2'42. G. Fusible. Color brown, reddish to resinous. yellow,yellow. Luster adamantine Originallyfound in tin-bearingsands of Greenbushes, Australia. In crystalsfrom Mesa Grande, San Diego Co., Cal. =

=

=

YTTROTANTALITE.

Orthorhombic. 110 A 110 mm'"

Cleavage:

b

=

b Axes a 56" 50'.

: c

0-5412

=

1

:

:

Crystalsprismatic,

M330.

(010) very

indistinct. Fracture small conchoidal. H. Luster submetallic to vitreous and Color greasy. black, brown, brownish yellow, straw-yellow. Streak gray to colorless. Opaque to subtranslucent. G.

5-5-5.

=

n

Comp. Er, Ce, etc.

=

5 '5-5 -9.

m

n

Essentially RR2(Ta,Nb)4Oi5.4H2O,with R The water may be secondary.

"

in

Fe, Ca, R

=

=

Y,

The

so-called yellow yttrotantalite of Ytterby and Kararfvet belongs to fergusonite. Occurs in Sweden at Ytterby,near Vaxholm, in red feldspar; at Finbo and Broddbo, near Falun, in southern Norway. Obs.

"

SAMARSKITE.

Orthorhombic.

Axes a : b lar prisms

0*5456 1 : 0-5178. Crystals rectangu(a(100), b (010),with e (101) prominent). Angles,mm'" 110 A 110 57" 14'; ee' 101 A 101 87". Faces flattened rough. in and Commonly massive, : c

=

=

embedded

=

grains.

Cleavage: Brittle.

H.

=

b

(010) imperfect.

5-6.

Fracture conchoidal. G. 5-6-5-8. Luster vitreous to Color velvet-black. Streak dark =

splendent. reddish brown. Nearly opaque. resinous,

Comp;

"

Index, 2*21.

nRTRs(Nb,Ta)6O2i with R

=

Fe, Ca, U02,

m

etc. ; R

=

cerium

and

yttrium metals chiefly.

In the closed tube decrepitates, glows,cracks open, and turns black. B.B, edges to a black glass. With salt of phosphorus in both flames an emerald-

592

MINERALOGY

DESCRIPTIVE

Epistolite. A niobate of uncertain composition. Analysis shows chieflySiO2, TiO2, folia. Basal In rectangularplates,also in aggregates of curved Monoclinic. Na^O, H2O. 2 '9. Color white, grayish, brownish. Refractive 1-1 '5. G. cleavage perfect. H. albite from in pegmatite veins or in massive Found index 1 '67. Julianehaab,Greenland. niobate of yttrium, uranium, lead, iron, etc. A Plumboniobite. Amorphous. =

=

H.

=

German

5-5-5. East

G.

to black.

brown

Color dark

4*81.

=

mines

Morogoro,

at

ANTIMONATES

Anhydrous Phosphates, Arsenates, Vanadates, Antimonates H3PO4, and

n

i

the

is

phosphoric acid

Normal have

VANADATES,

ARSENATES,

PHOSPHATES, A.

in mica

Salts

Oxygen 4.

Found

Africa.

consequently normal

phosphates

m

R3P04, R3(PO4)2 and

formulas

RPO4, and similarlyfor the arseof species conform comparatively small number to this Most than one metallic element,and in speciescontain more simple formula. the prominent Apatite Group the radical (CaF), (CaCl) or (PbCl) enters; Only

nates,

etc.

in the

Wagnerite Group

a

n

have

we

similarly(RF)

(ROH).

or

XENOTIME.

55" 30',zz" (111 A Til) Tetragonal. Axisc 0-6187, zz' (111 A 111) In crystals resembling zircon in habit; sometimes compounded with zircon in parallelposition(Fig.462, p. 173). In 972 973 =

=

82" 22'.

rolled grains.

Cleavage: m (110) perfect. Fracture uneven and H. splintery. Brittle. 4-5. G. 4-45-4-56. Luster resinous to vitreous. Color yellowish brown, reddish brown, hair-brown, flesh-red, grayish white, wine-yellow, pale yellow; streak pale brown, yellowish reddish. or Opaque. Optically+ 1 -72. o" =

=

=

.

e

1*81.

=

Comp. or

100

=

m

large amount;

cerium

"

Y203.P2O5 is

Essentiallyyttrium phosphate, YPO4 Phosphorus pentoxide 38 -6, yttria =

The

yttrium metals may include erbium present; also silicon and thorium as in

sometimes

monazite.

nl soluble Difficultly Diff

PP '

andDpfrfe7t

**

with moi?tene,d

m

u salt of

sulphuric acid colors

^^^

sometimes !?gram'te.veins;

uent

iftfemusoovT^Hesof B", S"1' *

tySonite Ml

in minute

An Switzerland:

6

^taKgfaluSf of SO d "shings of Clarksville, Hender^n Ga, CIolteMftchten'Co t^f Coouslythought to

the

phosphorus. Insoluble in acids. f"rm' but Distinguished by inferior

"

"

""*"

hardness

embedded

accessory

fr"m

flame

Braz"

constiterrone-

in N. C., Burke ^ "tile,etc,

Co.,

with'

PHOSPHATES,

ARSENATES,

593

ETC.

Crystalscommonly small, often flattened ||a (100)or axis times elongated || 6; some-

prismaticby extension v (111); also large and In masses coarse. yielding angular fragments; in rolled Switzerland Norwich, Ct. grains. Cleavage: c (001) sometimes perfect (parting?);also,a (100) distinct;6 sometimes showing parting||c (001),m (110). Fracture con(010)difficult; choidal to uneven. Brittle. H. 5-5 -5. G. 4-9-5-3; mostly 5*0 to 5-2. Luster incliningto resinous. Color hyacinth-red,clove-brown,reddish or Ax. pi. yellowishbrown. Subtransparentto subtranslucent. Optically+ 1" " b (010) and nearly ||a (100). Bxa Ac 4". axis to + Dispersion 2V v 1-786. 14". a weak; horizontal weak. 1-788. 7 p " ft of

=

=

.

=

=

=

=

=

1-837.

Comp. Most proper

Phosphate

"

analyses show amount

to

form

of the cerium

metals, essentially (Ce,La,Di)PO4.

the presence thorium

of ThO2 and SiO2,usually,but not always,in the silicate;that this is mechanically present is not certain

but possible. B.B. infusible,turns and when moistened with sulphuricacid colors Pyr., etc. gray, the flame bluish green. With borax gives a bead yellow while hot and colorless on cooling; saturated bead becomes enamel-white a soluble in hydrochloric on flaming. Difficultly "

acid. Obs.

Rather constituent of gneissoidrocks in abundantly distributed as an accessory Carolina and Brazil. Occurs near Zlatoust in the Ilmen regions,thus in North Mts., Russia, in granite. In Norway, near Arendal, and at Annerod. In small yellow or brown Found also in the gold crystals(turnerite]in Dauphine, France, and Switzerland. washings of Antioquia, Colombia; in the diamond gravels of Brazil. In crystalsfrom and Emmaville, New Trundle Condobolin South Wales; California Creek, Queensnear land; Olary, South Australia. In Madagascar at various localities. In the United States,formerly found with the sillimanite of Norwich, and at Portland, In largecoarse in albitic granitewith Conn.; also at Yorktown, N. Y. crystalsand masses In Alexander Co., N. C., in splendentcrystals; microlite, etc.,at Amelia Court-House, Va. in Mitchell,Madison, Burke, and McDowell counties,obtained in large quantitiesin rolled grains by washing the gravels. In the gold sands of southern Idaho. Monazite is named from in allusion to its rare occurrence. nova^iv, to be solitary, in wine-yellow prisms and grainsin the green and red apatiteof Arendal, occurs Cryptolite Norway, and is discovered on putting the apatitein dilute nitric acid. It is probably "

certain

monazite. Use. is the chief Monazite of incandescent gaslightmantles. "

Berzeliite. R3As2O8(R Color bright yellow. From

source

of thorium

oxide

Ca,Mg,Mn,Na2). Lungban, Sweden.

which

is used in the manufacture

G. 4-03. Isometric, usually massive. Pyrrharsenitefrom the Sjo mines, Sweden, contains also antimony; color yellowishred. is related, Caryinite,associated with berzeliite, but contains lead; massive (monoclinic). of lead,iron,and sometimes Monimolite. An antimonate calcium; in part, RsSbaOg. Color yellowish or brownish 6 '58. Usually in octahedrons; massive, incrusting. G. From the Harstig mine, Pajsberg,Sweden. green. =

=

=

MINERALOGY

DESCRIPTIVE

594

Perhaps Pb3As2O8.10FeAsO4.

Carminite. forms.

G.

=

fine needles; also in the Luise at mine

of

to tile-red. From

carmine

Color

4105.

clusters

In

roidal spheHor-

hausen, Nassau, Germany. In small crystalswith Color white, brownish

Pb3(AsO4)2.3PbCl2.Orthorhombic.

Georgiadesite.

luster.

Resinous 7'1. G. 3'5. outline. H. Found on lead slagsat Laurium, Greece. =

=

In small Bismuth vanadate, BiVO4. 0 Optically Color reddish brown. Schneeberg,Saxony; San Diego Co., Cal. 6-249.

=

-.

crystals.

orthorhombic

Pucherite.

G.

the

From

2 -50.

=

=

a

Orthophosphatesof

="

4.

Mine, H.

-.

=

4.

High

Orthorhombic

Triphylite Group.

0'4348

Li(Fe,Mn)P04 Li(Mn,Fe)PO4

Triphylite Lithiophilite Natrophilite

H.

Pucher

habit. Hexagonal-rhombohedral.Prismatic Mn3(AsO3)2. Optically basal cleavage. Color black, streak brown. From Langban, Sweden.

Armangite. Poor 4-23. G. refractive index.

hexagonal yellow.

:

b

: c

:

1

:

0'5265

NaMnPO4 an

alkali metal,lithium

or

sodium, with iron and

ganese. man-

TRIPHYLITE-LITHIOPHILITE.

Axes

Orthorhombic.

a

:

b

: c

=

0-4348

:

1

:

0'5265.

Crystalsrare,

ally usu-

massive,cleavable to compact.

coarse uneven. Commonly Cleavage: c (001) perfect;b (010)nearly perfect;m

and

faces

(110) interrupted.

Luster 3-42-3-56. H. G 4-5-5. subconchoidal. in vitreous to resinous. Color greenishgray to bluish triphylite;also pale Streak uncolored to grayish pink to yellow and clove-brown in lithiophilite. white. Transparent to translucent. Axial angle variable,0"-90". Mean Fracture

to

uneven

=

=

index,1-68. A phosphate of iron,manganese and lithium,Li(Fe,Mn)P04, Comp. from the bluish with little to the salmonvarying manganese gray TRIPHYLITE clove-brown littleiron. with but pink or LITHIOPHILITE "

TypicalTriphyliteis LiFePO4

Phosphorus pentoxide 45 '0,iron protoxide 45 '5,lithia is LiMnPO4 Typical Lithiophilite Phosphorus pentoxide 45 '3, manganese 100. Both Fe and Mn protoxide45'1,lithia 9'6 are always present. In the closed tube sometimes Pyr.,etc. turns to a dark color,and gives decrepitates, off traces of water. B.B. fuses at T5, coloringthe flame beautiful lithia-red in streaks, with a pale bluish green on the exterior of the cone With the fluxes reacts for of flame. iron and manganese; the iron reaction is feeble in pure lithiophilite. Soluble in hydrochloric 9'5

=

=

100.

=

=

"

acid. Obs.

Triphyliteis often associated with

at Rabenstein, near spodumene; occurs Peru, Me.; Grafton, N. H. Named from Tpis, and "j"v\ri, threefold, family,in allusion to its containing three phosphates. Lithiophilite occurs at Branch ville, Fairfield Co., Conn., in a vein of albitic granite,with spodumene, manganese phosphates, etc.; also at Norway, Me., in crystalsfrom Pala, Cal. Named from lithium and "j"t\6s, friend. Natrophilite.NaMnPO4. Near triphylite in form. Chiefly massive, cleavable. H. 4-5-5. G. 3-41. Color deep wine-yellow. Occurs sparinglyat Branchville,Conn. "

Bavaria;Keityo, Finland; Norwich,Mass.; Zwiesel^in

=

Graftomte.

=

(Fe,Mn,Ca)3P2O8. Monoclinic.

H.

salmon-pink, usually dark from alteration. Fusible. with tnphyllitein a pegmatite from Grafton, N. H.

G. Occurs

=5.

fresh Color when 37. in laminated intergrowths

=

PHOSPHATES,-

595

ETC.

ARSENATES,

Crystals short prismatic Beryllonite. A phosphate of sodium and beryllium, NaBePCX. H. 5'5-6. Luster G. 2*845. to tabular,orthorhombic. vitreous;on c (001) From 1*558. Stone/3 pearly. Colorless to white or pale yellowish. Optically ham, Me. =

=

=

"

.

Apatite Group R5(F,Cl)[(P,As,V)04]3 (R(F,Cl))R4[(P,As,V)04]3; 0-7346 (CaF)Ca4(PO4)3 Fluor-apatite c (CaCl)Ca4(PO4)3 Chlor-apatite 0-7362 (PbCl)Pb4(PO4)3 0-7224 (PbCl)Pb4(AsO4)3 0-7122 (PbCl)Pb4(VO4)3

formula

General

=

Apatite

=

or

Pyromorphite Mimetite Vanadinite

ing species,there are also certain intermediate compounds containlead and calcium; others with phosphorus and arsenic,or arsenic and vanadium, as calcium arsenate, Svabite, also seems to belong in this Further the rare noted beyond. The radicals CaO, Ca.OH, may possiblyreplace the CaF radical in apatite. A group. contains CO3, SiO2 and SO4 in addition to usual of the group, probable member wilkeite, contains strontium. radicals. Fermorite In addition to the above

GROUP in the hexagonal system, speciesof the APATITE crystallize that they all show, either by the subordinate faces,or in .etching-figures, class (p. 100). They are chemicallyphosphates, belong to the pyramidal of calcium or lead (alsomanganese), with chlorine or arsenates, vanadates is probably present as a univalent radical fluorine. The latter element CaF (orCaCl), etc.,in generalRF (orRC1), replacingone hydrogen atom in The

but

n

i

the acid

n

(RF)R4(PO4)3,and similarly This is a more correct way of viewingthe compositionthan sometimes adopted,viz.,3R3(PO4)2.RF2,etc.

R9(P04)3,so that

for the arsenates. the other method

the

generalformula

is

APATITE.

Hexagonal-pyramidal. Axis 976

c

=

07346. 978

977

cr,

0001

A

1012

ex,

0001

A

lOll

cy,

0001

A

rr',1012

A

=

22" 59'.

xxr,lOTl 88', 1121

A

1011

A

1211

=

40" 18'.

2021

=

59" 29'.

m^

1010

A

2131

0112

=

22" 31'.

ms,

1010

A

1121

979

=

37

=

48" 50'.

=

30" 20'.

=

44" 17'.

Crystalsvaryingfrom longprismaticto short prismaticand tabular. Also globularand reniform, with a fibrous or imperfectlycolumnar structure; massive, structure granularto compact. Fracture conchoidal so. Cleavage: c (0001)imperfect;m (1010) more

MINERALOGY

DESCRIPTIVE

596 and

Brittle.

uneven.

G massive. 4-5 when 5, sometimes btreak subresmous. to vitreous, inclining

H.

crystals. Luster sometimes usuallysea-green, bluish green; often violet-blue; brown. and Transparent to yellow,gray, red, flesh-red occasionally 1-6417. low. 1-6461,e co Birefringence Optically 3-23

3-17-

=

=

white.

white;

Color

opaque.

=

=

-.

Colorless to granular massive. from Murcia Spain is o riginally asparagus-stone, blue yellow,flesh-red, ereen is in greenishblue and bluish crystals from Norway, Arendal, Moroxite, yellowish green. in Siberia, (c)Francohte,from Wheal (6)Lasurapatiteis a sky-bluevarietywith lapis-lazuli stalactitic masses occurs in small crystalline England, Devonshire, Tavistock, near Franco, Var

cleavable or Crystallized,

Ordinary

1

"

and

(a) The

curving crystals.

and in minute

containing fluorine often with only Ordinary apatiteis fluor-apatite, up

fluorine and sometimes to 0'5 p. c.; rarelychlorine preponderates, calcium to 10'5 p. replacing 2. Manganapatite contains manganese

is c.

MnO;

color dark

isomorphous molecule,Ca4(CaO)(PO4)3 and given to the possible

Voelckeriteis name

3

.

of chlorine, entirelyabsent.

trace

a

.

concretionary Fibrous, concretionary,stalactitic. Phosphorite includes the fibrous from Eupyrchroite, and partly scaly mineral from Estremadura, Spain, and elsewhere. incrustoccurs Staffelite Crown Point, N. Y., belongs here; it is concentric in structure. reniform, or stalactitic masses, ing the phosphoriteof Staffel,Germany, in botryoidal, fibrous and radiating. See p. 597. are impure calcium 5. Earthy apatite; Osteolite. Mostly altered apatite; coprolites phosphate. 4.

Fluor-apatite (CaF)Ca4(PO4)3; (CaCl)Ca4(PO4)3;also written 3Ca3P2O8.CaF2 and Comp.

For

"

and

for

Chlor-apatite

There SCaaPaOs.CaCl;. The

compounds containingboth fluorine and chlorine. percentage compositionfor these normal varieties is as follows :

are

also intermediate

Fluor-apatiteP2O542'3 CaO Chlor-apatiteP2O541'0 CaO is much more Fluor-apatite the Alps, Spain, St. Lawrence

55'5 53 '8

F

3'8

C16'8

=

101'6

or

=

101-6

or

Ca3PsO8 92'25 Ca3P208 89'4

CaF2 CaCl2

775

=

100

10'6

=

100

than the other variety;here belongs the apatiteof common nent Apatites in which chlorine is promiCo., N. Y., Canada. this kinds. true is of some Norwegian are rare; B.B. in the forcepsfuses with difficulty the edges (F. on 4-5-5),coloring Pyr.,etc. the flame reddish yellow; moistened with sulphuricacid and heated colors the flame pale bluish green (phosphoricacid). Dissolves in hydrochloricand nitric acids,yieldingwith of calcium sulphate; the dilute nitric acid solution gives sulphuricacid a copiousprecipitate varieties will sometimes a precipitate of silver chloride on addition of silver nitrate. Most in a closed tube. when heat ed with potassium bisulphate give a slighttest for fluorine, Diff. Characterized by the common hexagonal form, but softer than beryl, being scratched by a knife; does not effervesce in acid (like fusible;yieldsa calcite) ; difficultly flame B.B. after being moistened with sulphuricacid. green Micro. fringence Recognized in thin sections by its moderately high relief;extremely low birethe interference (hence not often showing a distinet axial figurein basal sections), colors in ordinary sections scarcelyrisingabove gray of the firstorder; parallelextinction and negativeextension; columnar form; lack of color and cleavage; and by the rude cross partingseen as occasional cracks crossingthe prism. Artif. Apatite may be prepared artificially by fusing sodium phosphate with calcium =

"

"

"

"

fluoride Obs.

or

calcium

chloride.

in rocks of various kinds and ages, but is most common in metaApatite occurs metalliferous morphic crystallinerocks, especially in granular limestone and in many those of tin,in gneiss,syenite,hornblendic gneiss,mica schist,beds of veins,particularly iron ore; occasionally in serpentine. In the form of minute microscopic crystals it has an almost universal distribution as an accessory rock-forming mineral. It is found in all kinds of igneousrocks and is one of the earliest products of crystallization.In largercrystals it is characteristic of the pegmatite facies of igneous rocks,particularlythe granites, especially and occurs there associated with quartz, feldspar,tourmaline,muscovite, beryl,etc. It is sometimes present in ordinarystratifiedlimestone,beds of sandstone or shale of the Silurian, Carboniferous, Jurassic,Cretaceous,or Tertiary. It has been observed as the petrifying matenal

"

of wood.

PHOSPHATES,

ARSENATES,

597

ETC.

its localities are

Ehrenfriedersdorf in Saxony; Schwarzenstein, the Knappenand Zillertalin the Tyrol, Austria; St. Gothard, Tavetsch, etc., in Switzerland; Mussa-Alp in Piedmont, Italy,white or colorless; Zinnwald and Schlackenwald in Bohemia; at Gellivare,Sweden; in England, in Cornwall,with tin ores; in Cumberland, at Carrock Fells; in Devonshire, cream-colored at Bovey Tracey, and at Wheal Franco of Jumilla,in Murcia, Spain, is (francolite).The asparagus-stone or spargelstein paleyellowishgreen in color. Large quantitiesof apatiteare mined in Norway at Kragero; also at Odegaard,near Bamle, and elsewhere. In Me., on Long Island, Blue-hill Bay; in fine purple crystalsof gem-quality from In N. H., Westmoreland. In Mass., at Norwich; at Bolton abundant. Auburn. In Conn., at Branch ville (manganapatite) also greenish white and colorless;at Haddam in St. Lawrence In N. Y., common Neck. Co., in granular limestone, also Jefferson Co.; Sandford mine, East Moriah, Essex Co., in magnetite; near Edenville,Orange Co.; at Tilly iron mine. In Pa., at Leiperville, Foster Delaware In N. C., at Co.; in Chester Co. Stony Point, Alexander Co., etc. In lavender-colored crystalsfrom Mesa Grande, Cal. In extensive beds in the Laurentian gneissof Canada, usuallyassociated with limestone,

Among

in Untersulzbachtal

wand

,

and accompanied by pyroxene, mines other species. Prominent

amphibole, titanite, zircon,garnet, vesuvianite and many in Ottawa ingham, are County, Quebec, in the townships of BuckAlso in Renfrew Templeton, Portland, Hull, and Wakefield. county, Ontario, and in Lanark, Leeds, and Frontenac counties. named from older mineralogistshaving by Werner diraTaew, to deceive, Apatite was referred it to aquamarine, chrysolite, amethyst, fluorite, tourmaline,etc. Besides the definite mineral phosphates,including normal apatite,phosphorite, etc., there are also extensive deposits of amorphous phosphates, consistinglargelyof "bone of great economic cal importance, though not having a definite chemiphosphate" (CasPjOs), composition,and hence not strictlybelonging to pure mineralogy. Here belong the bone beds, guano, etc. Extensive phosphatic depositsalso phosphatic nodules, coprolites, in North occur Carolina,Alabama, Florida,Tennessee,and in the western states,Idaho, is bone phosphate of lime, mixed with the hydrous phosGuano phates, Utah, and Wyoming. calcium carbonate, and often a littlemagnesia, alumina, and generallywith some and other impurities. iron, silica, gypsum, fertilizers. Use. of mineral Apatite and phosphate rock are used chieflyas sources The mineral is be used as gem stones. Some clear finelycolored varieties of apatitemay for this purpose. too soft,however, to permit of extensive use A calcium carbonated STAFFELITE. phosphate. Occurs incrustingthe phosphorite of Staffel, Germany, in botryoidalor stalactitic masses, fibrous and radiating;it is the result "

of the

action of carbonated

H.

waters.

=4.

G.

3 '128.

=

Color

leek- to dark

green,

Bamle, Norway, is similar. member A of the Fermorite. Apatite Group. (Ca,Sr)4[Ca(OH,F)][(P,As)O4]3. 1'66. Index Color pale pinkish white to white. H. 3-52. Uniaxial, 5. G. at Sitapar,Chhindwara Found with manganese District,Central provinces,India. ores of Apatite Wilkeite. Probably a member 3Ca3(PO4)o.CaCO3.3Ca3((SiO4)(SO4)].CaO. Color 3*23. G. pale rose-red, yellow. Optically Group. Hexagonal. H. =5. Index, 1-64. Fusible at 5 '5. Dissolves in acids with separationof silica. In crystalline limestone at Crestmore, Riverside Co., Cal. from greenishyellow. Dahllite,

=

="

-

=

.

=

"

.

PYROMORPHITE.

Green

Lead

Ore.

Axis

Hexagonal pyramidal. often Crystals prismatic,

c

=

07362.

in rounded

barrel-shapedforms; in nearlyparallel prismaticcrystals branching groups slender down to a point. Often globular, position,tapering in wart-like and shapes,with usually botryoidalor reniform, and also a subcolumnar jibrous, granular. structure; subconFracture Cleavage: m (1010),x (1011)in traces. 6-5-7-1 G. 3-5-4. Brittle. H. mostly, choidal,uneven. of

also in

=

=

when

pure;

lime.

containing brown, of yellow, and

5-9-6-5, when

Luster

resinous.

different shades; Color green, sometimes wax-yellow and fine orange-yellow;also grayish Streak milk-white. white, sometimes yellowish. white to 2*050. co Optically Subtransparent to subtranslucent. =

"

.

e

=

2-042.

598

MINERALOGY

DESCRIPTIVE

described; sometimes yellow and in rounded as 1 Ordinary, (a) In crystals (6)In acicular and moss-like aggregations. resemblingcampylite(pseudo-campylite) the surface angular, (d) Fibrous, of crystals, having masses or (c) Concretionary groups (/)Earthy; incrusting. (e) Granular massive. of different shades, yellowish gray, 2 Polysphcerite.Containing lime; color brown 5'89-6'44. Rarely in separate crystals; pale yellow to nearly white; streak white; G. from Mies in Bohemia, is a brown Miesite, m ammillary. usually in groups, globular, Beaujeu, Prance; color Nussiere, near is similar and impure, from Nussierite variety 3. Chromiferous; color brilliant red and orange. 5'042. yellow greenishor grayish;G. 5 '5-6 '6. 5. Pseudomorphous; (a) after to white; G. 4. Arseniferous; color green cerussite. galena; (6) Var

"

forms

.

=

=

=

also written 3Pb3P2O8.PbCl2 lead 100-5,or Lead protoxide82-2,chlorine 2-6 pentoxide157, 100. 897, lead chloride 10-3

Comp.

or (PbCl)Pb4(PO4)3

"

=

=

Phosphorus phosphate

=

increases the species the amount as Calcium also replacesthe lead to a considerable extent. B.B. in the closed tube gives a white sublimate of lead chloride. flame bluish charcoal fuses without the on fuses coloring T5), green; (F. easily forceps a crystalline reduction to a globule,which on coolingassumes polyhedralform, while the the assay, yellow from lead oxide. With coal is coated white from lead chloride and, nearer varieties contain arsenic, and give the odor of soda on charcoal yieldsmetallic lead; some garlicin R.F. on charcoal. Soluble in nitric acid. Diff. Distinguishedby its hexagonal form; high specificgravity; resinous luster; blowpipe characters. Obs. principallyin veins,and accompanies other ores of lead. Pyromorphite occurs At Poullaouen and Huelgoet in Brittany,France; at Zschopau and other placesin Saxony, The

phosphorusis often replaced by arsenic,and

passes into mimetite. In the Pyr., etc. "

=

"

"

in Bohemia; in fine crystals at Ems, Braubach, in Nassau, Germany; at Pfibram,Bleistadt, Germany; also at Dernbach in Nassau; in Siberia at Beresov and in the Nerchinsk mining district;in England,in Cornwall, green and brown; Devon, gray; Derbyshire, green and From Broken red and orange. yellow; Cumberland, golden yellow; in Scotland,Leadhill, Hill and elsewhere,New South Wales. In the United States,has been found very fine at Phenixville, Pa. ; also in Me., at Lubec and Lenox; in N. Y., a mile south of Sing Sing; in Davidson Co., N. C., also in Cabarrus and Caldwell Cos.; from and Mace, Idaho. Mullan, Burke, Wardner Named from irvp, fire, form the globule assumes form, alludingto the crystalline vop"f"r), on cooling. This speciespasses into mimetite. Use.

A

"

minor

ore

of lead.

MIMETITE.

07224. Hexagonal-pyramidal. Axis c Habit of crystals like pyromorphite; sometimes rounded to globularforms. Also in mammillary crusts. Cleavage: x (1011) imperfect. Fracture uneven. Brittle. H. 3-5. 7-0-7-25. Luster G. resinous. Color pale yellow, passing into brown; orange-yellow;white or colorless. Streak white or nearly so. Sub transparent to translucent. 2-135. 2-118. Optically", co " =

=

=

=

=

Var1- Ordinary, (a) In crystals, usuallyin rounded aggregates. (6) Capillaryor marked in a varietyfrom St. Prix-sous-Beuvray, filamentous,especially France; somewhat like asbestus,and straw-yellowin color, (c)Concretionary. Campylite,from Drygill in Cumberland, England, has G. 7*218, and is in barrelshaped crystals(whence the name, from Kanirv\os,curved),yellowish to brown and brownish red; contains 3 p. c. P2O6. "

=

Comp.

"

(PbCl)Pb4(AsO4)3;also

written

pentoxide 23'2, lead protoxide 74-9,chlorine 90-7,lead chloride 9-3 100.

2-4

3Pb3As208.PbCl2 =

100'5,

or

Lead

=

Arsenic arsenate

=

the Phosphorus replaces

(p.599)

is

intermediate

arsenic in part, and calcium the lead. between mimetite and vanadinite.

Endlichite

MINERALOGY

DESCRIPTIVE

6QO

Monoclinic

Wagnerite Group.

a

1'9145

(MgF)MgP04 (RF)RP04, R

Wagnerite Triplite

AdSlte

Fe

=

R

Triploidite ROH)RP04,

:

Mn

=

Mn :

2

=

Fe

1, 1

:

3

=

(MgOH)CaAs04 (MgF)CaAs04 (MnOH)MnAsO4

Tilasite Sarkinite

:

ft

: c

1'5059; 71"

53'

:

1*4925; 71" 1-5642; 73"

46' 15'

:

1

1

:

:

1

:

:

1

:

1

1, etc.

1 T8572 2'1978

:

:b :

2'0017

5154; 62" 13*'

iron and manganese Phosphates (and arsenates)of magnesium (calcium), Formula R2FPO4 or (RF)RPO4, etc. containingfluorine (alsohydroxyl). WAGNERITE.

Axes, see above.

Monoclinic.

largeand

Crystalssometimes

Also

coarse.

massive. Fracture uneven (100),m (110)imperfect;c (001)in traces. Luster vitreous. 3*07-3' 14. G. 5-5*5. H. Brittle. and splintery. Color yellow,of different shades; often grayish,also flesh-red, Streak white. 1*569. 2V 26" (approx.). a Translucent. Optically+. greenish.

Cleavage:

a

=

=

=

=

ft

1'570.

=

=

7

1*582.

or Mg3P208. fluo-phosphateof magnesium, (MgF)MgPO4 11*8 fluorine 43 104*9, Phosphorus pentoxide '8, magnesia 49*3, MgF2 A littlecalcium replaces 100. deduct (O part of the magnesium. 2F) 4'9

Comp.

A

"

=

=

=

=

with B.B. in the forceps fuses at 4 to a greenish gray glass; moistened Pyr., etc. On fusion with With borax reacts for iron. sulphuricacid colors the flame bluish green. acts Rereaction. but is not completely dissolved;gives a faint manganese soda effervesces, With for fluorine. Soluble in nitric and hydrochloricacids. sulphuric acid evolves of hydrofluoric acid. fumes in the valley of HollenObs. Wagnerite (in small highly modified crystals)occurs graben, near Werfen, in Salzburg,Austria. Kjerulfine(massive,cleavable; also in coarse is from Kjorrestad,near Bamle, Norway. crystals) A In flattened prismatic calcium fluo-phosphate,perhaps (CaF)CaPO4. Spodiosite. 2 '94. orthorhombic Color ash-gray. From the Krangrufva, Wermland, crystals. G. and Nordmark, Sweden. "

"

,

"

=

TRIPLITE.

two

Monoclinic. Massive, imperfectlycrystalline.Cleavage: unequal in directions perpendicular to each other, ture distinct. Fracmuch the more one small conchoidal. H. 4-5 -5. G. ing Luster resinous,inclin3'44-3'S. to adamantine. Color brown or blackish brown. Streak yellowishgray brown. Subtranslucent to opaque. Mean index from 1 "66Optically+. =

or

=

1-68.

Comp. Mg. The

(RF)RP04

"

.

1:2;

ratio varies

or

R3P208.RF2 with R

widely from

Fe

:

Mn

=

=

1

Fe

and

:

1 to

Mn, also Ca and : : 1 (zwieselite)

2

1:7.

is a varietyfrom Horrsjoberg, Talktriplite Sweden; contains magnesium and calcium in largeamount. B.B. fuses easily at 1*5 to a black magnetic globule; moistened with Pyr.?etc. sulphuric acid colors the flame bluish green. With borax in O.F. gives an amethystinecolored glass(manganese) in R.F. a ganese. ; strong reaction for iron. With soda reacts for manWith sulphuricacid evolves hydrofluoricacid. Soluble in hydrochloricacid. by Alluaud at Limoges in France; Helsingfors,Finland; Stoneham, Me.; Branchville, Conn.; from Reagan mining district, White Pine Co., Nev. Zwieselite, "

~~

D

a

UMI

clove-brown

GRIPHITE. form

masses.

variety, is from Rabenstein,near A

Zwiesel in Bavaria.

problematicalphosphate related to triplite occurring in embedded From the Riverton lode near Harney City, Pennington Co., S. D.

reni-

PHOSPHATES,

ARSENATES,

601

ETC.

II

PHOSPHOFERRITE.

H6R9(PO4)3: R

Columnar. White to yellow or Fe, Mn,Ca, Mg. H. G. 4-5. 3' 16. pale green. Habendorf, Bavaria. but with the F replacedby (OH). Monoclinic. Triploidite.Like triplite, Commonly in crystallineaggregates. H. Fibrous to columnar. 4'5-5. 3*697. G. Color yellowish 1726. to reddish brown. From Optically+ 0 Branchville,Fair-field Co., =

=

=

=

=

=

.

Conn.

Monoclinic. (MgOH)CaAsO4. Axes, see p. 600; also massive. H. 5. Mean index,1 '67. From Nordgray or grayishyellow. Optically +. mark Langban, Sweden. Tilasite. Like adelite,but contains fluorine. Monoclinic. 1*660. Optically /3 From Langban, Sweden, and Kajlidongri,Jhabua, India. In monoclinic Sarkinite. (MnOH)MnAsO4. crystals; also in spherical forms. G. 4 '17. Color rose-red,flesh-red,reddish yellow. From the iron-manganese mines of Pajsberg, Sweden. Polyarseniteand Xantharsenite from the Sjo mine, Grythytte from Pajsberg, Sweden, are essentiallythe parish,Orebro, Sweden, and Chondrasenite Adelite.

G.

=

=

Color

374. and

=

"

.

=

same.

In small wedge-shapedcrystals. Monoclinic-clinohedral. Trigonite. Pb3MnH(AsO3)3. Perfect cleavage ||(010). Color sulphur-yellow, a. 2-3. 216. Ax. pi. 2*08. 7 |j (010) From Langban, Sweden. Herderite. A fluo-phpsphate of beryllium and calcium,Ca[Be(F,OH)]PO4. In prismatic G. 2 '99-3 *01. Luster crystals,monoclinic with complex twinning. H. =5. vitreous. From Color yellowishand greenish white. T612. the tin Optically", ft of Ehrenfriedersdorf,Saxony; mines from Epprechtstein, Bavaria; also at Stoneham, Auburn, Hebron, and Paris,Me. A basic phosphate of aluminium, Hamlinite. In colorless rhomboand strontium. 4 '5. G. 3* 16-3 '28. 1*620. hedral with Occurs crystals. H. Optically+. In the diamond sands of Diamantina, herderite,bertrandite,etc., at Stoneham, Me. also in Binnental, Switzerland Brazil. Found (originally thought to be a new speciesand named bowmannite) In chemical group A basic phosphate of lead and aluminium. with Plumbogummite. ish. brownhamlinite. Resembles Color yellowish, as incrustations. drops or coatingsof gum; From Roughten Gill,Cumberland, England. Hitchcockite from Canton mine, Ga., is closelyidentical. The material from Huelgoet, Brittany,France, is a mixture. and the cerium metals,closelyanalogous A basic phosphate of aluminium Florencite. it is related in form. to hamlinite to which 3Al2O3.Ce2O3.2P2O6.6H2O. Hexagonal, rhom3*58. G. Color rhombohedral. Basal bohedral. Habit cleavage. H. =5. pale Ouro Preto and Diamantina, Minas in sands from near yellow. Infusible. Found Geraes, Brazil. of A basic phosphate of aluminium Georceixite. and barium (with smaller amounts in rolled H. 6. calcium and cerium) Microcrystalline, pebbles. BaO.2Al2p3.P2O5.5H2O. the diamond From sands of Refractive index, 1*63. and white. 3*1. Color brown G. acidic in composition. Geraesite is similar but more Minas Geraes, Brazil. H.

=

=

=

.

=

=

=

=

o"

=

.

=

=

.

=

In Crandallite. 2CaO.4Al/)3.2P2O5.10H2O. fibrous. Color white to light gray. mine

near

basic phosphate and

A

2A12O3.P2O5.SO3.5H2O. =

to

cleavable masses. scopically MicroFound at Brooklyn

Silver City, Utah.

Harttite. H.

compact

Indices,1-58-1*60.

4'5-5.

G.

=

3*2.

Hexagonal. Color

sulphate

Usually

flesh-red.

From

of

aluminium

and

microcrystalline the

diamond

strontium, (Sr,Ca)O. as

sands

of

rolled Minas

pebbles. Geraes,

Brazil.

fluo-phosphate of lime,soda, and alumina, Na4CaAl(AlO)(F,OH)4(Pp4)2 2*94. 4*5. G. Cleavage perfect (100); imperfect (001). Indices, From Colorless or white. 1 '55-1 '59. Ehrenfriedersdorf, Saxony. alumina. A Lacroixite. oxide, and fluo-phosphate of soda, lime, manganese monoclinic. Pyramidal cleavage. Na4(Ca,Mn)4Al3(F,OH)4P3Oi6.2H2O. Probably Found at Ehrenfriedersdorf, Color pale yellow or 3*13. H. G. 4-1. green. Saxony. In monoclinic Durangite. A fluo-arsenate of sodium and aluminium, Na(AlF)AsO4. From Color index, 1*673. 3*94-4*07. orange-red. Mean Durango, crystals. G. A

Jezekite.

Monoclinic.

H.

=

=

=

Mexico.

=

=

MINERALOGY

DESCRIPTIVE

602

Hebronite.

AMBLYGONITE.

rarely distinct. Usually Polysynthetictwinning lamellae

forms

Triclinic. Crystalslarge and coarse; cleavable to columnar and compact massive. common.

less so, with pearlyluster; a_(100)somewhat Cleavage: c (001)perfect, M ca (001) A (110)difficult; vitreous; e (021) sometimes equallydistinct; 74" 40', cM (001) A (110) 92" 20'. G. 3'01-3'09. 6. H. Brittle. subconchoidal. to Fracture uneven white to Color pale greenish, to c on vitreous (001)pearly. Luster greasy, white. SubtransStreak white. brownish bluish, yellowish,grayish or

(100)

75"

=

30',ce (001)A

(021)

=

=

=

=

1'597. 1*593. 1'579. 0 a 7 parent to translucent. Optically and aluminium A fluo-phosphateof lithium,Li(AlF)PO4 or Comp. AlPO4.LiF Phosphorus pentoxide47*9, alumina 34-4, lithia 10-1, fluorine Sodium often replacespart of the 100. 12-9 2F) 5*3 105-3,deduct (0 fluorine. of the and hydroxyl part lithium, =

=

-.

=

"

=

=

=

=

In the closed tube yieldswater, which at a high heat is acid and corrodes etc. Pyr., white on cooling. the glass. B.B. fuses easily(at2) with intumescence, and becomes opaque tense Colors the flame yellowishred with traces of green; the Hebron varietygives an inWith moistened with sulphuric acid gives a bluish green to the flame. lithia-red; borax and salt of phosphorusforms a transparent colorless glass. In fine powder dissolves slowly in hydrochloricacid. easilyin sulphuricacid,more Diff. and by yieldinga red flame B.B., from feldspar, Distinguishedby its easy fusibility barite,calcite, etc.; also by the acid water in the tube from spodumene. Obs. Occurs near Penig in Saxony; Arendal, Norway; Montebras, Creuze, France. In the United States,in Me., at Hebron; also at Paris,Peru, etc.; Branchville, Conn., Pala, San Diego Co., Cal. The name amblygoniteis from anftXls, blunt,and yow, angle. "

"

"

Fremontite.

Natramblygonite. Natromontebrasite. (Na,Li)Al(OH,F)PO4. Monowith rough faces. Three cleavages. Usually in cleavage masses. Polysynthetictwinning shown under microscope. H. 5'5. G. 3 '04. Luster vitreous to greasy. Color,grayishwhite to white. Translucent to opaque. trix BisecOptically". nearly normal to basal cleavage. Easily fusible to a white enamel with strong sodium flame color. From a pegmatite near Canon City, Fremont County, Col. clinic. Crystalscoarse

=

B.

Basic

=

Phosphates

This section includes a series of well-characterized basic phosphates, a number of which fall into the Olivinite Group. Acid phosphates are sented repre-

by see

speciesonly, the littleknown

one

monetite,probably HCaPO4,

p. b06.

Olivenite OUvenite

Group.

Orthorhombic

Cu2(OH)AsO4 Cu2(OH)PO4 Zn2(OH)AsO4

Libethenite Adamite

Descloizite

0-9396

:

1

:

0-6726

0-9601

:

1

:

0-7019

0-9733

:

1

:

0-7158

0-9552

:

1

:

0-8045

(Pb,Zn)2(OH)VO4 a

:

b

: c

Cuprodescloizite

=

0-6368

:

1

:

0-8045

or

fa

:

b

: c

=

(Pb,Zn,Cu)2(OH)VO4

The OLIVENITE

GROUP includes several basic phosphates,arsenates,etc.,of copper, lead,with the general formula (ROH)RPO4,(ROH)RAsO4, 1 hey crystallize in the orthorhombic system with similar form. It is to zinc, and

?roup corresP"ndsin Group,

*"

p.

,

a

measure

600,which also includes basic members.

to the monoclinic

Wagnerite

PHOSPHATES,

ARSENATES,

603

ETC.

OLIVENITE.

Orthorhombic. mm'", w'f

110 101

110 A TOl A

Axes =

=

a

:

b

: c

=

0*9396

86" 26'. 71" 1U'.

1

:

ee',Oil

A

Oil

=

ve, 101

A

Oil

=

:

0-6726. 67" 51'. 47" 34'.

Crystals prismatic,often acicular. Also globular and fibers straightand divergent, reniform, indistinctly fibrous, rarelyirregular;also curved lamellar and granular. Cleavage: m (110),6(010), e (Oil) in traces. Fracture conchoidal' to uneven. H. Brittle. 3. G. 4-1-4-4. Luster adamantine to vitreous;of some fibrous varieties pearly. \ Color various shades of olive-green, passing into leek-,siskin-, and blackish also liver- and wood-brown; pistachio-, green; sometimes and white. Streak olive-green to brown. straw-yellow grayish Mean to 1-83. Subtransparent opaque. index, Var. (a) Crystallized,(b) Fibrous;finelyand divergentlyfibrous,of green, yellow, brown and gray, to white colors,with the surface sometimes velvetyor acicular;found investing the common variety or passing into it; called wood-copper or wood-arsenate. (c)Earthy; nodular or massive; sometimes soft enough to soil the fingers. =

=

"

Cu3As2O8Cu(OH)2 Comp. 407, cupricoxide 56-1,water 3-2 "

or =

4CuO.As2O5.H20

=

Arsenic

pentoxide

100.

In the closed tube gives water. B.B. fuses at 2, coloring the flame bluish cooling the fused mass crystalline.B.B. on charcoal fuses with appears givesoff arsenical fumes, and yieldsa metallic arsenide which with soda yields deflagration, With the fluxes reacts for copper. Soluble in nitric acid. a globuleof copper. in Cornwall, at various mines; Tavistock, in Obs. varieties occur The crystallized Devonshire; in Tyrol, Austria; the Banat, Hungary; Nizhni Tagilsk in the Ural Mts.; In the United States,in Utah, at the American Chile. Eagle and Mammoth mines, Tintic both in crystalsand wood-copper. The name olivenite alludes to the olive-green district,

Pyr., etc. and

green,

"

on

"

color. LIBETHENITE.

Orthorhombic.

Axes

a

:

b

: c

mm"',

110

A

ee',

Oil

A

=

110 Oil

0-9601 =

=

:

1

87" 40'. 70" 8'.

0-7019. Ill Ill

A

111

A

111

=

=

59" 4"'. 61" 47|'.

crystals usuallysmall,short prismaticin habit ; often Also globularor reniform and compact. Cleavage: a (100),b (010)very indistinct. Fracture In

united in druses.

3-6Brittle. H. 4. G. to uneven. resinous. Color olive-green, generallydark. Mean Translucent to subtranslucent. Streak olive-green.

subconchoidal

=

=

Luster

3*8.

index, 1'72.

Cu3P2O8.Cu(OH)2 or 4CuO.P2O5.H2O Comp. Phosphorus pentoxide 29'8, cupric oxide 66*4, water "

3'8

=

=

100.

B.B. fuses at 2 and colors In the closed tube yieldswater and turns black, Pyr.,etc. also an the flame emerald-green. On charcoal with soda gives metallic copper, sometimes with Fused with metallic lead on charcoal is reduced to metallic copper, arsenical odor. polyhedralbead the formation of lead phosphate, which treated in R.F. gives a crystalline Soluble in nitric acid. on cooling. With the fluxes reacts for copper. Occurs Obs. with chalcopyriteat Libethen, near Neusohl, Hungary; at Rheinat Nizhni Tagilsk in the Ural Mts.; from breitenbach and Ehl on the Rhine, Germany; trict, disin Cornwall, England. In Clifton-Morenci Viel-Salm, Belgium; in small quantities "

"

Ariz.

MINERALOGY

DESCRIPTIVE

604

Zn3P2O8 Zn(OH)2. Triclinic. Crystals striated and rounded, frequently Colorless to pale 4'1. G. 37. aggregates. Perfect basal cleavage. H. N. W. Rhodesia. Broken From Fusible. Hill, or yellow,brown, red, green. often grouped in crusts crystals, Zn3As-"O8.Zn(OH)2. In small orthorhombic Adamite. Color honey-yellow,violet, 4'34-4'35. roseG. 3'5. and granularaggregations.H. From 173. Cap Garonne, Chile; France; Mean Chanarcillo, colorless. index, red,green, of Laurion, Mte. from Valerio,Campiglia Marittima, Italy; at the ancient zinc mines taining Island of Thasos, Turkey. Varieties from Cap Garonne, Var, France, conFrom Greece. cobalt and copper have been called cobaltoadamiie and cuproadamite. Pb, Zn chiefly,and usually in Descloizite. R2V2O8.R(OH)2 or 4RO.V2O6.H2O; R often drusy; also massive, fibrous In small orthorhombic crystals, the ratio 1 : 1 approx. 5'9-6'2. Color H. 3 '5. G. surface. cherry-red and with mammillary radiated red or yellowish Streak orange to brownish brownish red, to lightor dark brown, black. Mean index,1'83. gray. Abundant at Lake From the Sierra de Cordoba, Argentina; Kappel in Carinthia. stone; TombGeorgetown and at Magdalena; in Ariz, near Valley,Sierra Co., N. M., also near Gold mine, near in Yavapai Co.; at the Mammoth Oracle,Final Co. with A massive variety,containingcopper (6'5to 9 p. c.),in crusts,and reniform masses in San Luis Potosi, also in a vein of argentiferousgalena in radiated structure, occurs A ramirite. cuprodescloizite, tritochorite, Zacatecas,Mexico; it has been variouslynamed incrustation on quartz at the Lucky Cuss mine, similar variety(11 p. c. CuO) occurs as an From Tombstone, Cochise Co., and in stalactites at Shattuck Arizona mine, Bisbee,Ariz. Camp Signal,San Bernardino Co., Cal. in nodular, stalactitic forms. be identical with descloizite. Massive: EUSYNCHITE may G. Color yellowishred, reddish brown, greenish. From burg Frei5 '596. Hofsgrund near in Baden, Germany. from Dahn The same be true of arceoxene Niedernear may Schlettenbach,Rhenish Bavaria, Germany. In small acicular crystals. Orthorhombic. Pyrobelonite. 4PbO.7MnO.2V2O5.3H2O. 5'377. Fire-red color. H. 3'5. G. High index. Probably related crystallographicallyto descloizite. From Langban, Sweden. DECHENITE. Composition usuallyaccepted as PbV2O6. nodular. Massive, botryoidal, G. 5'6-5'81. Color deep red to yellowishred and brownish red. From Nieder-Schlettenbach in the Lautertal,Rhenish Bavaria, Germany. Calciovolborthite. Probably (Cu,Ca)sVXMChi,Ca)(OH)8. In thin green tables;also granular. Mean index,2 '05. From Friedrichsrode,Thuringia, Germany. gray, fine crystalline Minerals from Richardson, southeastern Utah, and from near Baker City,Oregon, probably belong here. Orthorhombic. Higginsite. CuCa(OH)AsO4. Small 4'5. prismatic crystals. H. G. 4 '33. n 1745. Pleochroic, green, yellow-green, blue-green. From Higgins mine, Bisbee,Ariz. Tarbuttite,

in sheaf-like

=

=

=

=

=

=

=

=

=

=

=

=

=

=

Brackebuschite. TURANITE.

Muyun,

south

A of

Near

descloizite (monoclinic?). From

vanadate, 5CuO.V2O5.2H2O. copper Andidjan, Alai Mts., Turkestan.

the

State

Radiating fibrous.

Psittacinite. A vanadate of lead and copper, from the Silver Star thin coatings; also pulverulent. Color siskin- to olive-green. MOTTRAMITE. in

velvety black

A

vanadate

of lead and copper; From St. Mottram

incrustations.

of

Cordoba, From

gentina. Ar-

Tyuya-

Mon District,

In

possibly identical with psittacinite; Andrew's, Cheshire,England.

Furnacite. A basic chrom-arsenate of lead and In dark olive-green small copper. .prismatic crystals. From Djocie, French Equatorial Africa. Tsumebite. Preslite. A basic lead and phosphate. Orthorhombic? In copper small tabular 3'5. crystals. H G. 6'1. Color Index, " 178. emerald-green. Pleochroic,blue-greento yellow-green.Easily fusible. From Tsumeb, Otavi, German =

o.

W

.

=

Alrica.

CLINOCLASITE.

Monoclinic.

Aphanese.

Axes a : b : c 1-9069 : 1 : 3-8507; 0 80" 30' Crystals prismatic (TO (110)); also elongated ||6 axis; of ten* grouped in =

=

PHOSPHATES,

Also massive,

nearly sphericalforms.

605

ETC.

ARSENATES,

hemisphericalor reniform; structure

fibrous.

radiated

2'5-3. G. 4'19-4'37. Cleavage: c (001)highlyperfect.Brittle. H. to vitreous resinous. elsewhere Color c pearly; dark verdigris-green; internally Subtransexternallyblackish blue-green. Streak bluish green. =

=

Luster:

parent

to translucent.

Cu3As2O8.3Cu(OH)2 Comp. 30'3, cupricoxide 62'6,water 71 Pyr., etc.

Same

"

as

6CuO.As2O5.3H20

or

"

=

Arsenic

=

pentoxide

100.

for olivenite.

In Utah, Tintic district, Cornwall, with other ores of copper. at the mine. From in allusion to the basal Mammoth Collahurasi,Tarapaca, Chile. Named cleavage being oblique to the sides of the prism. In mammillated Erinite. Color fine emerCu3As2O8.2Cu(OH)2. crystalline ald-green. groups. Utah. From Cornwall; also the Tintic district, In dark emerald-green crystals (monoclinic). Dihydrite. Cu3P2Og.2Cu(OH)2. From Ehl near G.= H. 4-4'4. Linz on the Rhine, Germany ; the Ural Mts., etc. 4'5-5. In Pseudomalachite. Massive, resembling malachite in part Cu3P2O8.3Cu(OH)2. structure. color and Indices, 1*83-1*93. From Rheinbreitenbach,Germany; Nizhni Tagilsk,Russia, etc. Ehlite is closelyallied. Obs.

"

Occurs

in

=

Kraurite.

DUFRENITE.

Crystalsrare, small, and indistinct. Usuallymassive,in nodules; radiated fibrous with drusy surface. 3*5-4. Cleavage: a (100),probably also b (010),but indistinct. H. Luster dull 3'2-3'4. weak. Color G. or leek-green,olive-green, silky, Streak siskin-green. to yellowand brown. alters on exposure blackish green; Subtranslucent to nearly opaque. Stronglypleochroic.Indices,1'83-1'93. in 2Fe2O3.P2O5.3H2O Doubtful; Comp. part FeP04.Fe(OH)3 100. Phosphorus pentoxide27 -5,iron sesquioxide62'0,water 10*5 Orthorhombic.

=

=

=

"

=

=

but less water is given out in the closed tube. B.B. Same for vivianite, as Pyr., etc. fuses easilyto a slag. Obs. Occurs near Vienne, France; in Germany at HirschAnglar, Dept. of Haute mine near Waldgirmes; St. Benigna, berg in Westphalia and from the Rothlaufchen Bohemia; East Cornwall, England. In the United States,at Allentown, N. J.; in Rockbridge Co., Va., in radiated coarsely from Graf ton, N. H. fibrous masses; position Dufreniberauniteis a variety intermediate in combetween dufreniteand beraunite from Hellertown, Pa. "

"

LAZULITE.

Monoclinic:

Axes

at, 100

A

101

=

ppf, 111

A

111

=

:

a

b

: c

0-9750

=

:

ee',Til

30" 24'. 79" 40'.

111

pe,

1

1-6483; 0 :_

A

111

A

111

89" 14'.

=

80" 20'. 82" 30'.

=

=

986

pyramidal in habit. Also Crystals usually acute to compact. massive, granular uneven. Cleavage: prismatic, indistinct. Fracture vitreous. commonly a fine deep blue viewed along one axis,and a pale greenish blue along another. to Subtranslucent Streak white. Optically opaque. 1-639. 1'632. 1-603. 2V 69". a (3 7 5-6. Brittle. H. Color azure-blue; =

G.

Luster

3-057-3-122.

=

"

.

=

Comp. Fe

:

"

Mg(Ca)

RAL(OH)2P2O8 =

=

=

=

1

:

12, 1

:

with

for2 the mula pentoxide 45*4,alumina 32*6,iron

requires: Phosphorus 100. magnesia 8'5,water 5*8 =

2AlPO4.(Fe,Mg)(OH)2

or

6, 1

:

2, 2

:

3.

For

1

:

protoxide7*7,

MINERALOGY

DESCRIPTIVE

506

In the forceps whitens,cracks In the closed tube whitens and yieldswater. etc B.B. fusion falls to pieces,coloring the flame bluish green. swells up, and without The color of the flame mineral is restored. the of color green blue the solution cobalt with With the fluxes gives an with sulphuric acid. intense by moistening the assay is made more Unacted infusible mass. by acids, retaining charcoal an upon iron glass; with soda on perfectlyits blue color. also Horrsin Salzburg, Austria; Kneglach, in Styna; Werfen Obs. Occurs near

Pyr

"

open

"

from

joberg,Sweden;

Madagascar.

at Crowder's Mt., Gaston Co., N. C.; and on Graves Mt., with corundum Abundant Lincoln Co., Ga., with cyanite,rutile,etc. word, azw, meaning heaven, and alludes to The lazulite is derived from an Arabic name the color of the mineral.

In microscopic acicular crystals,sometimes stellate Ca3P2O8.2Al(OH)2. Devonshire. From Tavistock, groups. 3'OS. G. Color pale yellow. Compact. Cirrolite. Perhaps Ca3Al(PO4)3.Al(OH)3. at Westana, in Scania, Sweden. Occurs at the iron mine fibrous concretions. Arseniosiderite. Ca3Fe(AsO4)3.3Fe(OH)3. In yellowish brown From 3'520. Romaneche, near Macon, France; also at Schneeberg, G. Index, 3'83. Tavistockite.

white.

Color

=

=

Saxony. In small brownish Monoclinic. red prismatic crysMn3As2O8.4Mn(OH)2. the Moss From mine, Nordmark, and at Langban, Sweden. index, 1786. In prismatic crystals;also in grains. G.= Synadelphite. 2(Al,Mn)AsO4.5Mn(OH)2. From the Moss 3 '45-3 -50. Color brownish black to black. mine, Nordmark, Sweden. Allactite.

stals.

Mean

minute

In

Flinkite. MnAsO4.2Mn(OH)2. grouped in feather-like aggregates. mine, Pajsberg, Sweden.

G.

=

3 '87.

orthorhombic crystals,tabular ||c (001); Color greenish brown. From the Harstig

Hematolite.

In rhombohedral Perhaps (Al,Mn)AsO4.4Mn(OH)2. crystals. G. Mean brownish From the red, black on the surface. Index, 1730. mine, Nordmark, Sweden.

Moss

=

Color

3 -30-3 '40.

Retzian. A basic arsenate of the yttrium earths, manganese and calcium. rhombic Color chocolate- to chestnut-brown. 415. G. crystals. H. =4. Moss mine, Nordmark, Sweden. =

n

m

ii

In orthothe

From

ni

R Arseniopleite. Perhaps RgR^OH^AsO^e; R Mn, Ca, also Pb, Mg; Mn, also Fe. Color brownish red. Occurs Massive, cleavable. at the Sjo mine, Grythytte parish, Sweden, with rhodonite in crystallinelimestone. =

is

=

Manganostibiite. Hematostibiite. antimonates. In emHighly basic manganese bedded grains. Color black. at Nordmark, Sweden; hematostibiite Manganostibiite occurs from the Sjo mine, Grythytte parish,Sweden.

6'4.

Atelestite. Basic bismuth In arsenate, H2Bi3AsO8. Color sulphur-yellow. From Schneeberg,Saxony.

C. The

Normal

only important

monoclinic

VIVIANITE

Struvite.

group

P'

6

i'

G

=

etc.

hydrous phosphates is the

A

Mona

occurring

in

"r

phosphate. In orthorhombic-hemimorphic yeUowish; sli8htlysoluble. Index, 1'502. From

In layers resembling gymnite or opal. Colorless or the island of Sombrero, West Indies. is similar, Monile and Moneta in the West Indies,where it is associated with monetite, yellowish white triclinic crystals.

"L59' "

4

the normal

crystals

GROUP.

Collophanite. Ca3P2O8.H2O. "

among

Phosphates,

tabular

Hydrous ammonium-magnesium

Sanod r*k

Hydrous

minute

From

MINERALOGY

DESCRIPTIVE

608

includes hydrous phosphates of iron,magnesium, GROUP VIVIANITE The crystallization of water. cobalt,nickel and zinc,all with eightmolecules far as known, correspondclosely. so is monoclinic,and the angles, The

VIVIANITE.

71" 58'); often in Crystalsprismatic(mm'" 110 A 110 or divergent,fibrous, Also reniform and globular;structure

Monoclinic.

=

stellategroups.

earthy; also incrusting. Cleavage: b (010)highlyperfect;a (100)in traces; also 1'5 nearly_L c axis. Flexible in thin laminae; sectile. H.

fracture

fibrous G 2'58 faces other vitreous. metallic pearly; 2*68. Luster, b (010) pearly or Streak Colorless when unaltered,blue to green, deepening on exposure. and to liver-brown. colorless to bluish white, changing to indigo-blue Pleochroism after exposure. strong; Transparent to translucent; opaque =

"

2.

=

-

X

ft

Y cobalt-blue,

=

Comp.

Z

and

palegreenishyellow. Optically-f.

=

1-636. 7 Hydrous ferrous

1'604.

=

a

=

1*581.

=

"

phosphate,Fe3P208.8H20

oxide 28'3,iron protoxide43'0,water

287

=

=

Phosphorus pent-

100.

Many analysesshow the presence of iron sesquioxidedue to alteration. In the closed tube yields neutral water, whitens, and exfoliates. B.B. Pyr., etc. fuses at 1 "5, coloringthe flame bluish green, to a grayish black magnetic globule. With "

.

acid. Soluble in hydrochloric the fluxes reacts for iron. and tin veins; someOccurs associated with pyrrhotiteand pyrite in copper Obs. times veins with gold,traversinggraywacke; both friable and crystallized in narrow in beds of clay,and sometimes associated with limonite,or bog iron ore; often in cavities of fossils "

or

buried bones. Occurs at St. Agnes and of

elsewhere in Cornwall, England; at Bodenmais, Germany;

the

Ashio, Shimotsuke, Japan. A variety Transylvania. From from the Kertsch and Taman peninsulas,South Russia, that contains small quantitiesof and magnesium has been called paravivianite. The earthy variety,sometimes manganese called blue iron-earth or native Prussian blue (Fer azure), occurs in Greenland, Carinthia, Guatemala, Bolivia,Victoria,Australia,etc. In North in nodules, America, in N. J.,at Allentown, Monmouth Co., both crystallized, and earthy; at Mullica Hill,Gloucester Co. (mullicite}, in cylindrical In Va., in masses. In Ky., near Stafford Co. Eddyville. In Col. at Leadville; in Idaho, at Silver City. In Canada, with limonite at Vaudreuil. gold mines

Verespatak

in

Symplesite.Probably Fe3As2O8.8H2O. In small prismatic crystalsand in radiated 2 '957. Color pale indigo,inclined to celandine-green. From sphericalaggregates. G. Lobenstein,Germany; Hiittenberg,Carinthia. Bobierrite. Mg3P2O8.8H2O. In aggregates of minute crystals; also massive. less ColorFrom the of Mexillones, to white. the Chilian coast. on guano Hautefeuillite is like bobierrite,but contains calcium. Index Monoclinic. From 1*52. Bamle, Norway. =

Hoernesite.

foliated.

Mg3As2p8.8H2O.In crystalsresembling gypsum;

Color snow-white.

ERYTHRITE.

Cobalt

From

the Banat,

also columnar; stellar-

Hungary.

bloom.

Monoclinic. Crystalsprismaticand vertically striated. Also in globular and reniform shapes,having a drusy surface and a columnar times structure; somestellate. Also pulverulent and earthy,incrusting.

Cleavage:

b (010) highly perfect. Sectile. H. T5-2'5; least on b. Luster of 6 pearly; other faces adamantine to vitreous; also dull,earthy. Color crimson- and peach-red,sometimes gray. Streak a little paler than the color. Transparent to subtranslucent. Strongly pleochroic.

G.

=

=

2'948.

Optically

-.

a

=

1'626.

ft

=

1'661.

7

=

1'699.

PHOSPHATES,

ARSENATES,

609

ETC.

Arsenic pentoxide Hydrous cobalt arsenate, Co3As208.8H2O water 24' 1 100. cobalt is sometimes The protoxide37'5, placed reand calcium. by nickel,iron,

Comp.

=

"

38*4, cobalt

=

In

the closed tube yields water at a gentle heat and turns bluish; at a arsenic trioxide which condenses in crystalson the cool glass,and the residue has a dark gray or black color. B.B. in the forcepsfuses at 2 to a gray bead, and colors the flame light blue (arsenic). B.B. on charcoal gives an arsenical odor, and fuses to a dark gray arsenide,which with borax givesthe deep blue color characteristic of cobalt. Soluble in hydrochloricacid, giving a rose-red solution. Occurs Obs. at Schneeberg in Saxony, in micaceous in Baden; scales; Wolfach in Norway. From Modum the Veta Rica mine, Sierra Mojada, Coahuila, Mexico; Chile. In the United States,in Pa.,sparinglynear Philadelphia;in Nev., at Lovelock's station. from In crystalsfrom In Cal. Named red. Cobalt,Canada. epi"0p6s,

Pyr., etc.

"

higherheat givesoff

"

NiaAsaOs.SH^O.

In capillarycrystals; also massive Monoclinic. and Mean From Alleindex, 1'68. apple-green. Optically in Dauphine, France; Annaberg, Schneeberg and Riechelsdorf,Germany; in Col.; mont Nev.; Cobalt, Ontario,Canada. Cabrerite. (Ni,Mg)3As2O8.8H2O. Like erythrite in habit. Also fibrous,radiated; the Sierra Cabrera, Spain; at Laurion, reniform, granular. Color apple-green. From

Annabergite.

fine

Color

disseminated.

"

.

Greece. Color Massive, or in crusts. Kottigite. Hydrous zinc arsenate, ZnsAs2O8.8H2O. light carmine- and peach-blossom-red. Occurs with smaltite at the cobalt mine Daniel, near Schneeberg, Germany.

Rhabdophanite. Scovillite. A hydrous phosphate of the cerium and yttrium metals. Color brown, pinkish or 3'94-4'OL Massive, small mamillaryj as an incrustation. G. yellowishwhite. Rhabdophanite is from Cornwall; Scovillite is from the Scoville (limonite) bed in Salisbury,Conn. ore As a thin coating of minute Churchite. A hydrous phosphate of cerium and calcium. 3'14. Color pale smoke-gray tinged with flesh-red. From Cornwall,England. crystals. G. =

=

ages. Fine granular. Two Orthorhombic. pinacoidalcleavin rocks near disseminated Indices, 1 '82-2 '06. Found of Greenriver,Utah. In scales. Color province of sulphur-yellow. From

2UO3.3V2O6.15H2O.

Uvanite.

brownish yellow. Rock, 45 miles southwest

Color

Temple Ferganite. U3(VO4)2.6H2O. Turkestan. Fergana, Russian

Color dull green. Massive. Fernandinite. Readily soluble CaO.V^O^SVaOe.MHaO. Found at Minasragra, Peru. acids,partly soluble in water. In Monoclinic. Pascoite. Hydrous calcium vanadate, possibly2CaO.3V2O6.11H2O. Streak Color 2'46. G. 2'5. yellow. Indices, 177-1 '83. grains. H. orange. of Pasco, Peru. Found at Minasragra, Province Easily fusible. Soluble in water. Color As efflorescence. Pintadoite. calcium an 2CaO.V2O6.9H2O. vanadate, Hydrous Utah. in sandstone of surfaces Found Pintado, Canyon coating green. in

=

=

987

SCORODITE.

Axes

Orthorhombic. dd', pp',

120

A

111

A

120 111

=

=

a

:

b

60" 1'. 77" 8'.

: c .

=

0*8658 pp", pp'",

:

1

:

0-9541.

111

A

111

111

A

111

=

=

111" 6'. 65" 20'.

also prismatic. Also earthy, amorphous. octahedral, ture Fracd a (100),6(010) in traces. (120)imperfect; Cleavage: Habit

Luster vitreous 3'l-3'3. 3'5-4. G. Color paleleek-green subresinous. Streak white. Subtransparent to translucent.

Brittle.

uneven.

to subadamantine or

liver-brown.

H.

=

=

and

Mean

index, 1'84. ferric arsenate, FeAsO4.2H20 Hydrous Comp. 100. 49'8,iron sesquioxide34'6,water 15'6 "

=

=

Arsenic

pentoxide

610

MINERALOGY

DESCRIPTIVE

and turns yellow. B.B. fuses In the closed tube yields neutral water Pyr., etc. easily,coloringthe flame blue. B.B. on charcoal givesarsenical fumes, and with soda a acid. black magnetic scoria. Wit^hthe fluxes reacts for iron. Soluble in hydrochloric Schwarzenberg, Saxony; DernOften associated with arsenopyrite. From Obs. bach, Nassau, Germany; Lolling,Carinthia; Schlaggenwald, Bohemia; Nerchinsk,Siberia, From in the Cornish mines. Congo Free State. From Obira, in fine crystals;leek-green, Japan. at the Mammoth Occurs near Edenville,N. Y., with arsenopyrite;in Utah, Tintic district,, mine on enargite. As an incrustation on siliceous sinter of the Yellowstone geysers. From Cobalt, Ontario, Canada. from anopodov,garlic, Named alludingto the odor before the blowpipe. Monoclinic. Vilateite. H. 3-4. Hydrous iron phosphate with a littlemanganese. in pegmatite at La Vilate near Found 275. Color violet. Index, 174. G. Chanteloube, Haute Vienne, France. Two Purpurite. 2(Fe,Mn)PO4.H2O. Orthorhombic(?). In small irregularmasses. 4-4*5. G. 3 '4. Color deep red or reddish purple cleavages at right angles. H. Found at Kings Mt., Gaston Refractive index, 1*66-1*65,Fusible. Co.,N. C., sparingly from Pala, San Diego Co., Cal.,Hill City, S. D., and Branchville, Conn. Crystalsrare; in habit and angle near Strengite. FePO4.2H2O. scorodite;generally in sphericaland botryoidalforms. 2 '87. Color pale red. G. 172'. Optically+. 0 From iron mines near Giessen,Germany; also in Rockbridge Co.,Va., with dufrenite;irom Pala, Cal. Phosphosiderite. 2FePO4.3"H2O. An iron phosphate near strengite, but with 3|H2O. Color red. Index 173. From the Siegen mining district, Germany; from Sardinia. Barrandite. color pale shades of gray. (Al,Fe)PO4.2H2O. In spheroidalconcretions, Bohemia. Index, 1-57. From "

"

=

=

=

=

=

Variscite.

A1PO4.2H2O.

incrustations

with

Orthorhombic. Commonly in crystallineaggregates and surface. Color green. 1'556. Optically -. 0 Strongly in Saxon Voigtland; Montgomery Co., Ark.,on quartz in Co., Utah (Utahlite); crystalizedfrom Lucin, Utah.

reniform

=

pleochroic. From nodular

Messbach from Tooele

masses

Lucinite. habit.

Found

Comp.

Also

same

for

as

compact, massive.

H.

varisdte,A1PO4.2H2O. =

5.

with varisdte at Utahlite Hill,near

Callainite. a

Celtic grave

A1PO4.2"H2O. in

From

G.

Orthorhombic.

2*52.

Color green. Lucin, Boxelder Co., Utah. =

Massive; wax-like.

Octahedral

Indices,1 -56-1

Color apple- to emerald-green

'59

From

Lockmariaquer,Brittany.

Zepharovichite. A1PO4.3H2O. white.

=

Crystallineto compact.

Color

yellowish

or

grayish

Trenic in Bohemia.

Palmerite.

HK2A12(PO4)3.7H2O. Amorphous, pulverulent. Color white. Occurs as depositon Mte. Alburno,Salerno, Italy. Rosieresite. A hydrous phosphate of aluminium with lead and copper. In stalao2'2' yellow to brown. C.olor Index, 1*5. Isotropic.Infusible. Found in GJ= u68^ abandoned at Rosieres, copper mine Tarn, France. a

stratum

in

a

guano

yelbw"mR^Su

^

"5w^Arite; ^ hydrous In cleavable

""rr 3 Li,H)20.

^^

*******

iron-manganesephosphate

masses.

G.

=

3*45.

Color

"f

^^

needles'

Color

with lithia,Fe2O3.6MnO.4P2O6 dark brown. Indices,171-175

^ perpendicularto cleavaSe- Fusible" flamf givinglithium Trom piTa"C"aiange"red' SaLmonsite.

A

hydrous iron-manganesephosphate,Fe2O3.9MnO.4P2O5 14H,O COl0rbUff'

Acid

^4,1-65-1.67.Fou^d

Cleav-

Hydrous Phosphates,etc.

PHARMACOLITE. "

C"mmonly

Cleavage:6 (010) perfect. Fracture

in delicate si

uneven.

Flexible in thin laminse.

PHOSPHATES, H.

2-2;5.G.

=

Luster

to pearly. vitreous;on 6 (010)inclining or grayish; frequentlytinged red. Streak white. Translucent 1'583. 1'589. 1'594. a Optically 0 7 Arsenic pentoxide 53*3,lime 25'9, Probably HCaAsO4.2H2O

Color white to opaque.

=

=

-.

Comp.

=

=

=

"

20'8

water

2'64-273.

611

ETC.

ARSENATES,

100.

=

Obs. Found with arsenical ores of cobalt and silver, also with arsenopyrite; at Andreasberg in the Harz Mts., Germany; Riechelsdorf in Hesse, Germany; Joachimstal in from ^ap/za/cop, poison. Bohemia, Markirch, Alsace,etc. Named In minute Haidingerite. HCaAsO4.H2O. crystalaggregates, botryoidal and drusy. Color white. 2 -848. G. Index, 1 '67. From Joachimstal, Bohemia, with pharmacolite. In in incrustations. minute also Colorless Wapplerite. HCaAsO4.3"H2O. crystals; Found with pharmacolite at Joachimstal,Bohemia. to white. Brushite. In small slender monoclinic prisms: concretionarymassive. HCaPO4.2H2O. 1*545. Colorless to pale yellowish. " Occurs in guano. ciated, Metabrushite, similarlyassois a mineral similar to brushite but said to contain a is 2HCaPO4.3H2O. Stoffertite From littlemore water. depositson the island of Mona, West Indies. guano Martinite. H2Ca5(PO4)4.|H2O. From phosphorite deposits(from guano) in the island of Curacoa, West Indies. G. Hewettite. 2'5-2'6. In microscopic needles. Color CaO.3V2O5.9H2O. deep red. Pleochroic,lightorange-yellowto red. On heating loses water changing color through at Minasshades of brown to a bronze. Easily fusible. Found as an alteration of patronite "

=

=

=

Also observed

Peru.

ragra,

from

Paradox

Valley,Col.

In minute tabular orthorhombic as Comp. same tals. crysParadox changing from dark red to yellow-brown. From heating loses water Valley,Col.,and at Thompson's, Utah. In white orthorhombic crystals. Index, 1'52. From Newberyite. HMgPO4.3H2O. is a hydrous phosphate of Skipton Caves, Victoria. locality, Hannayite, from same guano Occurs in small of ammonium and magnesium. Schertelite,Mg(NH4)2H2(PO4)2.4H2O. tabular crystalsin hot guano depositsnear Skipton, southwest of Ballarat,Australia. In white crystalline Microcosmic Stercorite. salt. HNa(NH4)PO4.4H2O. and masses

for hewetlite.

Metahewettite. On

nodules

in guano.

In short prismatic crystals (monoclinic). Also H2Mn6(PO4)4.4H2O. massive, compact, or imperfectlyfibrous. Color yellowish,orange-red, rose, grayish. In the United of Bureaux, France. From T654. Limoges, commune (3 Optically States,at Branchville,Conn.; Pala, Cal. Color grayish white. Forbesite. H2(Ni,Co)2As2O8.SH2O. Structure fibro-crystalline.

Hureaulite.

=

"

.

From

Chile.

Atacama,

3(Ba,Pb)O.2P2O6.8H2O.

FERRAZITE.

Color dark

yellowishwhite.

G.

Basic

A

"fava"

found

in the diamond

sands of Brazil.

3 '0-3 '3.

=

Hydrous Phosphates,

etc.

In minute white crystals;also columnar. From Isoclasite. Ca3P2O8.Ca(OH)2.4H2O. Joachimstal,Bohemia. in spherical radiated groups. Mn3As2O8.3Mn(OH)2.2H2O. Commonly Hemafibrite. the Moss red to garnet-red, mine, Nordmark, becoming black. From Color brownish Sweden. EUCHROITE.

Orthorhombic. m

prismaticmm'"

Habit

Fracture

(Oil) in traces.

(110),

n

brittle. H.

=

G.

3 -5-4.

=

3-389.

110

A

Luster

vitreous.

leek-green. Transparent to translucent. Mean Arsenic Cu3As2Os.Cu(OH)2.6H2O Comp. 100. 187 oxide 47-1,water

or

=

"

110

=

small conchoidal

62" 40'. to

uneven.

Color

Cleavage: Rather

brightemerald-

index,1-70. pentoxide 34'2, cupric

=

Obs.

"

Occurs

in quartzose mica

size,having much

resemblance

able slate at Libethen in Hungary, in crystalsof considercolor. from evxpoa, beautiful dioptase. Named

to

612

MINERALOGY

DESCRIPTIVE

Orthorhombic. Usually Conichalcite. Perhaps (Cu,Ca)3As2O8.(Cu,Ca)(OH)2.|H2O. Color pistachio-greento emerald-green and massive, resembling malachite. reniform Tintic district, Utah. From Andalusia, Spain; Maya-Tass, Akmolinsk, Siberia (crystals);

mamillary

In (Pb,Cu)3As2O8.(Pb,Cu)(OH)2.H2O.

Bayldonite.

concretions,drusy.

Cornwall, England.

From

Color green.

Tagilite. Cu3P2O8.Cu(OH)2.2H2.O. In reniform or the Ural Mts. verdigris-to emerald-green. From Leucochalcite. Probably Cu3As2O8.Cu(OH)2.2H2O. in the Spessart,Germany. mine From the Wilhelmine

spheroidalconcretions; earthy.

Color

Found

Color grass-green. Africa.

=

In small in druses of

3ZnO.CuO.3As2O6.2H2O.

Barthite.

G. 419. Southwest

In white,

silkyacicular crystals.

monoclinic 3. (?) crystals. H. dolomite at Guchab, Otavi, German =

a

In of copper, barium, and calcium. A hydrous vanadate Volbprthite. Color olive-green, citron-yellow.Index, 1 '90. tables; in globularforms.

small From

six-sided the Ural

.

Mts. In Monoclinic. microscopic hair-like Hiigelite. A hydrous lead-zinc vanadate. Reichenbach near Lahr, Baden, crystals. Color orange-yellow to yellow-brown. From Germany. Cornwallite. Color emerCu3As2O8.2Cu(OH)2.H2O. Massive, resembling malachite. ald-green. From Cornwall; England. Usually in fan-shapedcrystalTyrolite. Tirolit. Perhaps Cu3As2O8.2Cu(OH)2.7H2O. line in foliated aggregates; also massive. Cleavage perfect,yielding soft thin groups; flexible laminae. Color pale green From incliningto sky-blue. Index, T70. Libethen, Hungary; Nerchinsk, Siberia;Falkenstein,Tyrol; etc. In the United States,in the Tintic district, "Utah. Some analyses yield CaCO3, usually regarded as an impurity,but it may

be essential.

In radiating and reticulated Spencerite. Zn3(PO4)2.Zn(OH)2.3H2p.Monoclinic. G. 3*12. H. crystals. Cleavages parallelto three pinacoids. Color white. 2*7. From 1-61. Hudson 0 Optically Bay Mine, Salmo, B. C. Hibbenite. Tabular parallelto a (100). 2Zn3(PO4)2.Zn(OH)2.6fH2O. Orthorhombic. G. H. Cleavages parallelto three pinacoids. Color white. 3 '21. 3 7. Optically From Hudson Bay Mine, Salmo, British Columbia. =

=

=

-.

=

=

"

.

CHALCOPHYLLITE.

Rhombohedral.

Axis

c

2761.

=

In

0001

72" 2'. also foliated crystals;

cr

tabular

1011

A

=

massive; in

druses.

Cleavage:

c

(0001) highly perfect;

r

(lOll) in

H. traces. 2. G. 2'4-2'66. Luster of of other faces vitreous subadamantine. or =

=

c

pearly;

Color emerald- or grass-green to verdigris-green.Streak somewhat paler than the color. Transparent to translucent. Opticallv 1-632. 1-575. " A highlybasic arsenate of formula uncertain,perhaps copper; ______^__

-

=

(??I!lp" 7"

uO. As2O5.14H20.

Pyr., etc.

In the closed tube decrepitates, yieldsmuch water, and gives a residue of In other respects like olivenite. Soluble in nitric acid,and in ammonia. *rom the copper mines near Redruth in Cornwall; at Sayda, Saxony; Moldawa from ChUeIn the United gary; States,in the Tintic district, Utah; "

-

olive-greenscales. Ubs.

"

BisbiAriz

Veszelyite.A a

hydrous phospho-arsenate of

greenish blue crystalline incrustation

copper

at

and

zinc, formula

Morawitza, in

the

1

Crystalsrare

uncertain.

Banat, Hungary.

WAVELLITE.

Orthorhombic.

Axes

a

:

b

: c

=

hemisphericalor

0*5049

:

:

0-3751.

Slobular with

Usu-

crystallinesurface,and

PHOSPHATES,

ARSENATES,

613

ETC.

p (101) and b (010) rather perfect. Fracture uneven to subBrittle. H. 3-25-4. G. 2-316-2-337. Luster vitreous, incliningto pearly and resinous. Color white, passing into yellow, Streak white. Translucent. Mean gray, brown, and black. index,T526

Cleavage:

conchoidal.

=

=

green'

Comp.

4A1PO4.2A1(OH)3.9H2O

"

26-8

38'0,water

=

Phosphorus

pentoxide

Fluorine is sometimes

100.

=

present, up

mina 35'2, aluto 2 p.

c.

In

the closed tube gives off much water, the last portions of which may react acid (fluorine).B.B. in the forcepsswells up and splitsinto fine infusible particles Gives a blue on ignitionwith cobalt solution. Soluble in coloringthe flame pale green. hydrochloricacid,and also in caustic potash. Obs. From Barnstaple in Devonshire, England; at Zbirow in Bohemia: at Frankenberg,Saxony; Arbrefontaine,Belgium; Montebras, France; Minas Geraes,Brazil,etc. In the United States at the slate quarriesof York Co., Pa.; White Horse Station Chester

Pyr., etc.

"

"

Valley R. R., Pa.; Magnet Fischerite.

Cove,

Ark.

In AlPO4.Al(OH)3.2^H2p.

Color green.

Index, 1'55.

From

Nizhni

small prismatic crystalsand Tagilsk in the Ural Mts.

Occurs Peganite. A1(PO4).A1(OH)3.UH2O. at Striegis, near Freiberg,Saxony.

in green

in

drusy

crusts.

crusts, of small prismatic crystals,

Turquoise.

TURQUOIS.

Triclinic. Crystalsminute and in angle near those of chakosiderite with be isomorphous. Usuallymassive; amorphous or cryptocrystalwhich it may line. Reniform, stalactitic, or and disseminated incrusting. In thin seams grains. Also in rolled masses. in massive material. Fracture Cleavage in two directions in crystals ; none small conchoidal. Rather brittle. H. 5-6. 2-6-2-83. G. Luster somewhat feeble. Color sky-blue, bluish green to apple-green, and greenish waxy, Streak white or greenish. Feebly subtranslucent to opaque. gray. cally Opti=

+

.

1-61.

=

a

j8

=

1-62.

A

7

=

=

1-65.

of aluminium

and copper hydrous phosphate CuO.3Al203. 2P205.9H2O or perhaps H6(CuOH)[Al(OH)2]6(PO4)4 Phosphorus pentoxide 100. 34-12,alumina 36-84,cupricoxide 9-57,water 19-47

Comp.

"

=

=

and A1(OH)2 mutually replace each other in the Penfield considers that the H,(CuOH) orthophosphoric molecule. In the closed tube decrepitates, yieldswater, and turns brown or black. Pyr., etc. and assumes B.B. in the forceps becomes brown but does not fuse; a glassy appearance, with hydrochloricacid the color'is at firstblue (copper moistened colors the flame green; Soluble in hydrochloricacid. chloride). With the fluxes reacts for copper. in narrow The highlyprizedoriental turquoisoccurs Obs. 6 mm. seams (2 to 4 or even in thickness)or in irregularpatches in the brecciated portions of a porphyritictrachyte and the surrounding clay slate in Persia,not far from Nishapur, Khorassan; in the Megara Mts. in Turkestan, 50 versts from Samarkand. Valley,Sinai; in the Kara-Tube in the Los Cerillos Mts., 20 m. S.E. of Santa Fe, New In the United States, occurs opened Mexico, in a trachyticrock, a localitylong mined by the Mexicans and in recent years reand extensivelyworked; in the Burro Mts., Grant Co., N. M.; pale green variety In crystalsnear near Lynch Station,Campbell Columbus, and in Lincoln Co., Nevada. "

"

Co., Va. treated to give it the tint desired. Natural turquois of inferior color is often artificially first found retain the color only so ctcncs vrhich are of a fine blue when Mor-ovrr, many long as they arc kept moist, and when dry they fade,become a dirtygreen, and are of littlo used in jewelry in former of the turquois (not artificial) value. Much centuries,as well the present, and that described in the earlyworks on minerals,was bone-turquois(called as from which is fossil bone, or tooth, colored by a phosphate of also odontolite, o*oy~, tooth), manifest under a microscope. Moreover, true turquois. iron. Its organic originbecomes when acid,gives a fine blue color with ammonia, which is not decomposed by hydrochloric true

of the odontolite. As an ornamental

Use.

"

material.

614

2A12O3.P2O6.4H2O.

Wardite.

in cavities of nodular

G.

MINERALOGY

DESCRIPTIVE

tations lightgreen or bluish green concretionary incrusH. Cedar 5. Valley, Utah. of variscite from

Forms

=

masses

277.

=

In

Sphserite. Perhaps 4A1PO4.6A1(OH)3. gray,

From

bluish.

near

globulardrusy

concretions.

Color

light

Benigna,Bohemia.

St.

In thin incrustinglayers,white or (Al,Fe)AsO4.2(Al,Fe)(OH)3.5H2O. Liskeardite. Liskeard, Cornwall,England. bluish. From or 2A1PO4.4A1(OH)3.12H2O. Massive; reniform or botryoidal. Colorless, Evansite. From Zsetcznik,Hungary; Gross-Tresny, Moravia; Tasmania; 1'485. n Ala.; Goldburg, Idaho. coalfield, milk-white to Perhaps 3A12O3.2P2O6.10H2O. Crypto-crystalline; CCERULEOLACTITE. also East Whiteland Germany; From Nassau, Katzenellnbogen, near lightcopper-blue. Township, Chester Co., Pa. G. 27. Augelite. 2A12O3.P2O5.3H2O. In tabular monoclinic crystalsand massive. From the iron mine T576. of Bolivia; from 0 Colorless to white. Optically+. The same localityhas also yielded the three following aluminium Westana, Sweden. phosphates. G. 2 '64. Colorless to grayish BERLINITE. 2A12O3.2P2O5.H20. Compact, massive.

milk-white,

-

Coosa

=

=

=

or

rose-red. cleavable. 4Al2O3.3P206.3H2O. Compact, indistinctly

TROLLEITE.

G.

Color

310.

=

pale green.

P2O5,Al203,MnO,CaO,H2O,etc.;formula

ATTACOLITE.

doubtful.

Massive.

G.=3'09.

Color salmon-red.

yellowto

tat

phosphate.

In rolled

4A1203.3P206.30H20.

VASHEGYITE. or

aluminium

An

MINASITE.

Massive. colored by iron oxide.

when

rust-brown

pebbles from

H.= From

Brazil.

G. iron mine

2-3.

=

Color

1'96.

Vashegy

at

white in Comi-

Gomor, Hungary. A

Soumansite.

Pyramidal

habit.

fluo-phosphate of aluminium H.

G.

4'5.

=

From

Fusible with intumescence.

=

and sodium with water. Colorless. Indices, 1 '55-1 '56. Montebras in Soumans, Creuse,France. 2"87.

Tetragonal.

Optically+.

PHARMACOSIDERITE.

Isometric-tetrahedral.

granular. Cleavage:

a

Commonly

in

cubes; also tetrahedral.

(100) imperfect. Fracture 2 -5.

989

very

Rather uneven. G. 2*9-3. Luster adamantine distinct. Color olive-, or grass-

Rarely

sectile.

H.

to greasy,

=

=

not

emerald-green,

yellowish brown, honey-yellow. Streak

green

to

brown, yellow,pale. Subtransparent to subtranslucent. 1-676. n Pyroelectric. Comp. Perhaps 6FeAs04.2Fe(OH)3.12H2O Arsenic pent oxide 43% iron sesquioxide40 '0,water =

"

=

16 -9

100.

=

Pyr.,etc.

.

,

from

varieties contain as

.

and

QapucxKov,poison,

iron. aidrjpos,

Occurs *" 2F^pA.Fe(OH)2.8H2O.

Iruro, Cornwall,England. From

rnnnl

stem

P

Bavaria

K2O.

for scorodite. Obs. at the mines in Cornwall. England, with of copper; ores at Schneeberg and Schwarzenberg,Saxony; at Schemmtz, Hungary. In Utah, at the Mammoth mine, Tintic district, "

v.. near Konigsberg,

Some

Same Obtained "

near

ii

St.

W'

.-

in small green

In radiated

tufts of

a

tabular

yellow

or

crystals(monobrownish

color.

Benigna in Bohemia; Lancaster Co Pa with FeO, MnO, CaO, MgO, A12O3. MonoPleochroic- G2'^From Hiihnerkobel,Raben=

MINERALOGY

DESCRIPTIVE

615 Tomn

A hvdrous

-

-

arsenate

of aluminium

and

copper,

uncertain;

formula

CueAl(As04)53CuAl(OH),20H2O analysSP'correspond nearly 24-9 water oxide 35-9,

10-3, cupric

pentoxide28-9, alumina

=

Arsenic phorus Phos-

=

to

100.

replacespart of the arsenic. cracks and turns olive-green. B.B water In the closed tube gives much fuses less readilythan olivenite to a dark gray slag; on decrepitate; open and givesreactions like olivenite. Soluble in nitric acid. charcoal cracks open, deflagrates, Cornwall; Herrengrund m Hungary. From Obs. Color dark green Massive to compact. Pvr

etc

"

does

but

not

"

Perhaps Cu2(FeO)2As2O8.3H2O. From Cornwall; Utah.

Chenevixite.

to

greenishyellow. Color

masses.

and

hydratedphosphateof aluminium turquois-blue.From Cornwall.

A

HENWOODITE.

In

copper.

of very Compact, made up Ceruleite. CuO.2Al2O3.As2O5.8H2O. From Huanaco, 2-8. Color, turquois-blue.Soluble in acids. G. Chile.

botryoidalglobular minute

crystals.

Taltal

province,

=

CuO.3Fe2O3.2P2O5.8H2O.

Chalcosiderite. should have 9H2O.

In sheaf-Jike Indices,1 '83-1 '93. From

green.

also from

ANDREWSITE, A

Kehoeite.

Probably isomorphous

crystalline groups,

as

incrustations.

with

Color

turquois and

lightsiskin-

Cornwall. chalcosiderite.

Cornwall, is near

hydrated phosphate of aluminium, zinc,etc.

Massive.

G.

=

2'34.

Galena, S. D.

From

Goyazite. Perhaps Ca3AljoP2O23.9H2O.

in the mineral and Strontia has been found In small rounded grains. Color yellowish

that it is identical with hamlinite. it is possible Minas Geraes, Brazil. From white.

(Mn,Fe,Ca)2Al(OH)(PO4)2.2H2O.Monoclinic.

Roscherite.

From

Ehrensfriedersdorf ,

Saxony. Uranite

Group

^

Copper Uranite.

TORBERNITE.

2*9361. Crystalsusuallysquare tables,sometimes Tetragonal. Axis c Also foliated, micaceous. very thin,againthick; less often pyramidal. Laminae 2-2-5. brittle. H. Cleavage: c (001) perfect,micaceous. other faces subadamantine. Color emerald!3'4-3'6. Luster of c pearly, G. and grass-green, and sometimes leek-,apple-,and siskin-green.Streak paler than the color. Transparent to subtranslucent. Opticallyuniaxial;negative, "

=

=

w

1-61.

=

12H2O 21*4

=

=

A

hydrous phosphate of uranium and copper, Cu(UO2)2P2O8. Phosphorus pentoxide14-1,uranium trioxide 56*6,copper 7'9,water 100. Arsenic may replacepart'of the phosphorus.

Comp.

"

In the closed tube yieldswater. Fuses at 2*5 to a blackish mass, Pyr., etc. and colors the flame green. With salt of phosphorusgivesa green bead,which with tin on charcoal red (copper). With becomes on coolingopaque soda on charcoal gives a globule of .Soluble in nitric acid. copper. Obs. From Germany at Schneeberg, etc., Saxony; Reichenbach, Baden; at "

"

Joachimstal, Bohemia;

From Ambert, Puy-de-D6me; France. Mt. Painter, South material from Gunnis Lake, Cornwall corresponds to Cu(UO2)2P2O8.8H2O and is the same the first dehydration product of torbernite,which as has been called meta-torbernite I. G. 3'68. T623. e=l'625. o"

Australia.

The

=

Zeimerite. and

color.

G.

=

Cu(UO");A",O8.SH2O. =

3'2.

co

=

1-64.

Cornwall. AUTUNITE.

Lime

From

In

tabular crystalsresembling torbernite in form Schneeberg, Saxony; near Joachimstal,Bohemia;

Uranite.

Orthorhombic. In thin tabular crystals,nearly tetragonal in form from torbernite in angle; also deviatingbut slightly micaceous. foliated,

and

PHOSPHATES,

ARSENATES,

617

ETC.

Laminae brittle. H. 2-2'5. G. Cleavage: basal,eminent. 3-05Luster of c (001)pearly,elsewhere subadamantine. Color lemon- to sulphur-yellow. Streak yellowish. Transparent to translucent. Optically Ax. pi.||6 (010). Bx _L c (001). a 1-553. 1-575. 1-577. 0 7 A hydrous phosphate of uranium and calcium,probably analogous Comp. to phorus Phostorbernite,Ca(UO2)2P2O8.8H2O or CaO.2UO3.P2O5.8H2O 100. pentoxide15*5,uranium trioxide 62-7,lime 6-1,water 15-7 =

=

3*19.

=

-.

=

=

"

=

=

Some analyses give 10 and others 12 molecules of water, but it is not certain that the additional amount is essential. Same for torbernite, but no reaction for copper. as Pyr., etc. Obs. With uraninite, at Johanngeorgenstadt and Falkenstein; in Italy as in Germany "

"

at

in

Lurisia,Cuneo;

Madagascar;

at

from

Tinh-Tuc, Tongking, China;

Mt.

Painter, C.,

In the United States,at Middletown South Australia. and Branchville,Conn. at mica mines in Mitchell Co.; in Alexander Co.; Black Hills,S. D.

In N.

Bassetite. autunite. 89" 17'. Monoclinic. Composition probably the same as /3 3'10. Color yelTwinned; tw. pi.6 (010). Cleavage parallelto three pinacoids. G. low. Transparent. Indices,1 '57-1 '58. From the Basset mines, Cornwall. Previously =

=

considered

to be

autunite.

Uranospinite. Probably Ca(UO2)2As2O8.8H2O. In thin tabular orthorhombic crystals From T63. near rectangularin outline. Color siskin-green. /3 Schneeberg, Saxony. Uranocircite. Color yellowBa(UO2)2P2O8.8H2O. In crystals similar to autunite. From Falkenstein,Saxon Voigtland,Germany. j8-= 1'62. green. =

Carnotite.

Approximately, K2O.2U2O3.V2O6.3H2O.

Orthorhombic.

In

the

form

of

plates|jc (001) Basal cleavage. Color yellow. /3 1 '86. powder, sometimes in crystalline Occurs as a yellow crystalline powder, or in looselycohering masses, intimatelymixed with It is found in largequantitiesin western Utah. Colorado and eastern quartzose material. Is mined there not only for its uranium and vanadium content but also for the small amount of radium it contains. Noted also from Radium Hill,near Olary, South Australia,and from Mauch near Chunk, Pa. at carnotite. Found calcium TYUYAMUNITE. Perhaps a CaO.2UO3.y2O5.4H2O. Fergana, Russian Central Asia. Tyuya-Muyun, Uranospathite. A hydrated uranyl phosphate. Orthorhombic, pseudo-tetragonal. In elongated tabular crystals. Cleavages parallelto the three pinacoids. Color yellow to From Previously considered to be autunite. Redruth, Cornwall. pale green. =

.

Color deep a pulverulent incrustation. Co., N. C. nal. Trogerite. (UO2)3As2O8.12H2O. In thin druses of tabular crystals.Probably tetragoColor lemon-yellow. From near Schneeberg, Saxony. Walpurgite. Probably Biio(UO2)3(OH)24(AsO4)4. In thin yellow crystalsresembling G. 5'76. near Color yellow. Index, 2 '00. From Schneeberg, Saxony. gypsum. aggregates. Color yellowish Rhagite. Perhaps 2BiAsO4.3Bi(OH)3. In crystalline near Schneeberg, Saxony. wax-yellow. From green, In A arsenate. aggregates. ARSENO-BISMITE. cryptocrystalline hydrous bismuth at Mammoth G. 5'7. Index, 1-6. Found with tinge of brown. Color yellowish green mine, Tintic district,Utah. In doubtful. and bismuth, formula of copper A hydrated basic arsenate Mixite. hemia; From Joachimstal,BoColor green to whitish. incrustation. acicular crystals;as an Utah. Wittichen, Baden; Tintic district,

Phosphuranylite.

4emon-yellow.

From

As (yO-2)3P2O8.6H2O.

Mitchell

=

=

Antimonates A among

number the

of antimonates

; also

Antimonites, Arsenites.

have

been

included

in the

preceding pages

phosphates,arsenates,etc.

of lead. Amorphous, reniform; also earthy or A hydrous antimonate Bindheimite. A result of the decomposition 2'0. Index, yellowish. Color brownish, incrusting. gray,

MINERALOGY

DESCRIPTIVE

518

thus

of other antimonial ores;

meite.' An antimonite

at Horhausen,

in

Germany;

Sevier

Cornwall,England;

of minute In groups square of calcium, perhaps CaSb2O4 183Color hyacinth-or honey-yellow, n 4713.' G. from LangGeraes. Mmas Atopite Miguel Burnier, =

5'5.

H. above St. Marcel, Piedmont; From species. Sweden, is probablythe same

octahedrons 1 87

ban,

=

G. 7'02. Color 3'5-4. crystals.H. Algeria. From Djebel-Nador,Constantme. 2 '35. brownish yellow. 0 massive, and as an Perhaps Pb4As2O7.2PbCl2. In crystals, Heliophyllite. Ecdemite. From Langban, Sweden; to Color bright yellow green. 6'89-7'14. G. incrustation. also Pajsberg(heliophyllite) united in diverging groups. Ochrolite. Probably Pb4Sb2O7.2PbCl2. In small crystals, Sweden. Pajsberg, Color sulphur-yellow.From crystals. From Copiapo, In small bluish green, tetragonal Trippkeite. nCuO.As2O3. Nadorite

In

PbClSbO2.

orthorhombic

=

=

=

=

.

Chile. Schafarzikite is described as isomorphous with Pernek, Comitat Pozsony, Hungary.

the formula, nFeO.P2O3.

with trippkeite

From

In

2FeO.Sb2O5. Tripuhyite. An iron antimonate. Tripuhy, Brazil. dull greenishyellow color. From

aggregates microcrystalline

Compact or earthy. Color Flajolotite.4FeSbO4.3H2O. Hammam From N'Bail,Constantine,Algiers. masses.

lemon-yellow.

In

of

a

nodular

ular Monoclinic. Crystals minute tabCatoptrite. 14(Mn,Fe)O.2(Al,Fe)2O3.2SiO2.Sb2O5. In 4 '5. Color black. 5 '5. G. parallelto 6 (010). Perfect basal cleavage. H. NordFrom Brattsfor mine, to red-brown red-yellow. r ed. thin splinters, Pleochroic, marken, Sweden. 5. orthorhombic crystals. H. Derbylite. An antimo-titanate of iron. In prismatic, G. 4-53. Color black. Tripuhy, Brazil. isometric octahedrons. In minute Lewisite. 5CaO.2TiO2.3Sb2O6. yellow to brown Tripuhy, Brazil. of lead and calcium, related to lewisite. In dark A titano-antimonate Mauzeliite. brown isometric octahedrons. Jakobsberg, Sweden. Chile. A doubtful antimonite of mercury; AMMIOLITE. forming a scarlet earthymass. =

=

=

=

Phosphates or

Arsenates

Carbonates, Sulphates,Borates

with

Podolite. 3Ca3(PO4)2.CaCO3. Hexagonal. In microscopic prismatic crystals,also in 1'64. 3'1. Occurs in cavities in the phosphorite Color yellow, ft spherulites. G. elite and See also staff nodules from near the Uschitza River, Podolien, southern Russia. dahllite, p. 597. A hydrated phosphate and sulphate of ferric iron. Diadochite. From Index, 1*606. Thuringia. Destinezite is similar;from Belgium. Pitticite. A hydrated arsenate and sulphate of ferric iron. Reniform and massive. Yellowish and reddish brown. Index, 1 -63. From Saxony, Cornwall, etc. In and calcium. Svanbergite. A hydrated phosphate and sulphate of aluminium rhombohedral From T64. crystals. Color yellow to yellowishbrown, rose-red, co Horrsjoberg,Sweden. Beudantite. A phosphate or arsenate with sulphate of ferric iron and lead; formula perhaps,3Fe2O3.2PbO.2SO3.As2O5.6H2O. In rhombohedral crystals. Color green to brown and black. Indices,175-1 '94. From and Horhausen, Nassau. Dernbach Corkite is same mineral from Cork, Ireland; Beaver Co., Utah. Phosphophyllite. 3Fe3P2O8.2Al(OH)SO4.9H2O, with Ca,Ba,Mg,Mn,K2 Monoclinic. Colorless to paleblue-green. 3 pinacoidalcleavages. H. 3-4. T65. G. 3 '08. n =

=

=

=

From

=

=

Habendorf,Bavaria.

Hinsdalite. In 2PbO.3Fe2O3.2SO3.P2O5.6H2O. Pseudo-rhombohedral. dull coarse, crystals. Cleavage, basal perfect. H. 4'5. G. 4'65. Colorless with greenishtone. Indices 1 -67-1 -69. Found at Golden Fleece mine, Hinsdale Co., Col. Lindackerite. In rosettes, and in reniform Perhaps 3NiO.6CuO.SO3.2As2O5.7H2O. Color verdigrismasses. to apple-green. From Bohemia. Joachimstal, =

=

BO

RATES

619

Monoclinic? In flattened Liineburgite. 3MgO.B2O3.P2O5.8H2O. fibrous masses, From Biaxial, Index, T53. earthy structure. Ltineburg,Hannover. and lead sulphate from A hydrous iron arsenate Lossenite. Laurion,Greece.

to

"

.

Nitrates

being largelysoluble in

Nitrates

The in

water

play but

unimportant role

an

Mineralogy. NITER.

SODA

Axis c Rhombohedral. 0-8276; rr" 1011 A morphous with calcite. Usuallymassive form, as

1101

73" 30'. Homceoincrustation or in beds. Cleavage: r (1011) perfect. Fracture conchoidal,seldom observable. T5-2. G. sectile. H. Rather 2'24-2'29. Luster vitreous. Color white; also reddish brown, gray and lemon-yellow. Transparent. Taste =

=

=

co T5874, cooling. Optically Sodium NaNO3 nitrate, Comp. -.

=

1'3361.

=

e

Nitrogen pentoxide 63'5,soda

=

"

=

=

an

36'5

100.

Deflagrates on charcoal with less violence than niter,causing a yellow Pyr., etc. light,and also deliquesces. Colors the flame intensely yellow. Dissolves in three parts of "

at 60" F. water Obs. From "

in Humboldt Use.

"

Niter.

=

silkytufts.

and

and

Tarapaca, northern Chile,and also the neighboring parts of Bolivia; also Co., Nev.; near Calico,San Bernardino Co., Cal. A source of nitrates. The depositsin Chile are of great importance. Orthorhombic. Potassium T505. In thin white crusts nitrate,KNO3. 0

Nitrocalcite. In Hydrous calcium nitrate,Ca(NO3)2.nH2O. In many limestone caverns, those of Kentucky. as masses.

efflorescent silky tufts

In efflorescences in limestone Nitromagnesite. Mg(NO3)2.nH2O. Nitrobarite. Barium nitrate,Ba(NO3)2. Isometric-tetartohedral.

caves. n

=

1'57.

From

Chile. In pyramidal orthorhombic Basic cupric nitrate,Cu(NO3)2.3Cu(OH)2. Gerhardtite. 1713. From the 3 '426. Color mines at emerald-green. /3 crystals. G. copper Jerome, Ariz. Monoclinic. In square tabular crystals. Colorless. Darapskite. NaNOs.Na2SO4.H2O. From Atacama, Chile. From Atacama, Chile. Nitroglauberite. 6NaNO3.2Na2SO4.3H2O. =

=

Lautarite.

yellowish.

From

-A

Dietzeite. H.

=

3-4.

Calcium iodate,Ca(IO3)2. In prismatic,monoclinic the sodium nitrate depositsof Atacama, Chile.

G.

=

calcium iodo-chromate. Monoclinic; commonly Color dark gold-yellow. From the same 370.

Oxygen 5. The

colorless crystals, fibrous

or

to

columnar.

region as lautarite.

Salts

BORAXES

duced aluminates, ferrates,etc.,allied chemically to the borates, have been already introamong

the oxides.

Chrysoberyl,p. 423,

They include the speciesof the Spinel Group,

pp.

418-423, also

etc.

SUSSEXITE.

In fibrous

Color white

with

veins. H. tingeof pink or or

seams a

=

3.

G.

=

3 -42.

Luster

yellow. Translucent.

silkyto pearly.

Index, T59.

MINERALOGY

DESCRIPTIVE

620

Comp.

R

=

Zn

Mn,

41 '5, magnesia protoxide,

manganese

(+ Zn)

where

HRB03,

"

:

Mg

3

=

:

and

Mg

=

Boron 8'8

15'6, water

trioxide 34 1, Here Mn

100.

=

2.

If turmeric in color and yieldsneutral water. a this water, and then with dilute hydrochloricacid, it assumes in the flame of a candle (F. 2), and B.B. in red color (boricacid). In the forcepsfuses With coloringthe flame intenselyyellowish green. mass, O F. yieldsa black crystalline in hydrochloricacid. Soluble for fluxes reacts the manganese. Mine Hill,Franklin Furnace, Sussex Co., N. J., with franklinite, Found on Obs. at Min? An intimate mixture of zincite and calcite,not uncommon etc. zincite willemite, of the genuine mineral tinctive. is disHill,is often mistaken for sussexite,but the ready fusibility In the closed tube darkens

Pyr., etc.

paper

is

moistened with

=

G.

Ludwigite. Perhaps 3MgO.B2O3.FeO.Fe2O3. Orthorhombic. Index, Color blackish green to nearly black. 3-91-4-02. =

From

Collbranite from

Morawitza, Hungary.

Korea

is

In T86.

finelyfibrous masses. Strongly pleochroic.

ludwigite.

3(Fe,Mg)O.B2O3.FeO.Fe2O3.Similar to ludwigitewith

VONSENITE.

ferrous iron.

more

Riverside;Cal.

Magnesioludwigite. 3MgO.B2O3.MgO.Fe2O3.

From

Mountain

Lake

mine, south of

Brighton, Utah. G.=

A

Nordenskioldine.

In

small

6. rectangular crystals. H. Langban, Sweden. calcium-tin borate, CaSn(BOi)2. In tabular rhombohedral 4'20. Color sulphur-yellow.From G. the Langesund fiord,

Pinakiolite. 3MgO.B2O3.MnO.Mn2O3. Luster metallic. Color black. 3-881.

=

From

5*5-6. crystals. H. Norway. In Aluminium borate, A1BO3. prismatic hexagonal Jeremejevite. Eichwaldite. Colorless G. 6'5. to 1'64. From Index, Mt. pale yellow. crystals. H. 3/28. in Eastern Siberia. Soktuj,Adun-Chalon range In orthorhombic grayish white Hambergite. Be2(OH)BO3. prismatic crystals. 2-347. H. 7-5. G. 1'588. From Optically+. way; 0 Langesund fiord, southern Norvarious localitiesin Madagascar. In small nodules;white outside,yellow within. Szaibelyite.2Mg5B4Ou.3H2O. From Rezbdnya, Hungary. =

=

=

=

=

=

=

BORACITE.

retrahedral in external form under ordinaryconditions, but orthorhombic and pseudo-isometric;the structure as isotropic, requiredby the form, only when heated to 265". (See

Isometric in molecular

and

structure

becomes Art. 429.) 991

993

\7

Habit

cubic and tetrahedral

or

octahedral;also dodecahedral.

usuallyisolated, embedded; less often in smooth, o, (111) dull or uneven.

Cleavage:o,oy crystals. G. to white,inclining in

=

in traces.

groups.

Faces

o

Crystals

(111) bright and

Fracture conchoidal, Brittle H uneven. =7 Luster vitreous, to adamantine. inclining Color Streak white. gray, yellow and green. to Subtransparent 2-9-3.

621

BORATES

translucent.

Commonly shows double refraction, which,however, disappears heatingto 265",when a section becomes isotropic.Refractive index,

upon n

1-667; 7

=

0-0107.

=

a

-

the oppositepolaritycorresponding to the position Strongly pyroelectric, of the + and tetrahedral faces (seepp. 306, 307). The faces of the dull tetrahedron o/ (111) form the analogous pole,those of the polishedform o (111) the antilogouspole. Boron trioxide 62*5, Mg7Cl2B16O3o or 6MgO.MgCl2.8B2O3 Comp. chlorine 7'9 deduct 1'8 100. magnesia 31'4, (O= Cl) 101'8, -

"

=

=

Var.

Ordinary.

1.

"

columnar

In

=

crystalsof varied habit.

2. Massive, with sometimes a subIt resembles a fine-grainedwhite marble or is the plumose interior of some crystalsof boracite.

of Rose. structure; stassfurtite

Parasite of Volger granularlimestone. Fe. 3. Eisenstassfurtite contains some The massive variety gives water in the closed tube. B.B. both varieties Pyr., etc. fuse at 2 with intumescence to a white crystalline pearl,coloringthe flame green; heated after moistening with cobalt solution assumes with oxide of a deep pink color. Mixed and heated on charcoal colors the flame deep azure-blue (copperchloride). Soluble copper in hydrochloricacid. Alters very slowlyon exposure, owing to the magnesium chloride present, which takes It is the frequent presence of this deliquescentchloride in the massive mineral, up water. thus originating, that led to the view that there was a hydrous boracite (stassfurtite). Parasite of Volger is a result of the same kind of alteration in the interior of crystalsof boracite; this alteration giving it its somewhat plumose character, and introducingwater. Obs. in beds of anhydrite, gypsum Observed at salt. In crystalsin Germany or Kalkberg and Schildstein in Llineburg, Hannover; at Segeberg, near Kiel, in Holstein; massive, or as part of the rock, also in crystals,at Stassfurt, Prussia;at Luneville, La "

"

France.

Meurthe,

Ascharite.

A

Index, 1*54.

hydrous magnesium

From

mineral from

Aschersleben

borate.

and

In white

lumps with boracite. Paternoite.

Neustassfurt, Germany.

G.

=

Sicily.

A borate of aluminium and potassium, with caesium and rubidium. in white, translucent dodecahedrons. H. 3 '41. n 8. G. metric-tetrahedral; red tourmaline Found from near on Ekaterinburg, Ural Mts.; from Madagascar. Warwickite. 3'36. (Mg, Fe)3TiB2O8. In elongated prismatic crystals. G.

Iso-

Rhodizite.

=

=

=

dark

brown

2'7.

similar

A

to dull

black.

From

=

T69.

Color

Edenville, N. Y.

A silico-borate of calcium, H5 Ca2B6SiOi4. In small white rounded nodules; Nova earthy. From Scotia;Lang, Los Angeles Co., and in San Bernardino Co., Cal. An incrustation at the Tuscan lagoons,Italy. Lagonite. Fe2O3.3B2O3.3H2O. Larderellite. From Tuscan the (NH4)2Bi0O16.5H2O. lagoons,Italy.

Howlite.

also

COLEMANITE.

69" 51'. 07748 Axes a : b : c : 1 : 0'5410;j3 72" 4'). Massive 110 110 short A Crystalsusually prismatic(mm'" cleavable to granularand compact. to Cleavable: b (010) highlyperfect;c (001)distinct. Fracture uneven to vitreous H. Luster 4-4'5. subconchoidal. G. 2*42. adamantine, brilliant. Colorless to milky white,yellowishwhite, gray. Transparent to 1'614. 1'592. translucent. 1'586. a Optically+ 0 7 Monoclinic.

=

=

=

=

=

=

=

=

.

Comp.

"

Ca2B6On.5H2O, perhaps HCa(BO2)3.2H20

50'9,lime 27*2,water

21*9

=

=

Boron

trioxide

100.

coloringthe flame exfoliates, sinters,and fuses imperfectly, decrepitates, Soluble in hot hydrochloricacid with separationof boric acid on cooling. First discovered in Death Valley,Inyo Co., Cal.; later in Calico district,San Neocolemanite Co. from Lang, Los Angeles Co., Cal., is identical with cole-

B.B.

Pyr. yellowishgreen. "

Obs.

"

Bernardino manite. PRICEITE.

Near

colemanite.

Curry Co., Oregon. Argentina.

Pandermite

Massive, friable and chalky. Color snow-white. from Asia nodules is similar; in compact "

From

Minor;

622

MINERALOGY

DESCRIPTIVE

In Monoclinic. large tabular crystals. Cleavage, Inyoite. 2CaO.3B2O3.13H2O. G. 1-87. Decrepitates and fuses with intumescence, Indices, 1 '49-1*52. (001). H. =2. Mt. Blanco district, Largely altered into meyerhofferite.From givinggreen flame. Death Furnace Valley,Inyo Co., Cal. Associated with colemanite. Creek, near on Triclinic crystalsprismatic,often tabular parallel Meyerhofferite. 2CaO.3B2O3.7H2O. 2. 2*12. G. Colorless to white. to a (100). Fibrous. dices, InCleavage, b (010). H. but with intumescence. Found 1 '50-1 '56. Fuses without decrepitation with inyoite (which see)as an alteration product. Pinnoite. Usually in nodules,radiated fibrous. MgB2O4.3H2O. Tetragonal-pyramidal. From 1'56. G. 2 '29. Color Stassfurt, Germany. sulphur- or straw-yellow, A Heintzite. of Hintzeite. Kaliborite. hydrous borate magnesium and potassium. In small monoclinic 4-5. G. aggregated together. H. 2*13. crystals,sometimes From Colorless to white, T525. Leopoldshall,Stassfurt,Germany. ft Hulsite. 12(Fe,Mg)O.2Fe2O3.lSnO2.3B2O".2H2O. Orthorhombic (?) as small crystals c

=

=

=

=

=

co

=

=

=

or

tabular

H.

masses.

G.

3.

=

Color

4 '3.

=

and

streak

black.

Fusible.

Found

in

metamorphosed limestone at a granite contact at Brooks mountain, Seward Peninsula, Alaska. locality with the composition Paigeileis a similar mineral from the same 30FeO.5Fe2O3.lSnO2.6B2O3.5H2O. BORAX.

Monoclinic.

Axes

a

:

b

: c

1-0995

=

ca,

001

A

100

mm'",

110

A

110

co,

001

A

111

994

=

=

=

:

1

:

0-5632; 0

73" 25'.

=

73" 25'.

cz,

A

221

=

64"

93"

oo', III

A

Til

=

57" 27'.

zz', 221

A

221

0'.

40" 31'.

001

=

8'.

83" 28'.

Crystals prismatic, sometimes large; resembling in habit and angles. Cleavage: a (100)perfect;m (110)less so; 6](010)in

pyroxene

Fracture conchoidal. Rather brittle. H. 2-2*5. T69-172. Luster vitreous to resinous; sometimes earthy. Color white; sometimes grayish,bluish or greenish. Streak white. Translucent to opaque. Taste sweetish feeble. alkaline, Ax. pi." b (010). Optically Bxa _L 6 (010). Bxo.rA c axis 56" 50'. 2V 39". a 1-447. 0 T470. 1-472. 7 traces.

G.

=

=

-

.

=

-

=

=

=

=

Comp. soda

"

Na2B4O7.10H2O

16-2,water 47-2

of bomx

=

or

Na2O.2B2O3.10H2O

Boron

trioxide 36'6.

100.

afterward Up.and F,~^?'B:fEUflS and

fuses to a transparent globule, called the glass it colors the flame around P"t*?*um bisulphate, the a " alkaline soMonBoi^g water "f

Tibet; the crude mineral is called .

two

the i

small alkaline lakes in

Co-; ,

which

included

also the niter (sodium carbonate) Called "=h^o-"- by Agricola

t

inolderin^ gold a

t^^^^^^^^^^

sclent

tJLEXITE.

are

^

" preservative;

Boronatrocalcite. Natronborocalcite.

acTcu"r,Tned massf',Ioose H.

of fine fibers, texture,consisting which

m

1. "f^ycrystas. ^ ColorS white. Tasteless. Ophcally r

at

G.

=

+.

"

=

1'65. Luster silkywithin. 1'500. 1-508. T520. (3 7 -

=

624

MINERALOGY

DESCRIPTIVE

the edges, sometimes on or coloring only slightlyrounded infusible, (copper). With borax and salt of phosphorus gives a yellow bead in in R.F. (uranium). With soda on charcoal gives a coating of lead O.F., becoming oxide,and frequentlythe odor of arsenic. Many specimens give reactions for sulphur and differs widely Soluble in nitric and sulphuricacids; the solubility arsenic in the open tube. able in different varieties, being greater in those kinds containingthe rare earths. Not attractStrongly radioactive. by the magnet. either as a primary constituent of graniticrocks As noted above, uraninite occurs Obs. Under the latter condition with ores of silver, lead,copper, etc. a secondary mineral or as at Johanngeorgenstadt, Marienberg, and in Germany it is found Schneeberg in Saxony; Occurs in Norway in and Pfibram; in Hungary at Rezbanya. at Joachimstal in Bohemia Moss, viz.: Annerod (broggerite), Elvestad,etc., pegmatitic veins at several points near associated with orthite, Arendal at the Garta feldsparquarry (deveite), also near fergusonite, etc. thorite, In the United States,at the Middletown feldsparquarry, Conn., in large octahedrons, in Glastonbury, a few miles N.E. of Middletown. At Branchville, rare; at Hale's quarry in albite. In N. C., at embedded Conn., in a pegmatite vein,as small octahedral crystals, the Flat Rock mine and other mica mines in Mitchell Co., rather abundant, but usually to gummite and uranophane; the crystals sometimes inch altered,in part or entirely, are an In S. C., at Marietta. and cubic in habit. In Texas, at the gadolinite or more across Central City, localityin Llano Co. (nivenite). In large quantitiesat Black Hawk, near Col. in the Bald Mountain Rather abundant Black Hills,S. D. Also with district, mica veins,Ottawa monazite, etc.,at the Villeneuye Co., Quebec, Canada.

Pyr., etc.

B.B.

"

flame

the outer

green green

"

Use.

As

"

or

of uranium

source

a

Gummite.

and

of radium

salts.

An

of uraninite of doubtful composition. alteration-product flattened pieces,looking much like gum. G. Luster 3'9-4'20. greasy. =

yellow

to

orange-red,reddish Co., N. C.

brown,

n

=

1'61.

From

In

rounded Color reddish many, Johanngeorgenstadt,Ger-

also Mitchell YTTROGUMMITE.

Occurs

with

THOROGUMMITE. in Llano locality

Occurs

with fergusonite, and cyrtolite,

cleveite

as

a

decomposition-product. other

speciesat the gadolinite

Co., Texas. Chiefly thorium

Thorianite. and uranium oxides. cubic habit. G. 9'3. Isometric, Color black. Radioactive. Obtained from gem gravelsof Balangoda,Ceylon. Also noted from Province of Betroka, Madagascar. =

Uranosphaerite. (BiO)2U2O7.3H2O.

yellow,brick-red.

From

near

In

half-globular aggregated forms.

Oxygen 6.

SULPHATES, A.

The

important BARITE and

Color orange-

Schneeberg,Saxony. Salts

CHROMATES,

Anhydrous GROUP

TELLURATES

Sulphates, etc.

is the

only one

among

the

phates anhydrous sul-

chromates.

A"mo"" sulphate,(NH4)2SO4. ipg"ite* forms, 1'523. ft Occurs about

=

0r

80*'

^

^

Orthorhombic. Usually in crusts and at Etna, Vesuvius, etc.

volcanoes,as C"m

nr^m^^T* hTrf

sulphate,Na2S04. In orthorhombic s?diu" crystals,pyramitwlnS (Fig"384' p- 160)' White to brownish. ^ti^ i"/77 Opticanv water" Often ob^rved in connection with salt /V ,Sol"b vT f thp Central Asia; similarlyelsewhere;also in South AnSfof ?nTa"n"reS nJfke TBalk,hash" States"f"rms extensive deposits the Rio vSdeAriz. ^ Ir? An"TaTrnaPrT' t,he ynited In Cal., at Borax San dal

"

T

aS

m

n

erae

on

Lake,

Bernardino

(K'Na)^O4. Co^wh^^6- "laSerite" cruste many3,' in' k U

Co.

Rhombohedral;

also

massive,

in

SULPHATES,

CHROMATES,

625

ETC.

GLAUBERITE.

Monoclinic. ca,

001

mm'",

110

In

Axes 100 110

A A

=

=

a

:

b

"

c

67" 49'. 96" 58'.

i'2200

=

:

1

:

T0275; /3

cs,

001

A

111

=

43"

cm,

001

A

110

=

75" 30f.

67" 49'.

2' 995

||c (001);also prismatic. Cleavage:c perfect. Fracture conchoidal. Brittle. H.

=

tabular crystals 2-5-3.

G.

2-7-2-85. Luster vitreous. Color sometimes brick-red. Streak saline. Optically". 2V slightly

pale yellow or white.

=

gray;

Taste

=

7". a 1-515. j8 characters change on

1-532.

1'536.

Optical y heating,see p. 297. Na2SO4.CaSO4 Comp. Sulphur trioxide 57'6, lime 20'1, soda 22'3 100; or, Sodium sulphate calcium 48 "9 100. 51'1, sulphate =

=

=

=

"

=

=

B.B.

turns white, and fuses at 1'5 to a white enamel, coloring Pyr.,etc. decrepitates, intenselyyellow. On charcoal fuses in O.F. to a clear bead; in R.F. a portion is absorbed by the charcoal,leaving an infusible hepatic residue. Soluble in hydrochloric acid. In water it loses its transparency,is partially dissolved,leavinga residue of calcium this is completely dissolved. sulphate,and in a large excess In crystalsin rock salt at Villa Rubia, in New Obs. Castile,Spain; also at Aussee and Hallstatt,Upper Austria; in Germany at Berchtesgaden, Bavaria; Westeregeln;Stassfurt. In crystalsin the Rio Verde Valley,Ariz.,with thenardite,mirabilite,etc.;Borax lake,San Bernardino Co., Cal. In highly modified Langbeinite. K2Mg2(SO4)3. Isometric-tetartohedral. colorless 2'83. 1'533. From crystals. G. n Westeregeln and Stassfurt,Germany; Hall, Tyrol; Punjab, India. "

the flame

"

=

=

Vanthoffite.

helmshall,

near

3Na2SO4.MgSO4.

Barite m

110 Barite

Celestite

Anglesite Anhydrite

Almost

colorless crystallinematerial

found

at

Wil-

Stassfurt,Prussia.

Group. A

m'"

A

110

Orthorhombic

dd'_ 102

78" 22J' 75" 50' 76" 16J'

BaSO4 SrSO4 PbSO4 CaS04

RS04.

(83" 33')

A

102

77" 43' 78" 49' 78" 47'

(58" 31')

The BARITE GROUP includes the sulphatesof barium, strontium,and lead, three specieswhich are closelyisomorphous,agreeingnot only in axial ratio but also in crystalline habit and cleavage. With these is also included calcium similar form; it sulphate,anhydrite,which has a related but not closely differs from the others conspicuously in cleavage. It is to be noted that the carbonates of the same metals form the isomorphous ARAGONITE GROUP, p. 437. BARITE.

Heavy

Axes

Orthorhombic. mm'", cd, co,

Spar.

110

A

110

001 001

A

102 Oil

A

=

=

=

Barytes. a

:

b

: c

78" 22|'. 38" 51 i'. 52" 43'.

G'8152

:

1

:

1-3136.

dd"f, 102 A

102

=

oo'", Oil

A

Oil

=

001

A

111

cz,

=

102" 17'. 74" 34'. 64" 19'.

Crystalscommonly tabular c (001),and united in diverginggroups having the axis b in common; most also prismatic, nating; frequently||axis b,d (102)predomialso ||axis c, m (110) prominent; again ||axis a, with o (Oil)prominent. Also in globularforms, fibrous or lamellar, crested;coarselylaminated,

MINERALOGY

DESCRIPTIVE

626

resembling white marble, and laminae convergent and often curved; granular, in stalagmite. earthy; colors sometimes banded as Fig. 996 the form yielded Cleavage: c (001)perfect;m (110)also perfect,

by cleavage; also

1004

1003

1002

1001

1000

999

998

997

996

Brittle. H.

6 =

(010)imperfect.

2'5-3;5.G.

Fracture

4'3-4'6.

=

even. un-

ter Lus-

pearly vitreous,incliningto resinous;sometimes white. Streak often less on m (110). c on (001), t o Color white; also inclining yellow,gray, blue,red, brown. Transparent to translucent or brown, dark rubbed. Sometimes fetid,when cally Optito opaque. 37" 30'.

=

a

1.636.

=

+. 1-637.

Ax. 7

=

pi.||6(010).

Bx

J_

a

(100). 2V

=

1-648.

Ordinary, (a)Crystalsusuallybroad or stout; sometimes very large; again in the crystalsprojecting slender needles. (6)Crested; massive aggregationsof tabular crystals, and loosely at surface into crest-like forms, (c)Columnar; the columns often coarse and either radiated or parallel;rarelyfine fibrous, (d) In globularor nodular aggregated, Bologna) is here concretions, subfibrous or columnar within. Bologna Stone (from near of wonder because of the phosphorescence it exhibited after included; it was earlya source made from it. (e) Lamellar, either heating with charcoal. "Bologna phosphorus" was as aggregations of curved scale-like plates. straightor curved; the latter sometimes (g)Compact or cryptocrystalline.(h) Earthy, (i)Stalactitic and stalag(/)Granular, mitic; similar in structure and originto calcareous stalactites and stalagmitesand of much beauty when polished, (h) Fetid; so called from the odor given off when struck or when matters two present. piecesare rubbed together,which odor may be due to carbonaceous The barite of Muzsaj and of Betler, near Rosenau, Hungary, was early called Wolnyn. Cawk is the ordinary barite of the Derbyshire lead mines. Dreelite,supposed to be rhomfrom Perkin's Mill,Templeton, Quebec (described bohedral, is simply barite. Michel-levyte as monoclinic),is peculiarin its pearly luster on m, twinning striations,etc. Barium sulphate,BaSO4 Comp. Sulphur trioxide 34'3, baryta 657 Var.

"

=

"

=

100.

Strontium sulphateis often present, also calcium sulphate;further,as impurities, silica, clay,bituminous or carbonaceous substances. B.B. decrepitatesand fuses at 3, coloringthe flame yellowish green; Pyr, etc. the, fused mass reacts alkaline with test paper. On charcoal-reduced to a sulphide. With soda givesat first a clear pearl,but on continued blowing yieldsa hepatic mass, which spreads out and soaks into the coal. This reacts for sulphur (p.340). Insoluble in acids. DifE. Characterized by high specific gravity (higherthan celestite, aragonite,albite, calcite,gypsum, etc.); cleavage; insolubility; green coloration of the blowpipe flame. Albite is harder and calcite effervesces with acid. Obs. Occurs commonly in connection with beds or veins of metallic of ores, especially lead, also copper, silver,cobalt, manganese, of the ore; also often as part of the gangue stibmte. Sometimes forms with hematite deposits. It is accompanies present in massive met with m secondary limestones and sandstones,sometimes forming distinct veins, and in "

"

"

SULPHATES,

CHROMATES,

ETC.

627

the former often in crystalsalong with calcite and celestite; in the latteroften with coooer Sometimes occupiesthe cavities of amygdaloidal basalt,porphyry,etc forms earthv in beds of marl. Occurs as the petrifyingmaterial of fossilsand masses occupying cavities

ores.

in

"

them.

obtained in England at the Dufton lead mines, Westmorelandalso in Lancashire; in Derbyshire, Staffordshire, etc.; Cleator Moor-'Alston In Moor. Scotland, in Argyleshire,at Strontian, Some of the most important of the European localities are Felsobanya, Nagybanya. Schemnitz, and Kremnitz many in Hungary, and Jlef eld,often with stibnite;Huttenberg, Carinthia;Freiberg, Marienberg in Saxony; Claustal in the Harz Mts.; Pribram, Bohemia; Auvergne, France. In the United States, formerly in Conn., at Cheshire^intersecting the red sandstone in veins with chalcocite and malachite. In N. Y., at Pillar Point, opposite Sackett's Harbor massive; at Scoharie, fibrous;in St. Lawrence Co.,crystalsat DeKalb; the crested variety In Pa., in crystalsat Perkiomen at Hammond. In Va., at Eldridge's lea^mine. gold In N. C., white ma^sw^aTCrowders Mt., Gaston mine in Buckingham Co. In Co., etc Tenn., on Brown's Creek; at Haysboro' near Nashville;in large veins in sandstone on the west end of Isle Roy ale,Lake Superior,and on Spar Island,north shore. In Mo. with the lead ores; in concretionary not uncommon forms at Salina, Saline Co., Kan In Col., at Sterling,Weld Co.; Apishapa Creek; also in El Paso and Fremont Cos. In fine Fort Wallace, N. M. near crystals, Crystals enclosingquartz sand, "sand barite,"from In distorted crystalsfrom the Bad Islands,S. D. Norman, Oklahoma. In Ontario, in Bathurst, and North Burgess, Lanark Co.; Malway, PeterboroughCo.' in Lake Superior, Jarvis,McKellars, and Pie islands, as largeveins on and near Fort William' Thunder Scotia,in veins in the slates of East River of the Five Islands) Bay. In Nova are crystals

Fine

and

Cumberland

Colchester Named Use.

"

Co. from papvs, heavy. Source of barium hydroxide used in the

pigment, to give weight

of refining

sugar;

ground and used

as

a

cloth,etc.

to paper,

Coelestine.

CELESTITE.

Orthorhombic.

Axes

a

:

b

: c

07790

=

:

1

:

1-2800.

1005

1006

mm"',

110

A

110

=

75" 50'.

cd, 001

A

102

d,

001

A

104

=

22" 20'.

co,

001

A

Oil

=

=

39" 24"'. 52" 0'.

Crystalsresemblingthose of barite in habit; commonly tabular 11c (001)or rarelypyramidal by the prominence of the prismatic||axis a or 6; also more forms \j/(133) or x (144). Also fibrous and radiated; sometimes globular; granular. occasionally Cleavage: c (001)perfect;ra (110)nearlyperfect;b (010)less distinct. G. 3'95-3'97. Luster vitreous, H. 3-3'5. Fracture uneven. sometimes often white. Color faint Streak t o white, times bluish,and someinclining pearly. b (010). Ax. pi.|| reddish. Transparent to subtranslucent. +. Optically 1'624. 1'622. 1'631. 51". a Bx _L a (100). 2V ft 7 =

=

=

=

=

(a) In crystalsof varied habit

=

noted

cate above; a tingeof a delia crystal. The variety from Montmartre, Paris, France, called apotome, is prismaticby extension of o (Oil) near and doubly terminated by the pyramid ^ (133). (6) Fibrous, either parallelor radiated. (e)Concretionary. (/)Earthy; impure (d) Granular, (c)Lamellar; of rare occurrence, usually with carbonate of lime or clay. Var.

"

blue

1.

Ordinary,

is very

common

and sometimes

as

belongs to only

a

part of

MINERALOGY

DESCRIPTIVE

628

Comp. tia 56'4

=

sulphate, SrSO4

Strontium

"

and barium

Calcium

100.

Sulphur trioxide

=

sometimes

are

43'6,

stron-

present.

fuses at 3 to a white pearl,coloringthe flame B.B. frequentlydecrepitates, Pyr.jetc. in R.F. is converted reacts alkaline. On charcoal fuses, and strontia-red;the fused mass this treated with hydrochloricacid and alcohol gives fusible hepatic mass; into a difficultly Insoluble in acids. With soda on charcoal reacts like barite. intenselyred flame. an Characterized by form,'cleavage,high specificgravity, red coloration of the Diff. effervesce with acids like the carbonates not Does (e.g.,strontianite); blowpipe flame. gravity lower than that of barite. specific of various Obs. Usually associated with limestone,or sandstone ages; occasionally with metalliferous ores, as with galena and sphaleriteat Condorcet, France; at Rezbanya, rock salt,as at Bex, Switzerland; Ischl, Austria; Liinealso in beds of gypsum, Hungary; fillscavities in fossils, sometimes with sulphur in some e.g., ammonites; berg, Hannover; Yate, Gloucester,England. volcanic regionsas at Girgenti,Sicily. From of a bluish tint,are found in limestone about Lake Huron, Specimens, finelycrystallized, Island, also on Strontian Island, Put-in-Bay,Lake Erie, and particularlyon Drummond "

"

"

at

N.

Kingston Y.

Chaumont

Canada; Syracuse, N.

in Ontario,

From

near

Y.

Bay,

Lake

Ontario,Schoharie, and

Lockport,

blue fibrous celestite occurs at Bell's Mills,Blair In Mineral Co., W. Va., a few miles south of Cumberland,

A

From Cumberland, Md. near Ohio. Md., in pyramidalblue crystals. At Tifflin,

Co., Pa.

In Texas, at Lampasas, large Valley, San Bernardino Co., Cal. In Canada, in Co.; Lansdowne, Leeds Co.; in radiatingfibrous Kingston, Frontenac

colemanite

crystals. With masses crystalline

at

Death

at

of Renfrew Co. in the Laurentian in allusion to the faint shades of blue often from ccelestis, Named celestial, present. Use. Used in the preparation of strontium nitrate for fireworks; other salts used

masses

"

in

the refiningof sugar,

ANGLESITE.

Axes

Orthorhombic.

a

:

b

: c

=

07852

1007

d,

:

1

:

1*2894.

1008

110

A

110

=

76"

16*'.

001

A

104

=

22"

19'.

1009

cd, 001

A

102

001

A

Oil

co,

=

=

39" 23'. 52" 12'.

tabular Some1times

11c (001); more often prismaticin habit,and in directions, m (110),d (102),o (Oil),predominatingin the pyramidal of varied types. Also massive, granular to com-

n all the three axial

ifferent cases;

pact; di.1

"" tme

nodular. stalactitic;

but interrupted.Fracture C1vJrageh -Ctt^"\m (1,1Sl oisti?,ct' H' :

in in

tny some

6;

specimens,

white, tinged

6'3~6'39-G;-= ^t8others

=

P

green,

and

Optically +.

opaque.

strong, B^persion

"".

WBUy

conchoiadaman-

to resinous inclining

m

yellow,gray,

Transparent to

Luster

2V

=

and vitreous. Color sometimes blue. Streak uncolored Ax. pi. ||6 (010) Bx 100)

60"-75".

T

a

=

1-877,

"

-1-882

L

T=

SULPHATES,

Comp.

Lead

"

CHROMATES,

sulphate,PbSO4

629

ETC.

Sulphur trioxide 26*4,lead oxide

=

73*6

100.

=

fuses in the flame of a candle (F. decrepitates, 1*5). On charcoal clear pearl,which on cooling becomes milk-white; in R.F. is reduced to metallic lead. with effervescence With soda on charcoal in R.F. gives metallic lead, soluble in nitric acid. and the soda is absorbed by the coal. Difficultly Characterized Diff. by high specificgravity; adamantine luster; cleavage; and by Cerussite effervesces in nitric acid. yieldinglead B.B. A result of the decomposition of galena, and often found in its cavities;also Obs. surrounds a nucleus of galena in concentric layers. First found in England at Pary's mine in crystals;at Leadhill, Scotland; in Gerin Anglesea; in Derbyshire and in Cumberland many at Claustal, in the Harz Mts.; near Siegen in Prussia; Schapbach and Badenweiler in Baden; in Hungary at Felsobanya and elsewhere; Nerchinsk, Siberia; and at Monte and Andalusia, Spain; massive in Siberia; in Australia,whence Poni, Sardinia; Granada At Broken In the Sierra Mojada, South Wales. it is exported to England. Hill, New quantities,mostly massive. Mexico, in immense lead In the United States in crystalsat Wheatley's mine, Phenixville, Pa. ; in Missouri View In Col. at mine, Carroll Co., Md. mines; in crystalsof varied habit at the Mountain than cerussite. At the Cerro Gordo mines of Cal. (argenvarious points,but less common tiferous In Ariz.,in the mines of the Castle'Dome trict, diswith other lead minerals. galena), In fine crystalsfrom Yuma Co., and elsewhere. Kingston and Wardner, Idaho; Eureka, Utah. from the locality, Named Anglesea, where it was firstfound. An ore of lead. Use.

Pyr., etc.

B.B.

"

fuses to

in O.F.

=

a

"

"

"

ANHYDRITE.

Orthorhombic.

Axes 110 101

mm'", rr\

A A

:

a

1TO TOl

=

=

b

: c

=

0'8933

:

1

:

1'OOOS.

ss',Oil

83" 33' 96" 30'

bo, 010

A A

Oil 111

=

=

90" 3' 56" 19'

tw. lamellae. Crystals as 1, tw. pi.d (012); 2, r (101)occasionally thick tabular,also

Twins: not common,

prismatic|| axis

1010

Usually

6.

1012

massive, cleavable, fibrous, times lamellar, granular, and someimpalpable. Cleavage: in the three pinactangular oidal directions yielding recfragments but with varying ease, thus, c (001)very

perfect; b (010) also perfect; less so. a (100) somewhat 1010, 1011, 'Stassfurt Fracture

1012, Aussee

sometimes

uneven,

Luster: c pearly, 2-899-2-985. 6 vitreous;in a closed tube; a somewhat greasy; sometimes a to pearly. Color white, vitreous inclining varieties, white. Streak brick-red. also grayish reddish or tinge; bluish,

splintery. Brittle. H. after heating in especially

=

3-3' 5.

G.

=

_

massive

grayish, Optically+ (3

1-576.

=

Ax. .

7

=

pi.||b (010).

Bx

J_

a

(100).

2V

=

42".

a

=

1-571.

1'614. massive

and

commonly crystalsrare, more 1. Ordinary, (a) Crystallized; (6) Fibrous; either parallel,radiated or cleavable in its three rectangular directions. kind from plumose, (c)Fine granular, (d) Scaly granular. Vulpiniteis a scalygranular A kind in it is cut and polishedfor ornamental purposes. in Italy; Lombardy, Vulpino Var.

"

concretionaryforms is the tripestone. Pseudomorphous; in cubes after rock-salt. Anhydrous calcium sulphate,CaS04 Comp.

contorted 2.

"

lime 41-2

=

100.

=

Sulphur trioxide, 58'8,

630

MINERALOGY

DESCRIPTIVE

B.B. fuses at 3, coloringthe flame reddish yellow, and yielding an enamelreduced to a sulphide; with soda On charcoal in R.F. which reacts alkaline. by the coal like barite; is,however, does not fuse to a clear globule,and is not absorbed silver. Soluble in hydrochloric acid. which blackens decomposed, and yieldsa mass Characterized Diff. by its cleavage in three rectangular directions (pseudo-cubic in with acids like the carbonates. does not effervesce aspect); harder than gypsum; in rocks of various ages, especiallyin limestone Occurs Obs. strata, and often the same in beds of rock-salt;at the salt and also very commonly that contain ordinary gypsum, mine Hall in Tyrol, Austria; of Bex, Switzerland; at Aussee, upper Austria, crystalnear lized Wieliczka and massive; Liineburg, Hannover, Kapnik in Hungary; Germany; in Poland; Ischl in Upper Austria; Berchtesgaden in Bavaria; Stassfurt, Germany, in fine in kieserite;in cavities in lava at Santorin Island. crystals,embedded In the United States, at Meriden, Conn.; at Lockport, N. Y., fine blue, in geodes of at West black limestone, with calcite and gypsum; Paterson, N. J.; in limestone at Nashville, Scotia itforms extensive beds. In Nova In the salt beds of central Kansas. Tenn., etc. Extensive beds are changes to gypsum. Anhydrite by absorption of moisture times somethus altered in part or throughout, as at Bex, in Switzerland, where, by digging down be found. 60 to 100 ft.,the unaltered anhydrite may Sometimes specimens of anhydrite the folia or over altered between the exterior. are

Pyr., etc.

"

like bead

"

"

"

In

CaSO4.

Bassanite. of slender

needles

in

white

opaque

parallelarrangement.

2 '69-2 elongation. G. ejected from Vesuvius.

76.

=

Transformed

Zinkosite.

ZnSO4. Reported Found Hydrocyanite. CuSO4. the eruption of 1868.

but. composed crystalshaving form of gypsum These show parallelextinction and positive into anhydrite at red heat. in blocks Found

occurring at

as

Vesuvius

at

as

mine

a a

pale

in the

Sierra

Almagrera, Spain.

to blue

green

incrustation

after

A mixture HOKUTOLITE. in variable proportions of lead and barium sulphates. A radioactive crystalline crust deposited by hot springs at Hokuto, Formosa. Millosevichite. Normal ferric and aluminium sulphate. As a violet incrustation, Alum Grotto, Island of Vulcano, Lipari Islands.

CROCOITE.

Monoclinic.

Axes

a

:

mm'", ck,

1n1Q

b

: c

0*9603

=

110

A

1TO

001

A

101

:

1

:

0*9159; 0

86" 19'. 49" 32'.

=

=

Crystals usually prismatic,habit columnar

and

77" 33'.

=

111

A

111

=

ct, 001

A

111

=

"',

varied.

Also

60" 50'. 46" 58'.

imperfectly

granular.

Cleavage:m (110) rather distinct;c (001), a (100) less so. Fracture small conchoidal to uneven. Sectile. H. 2*5-3. G. 5*9-6*1. Luster adamantine to vitreous. Color various shades Of bright hyacinth-red. Streak orange-yellow. Translucent. =

p

=

" 4"".

"

Comp. 3rl,

lead

"

Lead

chromate, PbCrO4

protoxide

68*9

=

=

Chromium

trioxide

100.

With and

^ rTi Ura'

nea'r NiT.rfH,*'

TnHuSLrvMolrf^

"^i^

TT

^tSVn crystalsin I"**

Mt?'; m

BraZl1'at ConS"^^

_

veins; ali" do

at

Mursinka

Campo; at Rezbanya infineCryStal8fr0m

MINERALOGY

DESCRIPTIVE

BROCHANTITE. Axes

Orthorhombic.

a

:

b

: c

07739

=

:

1

:

0'4871. _

(mm"' acicular crystals In groups of prismatic structure. reniform drusy crusts; massive with

Cleavage: 6(010) very

perfect ; m (110)in

110

traces.

110

A

75"

=

Fracture

28') and

uneven.

H.=

vitreous; a little pearly on the cleavage-face 3'907. Luster G. Streak palergreen. parent TransColor emerald-green,blackish green.

3'5-4.

=

6(101).

to translucent.

CuSO4.3Cu(OH)2 basic sulphate of.copper, oxide water 12'0 70'3, trioxide cupric 17'7, Sulphur

Comp. 3H2O

=

4CuO.S03.

or

A

"

100.

=

Yields water, and at a higher temperature sulphuricacid,in the closed tube, Pyr.,etc. With soda gives B.B. fuses,and on charcoal affords metallic copper. and becomes black. for sulphuricacid. the reaction from Gumeshevsk, Obs. Occurs in the Ural Mts. ; the konigme (or komgite) was and in Cornwall (inpart waringRoughten Gill,in Cumberland Ural Mts.; in England near ; in tonite);at Rezbanya, Hungary; in small beds at Krisuvig in Iceland (krisuvigite) In the United States, at Monarch and Tarapaca, Chile. Atacama Mexico (brongnartine); at the Mammoth mine; in mine, Chaffee Co., Col.; in Utah, at Frisco,in Tintic district, "

"

Bisbee,Ariz. crystals. Color greenish sulphate, Pb2SO6. In monoclinic From Leadhill, Scotland; Siberia; the Harz Mts., Germany. white, pale yellow or gray. monoclinic Dolerophanite. A basic cupric sulphate, Cu2SOs(?). In small brown crystals. From Vesuvius (eruptionof 1868). A basic sulphate of lead and Caledonite. Said perhaps 2(Pb,Cu)O.SO3.H2O. copper, In small prismaticorthorhombic at times to contain CO2. crystals. Color deep verdigrisFrom Leadhill, Scotland; Red Gill, Cumberland, bluish green. Index, 1'85. or green etc., England; Inyo Co., Cal.; Organ Mts., N. M.; Butte, Mon.; Atacama, Chile;New district,and

Ch'fton-Morenci

Basic

Lanarkite.

lead

Caledonia. A basic sulphate of lead and copper, Linarite. (Pb,Cu)SO4.(Pb,Cu)(OH)2. In deep From T838. blue monoclinic crystals. Optically land, Leadhill, Scotland; Cumber0 England; the Ural Mts.; Broken Hill,New South Wales; Sardinia. Also Inyo Co., Cal.; Eureka, Utah; Schiilz, Ariz.; Slocan, British Columbia. =

"

.

Perhaps CuSO4.2Cu(OH)2.

Antlerite.

mine, Mohave as

antlerite. Alumian.

Stelzneritefrom In prismaticcrystals. G.

In light green soft lumps. From the Antler Remolinos, Vallinar,Chile,is probablythe same

Co., Ariz.

Perhaps A12O3.2SO3.

C.

=

3 '9.

White

Normal

crystallineor

massive.

Sierra

Almagrera,

Hydrous Sulphates

Three EPSOMITE

well-characterized groups included here. are Two of these,the GROUP and the MELANTERITE GROUP, have the same general formula,RS04.7H20, but in the first the crystallization is orthorhombic, in the second monoclinic. The speciesare best known from the artificial crystalsof the laboratory;the native minerals are rarelycrystallized.There is also the isometric ALUM GROUP, to which the same remark is applicable.

Lecontite.

Comayagua,

(Na,NH4,K)2SO4.2H2O.

From

bat guano

in the

cave

of Las

Piedras,

near

Central America.

MIRABILITE.

Monoclinic.

Glauber

Salt.

Crystals like

pyroxene

in habit

and

angle. Usually in

efflorescent crusts.

Cleavage:a (100),perfect;e (001),b (010) in 1*481.

Luster vitreous.

Color white.

traces.

Transparentto

H.

=

opaque.

I'5-2. Taste

G.

=

cool,

SULPHATES, then

feebly saline and

T410.

Comp.

Optically "

Hydrous sodium

"

24'8,soda

bitter.

.

633

ETC.

2V

=

76".

a

=

1-396

19'3,water

55'9

=

sulphate,Na2SO4.10H2O

Sulphur trioxide

=

100.

=

In the closed tube much water; givesan intense yellow to the flame, Loses its water on exposure to dry air and falls to powder. Occurs at Ischl,Hallstadt,and Aussee in Upper Austria; also in

Pyr.,etc.

6

1-419.

=

7

CHROMATES,

"

Very

soluble in water. Obs.

Hungary,

"

Switzerland, Italy; at the hot springsat Carlsbad, Bohemia, etc. Large quantitiesof this sodium sulphate are obtained from the waters of Great Salt Lake, Utah. Monoclinic.

MgSO4.H2O.

Kieserite.

white, grayish,yellowish. Optically+.

Usually massive,granular to compact. Color 1'535. From Stassfurt,Germany; Hallstadt,

ft

=

Austria; India. Monoclinic. FeSO4.H2O. Isomorphous with kieserite. In pyramids. with other iron sulphates from Szomolnok, Found yellow or brown. from near Apparently identical with ferropallidite Copiapo, Chile. Stalactitic. Whitish, reddish. MnSO4.H2O. From Felsobdnya,Hungary.

Szomolnokite.

G.

3 '08.

=

Hungary. Szmikite.

Color

GYPSUM.

Monoclinic.

Axes

a

:

mm'

110

A

110

=

cd,

001

A

101

=

ct,

001

A

101

ce,

001

A

103

vv',

Oil

A

Oil

=

=

=

b

=

0'6899

0-4124; 0

=

42'. _80"

"', 111 A 111 nn', 111 A Til ml, 110 A 111 110 A 111 mn, 1017

1016

1015

1014

: c

68" 30'. 28" 17'. 33" 8*'. 11" 29'. 44" 17|'.

=

=

=

=

36" 12'. 41" 20'.

49" 9'. 59" 15'.

1018

6 (010)or prisform flattened || matic Crystalsusuallysimplein habit,common ular to acicular 11c axis;againprismatic by extension o{l (111). Also lenticby rounding of I (111)and e (103). The form e (103),whose faces are usuallyrough and convex, is nearlyat rightanglesto the vertical axis (edge m (110)/w'"(110),hence the apparent hemimorphic character of the twin (Fig.1018). Simple crystalsoften with warped as well as curved surfaces. often granularmassive; and sometimes Also foliated massive; lamellar-stellate; often the nearly impalpable. Twins: tw. pi.a (100),very common, familiar swallow-tail twins.

Cleavage: 6(010) eminent, yieldingeasilythin polishedfolia;a (100), surface with conchoidal fracture;n(lll),with a fibrous fracture || "(101); a cleavage fragment has the rhombic form of Fig.1019, with plane l'5-2. G. 2*3 14-2'328,when in pure crystals. anglesof 66" and 114". H.

givinga

=

=

(010) pearly and shining,other faces sub vitreous. Massive sometimes dull earthy. Color usuallywhite; sometimes varieties often glistening, often varieties blue; impure honey-yellow, ocher-yellow, flesh-red, gray, to white. Streak reddish brown. Transparent or red, opaque. black,brown, Luster

of

b

MINERALOGY

DESCRIPTIVE

634

4 52i" (at 9*4" C.), Ax. pi. ||6 (010),and Bx A c axis Optically+ Q" inclined strong. Bxr A Bxw (cf.Fig. 1019). Dispersionp " v; also =

"

.

=

30'.

2V

58".

=

"

|8

1-520.

heat

=

1?523.

=

1-530.

see opticalproperties,

the

on

7

On

the

effect of

p. 297.

Selenite; colorless, or ent; transpar1. Crystallized, Var. ually broad folia,often large. Usor in distinct crystals, flexible and yielding a fibrous fracture ||t (101), but

1019

"

the variety from brittle.

Montmartre

near

Paris, France, rather

fine. Called Satin spar, when or 2. Fibrous; coarse fine-fibrous,with pearly opalescence. or 3. Massive; Alabaster, a fine-grainedvariety,white

delicatelyshaded; earthy or rock-gypsum, a dull-colored rock, often impure with clay, calcium carbonate or silica. Also, in caves, curious curved forms, often grouped in rosettes and other shapes. calcium sulphate, Hydrous Comp. "

CaS04.2H2O water

20'9

=

=

Sulphur trioxide 46-6, lime 32-5, 100.

Fuses at 2 '5-3, closed tube gives off water and becomes opaque. 629. reddish yellow. For other reactions see ANHYDRITE, Ignited p. when with water moistened, and at a temperature not exceeding 260" C., it again combines becomes firmly solid. Soluble in hydrochloric acid, and also in 400 to 500 parts of water. and by cleavages in crystallized Characterized Diff. by its softness in all varieties, like the zeolites;harder like effervesce acids not with it calcite, nor gelatinize does kinds; in the closed tube. water than talc and yieldsmuch with various stratified rocks, Obs. Gypsum often forms extensive beds in connection It occurs occasionally in crystalline especiallylimestones, and marlites or clay beds. It is also a product of volcanoes, occurring about fumaroles, or where rocks. sulphur are escaping,being formed from the sulphuric acid generated, and the lime afforded gases by the decomposing lavas. It is also produced by the decomposition of pyrite when lime and brines,in which is present. Gypsum is also deposited on the evaporation of sea-water it exists in solution. Fine specimens are found in the salt mines of Bex in Switzerland; Hall in Tyrol, Austria; the sulphur mines of Sicily;in the clay of Shotover Hill, near Oxford, England; and large A noted localityof alabaster occurs lenticular crystalsat Montmartre, near Paris, France. it is taken to Florence for the manufacture at Castelino, 35 m. from Leghorn, Italy,whence of vases, figures, etc. Occurs in extensive beds in several of the United States, and more particularlyN. Y., Iowa, Mich., Okla., Texas, Ohio, and Ark., and is usually associated with salt springs,also with rock salt. Also on a large scale in Nova Scotia, etc. Handsome selenite and snowy in N. Y., near occur Lockport in limestone. gypsum In Md., large grouped crystalson the St. Mary's in clay. In Ohio, large transparent crystalshave been found at Ellsworth and Canfield,Trumbull In Tenn., selenite and Co. alabaster in Davidson In Ky., in Mammoth Co. Cave, it has the forms of rosettes, or in isolated crystalsand masses, flowers,vines, and shrubbery. Also common in the Cretaceous claysin the western United States. In enormous several feet in length,in crystals,

Pyr., etc. coloringthe

"

In the

flame

"

"

Wayne which

Co., Utah.

In Nova

Scotia, in Sussex, Kings Co., largesingleand grouped crystals, symmetrically disseminated sand. from yy^os,the Greek for the mineral, but more especiallyfor the calcined The derivation' ordinarilysuggested, from tyeiv, to cook, corre777, earth, and sponds

mostly contain much

Named

mineral. with this, the most of the word common use the Greeks. among Burnt gypsum is called Plaster-of-Paris, because the Montmartre quarries,near gypsum Pans, are, and have long been, famous for affordingit. Use. In the manufacture of plaster-of-Paris used for molds and casts and as "staff erection of temporary buildings; in making adamant in plaster for interior use; as land plaster for fertilizer; alabaster for ornamental as purposes. "

"

Hesite. from

(Mn,Zn,Fe)SO4.4H2O.

Colorado.

In

loosely adherent

aggregates.

Color

clear green,

SULPHATES,

Epsomite

CHROMATES,

RS04.7H20.

Group.

Epsomite

MgS04.7H2O (Fe,Mg)S04.7H20

Goslarite

ZnSO4.7H2O

Ferro-goslarite

a

:

b

: c

=

NiSO4.7H2O

EPSOMITE.

0-9902

:

1

:

0-5709

0-9807

:

1

:

0-5631

0-9816

:

1

:

0-5655

Salt.

Epsom

Orthorhombic.

Usuallyin botryoidalmasses

and delicately fibrous crusts. 2-0-2-5. (010)very perfect. Fracture conchoidal. H. G. Luster vitreous to earthy. Streak and color white. 1*751. Transparent Taste translucent. bitter and saline. Optically 2V 52". a 6

Cleavage: to

Orthorhombic

(Zn,Fe)SO4.7H2O

Morenosite

=

635

ETC.

=

=

=

"

=

.

1-433.

ft

1-455.

=

Comp.

1-461.

=

T

Hydrous magnesium

"

ide 32-5, magnesia 16-3,water Obs.

sulphate,MgSO4.7H2O

51-2

Sulphur triox-

=

100.

=

in mineral

Common

waters, and as a delicate fibrous or capillary efflorescence on In the former elsewhere. state it exists at Epsom, in Bohemia. At Idria in Carniola, England, and at Sedlitz and Saidschitz (orSaidschiitz) in silky fibers,and is hence called hair salt by the workmen. Also obtained Austria, it occurs Paris. at the gypsum Also found at Vesuvius, at quarries of Montmartre, near the eruptions of 1850 and 1855. of Kentucky, Tennessee, and The floors of the limestone caves Indiana, are in many instances covered with epsomite, in minute crystals,mingled with the earth. In the like snowballs. From Mammoth Laramie Cave, Ky., it adheres to the roof in loose masses Leona Co., Cal.; Cripple Creek, Col. Basin, Wy.; near Heights, Alameda "

of mines, and rocks, in the galleries

massive. Color Commonly white, reddish, yellowish. by the decomposition of sphalerite,and found in the mine of mines, as at the Rammelsberg Goslar, in the Harz Mts., Germany, near passages with at the Gagnon In Mon. mine, Butte. (4*9 p. c. FeSO4) occurs etc. Ferro-goslarite as a City, Jasper Co., Mo. Cuprogoslarite(13'4 p. c. CuSO-j) occurs sphaleriteat Webb zinc mine at Galena, Kan. lightgreenish blue incrustation on the wall of an abandoned In acicular crystals;also fibrous,as efflorescence. Morenosite. an NiSO4.7H2O. A result of the alteration of nickel ores, 1 '489. Color apple-greento greenishwhite. 0 as near Cape Hortegal,in Galicia; Riechelsdorf, in Hesse, Germany; Zermatt, Switzerland, containing magnesium.

ZnSO4.7H2O.

Goslarite.

Optically

0

"

.

=

Formed

1'480.

=

Melanterite

FeSO4.7H20

Melanterite Luckite Mallardite

Monoclinic

RS04.7H2O.

Group.

a

:

b

: c

1 -1828

:

1

:

1 -5427

ft

=

75" 44'

(Fe,Mn)SO4.7H2O MnSO4.7H2O

Pisanite

(Fe,Cu)SO4.7H2O

1-1609

:

1

:

1-5110

Bieberite

CoSO4.7H20

1-1815

:

1

:

1-5325

74" 38' 75" 20'

1-1622

:

1

;

1-500

74" 24'

Cupromagnesite (Cu,Mg)SO4.7H2O CuSO4.7H2O CuSO4.5H2O

Boothite

Chalcanthite a

:

b

: c

=

0-5656

:

1

:

0-5507;

Triclinic a

=

82"

21',ft

=

73"

11',7

=

77" 37'.

specieshere included are the ordinaryvitriols. They are identical in and are regarded as with the speciesof the Epsomite group, The copper under crystallization. oblique essentially the same compound in the others and confrom tains crystallization, sulphate,chalcanthite,diverges The

generalformula

but 5 molecules

of water.

MINERALOGY

DESCRIPTIVE

636

Copperas.

MELANTERITE.

and concretionary; fibrous,stalactitic, Usually capillary, Fraoless so. m (110) c (001)perfect; also massive,pulverulent.Cleavage: Color, 1-89-1-90. Luster vitreous. 2. G. Brittle. H. on yellowish exposure. becoming into white; various shades of -green, passing

Monoclinic.

turernchoidal.

=

=

Streak uncolored. Subtransparent to 2V + and metallic. Optically

=

sweetish

Taste translucent. 1-471. 86". a

ft

=

=

gent, astrin-

1-478.

7

=

.

1 *486

Comp

Hydrous

"

ferrous

sulphate, FeSO4.7H2O

45*3 28-8, iron protoxide25-9, water iron. the of sometimes replacepart

and

Manganese

100.

=

Sulphur trioxide

=

magnesium

Goslar in the of pyriteor marcasite; thus near the decomposition sewhere. and e Usually Sweden, Falun, in Bodenmais Bavaria; Mts Germany; Harz Leona In crystalsfrom near efflorescence. as an United States, in the accompanies pyrite the from "Lucky Boy is MnO) mine, c. Heights,Alameda Co., Cal. Luckite (1'9 p. Butterfield Canon, Utah. the mine Lucky MnSO4.7H2O. Fibrous, massive; colorless. From Mallardite. from

Proceeds

Obs

Boy," south of Salt Lake, Utah.

(Fe,Cu)SO4.7H2O. CuO

Pisanite. Color

forms. Leona

blue. Heights, Cal. A

SALVADORITE. Chile.

From

Turkey.

10 to From

15

p.

c.

Bingham,

pisanite.

vitriol near copper-iron

In concretionary and stalactitic Tenn." near Utah; Ducktown, From

the Salvador

mine

Quetena,

CoSO4.7H2O. Usually in stalactites and crusts. Color flesh- and rose-red. Bieber, in Hesse, Germany, etc. 1'94. Color blue, G. H. 2-2'5. CuSO4.7H2O. Usually massive. Boothite. Alameda Leona Co., Heights, Alma mine, near Found at chalcanthite. pyrite than paler and at a copper mine near Campo Seco, Calaveras Co., Cal. Bieberite.

From

=

=

CUPROMAGNESITE.

(Cu,Mg)SO4.7H2O.

CHALCANTHITE.

Blue Vitriol.

Triclinic.

From

Vesuvius.

Crystalscommonly flattened ||p (111).

with stalactitic, reniform,_sometimes

Occurs

also

massive,

fibrous structure.

conchoidal. Berlin-blue Color vitreous. 2-5. G. -30. Brittle. of differentshades ; sometimes a littlegreenish. Streak uncolored. to sky-blue, Taste metallic and nauseous. Optically Subtransparentto translucent. 2V 56". a 1-516. 1-539. 1'546. ft 7 Comp. Hydrous cupric sulphate, CuSO4.5H20 Sulphur trioxide 100. 32-1,cupricoxide 31-8,water 361 M

Cleavage: H.

(110),p (111) imperfect. Fracture

(110),m =

=

Luster

212-2

"

.

=

=

=

=

=

"

=

In the closed tube yieldswater, and at a higher temperature oxide. sulphur triwith soda on charcoal yields metallic copper. With the fluxes reacts for Soluble in water; a drop of the solution placed on a surface of iron coats it with

Pyr., etc.

"

B.B. copper.

metallic copper. Obs.

in waters issuingfrom mines and in connection with rocks containing the alteration of which it is formed; thus at the Rammelsberg mine near Goslar in the Harz Mts., Germany; Falun in Sweden; Parys mine, Anglesea,England; at various mines in County Wicklow, Ireland; Rio Tinto mine, Spain; Zajecar,Servia. From the Hiwassee copper mine, also in largequantitiesat other mines, in Polk Co., Tenn. In Ariz.,near Clifton,Graham Leona Co., and Jerome, Yavapai Co.; in Cal. near Heights, Alameda Co.; from Ely and Reno, Nev. "

Found

chalcopyrite, by

Syngenite. Kaluzite. or milky-white. 0 =

less CaSO4.K2SO4.H2O. In prismatic(monoclinic)crystals. ColorFrom Kalusz, Galicia.

1 '517.

SULPHATES.

CHROMATES,

MgSO4.Na2SO4.2|H2O.

Loweite.

Tetragonal.

Massive, cleavable.

Color

pale yellow.

Austria. Ischl,

From

Index, 1'49.

637

ETC.

MgSO4.Na2SO4.4H2O.

Crystals short prismatic,monoclinic; also massive Colorless to greenish,yellowish, red. 1/488. Optically ft From the salt mines of Ischl and at Hallstadt (simonyite), Austria; at Stassfurt,Germany; the salt lakes of Astrakhan From Soda Lake, San (astrakanite), Asia; India; Chile,etc. Luis Obispo Co., Cal Blodite.

granular

or

compact.

=

"

.

In

Leonite. MgSO4.K2SO4.4H2O. 1-487. 0 Germany. poldshall,

monoclinic

crystals from

Westeregeln and

Leo-

=

Boussingaultite.

Italy. Index,

1'463. replaces the

/3

copper

From

the

boric

acid

lagoons, Tuscany.

incrustation. As a white crystalline Monoclinic. Vesuvius with cyanochroite, an isomorphous speciesin Also at Stassfurt (schoenite)and Aschersleben, magnesium. Galicia.

MgSO4.K2SO4.6H2.O.

Picromerite.

Optically +. which

(NH4)2SO4.MgSO4.6H2O.

1-474.

=

From

Germany; Galusz in East Polyhalite. 2CaSO4.MgSO4.K2SO4.2H2O.

Triclinic. Usually in compact fibrous or 1'562. flesh- or brick-red. the at Occurs Optically ft at Berchtesgaden, Bavaria; mines of Ischl, Hallstadt, etc., in Austria; in Germany Stassfurt, Prussia.

lamellar

Color

masses.

Hexahydrite. 1"76. B.B. taste.

G.

=

=

"

.

fibrous to Columnar structure. Cleavage prismatic. Pearly luster. Opaque. light green tone. Salty, bitter but does not fuse. in Lillooet district, Found yields water

MgSO4.6H2O. with

Color, white

exfoliates and British Columbia.

Alum

RA1(SO4)2.12H2O

Isometric

Group.

R2SO4.A12(SO4)3.24H2O. KA1(SO4)2.12H20 (NH4)A1(S04)2.12H2O

or

Potash Alum Ammonia Alum Soda Alum

Kalinite

Tschermigite Mendozite

NaAl(SO4)2.12H2O

isometric in crystallization are and, chemically,are 12 (i.e., metal if the forwith alkali and mula aluminium of an hydrous sulphates The specieslisted above occur is doubled, 24) molecules of water. very sparinglyin nature, and are best known in artificialform in the laboratory. ALUMS

The

proper

The HALOTRICHITES are commonly fibrous obliquein crystallization, very with magnesium, manganese, in structure, and are hydrous sulphatesof aluminium is given as 22 molecules, and in of water in some cases etc. ; the amount Here belong: the two. others 24, but it is not always easy to decide between Pickeringit". Magnesia and

In

MgSO4.Al2(SO4)3.22H2O.

Alum.

long fibrous

masses;

in efflorescences.

Halotrichite.

Iron

FeSO4.Al2(SO4)3.24H2O.

Alum.

In

yellowish silky fibrous forms.

Index, 1.48. Bilinite.

FeSO4.Fe2(SO4)3.24H2O.Radiating

Schwaz, near Bilin,Bohemia. Apjohnite. Manganese In fibrous

or

asbestiform

Dietrichite.

also

as

crusts

and

Fe2(SO4)3.9H2O. Rhombohedral. From 1-550. Optically+. Chile (not from Coquimbo). Quenstedtite. Fe2(SO4)3.10H2O.In reddish Chile.

white

to

Bushmanite

yellow.

From

contains

MgO.

efflorescences.

(Zn,Fe,Mn)SO4.Al2(SO4)3.22H2O.

Coquimbite.

brownish.

Color

MnSO4.Al2(SO4)3.24H2O.

Alum.

masses;

fibrous.

"

=

Color massive. Granular the Tierra Amarilla near tabular

crystals. With

lowish, white,yelCopiapo, coquimbite,

638

MINERALOGY

DESCRIPTIVE

Muyellow efflorescence on graphite. From orange Perhaps identical with copiapite. fibrous masses or crusts; massive. Alunogen. A12(SO4)3.18H2O.Usually in delicate many; Bilm, Bohemia; Bodenmais, Gernear Color white, or tinged with yellowor red. From Fjom Cripple Creek, Doughty Pusterthal, Tyrol,Austria; from Vesuvius; Elba. Springs,and Alum Gulch, Col. sulphatedepositedby the alkaline waters of the A hydratedaluminium DOUGHTYITE. Doughty Springs in Col. Krohnkite. CuSO4.Na2SO4.2H2O. Monoclinic crystalline;massive, coarsely fibrous. From 1'577. Calama, Atacama, Chuquicamata, /3 Color azure-blue. Optically Autofagasta,and Collahurasi, Tarapaca, Chile. Habit fect Natrochalcite. pyramidal. PerCu4(OH)2(SO4)2.Na2SO4.2H2O.Monoclinic. '3. Color 2 1-65. G. H. 4 -5. bright emerald-green. basal 0 cleavage. Found at Chuquicamata, Autofagasta,Chile. Found PHILLIPITE. at the Perhaps CuSO4.Fe2(SO4)3.nH2O. In blue fibrous masses. of Santiago, Chile. copper mines in the Cordilleras of Condes, province Ferronatrite. Rarely in acicular crystals; 3Na2SO4.Fe2(SO4)3.6H2O. Rhombohedral. Color greenish or gray to white. 1-558. Optically+" eo usuallyin sphericalforms.

Fe2(SO4)3.12H2O?An

Ihleite.

grau, Bohemia.

=

"

.

=

=

=

=

Sierra Gorda

From

Caracoles, Chile.

near

FeSO4.Fe2(SO4)3.14H2O.

Romerite.

Basic Langite.

Near

crusts.

tabular

In

Goslar in the Harz

From

Color chesnut-brown.

triclinic crystals; granular, massive. Persia; Chile.

Mts., Germany;

Hydrous Sulphates

brochantite. CuSO4.3Cu(OH)2.H2O. Usually in Color blue to greenishblue. From Cornwall.

fibre-lamellar, cretionary con-

with one-fifth of the copper Herrengrundite. 2(CuOH)2SO4.Cu(OH)2.3H2O replaced by calcium. In thin tabular monoclinic crystals;usually in sphericalgroups. Color From emerald-green,bluish green. Herrengrund, Hungary. Vernadskite. In aggregates of minute 3CuSO4.Cu(OH)2.4H2O. 3'5. crystals. H. Occurs as an alteration of dolerophanite at Vesuvius. Kamarezite. A hydrous basic copper sulphate from Laurion,Greece. In velvet-like druses;in Cyanotrichite.Lettsomite. Perhaps 4CuO.Al2O3.SO3.8H2O. Color bright blue. From Moldawa sphericalforms. in the Banat, Hungary; ronne, Cap Ga=

France.

In Utah

and

Arizona.

Serpierite.A basic sulphateof Color bluish green.

From

and zinc.

copper

In minute

tabular, crystals,

in tufts.

Laurion, Greece.

Beaverite. CuO.PbO.Fe2O3.2SO3.4H2O. canary-yellow. Refractive index " 174.

Hexagonal ? From

Horn

In microscopicplates Color Silver mine, Frisco, Beaver Co

Utah.

Vegasite. PbO.3Fe2O3.3SO3.6H2O. Hexagonal. In microscopic fibrous crystalssometimes showing hexagonalplates. Optically Indices,1 75-1 '82. Found in Yellow Pine Las Vegas, Nev. near district, -

.

COPIAPITE.

Monoclinic.

Usuallyin loose aggregationsof crystalline or granular scales, mcrusting. Cleavage: b (010)..H. 2-5. G. 2-103. Luster pearly. Color sulphur-yello citron-yellow.Translucent. 1-527. Optically a 0

massive;

=

=

y

1'572.

=

Comp."A tnoxide

basic ferric 38

-3,iron

sulphate,perhaps 2Fe2O3.5SO3.18H2O

sesquioxide30-6,water

31-1

=

in

species.

=

phur Sul-

100.

vaguely applied. "arSe^nrl Wh/Ch fnl^l been.83mew^t !l?S here and part also to other related Janosite t

='

=

-.

l'O4/.

It

seems

is identical with

to

belong in

copiapit?.

640

MINERALOGY

DESCRIPTIVE

Cleavage:

c

(0001) distinct;r (lOll)in traces. varieties splintery;and sometimes

uneven;

flat

Fracture

earthy.

of massive

vitreous,basal

conchoidal,

Brittle.

H.

=

plane somewhat

pearly. r G. 2-58-2:752. Streak white. Transparent to Color white, sometimes grayish or reddish. 1'592. 1-572. subtranslucent. e co Optically+ and Basic hydrous sulphate of aluminium potassium, K2A16 Comp. water 13 -0 alumina trioxide 37'0, 11-4, potash 38'6, Sulphur (OH)i2(SO4)4 3-5-4.

of

Luster

=

=

=

.

"

=

=

Pyr., etc. also

oxides.

"

at

a

tube yields water, sometimes sulphurous and sulphuric

In the closed

higher temperature

With affords a fine blue color. Soluble in sulphuric acid. it has been in trachytic and allied rocks, where

soda

solution

cobalt

with

Heated

is infusible.

decrepitates,and sulphate, and

B.B.

ammonium

soda, natroalunite.

considerable

contains

Sometimes

100.

and

charcoal

infusible,but yieldsa hepatic mass. Obs.

Forms

"

seams

formed

as

a

result

at Tolfa, near as Civitavecchia, sulphurous vapors; Italy; in Hungary; on Milo, Grecian Archipelago; at Mt. Dore, France; Kinkwaseki, Formosa. In the United States, associated with diaspore,in rhombohedral lar crystals,tabuthrough the presence of c (0001) at the Rosita Hills,Custer Co., and from Red Mt., Col.; Marysvale, Utah; Goldfield and near Sulphur, Nev.

of the alteration of the rock by

of

means

JAROSITE. Axis

_Rhombohedral. 1011

55" 16'.

=

massive;

Often

c

1-2492;

=

in druses

rr' lOll

of minute

3-15-3-26.

=

TlOl

=

90"

crystals;also

45', cr 0001 A fibrous,granular

in

nodules,or as an incrustation. Cleavage: c (0001) distinct. Fracture

G.

A

Luster

vitreous

to

Brittle.

uneven.

subadamantine

H.

2-5-3-5.

=

brilliant,also dull. Streak yellow, shining. :

Color

ocher-yellow,yellowishbrown, clove-brown. 1-74. Optically+. 177. co e Comp. K2Fe6(OH)i2(SO4)4 Sulphur trioxide 31*9, iron sesquixoide =

=

"

=

47-9,potash 9-4,water Obs.

10'8

=

100.

The

originalGelbeisenerz was from Luschitz, between Kolosoruk and Bilin, coal; and later from Modum, Norway, in alum slate. The jarositewas from Barranco Jaroso, in the Sierra Almagrera, Spain; Schlaggenwald, Bohemia; Elba; In the United Chocaya, Potosi, Bolivia. States on quartz in the Vulture mine, Ariz.; in Chaffee County, Col.; Tintic district, Utah; Lawrence Ana Co. N. M Co., S. D.; Dona Bisbee, Ariz.; Brewster Co., Texas. Natrojarosite. Na*Fe6(OH)12(SO4)4. Rhombohedral. In minute tabular crvstals. Color From yellow-brown. Soda Springs Valley,Esmeralda Co., Nev. "

Bohemia,

in brown

"

^

Plumbojarosite. PbFe6(OH)12(SO4)4. Rhombohedral. Color

dark

brown.

In

Found

in

fumerole

K20.3A1203.4SO

depositsat

Vesuvius.

9H20.

rounded

In

N^S"4-Al2(S"4)3-5A1(OH)3.H20.Compact. In minute From^m^6* ?erihapS 6?a9-A1^3.3S03.33H20. From limestone-inclusions m

of

minute

tabular

crystals.

Cook's

Peak, N. M., and in Beaver County, Utah. 3(K,Na)2SO4.4PbSO4? In microscopicplates,often hexagonal

Palmierite. Fusible.

Colorless.

From

lava, near

Mayen,

Rhenish

masses,

similar

White. colorless

in outline.

to

From

Almeria,

acicular

Prussia; Tombstone,

compact

crystals.

An/

641

MOLYBDATES

TUNGSTATES,

G. " 3 '3. Indices, 1 '57-1 -61. Infusible. Readily soluble in canary-yellow. H. =2. From Gilpin Co., Col. In Uranopilite. Perhaps CaUgSaOai^SH^O. velvety incrustations;yellow. From Johanngeorgenstadt, Germany. uraconite uncertain uranium are Zippeite,voglianite, sulphates, from Joachimstal, acids.

Bohemia.

Minasragrite. An acid hydrous vanadyl sulphate (V2O2)H2(SO4)".15HjO. Probably In granular aggregates, small mammillary masses, in spherulites. Two or cleavages. Color blue. Indices 1-5 1-1 '54. Strongly pleochroic,deep blue to colorless. Found efflorescence on patronitefrom MinasEasily fusible. Soluble in cold water. as an monoclinic.

Peru.

ragra,

A hydrated acid ferric sulphate.Fe2O3.4SO3.9H2O. Rhomboclase. Basal cleavage. Colorless. Occurs at Szomolnok, Hungary.

In rhombic

plates.

Tellurates; also Tellurites,Selenites In earthy incrustations;yellowish to white. Montanite. From Highland, Mon., with tetradymite. Emmonsite. Probably a hydrated ferric tellurite. In thin yellow-greenscales. From

Ariz.

Tombstone,

near

Durdenite.

ferric tellurite, Fe2(TeOs)3.4H2O. In small Honduras.

Hydrous

greenishyellow.

In small blue monoclinic cupric selenite,CuSeO3.2H2O. selenides. Argentina, with silver, copper is lead selenite and COBALTOMENITE from probably cobalt selenite,

Hydrous

Chalcomenite.

the Cerro

crystals.From MOLYBDOMENITE

the

same

mammillary forms;

de Cacheuta,

localityas chalcomenite. Salts

Oxygen 7.

The monoclinic included here.

MOLYBDATES

TUNGSTATES,

Wolframite

Group and the tetragonalScheelite Group Group

Wolframite (Fe,Mn)WO4

Wolframite Hiibnerite

a

:

b

: c

are

=

MnWO4

0-8300

:

1

:

0-8678

0-8362

:

1

:

0-8668

89" 22' 89"

WOLFRAMITE.

Monoclimc.

Axes

mm'",

110

A

110

at,

100

A

102

=

=

a

c

:

=

0-8300

79" 23'.

ay', 100

61" 54'.

ff',

Oil

:

1

:

0-8678;

A

102

=

62" 54'

A

Oil

=

81" 54'.

89"

22'

1020

(1)tw. axis c with a (100)as comp.-face;(2) tw. pi. k (023),Fig. 449, p. 171. Crystals commonly tabular ||a (100); also prismatic. Faces in prismatic coarse striated. Often bladed, lamellar, zone vertically divergentcolumnar, granular. perfect; also parting || Cleavage: b (010) very Brittle. H. Fracture uneven. t and a || (102). (100), Twins:

=

5-5-5.

G.

=

7-2-7-5.

grayishor brownish black. 1*93. magnetic. 0 =

Color dark submetallic. Streak nearlyblack. Opaque,

Luster

Sometimes

weakly

642

MINERALOGY

DESCRIPTIVE

Comp.

(Fe,Mn)W04. Fe : Mn Tungstate of iron and manganese and 2 3 47 p. c.) : (FeO 9'5,MnO 14-0). (FeO 18-9,MnO

"

4 : 1 chiefly

=

Fuses B.B. easily(F. surface 2-5-3)to a globule,which has a crystalline Pyr.,etc. With salt of phosphorus gives a clear reddish yellow glass while hot is magnetic. rated, which is paleron cooling;in R.F. becomes dark red; on charcoal with tin,if not too satuthe bead assumes on coolinga green color,which continued treatment in R.F. changes to reddish yellow. With soda and niter on platinum foil fuses to a bluish green manganate. ciently Decomposed by aqua regia with separationof tungsticacid as a yellow powder. Suffihydrochloricacid, to give a decomposed by concentrated sulphuricacid, or even colorless solution, which, treated with metallic zinc, becomes intenselyblue, but soon =

"

and

bleaches

dilution.

on

is often associated with tin ores; also in quartz, with native bismuth, In Bohemia in fine crystalsat Schlackenwald, etc. scheelite,pyrite,galena,sphalerite, Zinnwald, Bohemia; in Germany at Schneeberg, Freiberg,Altenberg, Neudorf; at Nerchinsk, Obs.

Wolframite

"

Siberia;Chanteloup, near Limoges, France; near Redruth and elsewhere in Cornwall From tin ores. Sardinia; Greenland; Central Provinces, India. In South With tin stone at various points in New America, at Oruro in Bolivia. South Wales. In the United States at Lane's mine, Monroe, Conn.; Flowe mine, Mecklenburg Co., N. C., with scheelite;in Mo., near Mine la Motte; Laurence Co., S. D.; Boulder Co.] with

Col.;Ariz. Use.

An

"

ore

Hiibnerite.

of tungsten.

Near

20 to 25 p. c. MnO. wolframite,but containing Usuallyin bladed forms,rarelyin distinct terminated crystals. Color brownish red to hair-brown to nearly black. Streak yellowishbrown, greenishgray. Often translucent, 2 '24. Mammoth ft district, Nev.; Ouray County, Col.,and near Silyerton, San Juan Co.; Black Hills,S. D.; Dragoon, Ariz. Also in Peru, and in rhodochrosite at Adervielle in the Pyrenees. =

Scheelite Scheelite

Group.

CaW04

Tetragonal-pyramidal

pp' (111 A 111)

=

Cuprotungstite CuWO4 Cuproscheelite (Ca,Cu)W04 Powellite Ca(Mo,W)04 Stolzite Wulfenite

79"

55J'

80" 1' 80" 15' 80" 22'

PbW04 PbMo04

c

=

1-5360

c

=

1-5445

c

=

T5667

c

=

1-5771

The

SCHEELITE GROUP includes the tungstatesand molybdates of calcium also In crystallization lead; copper. they belong to the Pyramidal class of the TetragonalSystem. Wulfenite is probably and

hemimorphic.

SCHEELITE.

Axis Tetragonal-pyramidal. ee', 101 A Oil ce,

001

1021

Forms:

A

101

=

=

72" 40*'. 56" 56'. 1022

0

(102), e (101).

c

=

1-5356. pp', cp,

1023

111 001

A

ill

A

111

=

=

79" 55*' 65" 16|'. 1024

ft (113), p (111), k (515), ft (313), ,,(131)

TUNGSTATES,

643

MOLYBDATES

Twins:

(1)tw. pi.a (100),both contact- and penetration-twins(Fig.416, octahedral,also tabular. Symmetry shown by faces k, h, s (Fig.1023). Also reniform with columnar structure;massive granular. Cleavage: p (111)most distinct;e (101)interrupted. Fracture uneven. Brittle. H. 4-5-5. G. 5-9-6-1. Luster vitreous, to adamantine. inclining Color white,yellowishwhite,pale yellow,brownish,greenish, reddish. Streak white. Transparent to translucent. Optically-f. Indices: w 167). Habit

p.

=

=

=

1-918.

Comp. 19-4

1-934.

=

e

Calcium

"

tungstate, CaWO4

Tungsten

=

trioxide

80-6, lime

100.

=

Molybdenum

is

usuallypresent (to 8

p.

c.). Copper

replacecalcium, see

may

cupro-

scheelite. B.B. in the forceps fuses at 5 to a semi-transparentglass. Soluble with Pyr., etc. borax to a transparent glass,which afterward becomes and crystalline.With salt opaque of phosphorus forms a glass,colorless in outer flame, in inner green when hot, and fine blue when cold; varieties containingiron requireto be treated on charcoal with tin before the blue color appears. In hydrochloricor nitric acid decomposed, leavinga yellow powder The soluble in ammonia. hydrochloricacid solution treated with tin and boiled assumes a blue color,later changing to brown. Obs. Scheelite is usually associated with crystalline rocks, and is commonly found in connection with cassiterite, topaz, fluorite, apatite,molybdenite, or wolframite,in quartz; also associated with gold. Thus at Schlackenwald and Zinnwald, Bohemia; Altenberg, in the UnterSaxony; Riesengrund in the Riesengebirge,Germany; the Knappenwand sulzbachtal, Tyrol, Austria; Carrock Fells in Cumberland, England; Traversella in Piedmont, land. (containingTa2O5); Sweden; Pitkaranta in FinItaly; Meymac, Correze, France In New South Wales, at Adelong, from a gold mine; New Zealand, massive; Mt. Sonora, Mexico. Ramsay, Tasmania, with cassiterite. From In the United States, at Lane's Mine, Monroe, and at Trumbull, Conn.; Flowe mine, Mecklenburg Co., N. C.; the Mammoth mining district,Nev.; with gold at the Charity mine, Warren's, Idaho; Lake Co., Col.; Atolia mining field,Cal.; White Pine Co., Nev.; In quartz veins in Risborough and Marlow, Beauce Dragoon, Ariz. county, Quebec. "

"

Use.

"

An

ore

of

tungsten.

From the copper mines of Llamuco, near Cuprotungstite. Cupric tungstate, CuWO4. from the vicinityof La Paz, Lower California,is Santiago, Chile. CUPROSCHEELITE, From Montoro, Spain; from Yeoral, New (Ca,Cu)WO4, with 6'8 p. c. CuO; color green.

South

Wales.

Calciuni molybdate with calcium tungstate (10 p. c. WO3), Ca(Mo,W)O4. From 4'349. 2 '00. western w Idaho; yellow tetragonal pyramids. G. Houghton Co., Mich.; from Llano Co., Texas, and Nye Co., Nev. In pyramidal tetragonalcrystals. H. 2-75-3. Stolzite. Lead tungstate, PbWO4. brown. 2'269. Color green to gray Zinnwald, G. Optically 7-87-8-13. or "o From LoudSouth Wales. Hill, New Bohemia; Sardinia; Minas Geraes, Brazil; Broken Mass. ville, but is referred to the monoclinic composition as stolzite, Raspite. Has the same From the In small tabular crystals. Color brownish yellow. Index, 2*60. system. South Wales;. Minas Geraes, Brazil. Broken Hill mines, New In tabular tetragonalcrystals, apparently hemimorphic. Chillagite. 3PbWO4.PbMoO4. From 7'5. H. 3 -5. G. Chillagoe,Queensland. Color yellow to brownish. Powellite.

In minute

=

=

=

=

-.

=

=

=

WULFENITE.

hemimorphic. Tetragonal-pyramidal; cu,

001

A

102

=

ce,

001 001

A

101

=

A

111

=

en,

38" 15'. 57" 37'. 65" 51'.

Axis

c

=

1-5771.

uu', 102 A 012 ee', 101 A Oil nn't 111 A Til

=

=

=

51" 56'. 73" 20'. 80" 22'.

quently Crystalscommonly square tabular, sometimes extremely thin; less fredistinct. sometimes also prismatic. Hemimorphism octahedral; or fine,firmlycohesive. Also granularlymassive, coarse

MINERALOGY

DESCRIPTIVE

644 Cleavage-

n

smooth;

(111) very

subconchoidal. Brittle. Color waxadamantine.

c

(001),s (113)less distinct. Luster

67-7-0. 275-3. H. and siskinto orange-yellow, G.

=

=

Fracture resinous or

yellowish olive-green,

1028

1027

gray,

brown; also to nearly colorless, Subtransparent to subtranslucent. 2-304. 2-402,er

grayishwhite white.

Streak Indices:

Comp.

=

=

"*

Lead

"

oxide 607

100.

=

to bright red. Optically negative.

orange

molybdate, PbMo04 sometimes

Calcium

Molybdenum trioxide 39'3, lead replacesthe lead. =

and fuses below 2. With salt 9fphosphorus in O.F. gives decrepitates Pyr., With soda on charcoal yields dark green. glass,which in R.F. becomes a yellowishgreen metallic lead. Decomposed on evaporation with hydrochloricacid, with the formation of and adding metallic lead chloride and molybdic oxide; on moistening the residue with water zinc,it givesan intense blue color,which does not fade on dilution of the liquid. in veins with other ores of lead. At Bleiberg,Carinthia; Rezbanya, Obs. -^Occurs in the Banat, Hungary; Annaberg, Schneeberg, Hungary; Pfibram, Austria; Moldawa Germany; Sardinia; Broken Hill,New South Wales. In the United States, sparinglyat the Southampton lead mine, and at Quincy, Mass., lode and at Eureka in and near Sing Sing,N. Y.; near Phenixville, Pa.; at the Comstock Nev. ; in largethin orange-yellowtables at the Tecomah In N. M., pale yellow mine, Utah. in the Organ Mts. In Ariz., largedeep red crystalsat the Hamburg and* other crystals Yuma Co., often with red vanadinite; also at the Castle Dome district,30 miles mines, distant;at the Mammoth gold mine near Oracle,Pinal Co., with vanadinite and descloizite. Named after the Austrian mineralogistWulfen (1728-1805). Use. An ore of molybdenum. etc.

B.B.

"

"

Reinite.

Ferrous tungstate, FeWO4. H. 4. 6*64. G.

In blackish brown

tetragonalpyramids, perhaps Kimbosan, Japan. Koechlinite. A molybdate of bismuth, Bi2O3.MoO3. In minute Orthorhombic. lar tabucrystals. Cleavage,a (100). Color, greenishyellow. Index, 2'55. Easily fusible. From Schneeberg,Saxony, Germany. In microscopichexagonal plates. Color pale yelFerritungstite.Fe2O3.WO3.6H2O. low to brownish yellow. Decomposed by acids leavingyellow tungsticoxide. Product of oxidation of Wolframite from Germania Deer Trail district, Tungsten mine. Wash.

pseudomorphous.

=

VII.

=

SALTS

OF

ORGANIC

ACIDS

Oxalates, Mellates Whewellite. +. Optically Oxammite.

Islands,Peru.

Calcium 0

"555.

Ammonium

oxalate,CaC2O4.H2O. In sfmall colorless monoclinic crystals. From Saxony, with coal; also from Bohemia and Alsace. oxalate,(NH4)2C2O4.2H2O. From the guano of the Guanape

HYDROCARBON

645

COMPOUNDS

Hydrous ferrous oxalate,FeC2O4.2H2O. Orthorhombic. Color yellow. Bilin,Bohemia; Capo d'Arco, Elba. Mellite. Hydrous aluminium mellate, Al2Ci2Oi2.1SH2O. In square tetragonalpyramids; also 1 -55^-1 massive, granular. G. '65. Color honey-yellow. Optically T539. Occurs in brown coal in Thuringia, Bohemia, etc.

Humboldtine.

/5

=

From

1-561.

near

=

"

.

w

=

VIII.

HYDROCARBON

COMPOUNDS

The

Hydrocarbon compounds in general,with few exceptions,are not homogeneous substances, mixtures, which by the action of solvents or by fractional distillation may be separated into two or more component parts. They are hence not definite mineral species and do not strictly belong to pure Mineralogy,rather, with the recent gums and resins,to Chemistry or, so far as they are of practicalvalue,to Economic Geology. In the following part with great brevity. pages they are treated for the most but

1.

Simple Hydrocarbons. SCHEERERITE.

(CH4).

of the Paraffin Series CraH2n+2. crystals. Perhaps a polymer of marsh-gas

Chieflymembers

whitish monoclinic in brown coal at Uznach, In

Found

Tallow. yellowish. Indices,1 '47-1 '50. Ratio Mountain

HATCHETTITE.

Switzerland.

In thin of C to H

plates,or massive. =

Merthyr-Tydvilin Glamorganshire, England;

near

nearly1:1. from

Galicia.

A native crystallized PARAFFIN. paraffinhas been described in basaltic lava near Paterno, Sicily.Indices, 1*49-1 '52.

Mineral

Like soft wax. Color the Coal-measures

From

occurring in cavities

as

in part.

Like wax and consistency. or spermaceti in appearance often leek-green, yellowish,brownish yellow,brown. and consistingchiefly of one of the higher memIndices, 1 '51-1 "54. Essentiallya paraffin, bers of the series. Occurs in beds of coal, or associated bituminous deposits,as at Slanik, in southern Utah on a Moldavia; Roumania; Boryslaw in the Carpathians. Also occurs largescale. OZOCERITE.

Colorless

wax

when

to white

pure;

Zietrisikite, Chrismatite, Urpethiteare FICHTELITE.

layersof pine

In wood

Borkovic, Bohemia. NAPALITE.

C3H4.

From

white

from

monoclinic

near

peat-beds,near

Hartite

has

a

ozocerite.

crystals. Perhaps CsHg. Occurs in thin Redwitz, in the Fichtelgebirge, Bavaria; from

tabular

similar

occurrence.

of the consistency of shoemaker's substance A yellow bituminous mine in Pope Valley,Napa county, Cal. the Phoenix mercury

wax.

Oxygenated Hydrocarbons

2.

H. 2-2 '5. G. 1'096. with fracture. conchoidal In irregularmasses, AMBER. Color yellow,sometimes reddish, brownish, and whitish, often clouded, Luster resinous. to 150" begins to soften, sometimes fluorescent. Transparent to translucent. Heated 40 : 64 : 4. Ratio for C : H : O and finally melts at 250"-300". succinite (yielding succinic is separated mineralogicatly Part of the so-called amber as the Atlantic coast of the other regions (e.g., acid). Other related fossil resins from many Some of them have been called retinite, United glessite, gedanite, States)have been noted. =

=

=

rumanite,

etc. simetite,krantzite, chemawinite, delatynite,

the Prussian coast of the Baltic from Dantzig to Memel; and the Russian Baltic provinces. It is mined after a heavy storm. the shores cast up by the waves on this is Amber and the similar fossil resins are of vegetableorigin,altered by fossilization; of inferred both from its native situation with coal,or fossil wood, and from the occurrence called yXtxTpov, the ancients, and to was insects early known incased in it. Amber has been derived the word of its electrical susceptibilities, electrum, whence, on account Amber

occurs

abundantly

on

coasts of Denmark, extensively,and is also found

also

on

the

Sweden,

electricity. blue clay. It is like the resin copal in COPALITE, or Highgate resin,is from the London in alcohol. Color clear pale difficult and solubility hardness, color, luster,transparency,

yellow to dirty gray

and

dirty brown.

Emits

a

resinous

aromatic

odor when

broken.

MINERALOGY

DESCRIPTIVE

peat deposits etc : or in the torbamte Boghead coal Occurs in dull,brown, porous lumps Bathville, Scotland. Torbane Hill, of lands the formation) adjoining

followingare

The

BATHVILLITE

occurringwith oxygenatedhydrocarbons

Crrbonfferous riin,else material which ^atoed be

fnf the

I?may

or

an

has

coal and

filtrated into the cavity from

the

surrounding torbanite.

shale; scales disseminated through a laminated dissolved at all by alcohol, ether,benzene. Remarkable as yielding 5 '3 p. c, heated. when even the rock is called combustible the river Mersey, north side of Tasmania; In minute

TASMANITE

reddish brown

diameter about 0'03 of scales Tcarbon disulphide, turpentine

average

Vom sufpto! DYSODILE gave 2 3 p.

in.

Not

sis Analyelastic; yellowor greenishgray. slightly flexible, In very thin folia, and at Melili,Sicily, From deposits lignite 7 and 1 c. nitrogen. p. sulphur

c.

elsewhere. the brown A white, wax-like substance, separatedfrom other products from are Weissenfels. Geomyriciteand geocerellite coal. Between Also from the Gesterwitz brown LEUCOPETRITE.

GEOCERITE near

coal ot Gesterwitz,

the a

same

source.

resin and

wax

in

physicalcharacters. From

PYRORETINITE.

brown

coal

near

Aussig, Bohemia.

An black. brownish masses; In elastic or partlyjelly-like DOPPLERITE. for C, H, Ratio acid. to humic related acids, different of mixture or Bavaria. in Styria;Fichtelgebirge, Aussee From 10 : 12 : 5. peat beds near white and In the state Idria. of cinnabar the pure Occurs with IDRIALITE. in structure.

pyrite and and

the presence

mercury

FLAGSTAFFITE. =

1'092.

The

crystalline

found only impure, being mixed with cinnabar, clay, and some its combustibility brownish black earthy material, called, from a of mercury, inflammable cinnabar. the Occurs in hard, brittle platesor nodules,lightgreen in color. From mine, Lake Co., Cal. See also napalite,p. 645.

In nature in gypsum

POSEPNYTE. Great Western

G.

acid substance

O, nearly

Found

Ci2H24O3. Orthorhombic. in cracks of buried tree

followingare stillmore

In

minute

trunks,near

prisms. Colorless,

n

=

T51.

Ariz. Flagstaff.

complex native hydrocarboncompounds of great importance

from an economic standpoint. Mineral oil. Kerosene. PETROLEUM. Petroleum. NAPHTHA; Mineral Tar. Maltha. PITT ASPHALT: Liquids or oils,in the crude state of disagreeableodor; varying widely in color,from color the most and nearly black, the greenishbrown colorless to dark yellow or brown also in consistencyfrom thin flowing kinds to those that are thick and viscous; common;

in specific gravityfrom 0'6 to 0*9. Petroleum, proper, passes by insensible gradations into pittasphalt or maltha (viscidbitumen) ; and the latter as insensiblyinto asphaltor solid bitumen. of the paraffinseries, Chemically, petroleum consists for the most part of members The CnH2n+2, varying from marsh gas, CH4, to the solid forms. olefines,CreH2w, are also present in smaller amount. oils. Those of the" true of the American This is especially Caucasus have a higherdensity,the volatile constituents are less prominent, they distillat about 150" and contain the benzenes, CnH2n-6, in considerable amount. There are present also members of the series CnH2n-8. the The German petroleum is intermediate between and the Caucasian. American The Canadian petroleum is especiallyrich in the solid and

paraffins. Petroleum in rocks or deposits of nearly all geologicalages, from the Lower occurs Silurian to the present epoch. It is associated most abundantly with argillaceousshales, sands, and sandstones,but is found also permeating limestones,giving them a bituminous odor, and rendering them sometimes of oil. From these oleiferous a considerable source shales,sands and limestones the oil often exudes, and appears floatingon the streams or lakes of the region,or rises in oil springs. It also exists collected in subterranean cavities in certain rocks, whence it issues in jetsor fountains whenever outlet is made by Coring. an The oil which fillsthe cavities has ordinarilybeen derived from the subjacent rocks; for the strata in which the cavities exist are The conditions frequentlybarren sandstones. required for the production of such subterranean accumulations minous would be therefore a bituelse oil-producing or oil-bearing at a greater or less depth below; cavities stratum to receive the oil;an overlyingstratum of close-grained shale or limestone,not allowing of the easy escape of the naphtha vapors.

MINERALOGY

DESCRIPTIVE

548

stillretain it passes from forms which Thus the extent to which this change has gone on. and through those with less of volatile or of the wood (peat,lignite) he origmal kinds which approach graphite. matter to anthracite and further to bituni Luster bright,often submetalhc, iron1'32-1'7. G. 2-2 '5. H ANTHRACITE 1 Volatile matter after drying 3^6 conchoidal. Fracture black and frequentlyiridescent. The anthracites of Pennsylvania contain of flame feeble a pale color with Burns a p. c. Wales 80-83; of 88-95; of France ordinarily85-93 per cent of carbon; those of South Anthracite graduates through 94 per cent. sometimes Russia, southern of Saxony 81; volatile and containing more semi-anthracite into bituminous coal, becoming less hard anthracite. is called free-burning intermediate variety and an matter; smoky flame, and gives out on in the fire with a yellow, Burns COAL. BITUMINOUS 2 The ordinarybituminous bituminous. hence the name oils

structure

S

=

=

'

or tar; distillationhydrocarbon (ashexcluded); while the so-called coals contain from 5-15 p. c. (rarely16 or 17) of oxygen of 15-36 p. c. of 100 brown coal or lignitecontains from 20-36 p. c., after the expulsion,at have Both 4-7 a bright, from is usually c. in each of The amount p. water. hydrogen with anthracite, rather fragile compared are firm texture, compact a luster, pitchy,greasy the 1 '14-1 '40. The brown coals have often a brownish black color,whence and have G. ous and others they shade into ordinary bituminthese in but and respects more oxygen, name, castle, 1 '26-1 '37; of Newcoals. The ordinary bituminous coal of Pennsylvaniahas G. England, 1'27; of Scotland, 1 '27-1 '32; of France, 1 "2-1 "33; of Belgium, 1'27-1'3. ,

=

=

most prominent kinds are the following: (a) Caking or Coking Coal. A bituminous coal which softens and becomes pasty or semitakes placeat the temperature of incipient decomposition, viscid in the fire. This softening On increasingthe heat, the volatile of bubbles of gas. and is attended with the escape driven off, are products which- result from the ultimate decomposition of the softened mass of coke left and a coherent, grayishblack, cellular or fritted mass (coke)is left. Amount varies from 50-85 p. c. (or part not volatile) mate (6) Non-Caking Coal. Like the precedingin all external characters, and often in ultiof incipient composition; but burning freelywithout softeningor any appearance fusion. There are all gradationsbetween caking and non-caking bituminous coals. (c) Cannel Coal (ParrotCoal). A varietyof bituminous coal, and often caking; but in composition,as shown extent from the precedingin texture, and to some by its differing productson distillation. It is compact, with littleor no luster,and without any appearance of a banded structure; and it breaks with a conchoidal fracture and smooth surface; color dull black or grayishblack. tile On distillationit affords,after drying,40 to 66 p. c. of volacating matter, and the material volatilized,includes a largeproportion of burning and lubrioils,much largerthan the above kinds of bituminous coal; whence it is extensively used for the manufacture of such oils. It graduates into oil-producingcoaly shales, the Torbanite is a varietyof cannel coal of a dark more compact of which it much resembles. brown color,from Torbane Hill,near Bathgate, Scotland; also called Boghead Cannel. (d) Brown Coal (Lignite).The prominent characteristics of brown coal have already been mentioned. They are non-caking,but afford a largeproportion of volatile matter; sometimes but often rather dull and brownish black. G. 1 '15-1 '3. Brown pitch-black, coal is often called lignite.But this term is sometimes restricted to masses of coal which stillretain the form of the original wood. Jet is a black varietyof brown coal, compact in texture,and taking a good polish,whence its use in jewelry. Coal occurs in beds, interstratifiedwith shales, sandstones, and conglomerates, and sometimes limestones, forming distinct layers,which vary from a fraction of an inch to 30 feet or more in thickness. In the United States,the anthracites occur east of the Alleghany and fracturings, while the bituminrange, in rocks that have undergone great contortions ous

The

=

coals

found extensively in many States farther west, in rocks that have been less this fact and other observations have led geologists to the view that the anthracites have lost their bitumen by the action of heat. The origin of coal is mainly vegetable, though animal life has contributed somewhat to the result. The beds were once beds of vegetation, analogous,in most respects,in mode of formation to the peat beds of modern times,yet in mode of burial often of a This vegetable very different character. origin is proved not only by the occurrence of the leaves, and logsof plantsin the coal, stems but also by the presence throughout its texture, in many cases, of the forms of the original resi also by the direct observation that peat is a transition state between unaltered vegebrown coal" being sometimes found passing completelyinto true brown " s * i coal. Peat differsfrom true coal in want of homogeneity,it visiblycontainingvegetable fibers only partially altered;and wherever changed to a fine-textured homogeneous material, even though hardlyconsolidated, it may be true brown coal. .bor an account of the chief coal fields, as also of the geological relations of the different coal deposits, reference is made to works on Economic Geology. are

disturbed;and

APPENDIX

ON

THE

DRAWING

OF

A.

CRYSTAL

FIGURES

IN the representationof crystalsby figuresit is customary to draw their edges as if they definite plane. Two sorts of projectionare projected upon some graphic used; the orthoin which the lines of projectionfall at rightangles and the clinographic where they fall at obliqueangles upon the plane of projection. The second of these projections is the more important, and must be treated here in some detail. Two points are to be noted in regard to it. In the firstplace,in the drawings of crystalsthe point of view is supposed to be at an infinite distance,and it follows from this that all lines which are parallel the on were

in the drawing. parallel In the second place,in all ordinary cases, it is the complete ideal that is,the crystalwith its full geometrical symmetry as

crystalappear

crystalwhich explained on

is sented, repre10 to

pp.

13

(cf.note on p. 13). general,drawings of crystalsare made, either by constructing the figure upon a projectionof its crystalaxes, using the interceptsof the different faces upon the axes in order the directions of the edges or by constructingthe figurefrom the gnomonic to determine Both of these methods (or stereographic)projection of the crystalforms. have their advantages and disadvantages. By drawing the crystalfigureby the aid of a projection the symmetry of its crystalaxes of the crystaland the relations of its faces to the axes are emphasized. In many a projectionof the poles of the cases, however, drawing from crystalfaces is simplerand takes less time. The student should be able to use both methods and consequently both are described below. In

DRAWING

OF

CRYSTALS

UPON CRYSTAL

PROJECTION

PROJECTIONS

OF

THEIR

AXES OF

THE

AXES

/ .

The projectionof the particularaxes required is obviously the firststep in the process. These axes be most can easilyobtained by making use of the Penfield Axial Protractor, The customary directions of the axes for the isometric, illustrated in Fig. 1030. * tetragonal, orthorhombic and hexagonal systems are given on the protractor and it is a simple matter, as explained below, to determine the directions of the inclined axes of the monoclinic and triclinic systems. Penfield drawing charts giving the projectionof the isometric axes, which are easilymodified for the tetragonaland orthorhombic onal systems, and of the hexag(see Figs. 1031, 1032) are also quite convenient. axes, Isometric The followingexplanation of the making of the projectionof the System. has been taken largelyfrom Penfield's description, isometric axes f clear the principlesupon which the projectionof the isometric Figure 1033 will make "

based. are of a cube in two A B C D, after

Figure 1033A positions, one,

is

orthographicprojection(a plan, as seen from above) b c d, in what be called normal position, the other, may its vertical axis. The brokenof 18" 26' to the left about a revolution dashed lines throughout represent the axes. Figure 1033B is likewise an orthographic viewed from in front,the eye projectionof a cube in the positionA B C D of A, when or point of vision being on a level with the crystal. In the positionchosen, the apparent width of the side face B C B' C' is one-third that of the front face ABA' Bf, this axes

an

a

being dependent upon the angle of revolution 18" 26',the tangent of which is equal to f. To construct the angle 18" 26',draw a perpendicularat any point on the horizontal line, X Y, figure1033A as at o, make op equal one-third Oo, and join O and p. The next is to change from orthographic to clinographicprojection. In step in the construction it is supposed that the eye or point of solidity order to give crystalfiguresthe appearance "

* The various Penfield Sheffield Scientific School t On Crystal Drawing;

be obtained crystaldrawing apparatus may of Yale University, New Haven, Conn, Am. J. Sc., 19, 39, 1905.

649

from

the

Mineralogical.Laboratory of the

APPENDIX

650

A

1030

Protractor

for

plottingcrystallographicaxes;

one-third

of the engraved

axes

size

(afterPenfield)

1032

1031

Scheme

natural

of the isometric and

hexagonal systems, one-sixth natural

size (afterPenfield)

APPENDIX

A

651

of vision is raiseji, that one looks down so at an angle upon the crystal;thus, in the case under consideration, figure1033C, the top face of the cube comes into view. The position of the crystal,however, is not changed, and the plane upon which the projectionis made vertical. From A it may remains be seen that the positiveends of the axes a\ and a2 are forward of the 1033 ImeXY, the distances a\x and "2 y being as 3 : 1. In be imagined, and B it must by the aid of a model it easilybe seen, that the extremities of these same may to the front of an imaginary vertical plane (the are axes of XY above) passing through the center of projection the crystal,the distance being the same as ai x and a2 In D the distance ax is drawn the y of the plan. to same length as a\x of the plan, and the amount which it is supposed that the eye is raised,indicated by the arrow, is such that a, instead of being projected horizontallyto x, is projected at an inclination of 9" the horizontal to w, the distance xw being one28' from the sixth of ax; hence angle 9" 28' is such that its tangent is |. Looking down upon a solid at an angle, and stillmaking the projectionon a vertical plane,may

designated as clinographic projection;accordingly, of a cube in clinographic projection plot the axes the conformity with figures A, B and D draw horizontal construction line hk, figureC, and cross it in vertical alignment with the by four perpendiculars B. Then "i and a2 of figuresA and points "i, a2, the extremities of the first, determine a\ axis by a\, of figureD, or oneequal to xw laying off distances sixth ai x of figureA, locatingthem below and above be

to in

"

"

"

horizontal

line hk.

The line ai, a\ is thus the front-to-back axis. In like determine the extremities of the second manner axis, 02, by laying off distances equal to one-thircUcw "2, of figureD, or one-sixth a2y of figureA, plotted below is thus~tKe~ The line a2, and above the line hk. a2 axis. It is projection of the second, or right-tp-left important to keep in mind that in clinographicprojection there is no foreshorteningof vertical distances. In figureC the axis a2, a2 is somewhat, and a\, "i much of the' foreshortened,yet both represent axes the

projection of

the

"

or first,

"

"

"

same

length as

the

vertical, a3,

"

"

a3.

of choice that the angle of It is wholly a matter in figure 1033A is 18" 26',and revolution shown that of the the eye is raised so as to look down a crystal at Development of the axes upon in isometric orthographic system of 9" 28' from the indicated an horizontal,as angle by and clinographic projection Also it is evident that these angles may figure1033D. (afterPenfield) be varied to suit any specialrequirement. As a matter of fact,however, the angles 18" 26' and 9" 28' have been well chosen and are established by long usage, and practically all the figuresin clinographic treatises on crystallographyand mineralogy, have projection,found in modern with them. in accordance been drawn hombic orthorOrthorhombic The projectionof tetragonal and Systems. Tetragonal and be easilyobtained from the isometric axes axes can by modifying the lengthsof the with zircon to the axial ratio of the desired crystal. For instance various axes to conform 0.64 in respect to the equal lengthsof the horizontal the vertical axis has a relative length of c axes. tion By taking 0.64 of the unit length of the vertical axis of the isometric projecfor a zircon figureare The Penfield axial charts all give obtained. the crystalaxes decimal parts of the unit length of the isometric vertical axis,so that any proportion of In the orthorhombic be found at once. this length can system the lengths of both the a scribed be obtained as deThe desired point upon the c axis can and c axes be modified. must be found by some In the case of the a axis the required point can above. simple of construction. method If,as is the case in the Penfield charts,a plan of the unforeshortbe laid off directlyupon ened horizontal axes is given in a top view, the desired length can "

=

the

A

APPENDIX

652 a

of the decimal by means projection orthographic its clinographicprojection.Or the proper upon

axis in this

verticallydown

scale and distance

then

projected be laid oft

can

from this point parallelto a line of a line drawn the proper proportional isometric the of projection a c by intersection. part of the a axis can be determined the hexagonal axes For projecting Hexagonal System. 1034 of as were be made use principles may exactly the same of isometric the construction axes. in the Figure employed 1034A is an orthographic projection,a plan, of a hexagonal of them, ai, 02, etc., after a prism in two positions,one be called normal posirevolution of 18" 26' from what may tion. In figure1034B the extremities of the horizontal axes the horizontal construction of A have been projecteddown upon forward of the line hk, and a\, a2 and are a3 which ographic the line hk in the clinlocated below in A are line XY hk being one-sixth the distances from projection, of dix, (hy and Figure 1034C is a scheme for asz of A. the extremities of the axes are gettingthe distances which dropped. The vertical axis in 1034B has been given the same length as the axes of the plan. In the case of the monoclinic Monoclinic System. be the inclination and length of the a axis must axes The in each case. axial chart, Fig. 1030, can determined The ellipse be most convenientlyused for this purpose. C gives the trace of in the figure,lettered A, C, A, the ends of the a and c axes as they are revolved in the A C plane. To find,therefore,the inclination of the a to lay off the angle /8 by means axis it is only necessary of the graduation given on this ellipse. The unit length of in various ways. the a axis may be determined The plan of the axes given at the top of the chart may be used for this of Development of the axes of procedure Fig. 1035 will illustrate the method purpose. the hexagonal system in of orthoclase, where 64" and applied in the case as 0 ographic and clinorthographic The foreshortened 0.66. termined a length of the a axis is deprojection (after indicated and then this length can be projected as Penfield) downward the inclined a axis,the direction vertically upon of which has been previouslydetermined above. as described Triclinic System. In the construction of triclinic axes the inclination of the a axis and its length are determined in exactly the same described in the preceding manner as paragraph in the case of the monoclinic system. The direction of the 6 axis is determined The vertical plane of the 6 and c axes is as follows. revolved about the c axis through such an angle as 10"5 will conform to the angle between the pinacoids 100 and 010. Care must be taken to note whether this plane is to be revolved toward the front or toward the back. If the angle between the normals to 100 and 010 is greater than 90" the right hand end of this plane is to be revolved toward the front. Figure 1036, which is a simplifiedportion of the axial chart, shows the necessary in construction order to obtain the direction of the 6 axis in the of rhodonite in which 100 A 010 case 94" 26' and 103" 18'. The plane of the b-c axes a will pass through the point p which is 94" 26' from -a. To locate the point 6',which is the point where the 6 axis would emerge from the sphere, draw through the point p two or more chords from points where the vertical ellipses of the chart cross the horizontal ellipse,as lines a-p. -a-p. b-p, in figure 1036. the vertical axis and

on

then

ioinine the extremities of the

by

means

and

axes

"

"

"

"

"

"

"

=

=

"

=

=

Ihen which

from

points

these same vertical ellipses the horizontal plane draw chords parallelto the firstseries as x-x',y-y',z-z'. The point where these three chords meet determines the positionof 6' and a line from this point drawn through the center of the are

on

13" 18' below

APPENDIX

653

A

chart determines the direction of the b axis, since it Ues in the vertical plane and proper makes the angle a, 103" 18',with the c axis. The foreshortened length of the 6 axis can be determined by the use of the orthographic projectionof the a and b axes at the top of the chart in exactly the same described under the monoclinic system and the manner as be projectedverticallydownward point thus determined the line of the b axis may upon of the clinographicprojection as It must be already determined. 1036 remembered, however, that the graphic positionof the b axis in the orthoconform projection must to the position of the plane of in the case the b and c axes of or rhodonite have its right hand end at an angle of 94" 26' with the negative end of the projectionof the

a

axis.

Drawing Aid

of

Axes.

"

In

of Crystal Figures by their Projections of order

to

determine

in

the

drawing the direction of any edge between two crystalfaces it is necessary to establish two to these two faces. points,both of which shall be common A line connecting two such points will obviouslyhave the desired direction. The positions of these points is commonly established by use of the linear or Quendstedt projection as explained in the followingparagraphs, which have been taken almost verbatim from Penfield's descriptionof the process. The principleupon which the linear projectionis based is very simple: Everyface of a but without crystal(shifted if necessary, change of direction)is made to intersect the vertical axis at UNITY, and then its intersection with the horizontal plane,or the plane of the a and b axis is indicated by a line. For instance if a given face has the indices 111 it is clear that its linear projectionwould be a line passing through la and 16,since the face under these conditions will also pass through Ic. If,however, the indices of the face are 112 it will only pass through 1/2 c when it passes through la and 15. In order to fulfill, therefore,the requirements of the linear projection 1037 that the plane should pass through Ic the indices must be multipliedby two and then under these conditions the line in which the plane intercepts the horizontal plane, or in other words the linear projectionof the face,will pass through 2a and 26. In the case of a prism face with the indices 110, its linear direction as a line joining projectionwill be a line having the same la and 16 but passing through the point of intersection of these as a only prism can axes, since a vertical plane such it also includes the c axis and so must through Ic when pass have its linear projectionpass through the point of intersection of the three axes. it is desired to find the direction of an edge made When meeting of any two faces,the lines representingthe linear "-

by the projection sect they inter-

of the faces are first drawn, and the point where faces is deteris noted. mined, Thus a point common to both is located in the plane of the a and 6 axes. A which the vertical to the two faces is unity on second point common axis,and a line from this point to where the lines of the linear projectionintersect gives the desired direction. chosen from the orthorhombic A simple illustration, system, how the linear projection may be employed to show will serve of barite,such as in drawing. The example is a combination in figure1037. is shown The axial ratio of barite is as follows: a

On

the orthographic axes

:

b

: c

=

0'8152

:

1

:

1'3136

figureand the symbols are, base c (001), d (102). prism m (110),brachydome o (Oil) and macrodome Figure 1038 represents the details of construction of the in figure1037. orthographic and clinographicprojectionsshown the axial lengths a and 6 are located,the vertical axis c being The

forms

shown

in the

654

APPENDIX

A

1038

: oo 6 ; c),the lines xy and x'y',through 2a parallelto the 6 axis: The prism m (110) ditions parallelto the vertical axis,hence in order that such a plane shall satisfy the conbe of the linear projectionand pass through unity on the vertical axis, it must considered as shifted (without change of direction) until it passes through the center: to the Its linear projection therefore is represented by the lines yz and y'z',parallel the on directions la to 16 on the two sets of axes. Since a linear projection is made plane of the a and 6 axes, the intersection of any face with the base (001) has the same sections direction as the line representingits linear projection. It is well to note that the interand z' in with another. and and vertical z are one x',y' alignment x, y Concerningthe drawing of figure1038, it is a simple matter to proportionthe general outline of the barite crystalin orthographicprojection. The direction of the edge between d, 102, and o, Oil, is determined by findingthe point x, where the lines of the linear projection of d and o intersect, and drawing the edge parallelto the direction from x to the to center c. The intersection of the prism m, 110, with d and o is a straightline,parallel the direction la to 16 or y to z. convenient To construct the clinorraphicfigure, at some point beneath, the axes the horizontal middle edges of the crystalmay be drawn parallel to the a and 6 axes, their lengths and intersections being determined by carrying down perpendicularsfrom the orthographic projection above. d, The intersection between

(2a

is

A

are

steD

A

APPENDIX

656

To insure 60" 31'. in plot001 A 232 ting accuracy 54" 37' and P 010 A 230 of the protractorhave been regardedas unity. The first the full lengthsof the axes the position of the twinning plane, 232. the clinographicprojection is to locate on =

=

=

=

Fig. 1041 as the triangle 3/2c. The next step is find the position of the twinning axis to this plane. to will be normal The which coordinates of this twinning axis are given The by the "f"and p angles quoted abov". point p which is 54" 37' back from the pole to 010 or b marks _theplace where the normal to the prism face 230 would ejnerge from the to is the sphere. The normal 232, which the meridian on twinning axis will emerge that runs through the point p and at such a distance below it that it will make the angle the negative end of the c axis. 60" 31' with Chords are drawn to p from the points where from

the

in

is shown

This

1041

3/2a

-

a

and

to

b

b to

axes

sphere and then

-

meet chords

the

equator

of

parallelto these

the are

points x, y and z which are in each case 60" 31' from the point where the negative end of the c axis cuts the spherical surface. The common meeting point of the twinning axis pierces the sphericalsurface. these chords T marks the place where the point t at which The the twinning axis cuts next the step is to determine at right angles to the line connecting twinning plane. The line OPp is by construction -3/2a and 16. Therefore a vertical plane which is normal to the twinning plane would intersect that plane in the line connecting" 3 /2c and P. The twinning axis OT would He in this plane also. Consequently the point t, where OT and -3/2c-P intersect would Ke both on the twinning axis and in the twinning plane. In order to 1042 drawn

the method clearer Fig. 1042

make

from

the

of construction is

given. Here twinning axis is repeated from Fig. 1041. The twin position of the crystalis to be found by revolving it from its normal positionthrough an arc of 180", using the twinning axis as the the

axis

of revolution. This will the twinning plane about the point t as a pivot and upon so transpos3 the points-3/2a, 6 turn

points equidistant opposite position. By drawing lines through t and layingoff equal distances beyond that point the new points-3/2A,

and

from

-3/2c

to

it in

an

B

and -3/2C will be obtained. These points lie upon the three in their twin positionand so axes determine their directions. The plotting of the twin axes the top view in follows similar methods. In order to make the construction learer a separate figure.Fig. 1043, is given. The line 0-t is laid off at an angle of 4" 37' to the 6 axis. Upon this 1S Projection

ith* th^"

founlby

meS

6

upward from

which 0"?1a,r"Uud Y

methods

the

the

view clinographic

below. This ^olved 180" to their twin of construction and the directions of axes

are

APPENDIX

657

A

Upon the twin axes found in this way the portion of the crystalin twin positionis drawn in exactly the same if it was in the normal manner as position. (2). To plotthe axes for the calcitetwin shown in Fig. 1044. In this case it was desired to scalenohedron a represent twinned the rhombohedron upon 1043 that the / (0221) and so drawn twinning plane should be vertical and have the positionof 6 (010) of orthorhombic an crystal. The c angle from (001) to / (0221) \ equals 63" 7'. In order to make the face / vertical, the vertical axis be inclined at an must angle of 26" 53', or the angle between the of the two individuals c axes posing comthe twin would be double this or 53" 46'. These relations are in Fig 1045. As indicated shown in Fig. 1046 the position of these are easily axes, c and C in the figure, obtained at inclinations of 26" 53* by use of the graduation of the vertical ellipsethat passes through B and -B. The points X,X' and Y, Y' indicate the intersections with this same eclipseof the two planes in containing the a\, a-2 and a3 axes their respectiveinclined positions, and the angles -BX, BX', and BY -BY' tion being in each case equal to 26" 53'. In order to have the twinning plane occupy a posicrystalit is necessary to revolve the axes so parallelto the 010 plane of an orthorhombic

\

1045

1044

1045

that

one

of the

axis such

a

hexagonal

axes

shall coincide with the

positionof

the

a

hombic axis of the orthor-

The two other hexagonal axes correspondingto the Fig. 1046. therefore lie in a plane which includes -a3, as and the pointsX and X' and have c must positionsthat they will make angles of 60" with -o3, a3. The construction necessary

system,

as

-a3, a3 in

APPENDIX

A

the two chords lettered x-x' Draw is as follows: the ends of these axes the direction of a chord that t o and and parallel a3 that are 60" from -as chords y-y the two through the draw In a similar way X. and -B would that of direction the a chord t o and from parallel a,, -a, that are 60" of second "r sets of chords of these two The intersections X. and B the points through The hexagon of these respective axes. points* and -a* which are the ends that liein a plane perpendicular the of ends "2 and as axes the fll, connects the in shown figure that belong to the axis C are to be found m a similar way. The set of axes to the axis c. 0'854 obtained by multiplying that of calcite c The length of the verticalaxis is to be This is transferred obtained or 2'562 line the length vertical the by three and layingoff on The desired figureof to the line p-p. line p'-p' parallel to the twin axis c by drawing the of inclined axes. sets two these drawn upon the calcite twin is to be to

determine

SrouKh^Snte ^Hhrough Sts wou?d pis determfnTthe

=

DRAWING

CRYSTALS

BY

OF

USE

THE

STEREOGRAPHIC

AND

GNOMONIC

PROJECTIONS

of from the projections of drawing crystals The followingexplanationof the methods from Penfield's description.* their forms has been taken with only minor modifications PROJECTION STEREOGRAPHIC THE OF 1. USE been has chosen; the construction of a a the generalexample method, In explaining graphic Figure 1047A represents a stenoof the triclinicsystem. of axinite, drawing of a crystal M (111), forms a (100), of m (110), (110), axinite, of the p ordinary projection theirs*meridian,locatingthe positionof 010, by the figure, r (111)and s (201). As shown has been chosen at 20" from the horizontal direction SS'. it appears as projectionof an axinite crystal, Figure 1047B is a plan,or an orthographic It derived from the be stereovertical axis. the of direction in the may at looked when The follows: direction of the paralleledges in a simple manner, as graphic projection to a tangent at m, s, r, m', A, is parallel made by the intersections of the faces in the zone be had most easilyby laying a straightedge from either m or m', and this direction may of a 90" triangle, transposingthe direction to B, as shown by the to m' and, by means m "

construction. construction The

next be be called a parallel-perspective view, may may clinographicprojectionlike the usual crystaldrawings from axes, the sphere, represented by on a plane intersecting but an orthographicprojection,made the stereographicprojection, A, along the great circle SES'; the distance EC being 10". of course, have any desired inclination The plane on which a drawing is to be made may, but by making the distance CE equal 10" and taking the firstmeridian at 20" or position, effects of plan and parallelperspectiveare produced as in the from S, almost the same of drawing from axes^ where the eye is raised 9" 28' and the crystal conventional method

explained: It

is not

of C, which a

turned 18" 26'. The easiest way to explainthe construction of C from A is to imagine the sphere,represented by the stereographicprojection,as revolved 80" about an axis joiningS and S', or until the great circleSES' becomes horizontal. After such a revolution,the stereographic projectionshown in A would appear as in D, and the parallel-perspective drawing, E, B was This could then be derived from D in exactlythe same derived from A. manner as is,for example, because the great circle through m, s and r, D, intersects the graduated circle at x, where the pole of a vertical plane in the same would fall,provided one zone were present; hence the intersection of such a surface with the horizontal plane,and, consequently, the direction of the edges of the zone, would be parallel In to a tangent at z: other words, E is a plan of a crystalin the positionrepresentedby the stereographicprojection, D. Although not a difficult matter to transpose the poles of a stereographic projectionso as to derive D from A, it takes both time and skill to do the work with accuracy, and it is not at all necessary to go through the operation. To find the direction of the edges of any zone in C, for example m s r, note firstin A the point x, where the great circlesm s r and SES' cross. During the supposed revolution of 80" about the axis SS', the pole x follows the arc of a small circle and falls finallyat x' (the same positionas x of D) and a line at rightangles to a diameter through x',as shown by the construction,is the desired direction for C. Similarlyfor the zones and MspM', their intersections pr, MrM' with SES' at w, y and z are transposed by the revolution of 80" to w', y' and z'. The transposition of the polesw, x, y and z, A, to w',x',y' and z' easilybe accomplished may *

Am.

J.

Sc.,21, 206, 1906.

APPENDIX

in the

followingways:

A

659

of the Penfield transparent, small-circle (1) By means tractor pro(*ig-68, p. 39) the distances of w, x, y and z from either S or S' be determined may and the corresponding number of degrees counted off on the graduated circle. (2) "

1047

Development

of

a

plan and parallel-perspective figureof axinite,triclinicsystem a stereographicprojection(afterPenfield)

from

pole P of the great circle SES', where P is 90" from E or 80" from C, and of a stereographicscale or protractor (Fig.62, p. 35) : A straightline by means drawn through P and x will so intersect the graduated circle at x',that S'x and S'x' are agined for this is not easilycomprehended from A, but if it is imequal in degrees. The reason that the projectionis revolved 90" about an axis A A', so as to bring S' at the center, the important poles and great circles to be considered will appear as in figure1048, where P and C' are the poles,respectively, of the great circles ES'E' and AS' A', and x is 41 "" It is evident from the symmetry of figure1048 that a plane from S' as in figure1047 A. surface touching at C', P and x will so intersect the great circle AS' A' that the distances S'x and S'x' are equal. Now a plane passing through C", P, x and x',if extended, would but since this circle passes through shown in the figure, intersect the sphere as a small circle, C', which in figure 1047A is the pole of the stereographicprojection(antipodalto C), it tions will be projected in figureA as a straightline,drawn through P and x, since the intersecthe plane of projectionof all planes that pass through the point of vision of the upon projectionwill appear as straightlines. (3) In figure1048 B is located midway between E Find

first the

is located

A

APPENDIX

660

evident from the and W, 40" from C, is its pole: It is now and A' BS'B' is a great circle, intersects the great circle and x so W circle through that a great of the figure symmetry the foregoing relations that the distances S'x and S'x' are equal. Transferring A"A' C, is the pole of the to figure1047A, W, 40" from a great circle drawn great circle SBS', and through W and x falls at x'. However, it is not the great circle through W to draw necessary and x to locate the point x' on the graduated circle: By centering the Penfield transparent great circle protractor,(Fig.67, p. 39) at C, and great turning it so that W and x fallon the same be transposed to x',and the point x may circle, in be found other points,wf, y' and z',would like manner. of transposing x The three foregoingmethods tox',z to z',etc.,are about equally simple,and be it may pointed out that, supplied with transparent stereographic protractors, and having the polesof a crystalplotted in stereoit is only necessary to draw graphic projection, point, the great circle SES' and to locate one either W or P, in order to find the directions responding needed for a parallel-perspective drawing, corto figure1047C. Thus, with only a great circle protractor,the great circle through be traced, and its zone the poles of any may noted and spaced off with dividers from either S or S'; then intersection with SES' is determined, and where and W the great circle through the intersection just found be had of by means it falls on the divided circle noted, when the desired direction may a

as straightedge and 90" triangle, alreadyexplained.

2.

DRAWING

OF

TWIN

CRYSTALS

BY

USE

OF

THE

STEREOGRAPHIC

PROJECTION

In the great majority of cases be most advantageously the drawing of twin crystalscan It is only necessary accomplished by the use of a stereographicprojectionof their forms. first to prepare a projectionshowing the poles of the faces in the normal and twin positions and then follow the methods The preparation of the desired prooutlined above. jection however, need some explanation. An illustrative example is given below may, twins taken from an article by Ford and Tillotson on some of orthoclase.* Bavenno According to the Baveno law of twinning the n (021) face becomes the twinning plane and as the angle c A n 44" 56 1/2' the angle between c' (twin position) becomes c and 89" 53'. For the purposes of drawing it is quite accurate that this enough to assume angle is exactly90" and that accordinglythe r. face of the twin will occupy a positionparallel =

to that of the b face of the normal

individual.

Fig. 1049 shows the forms observed of the crystalsboth in normal and in twin positions, the faces in twin positionbeing indicated by (')after their open circles and a prime mark while the zones in twin positionare in dashed respectiveletters, lines. Starting drawn out with the forms in normal position,the firstface to transp9seis the base c. This form, from the law of the twinning,will be position transposed to c' where it occupies the same as 6 of the normal and it necessarily follows that 6 itselfin being transposed will individual, to b' at the point where the normal c is located. come In turning therefore the crystalto the left from normal to twin position,the fades c and 6 travel along the great circle I through an arc of 90" until they reach their respective twin positions. We have,in other words, revolved the crystal90" to the left about an axis which is parallelto the faces of the zone I. The pole of this axis is located on the stereographicprojectionat 90" from the great circle I and falls on the straightline II, another great circle which intersects zone I at rightangles. This pole P is readilylocated by the stereographic protractor on the great circle II at 90" from c. The volve problem then is to rethe poles of the faces from their normal positionsabout the point P to the left and through an arc of 90" in each case. During the revolution the poles of the n faces remain on the great circle I and as the K) angle n A n the location of their poleswhen in twin positionis identical with that of =

,

Am.

J.

Sc.,26, 149, 1908.

APPENDIX

the normal its normal

have

position and n' fallson top of n. We its twin position, since P remains

to

determined

the twin

positionof

c.

The

661

A

now transposethe great circleII from stationaryduring the revolution and we dashed arc II' gives the twin positionof the can

1049

The twin positionof y must lie on arc II' and can be readilylocated at y', the intersection of arc II' with a small circle about P having the radius P Ay. It is now possibleto construct the arc of the zone III in its transposedpositionIII',for we have two of the points,y' and n' of the latter, already located. By the aid of the Penfield transparent great circle protractor the positionof the arc of the great circle on which these two points On this arc, III',o' and m' must also lie. Their positionsare most lie can be determined. easilydetermined by drawing arcs of small circles about b' with the requiredradii,6 A o 59" 22 1/2' and the points at which they intersect arc III' locate the 63" 8', b A //* At the same time the correspondingpoints on IV may be positionof the poles o' and mf. But one other form remains arc. Jocated,it being noted that IV and III are the same We the prism z. to be transposed, have already 6' and m' located and it is a simple matter with the aid of the great circle protractor to determine the positionof the great circle 6' with the proper radius,b/\z which they lie. Then a small circle about 29" 24', upon determines at once by its intersections with this arc the positionof the polesof the z faces. be pointed out that if it should be desired to make of the methods of the It may use gnonomic projectionfor the drawing of the figuresas described below, the stereographic projectionof the forms may be readilytransformed into a gnomonic projectionby doubling the angular distance from the center of the projectionto each pole by the use of the stereo-

great circle II.

=

=

=

graphic protractor, Fig. 62, p. 3.

35.

USE

OF

THE

GNOMONIC

PROJECTION

the method of drawing a simple combination of barite has been chosen. an illustration, in figure1050 are c (001),m The forms shown (110),o (Oil) and d (102). The location of the poles in the gnomonic projectionis shown in A, where, as in figure1047A. the first As

APPENDIX

662 meridian

is taken

locations of S In any

plan

such

A

The SS poles of the prism m and the horizontal direction at 20" from the fall projection at infinity. in 1047A) gnomonic and S' (compare figure made by the meeting of two faces figure1050B, the direction of an edge as .

1050 A

at oo tfatoo

y

at oo

is at rightangles to a line joiningthe poles of the faces,shown and c. at 90" to the line joining m"

in

figures A and

B

by

the

rection di-

is an orthographic projection (compare figures plane passing through S and S', and intersecting the sphere on which gnomonic projection is based as a great circle passing through E, figure 1050A, This great circle is called by Goldand drawn parallelto SS', the distance cE being 10": and d, m"' and c, and the Leitlinie. m To find such intersections as between schmidt figureC, note, as in figure 1047A, where the great circles through the poles of the faces intersect the Leitlinie;thus, the one through m'" and c at x, and that through m and d Next t o d and m" at infinity) since at y. imagine the points m m are m", parallel (through latter pomts, however, are located x and y transposed as in figure1047 A to x' and y',which at infinity:This transpositionis done by locating first the so-called Winkelpunkt, W, of Goldschmidt, 40" from c in figure1050A, and as in figure1047A, 90" from a point B, which is an equal number of degrees from E and A' (compare figure1048). Of the three methods be easilyapplied in the gnomgiven above for transposing x and y to x' and y',the third may onic projection. Great circles,or straight lines,through W and x and W and y, figure ing would is accomplished by drawx' and y',which determine 1050A, if continued to infinity, and lines parallelto Wx It is not necessary, Wy through the center. however, to draw the lines Wx and Wy, nor the parallellines through the center; all that is needed to find the directions of the edges m'" A c and m A d is to lay a straightedge from W to x, respectively W to y, and with a 90" triangletranspose the directions in to C, as indicated the drawings. The the interrelations worked for principlesare exactly the same as put of figures1047A and C. As in the case of the stereographic projection,it is evident that, of the given poles a to crystalplotted in the gnomonic projection, it would be necessary draw only one and to locate one line,the Leitlinie, point, the Winkelpunkt, W, in order to find all possible directions for a plan and parallel-perspectiveviews, corresponding to figures1050B and C. The

1047 A

view, 1050C, parallel-perspective

and the

C)

drawn

on

a

B

APPENDIX

664

Dietrichite,(Zn,Fe,Mn)SO4.Al2(SO4)H3.222O H2Al2(Si03)4. PYROPHYLLITE, Alunogen, A12(SO4)3.18H2O. Allophane,Al2Si06.5H20. Cyanotrichite,4CuO.Al2O3.SO3.8H2O. Melite,2(Al,Fe)203.S102.8H20. Knoxvillite,Hydrous, Fe,Al,Cr,sulphate. 2Al2O3.SiO2.9H2O. Collyrite, Cyprusite, 7Fe2O3.A12O3.10SO3. 14H2O. 8Al2O3.3SiO2.30H2O. Schrotterite, Aluminite, A12O3.SO3.9H2O. Hamlinite, Al,Sr,phosphate Paraluminite,2A12O3.SO3.10H2O. Plumbogummite, Pb,Al, phosphate. Felsobanyite.2A12O3.SO3.10H2O. Al,Ce, phosphate. Florencite, Voltaite,3(K2,Fe)O.2(Al,Fe)2O3.6SO3.9H2O. BaO.2Al2O3.P2O6.5H2O. Georceixite, ALUNITE, K2A16(OH)12.(SO4)4. 2CaO.4 A12O3.2P2O5.10H2O. Crandallite, K2O.3A12O3.4SO3.9H2O. Lowigite, (Sr,Ca)O.2Al2O3.P2O6.SO3.5H2O. Harttite, Almeriite,Na2SO4.Al2(SO4)3.5Al(OH)3.H2O. Durangite, Na(AlF)AsO4. Ettringite,6CaO.Al2O3.3SO3.33H2O. Amblygonite,Li(AlF)PO4 Zincaluminite,2ZnSO4.4Zn(OH)2.6Al(OH)3. Fremontite, (Na,Li)Al(OH,F)PO4. 5H2O. Lazulite,2AlPO4.(Fe,Mg)(OH)2. Mellite,A12C12O12.18H2O. Tavistockite,Ca3P2O3.2Al(OH)2. Ca3Al(PO4)3.Al(OH)3. Cirrolite, 2(Al,Mn)AsO4.5Mn(OH)2. Synadelphite, Hematolite, (Al,Mn)AsO4.4Mn(OH)2. Barrandite,(Al,Fe)PO4.2H2O. A1PO4.2H2O. Variscite, Lucinite,A1PO4.2H2O. A1PO4.2"H2O. Callainite, A1PO4.3H2O. Zepharovichite,

Palmerite,HK2A12(PO4)3.7H2O. Hydrous, Al,Pb,Cu, phosphate. Rosier6site, WAVELLITE, 4A1PO4.2A1(OH)3.9H2O. AlPO4.Al(OH)3.2iH2O. Fischerite, Peganite,A1PO4.A1(OH)3.HH2O. TURQUOIS,

ANTIMONY NOTE

:

The

"

antimonates

are

not

cluded in-

in this list.

Allemontite,SbAs3. NATIVE ANTIMONY, Sb. Stibnite,Sb2S3. Kermesite, Sb2S2O. Senarmontite, Valentinite,Sb2O3. Cervantite,Sb2O3.Sb2O6. H2Sb2O5. Stibiconite, (SbO)2(Ta,Nb)2O6. Stibiotantalite,

CuO.3Al2O3.2P2O5.9H2O.

Wardite, 2A12O3.P2O6.4H2O. 4A1PO4.6A1(OH)3. Sphserite, (OH)". Liskeardite,(Al,Fe)AsO4.2(Al,Fe) 5H2O.

ARSENIC NOTE in

:

"

The

arsenates

are

not

included

this Ust.

NATIVE ARSENIC, As. Evansite,2A1PO4.4A1(OH)3.12H2O. SbAs3. Allemontite, 3 A12O3.2P2O5.10H2O. Coeruleolactite, REALGAR, AsS. Angelite,2Al2O3.P2O6.3H2q. ORPIMENT, As2S3. Attacolite 1 Hydrous Berlinite,Trolleite, FeAsS. Arsenopyrite, Minasite,Vashegyite jAlphosphates As2O3. Soumansite,Hydrous, Al,Na,fluo-phosphate. Arsenolite,Claudetite, Childrenite,2AlPO4.2Fe(OH)3.2H2O. BARIUM Eosphorite,2AlPO4.2(Mn,Fe) (OH)3.2H2O. Witherite,BaCO3. Egueiite,Hydrous, Fe,Al,Ca,phosphate. Bromlite, (Ba,Ca)CO3. Liroconite, Cu6Al(AsO4)5.3CuAl(OH)6. '

20H2O.

Henwoodite,Al,Cu, hydrous phosphate. Ceruleite, CuO.2Al2O3.As2O5.8H2O. Kehoite,Hydrous, Al,Zn,phosphate. Goyazite,Ca3Al10 P2O23.9H2O. Rosch6rite, (Mn,Fe,Ca)2Al(OH) (PO4)2.2H2O. Svanbergite,Hydrous Al, Ca, phosphate and sulphate. A1BO3. Teremejevite, Rhodizite, A1,K, borate. Millosevichite, (Fe,Al)2(SO4)3. Spangolite, Cu6AlClSO10.9H2O. Alumian,A12O3.2SO3. KaUnite,KA1(SO4)2.12H2O. Tschermigite, (NH4)A1(SO4)2.12H2O. Mendozite,NaAl(SO4)2.12H2O. Pickeringite, MgSO4.Al2(SO4)3.22H2O. Halotrichite, FeSO4.Al2(SO4)3.24H2O. Apjohnite, MnSO4.Al2(S04)3.24H2O.

BaCO3.CaCO3. Barytocalcite, Hyalophane, (K2,Ba)Al2(SiO3)4.

Celsian,BaAl2Si2O8. Cappelenite,Y,Ba, boro-silicate. Hyalotekite, (Pb,Ba,Ca)B2(SiO3)12. Barylite,Ba4Al4Si7O24. Taramellite,Ba^e'' Fe4'" SiidOM. Brewsterite,H4(Sr,Ba,Ca)Al2(SiO3)6.3H2O. Wellsite,(Ba,Ca,K2)Al2Si3Oi0.3H2O. Harmotone, (K2,Ba)Al2Si5Oi4.5H2O. Edingtonite,BaAl2Si3Oi0.3H2O. Benitoite,BaTiSi3O9. Leucosphenite, Na4Ba(TiO)2(Si2O5)5. Georceixite,BaO.2Al2O3.P2O5.5H2O. Ferrazite,3(Ba,Pb)O.2P2O5.8H2O. Volborthite,Cu,Ba,Ca, vanadate. Uranocircite,Ba(UO2)2P2O8.8H2O. Nitrobarite,Ba(NO3)2. Barite,BaS04.

APPENDIX

B

665

BERYLLIUM

CESIUM

Chrysoberyl,BeAl2O4. Eudidymite, Epididymite, HNaBeS.\3O8. Beryl, Be3Al2(SiO3)6.

Pollucite, 2Cs2O.2Al2O3.9SiO2.H2O.

Rhodizite,Al,K,Cs,borate. CALCIUM

Helvite,(Be,Mn,Fe)7Si3Oi2S. Danalite, (Be,Fe,Zn,Mn)7Si3Oi2S. Phenacite, Be2SiO4. Trimerite,(Mn,Ca)2SiO4.Be2SiO4. Euclase, HBeAlSiO5. Gadolinite,Be2FeY2Si2O10. Bertrandite,H2Be4Si2O9. Beryllonite,NaBePO4. Herderite,Ca[Be(F,OH)]PO4. Hambergite, Be2(OH)BO3. BISMUTH NATIVE BISMUTH, Bi. BlSMUTHINITE, Bl2S3. Guanajuatite, Bi2Se3. Tetradymite, Bi2(Te,S)3. Grunlingite,Bi4TeS3. Joseite,Wehrlite, bismuth tellurides. Daubreete, Bi, oxychloride. Bismite, Bi2O3. Bi2(CO3)3.2Bi2O3. Bismutosparite, Bismutite,Bi2O3.CO2.H2q. Bi4Si3Oi2. Eulytite,Agricolite, Pucherite,BiVO4.

H2Bi3AsO8. Atelestite,

Walpurgite, Bi10(UO2)3(OH)24(AsO4)4. Rhagite, 2BiAsO4.3Bi(OH)3. Arseno-bismite,hydrous Bi arsenate. Mixite,Hydrous Cu, Bi, arsenate. Uranosphaerite, (BiO)2U2O7.3H2O. Montanite, Bi2p3.Te03.2H2O. Bi2O3.MoO3. Koechlinite, BORON NOTE : this list.

"

The

borates

B(OH)3. Sassolite, Cappelenite, Y,Ba,

are

not

included in

boro-silicate.

Hy alotekite,(Pb Ba,Ca) B2 (SiO3)". DANBURITE, CaB2(SiO4)2. Datolite,HCaBSiO5. .

Homilite,Ca2FeB2Si2Oi0. Axinite,Ca,Al, boro-silicate. Tourmaline, complex boro-silicate.

Dumortierite,8AL"O3.B,O3.6SiO2.H2O. 10(Ca,Mg)O.5Al2O3.B2O3.6SiO2. Serendibite, Manandonite, H44Li4Ali4B4.Si6O53. Bakerite,Hydrous Ca, boro-silicate. NaB(SiO3)2.H2O. Searlesite, Luneburgite,3MgO.B2O3.P2O5.8H2O. CADMIUM

Greenockite,CdS. Cadmiumoxide, CdO. Otavite,Cd carbonate.

Oldhamite, CaS. CaF2. Fluorite, CaCl2. Hydrophilite, Yttrofluorite, (Ca3,Y2)F6.

Nocerite,2(Ca,Mg)F2.(Ca.Mg)O.

Tachhydrite,CaCl2.2MgCl2.12H2O. Prosopite, CaF2.2Al(F.OH)3. Pachnolite, Thomsenolite, NaF.CaF2.AlF3. H2O. Gearksutite. CaF2.Al(F,OH)3.H2O.

Creedite, 2CaF2.2Al(F,OH)3.CaSO4.2H2O. Yttrocerite, (Y,Er,Ce)F3.5CaF2.H2O. UhUgite,Ca(Ti,Zr)O5.Al(Ti,Al)O5. Calcite,CaCO3. Dolomite, CaCO3.MgCO3.

Ankerite,CaCO3.(Mg,Fe,Mn)CO3. Aragonite,CaCO3.

Bromlite,(Ba,Ca)CO3. Barytocalcite, BaCO3.CaCO3 Parisite,[(Ce,La,Di)F]2Ca(CO3)2. Pirssonite, CaCO3.Na2CO3.2H2O. Gay-Lussite,CaCO3.Na2CO3.5H2O. Gajite,basic,hydrous,Ca, Mg, carbonate.

Uranothallite, 2CaCO3.U(CO3)2.10H2O. Liebigite, Hydrous Ca,U, carbonate. Voglite,Hydrous U,Ca,Cu, carbonate. Milarite, HKCa2Al2(Si2O5)6. Rivaite,(Ca,Na2)Si2O6. Mixtures A^desinT

of NaAlSi308

and

CaAl2Si2O8.

Labradorite

Anorthite,CaAl2Si2O8. Anemousite, Na2O.2CaO.3Al2O3.9SiO2. Pyroxene, Ca,Mg, etc.,silicate. Wollastonite,CaSiO3. PECTOLITE, HNaCa2(SiO3)3.

Schizoh'te, HNa(Ca,Mn)2(SiO3)3. near Rosenbuschite, pectolitewith Zr. Wohlerite,Zr-silicate and niobate of Ca,Na. Lavenite,Zr-silicate of Mn,Ca. Babingtonite, (Ca,Fe,Mn)SiO3 with Fe2(SiO3)3.

Hiortdahlite, (Na2,Ca)(Si,Zr)O3. Amphibole, Ca, Mg, etc.,silicate. Arfvedsonite,Na,Ca,Fe, silicate. Leucophanite i fluo-sihcate. Meliphanite I***","" AT

T"

n

a

-i-

Custerite, Ca2(OH,F)SiO3. Didymolite,2CaO.3Al2O3.9SiO2. Ganomalite,Pb4(PbOH)2Ca4(Si2O7)3. Nasonite,Pb4(PbCl)2Ca4(Si2O7)3. Margarosanite,Pb(Ca,Mn)2(SiO3)3. Ca2ZnSi2O7. Hardystonite, Rocblingite, 5(H2CaSiO4).2(CaPbSO4). Haiiynite, Na2Ca(NaSO4.Al)Al2(SiO4)3. Grossularite,Ca3Al2(SiO4)3. Andradite, Ca3Fe2(SiO4)3.

566

APPENDIX

Ca3Cr2(SiO4)3. Schorlomite,Ca3(Fe,Ti2)[(Si,Ti)O"]. MonticeUite,CaMgSiO4. UVAROVITE,

B

Thomsonite, (Na2,Ca)Al2Si2O8.2"H2O. Hydrpthomsonite; (H2,Na2,Ca)Ali"Si2O8. 5H2O.

Arduinite,Ca,Na, zeolite. Echellite,(Ca,Na2)O.2Al2O3.3SiO2.4H2O. Trimerite,(Mn,Ca)2SiO4.Be2SiO4. Epidesmine, (Na2,Ca)Al2Si6Oi6.6H2O. of Mixtures GROUP, SCAPOLITE CaAl2Si7Oi8.7H2O. Stellerite, and Na4Al3Si9O24Cl. Ca4Al6Si6O25 H2CaK2Na2Al2Si6Oi7.5H2O. Erionite, ( Ca,Na2)3Al2(SiO4)3. Sarcolite, Bavenite, Ca3Al2(SiO3)6.H2O. Na2(Ca,Mg)n (Al,Fe)4(SiO4)9. Melilite, Bityite,Hydrous, Ca,Al, silicate. Cebollite, Margarite, H2CaAl4Si2Oi2. Gehlenite, Seybertite,H3(Mg,Ca)5Al5Si2Oi8. Vesuvianite,Ca6[Al(OH,F)]Al2(Si04)6. Xanthophyllite, H8(Mg,Ca)i4Al16Si5O62. CaB2(SiO4)2. DANBURITE, Griffithite,4(Mg,Fe,Ca)O(Al,Fe)2O3.5SiO2. 2(K,Na)2O.8CaO.5(Al,Fe,Ce)2O3. Guarinite, Glaucochroite,CaMnSiO4.

7H2O.

10SiO2. Datolite,HCaBSiO5. Homilite,CazFeB^iAo.

Cenosite,H4Ca2(Y,Er)2CSi4Oi7.

PlazoUte,3CaO.Al2O3.2(SiO2,CO2).2H2O.

Thaumasite, CaSiO3.CaCO3.CaSO4. 15H2O. ZOISITE,Ca2(AlOH)Al2(SiO4)3. Epidote, Ca2[(Al,Fe)OH](Al,Fe)2(SiO4)3. Spurrite,2Ca2SiO4.CaCO3. Uranophane, CaO.2UO3.2SiO2.6H2O. Piedmontite,Ca2(AlOH) (Al,Mn)2(SiO4)3. Bakerite,Hydrous Ca boro-silicate. (Al,Ce,Fe)2(SiO4)3. Allanite,(Ca,Fe)2(AlOH) boro-silicate. TINANITE, CaTiSiO5. Ca,Al, AXINITE, Molengraafite, Ca,Na, titano-silicate. PREHNITE, HzCa^SiO^. Keilhauite, Ca,Al,Fe,Y,titano-silicate. Harstigite,Mn,Ca, silicate Joaquinite, Ca,Fe, titano-silicate. Cuspidine,Ca2Si(O,F2)4. CaTiO3. Perovskite, ILVAITE, CaFe3(FeOH)(SiO4)2. Dysanalyte,Ca,Fe, titano-niobate. Clinohedrite,H2CaZnSiO6. Pyrochlore,Ca,Ce, niobate. Stokesite,H4CaSnSi3Oii. Lawsonite, Hibschite,H4CaAl2Si2Oi0. Koppite,Ca,Ce,niobate Beckelite,Ca3(Ce,La,Di)4Si3O15. RNb2O6F2.RSiO3. Angaralite,2(Ca,Mg)0.5(Al.Fe)2O3.6SiO2.Chalcolamprite, Serendibite,10(Ca,Mg)O.5Al2O3.B2O3.6SiO2. Microlite,Ca2Ta2O7. Berzeliite, (Ca,Mg,Mn,Na1)8A8aO8. H2Ca4Mg3Si2O7Fi0. Silicomagnesiofluorite, Gro thine,Ca,Al, silicate. Graftonite, (Fe,Mn,Ca)3P2O8. Apatite,Ca4(CaF)(PO4)3. Aloisite, Fe,Ca,Mg,Na, silicate. Fermorite,(Ca,Sr)4[Ca(OH,F)][(P,As)O4]3 Inesite,H2(Mn,Ca)6Si6Oi9.3H2O. Ca2SiO4.H2O. Hillebrandite, Wilkeite,3Ca3(PO4)2.CaCO3.3Ca3[(SiO4) (SO4)].CaO. Crestmoreite,4H2CaSiO4.3H2O. ,

-2CaSiO5.H2O. Svabite,Ca arsenate. Riversideite, Spodiosite, (CaF)CaPO4. Lotrite,3(Ca,Mg)0.2(Al,Fe)203.4Si02.2H20

Okenite, H2CaSi2O5.H2O. Gyre-lite, H2Ca2Si3O9.H2O. APOPHYLLITE, H7KCa4(SiO3)8.4"H2O. Ptilolite.(Ca,K2,Na,)Al2Si10O24.5H2O.

AdeHte (MgOH)CaAsO4. Tilasite (MgF)CaAsO4.

Herderite,Ca[Be(F,OH)]PO4. Jezekite, Na4CaAl(AlO) (F,OH)4(PO4)2. Crandallite, 2CaO.4Al2O3.2P2O5.10H20. Lacroixite, Na4(Ca,Mn)4Al3(F,OH)4P3Oi6.

Mordemte, (Ca,K2,Na2)Al2Sii0O24.20H2O. HEULANDITE, H4CaAl2(SiO3)6.3H2O. Brewsterite, H4(Sr,Ba,Ca)Al2(SiO3)6.3H2O. 2H2O. H4CaAl2 (SiO3)6.3H2O. Epistilbite, Calciovolborthite, (Cu,Ca) 3V2O8.(Cu,Ca) Wellsite,(Ba,Ca,K2)Al2Si3O10.3H2O. (OH)2. Phillipsite, (K2,Ca)Al2Si4Oi2.4iH2O. Tavistockite, Ca3P2O8.2Al(OH)2. StUbite,(Na2,Ca)Al2Si6Oi6.6H2O. Cirrolite, Ca3Al(PO4)3.Al(OH)3. Flokite, H8(Ca,Na2)Al2Si9O26.2H2O. Ca3Fe (AsO4)3.3Fe(OH) 3. Arseniosiderite, Gismondite,CaAl2Si2O8.4H2O. Retzian,Y,Mn,Ca, arsenate. Laumontite,H4CaAl2Si4Oi4.2H2O. Arseniopleite, (Mn, Ca) 9 (Mn, Fe)2(OH) 6 Laubanite,Ca2Al2Si5Oi5.6H2O. (AsO4)6. CHABAZITE,(Ca,Na2)Al2Si4Oi2.6H2O. Ca3P2O8.H2O. Collophanite, Gmelinite, (Na2,Ca)Al2Si4Oi2.6H2O. Pyrophosphorite, Mg2P2O7.4(Ca3P2O8. Levynite,CaAl2Si3O10.5H2O. Ca2P207). Faujasite, H4Na2CaAl4Si,0O38. 18H2O. Roselite, (Ca,Co,Mg)3As2O8.2H2O. Scolecite, Ca(AlOH)3(SiO3)3.2HnO. Brandite,Ca2MnAs2O8.2H2O. MS5%" N^^SiaOio^HaO +2[CaAl2Si3O10 Fairfieldite, Ca2MnP2O8.2H2O. 3H2OJ. Messelite, (Ca,Fe)3P2O8.2iH2O. Gonnardite, (Ca,Na2)2Al2Si6O15.5^H2O. Anapaite,(Ca,Fe)3P2O8.4H2O.

APPENDIX

(Ca,Mg)As2O8.6H2O. Picropharmacolite, Churchite, Hydrous Ca,Ce" phosphate. Fernandinite,CaO.V2O4.5V2O5.14H2O. Pascoite,2CaO.3V2O5.llH2O. Pintadoite,2CaO.V2O5.9H2O. Pharmacolite, HCaAsO4.2H2O. Haidingerite,HCaAsO4.H2O. Wapplerite,HCaAsO4.3"H2O. Brushite,HCaPO4.2H2O. Martinite,H2Ca5(PO4)44H2O. Hewettite Metahewettite

\pao

W O QTT O }"-aO.3V2O5.9H2O.

Ca3P2O8.Ca(OH)2.4H2O. Isoclasite, Conichalcite,(Cu,Ca)3As2O8.(Cu,Ca) (OH)2. ^H20. Volborthite,Cu,Ba,Ca, vanadate. Mazapilite,Ca3Fe2(AsO4)4.2FeO(OH).5H2O. Yukonite, (Ca3,Fe2'")(AsO4)2.2Fe(OH)3. -

667

B

Bastnasite,(CeF)CO3. Ancylite,4Ce(OH)CO3.3SrCO3.3H2O. Ambatoarinite, Rare earths,Sr,carbonate. Lanthanite, La2(CO3)3.9H2O. Melanocerite

Ca,Ce,Y, fluo-sihcates. Caryocerite Steenstrupine Tritomite,Th,Ce,Y,Ca, fluo-silicate. Mackintoshite,U,Th,Ce, sihcate. Allanite,Ca,Fe,Ce,Al, silicate. Cerite,Ce, etc.,silicate. Beckelite,Ca3(Ce,La,Di)4Si3O15. Ce, etc.,Al,Mn,Ca, silicate. Hellandite, Bazzite,Sc.,etc.,silicate. Britholite, Ce, etc.,silicate and phosphate. Erikite,Ce, etc.,sihcate and phosphate. Ce,Fe, titano-silicate. Tscheffkinite, Johnstrupite ]

|Ce,etc.,titano-silicates.

Mosandrite

5H2O.

Calcioferrite,Ca3Fe2(PO4)4.Fe(OH)3.8H2O.Rinkite Borickite,Ca3Fe2(PO4)4.12Fe(OH)3.6H2O. Egueiite,Hydrous Fe,Al,Ca, phosphate. Goyazite, Ca3Ali0P2O23.9H2O. Roscherite,(Mn,Fe,Ca)2Al(OH) (PO4)2. 2H2O.

Ca(UO2)2P2O,8H2O. Uranospinite,Ca(UO2)2As2O8.8H2O.

Tyuyamunite, CaO.2UO3.V2O5.4H2O.

Knopite, Ca,Ce, titanate. Pyrochlore,Ca,Ce, niobate.

Chalcplamprite, Koppite, Ca,Ce, niobate. Fergusonite,Y,Er,Ce,U,niobate. Sipylite,Er,Ce, niobate. Yttrotantalite, Fe,Ca,Y,Er,Ce,tantalate. Samarskite, Fe,Ca,U,Ce,Y,niobate. Aeschynite,Ce, niobate-titanate. Polymignite, Ce, Fe, Ca, niobate-titanate.

Romeite, CaSb2O4. Lewisite,5CaO.2TiO2.3Sb2O5. Mauzeliite,Pb,Ca, titano-antimonate. Podolite,3Ca3(PO4)2.CaCO3. Svanbergite,Hydrous Al,Ca,phosphate and sulphate. Ca(NO3)2.rcH2O. Nitrocalcite, Lautarite,Ca(IO3)2. Dietzeite,Ca iodo-chroniate. Nordenskioldine,CaSn(BO3)2. Howlite, H5Ca2B5SiOi4. COLEMANITE, Ca2B6On.5H2O. Inyoite,2CaO.3B2O3.13H2O. Meyerhofferite,2CaO.3B2O3.7H2O. Ulexite,NaCaB5O9.8H2O. Bechilite,CaB4O7.4H2O. Hydroboracite, CaMgB6On.6H2O. GLAUBERITE, Na2SO4.CaSO4. Anhydrite \r"oQr"

Daubreelite,FeS.Cr2S3. Chromite, FeO.Cr2O3. 2MgCO3.5Mg(OH)2.2Cr(OH)3. Stichtite, Uvarovite, Ca3Cr2(SiO4)3. Furnacite,Pb,Cu, chrom-arsenate. Dietzite,Ca iodo-chromate. CROCOITE, PbCrO4. 3PbO.2CrO3. Phcenicochroite,

Bassanite

2(Pb,Cu)CrO4.(Pb,Cu)3P2O8. Vauquelinite,,

|CaSO^

Gypsum, CaSO4.2H2O. Syngenite, CaSO4.K2SO4.H2O. Polyhahte, 2CaSO4.MgSO4.K2SO4.2H2O. Ettringite,6CaO.Al2O3.3SO3.33H2O. Uranopilite,CaU8S2O3i.25H2O. SCHEELITE, CaWO4. Powellite,Ca(Mo,W)O4. Whewellite, CaC2O4.H2O. CERIUM

EARTHS

Tysonite, (Ce,La,Di)F3. Fluocerite,(Ce,La,Di)2OF4. Yttrocerite,(Y,Er,Ce)F3.5CaF2.H2Q. Parisite,[(Ce,La,Di)F]2.CaCO3.

Euxenite

Y,Ce,U, niobate-

Polycrase Blomstrandine-Priorite

titanates.

MONAZITE, (Ce,La,Di)P'O4. Florencite,Ce,Al, phosphate. Rhabdophanite, Hydrous Ce,Y, phosphate. Churchite, Hydrous Ce,Ca, phosphate. CHROMIUM

Pb, arseno-chromate. Bellite, Knoxvillite,Hydrous Fe,Al,Cr,sulphate. Redingtonite,Hydrous Cr sulphate. COBALT

Sychnodymite, (Co,Cu)4S5. ,

Co3S4.

CuCo2S4. Carrollite, Badenite, (Co,Ni,Fe)2(As,Bi)3. (Co,Ni,Fe)S2. Cobaltnickelpyrite, SMALTITE, CoAs2. COBALTITE, CoAsS. Willyamite, CoS2.NiS2.CoSb2.NiSb2. Villamaninite,Cu,Ni,Co,Fe,sulphide.

APPENDIX

668 Skutterudite,CoAs3. CoAs2. Safflorite,

Glaucodot, (Co,Fe)AsS.

iwocuKCj

v"""jv"")"

"

"

0/5

*

Co3As2O8.8H2O. Erythrite, Forbesite,H2(Ni,Co)2As2O8.8H2O. CoSO4.7H2O. Bieberite, COPPER Native

Copper, Cu.

Horsfordite, CueSb. Domeykite, Cu3As. Mohawkite, Cu3As. CuoAs. Algodonite, Whitneyite, Cu^As.

B

Cumengite, 4PbCl2.4CuO.5H2O. Hydrous Cu chloride. Tallingite, Cuprite,Cu2O. Tenorite,Paramelaconite, CuO. Crednerite,3CuO.2Zn2O3. Rosasite,2CuO.3CuCO3.5ZnCO3? Malachite, CuCO3.Cu(OH)2. Azurite,2CuCO3.Cu(OH)2.

Aurichalcite,2(Zn,Cu)CO3.3(Zn,Cu)(OH)". Voglite,Hydrous U,Ca,Cu, carbonate. Dioptase, H2CuSiO4. Plancheite,H4Cu7(Cu.OH)8(SiO3)12. CHRYSOCOLLA,

CuSiO3.2H2O.

Shattuckite,2CuSiO3.HiiO. Bisbeeite,CuSiO3.H2O Olivenite,Cu2(OH)AsO4. Libethenite,Cu2(OH)PO4. (Cu,Ca)3V2O8. Calciovolborthite,

'

Cu4AgS. Cocinerite, Rickardite,Cu4Te3. Cu2Se. Berzelianite, Eucairite,Cu2Se.Ag2Se. Zorgite,Pb,Cu, selenide. Crookesite,Cu,Tl, selenide. Umangite, CuSe.Cu2Se. Chalcocite,Cu2S.

Stromeyrite,(Ag,Cu)2S. Chalmersite,Cu2S.Fe4S6. COVELLITE, CuS.

Sychnodymite,(Co,Cu)4S6. Boniite, Cu6FeS4. CarroUite,CuS.Co2S3. CuFeS2. Chalcopyrite,

Cu,Ni,Co,Fe, sulphide. Villamaninite, Eichbergite,(Cu;Fe)2S.3(Bi,Sb)2S3. 5CuFeS2.2Sb2S3.7Bi2S3. Histrixite, 3Cu2S.4Bi2S3. Cuprobismutite, Cu2S.Bi2S3. Emplectite, Cu2S.Sb2S3. Chalcostibite, Hutchinsonite,(Tl,Ag,Cu)2S.As2S3+ PbS. As2S3? 3Cu2S.Bi2S3. Klaprotholite,

Bournonite,3(Pb,Cu2)S.Sb2S3. 3(Pb,Cu2)S.As2S3. Seligmannite, Aikinite,2PbS.Cu2S.Bi2S3. 3Cu2S.Bi2S3. Wittichenite, 3(Cu2,Ag2,Fe)S.Sb2S3. Stylotypite, 7[Pb,(Ag,Cu)2]S.2As2S3. Lengenbachite, Falkenhaynite,3Cu2S.Sb2S3. Tetrahedrite,4Cu2S.Sb2S3. TENNANTITE, 4Cu2S.As2S3. 5Cu2S. (Sb,As,Bi)2(S.Te)8. Goldfieldite, Enargite,3Cu2S.As2S5. Famatinite,3Cu2S.Sb2S5. Sulvanite,3Cu2S.V2S6. Epigenite,4Cu2S.3FeS.As2S6. STANNITE, Cu2S.FeS.SnS2.

Nantokite,CuCl. Marshite,Cul. Miersite,4AgI.CuI. ATACAMITE, CuCl2.3Cu(OH)2. PbCl2.CuO.H2O. Percylite, Boleite. 9PbCk8CuO.3AgC1.9H2O. 5PbCl2.4CuO.6H2O. Pseudoboleite,

(Cu,Ca)(OH),. Turanite, 5CuO.V2O5.2H2O.

Furncite,Pb,Cu, chrom-arsenate. Tsumebite, Pb,Cu, phosphate. CUnoclasite,Cu3As2O8.3Cu(OH)2. Erinite,Cu3As2O8.2Cu(OH)2. Dihydrite, Cu3P2O8.2Cu(OH)2. Pseudomalachite, Cu3P2O8.3Cu (OH)2. Cu3As2O8.5H2O. Trichalcite, Hydrous Al,Pb,Cu, phosphate. Rosieresite, Eucroite,Cu3As2O8.Cu(OH)2.6H2O. Conichalcite,(Cu,Ca)3As2O8.(Cu,Ca)(OH)2. (Pb,Cu) (OH)2. Bayldonite, (Pb,Cu)3As2O8. Tagihte, Cu3P2O8.Cu(OH)2.2H2O. Leucochalcite,Cu3As2O8.Cu(OH)2.2H2O. Barthite,3ZnO.CuO.3As2O5.2H2O. Volborthite,Hydrous, Cu,Ba,Ca, vanadate. Cornwallite,Cu3As2O8.2Cu(OH)2.H2O. Tyrolite,Cu3As2O8.2Cu(OH)2.7H2O. Chalcophyllite,7CuO. As2O5.14H2O. Cu,Zn, phospho-arVeszelyite, Hydrous senate.

Turquois, CuO.3Al2O3.2P2O5.9H2O. Liroconite,Cu6Al(AsO4)5.3CuAl(OH)5.20H20 Chenevixite,Cu2(FeO)2As2O8.3H2O. Henwoodite, Al,Cu, hydrous phosphate. Ceruleite,CuO.2Al2O3.As2O6.8H2O. CuO.2Fe2O3.2P2O5.8H2O. Chalcosiderite, Torbernite,Cu(UO2)2P2O8.8H2O. Zeunerite,Cu(UO2)2As2O8.8H2O. Mixite, Hydrous Cu,Bi, arsenate. Trippkeite,Cu, arsenite. 3NiO.6CuO.SO3.2As2O5.7H2O. Lindackerite,

Gerhardtite,Cu(NO3)2.3Cu(OH)2.

Hydrocyanite,CuSO4. Vauquehnite,2(Pb,Cu)CrO4. (Pb,Cu)3P2O8. CuSO4.2CuCl2. 19Cu(OH)2.H2O. Connellite, Spangolite,Cu6AlClSOi0.9H2O. BROCHANTITE, CuSO4.3Cu(OH)2. Dolerophanite, Cu2SO5. 2(Pb,Cu)O.SO3.H2O. Caledonite,

APPENDIX

Linarite,(Pb,Cu)SO4. (Pb,Cu) (OH)* Anthrite,CuSO4.2Cu(OH)2. Pisanite,(Fe,Cu)SO4.7H2O. Boothite, CuSO4.7H2O. Cupromagnesite, (Cu,Mg)SO4.7H2O. CHALCANTHITE, CuSO4.5H2O. Krohnkite, CuSO4.Na2SO4.2H2O.

669

B

Vredenburgite, 3Mn3O4.2Fe2O3.

Hercynite, FeO.Al2O3. Magnetite, FeO.Fe2O3. (Fe.Zn.Mn)O. FRANKLINITE, (Fe,Mn),Os. Magnesioferrite, MgO.Fe2O3. Jacobsite,(Mn,Mg)O.(Fe,Mn)2Oa. Natrochalcite,Cu4(OH)2(SO4)2.Na2SO4.2H2OChromite, FeO.Cr2O3 Phillipite, CuSO4.Fe2(SO4)3.nH2O. Pseudobrookite, Fe4(TiO4)3. Langite, CuSO4.3Cu(OH)2.H2O. Bixbyite,FeO.MnO2. Herrengrundite,2(CuOH)2SO4.Cu(OH)2. Gothite,Fe2O3.H2O. Lepidocrocite,Fe2O3.H2O. Vernadskite,3CuSO4.Cu(OH)2.4H2O. Kamarezite, Hydrous basic Cu sulphate. Limonite, 2Fe2O3.3H2O. Cyanotrichite,4CuO.Al?O3.SO3.8H2O. Turgite,2Fe2O3.H2O. Serpierite, Hydrous basic Cu,Zn, sulphate. Hydrogothite, 3Fe2O3.4H2O. Xanthosiderite,Fe2O3.2H2O. Beaverite,CuO.PbO.Fe2O3.2SO3.4H2O. Esmeraldaite, Fe2O3.4H2O. Johannite, Hydrous Cu,U, sulphate. Gilpinite,(Cu,Fe,Na2)O.UO3.SO3.4H2O. Pyroaurite,Fe(OH)3.3Mg(OH)2.3H2O. Chalcomenite, CuSeO3.2H2O. Skemmatite, 3MnO2.2Fe2O3.6H2O. Cuprotiungstite,CuWO4. Beldongrite,6Mn2O3.Fe2O3.8H2O. Ankerite,2CaCO3.MgCO3.FeCO3. GOLD Mesitite,2MgCO3.FeCO3. Native Pistomesite,MgCO3.FeC03. Gold, Au. Siderite,FeCO3. Petzite,(Ag,Au)2Te. BrugnateUite,MgCO3.5Mg(OH)2.Fe(OH)3. SYLVANITE, (Au,Ag)Te2. 4H2O. Krennerite, (Au,Ag)Te2. HYPERSTHENE, (Fe,Mg)SiO3. CALAVERITE, AuTe2. ACMITE, NaFe(SiO3)2. Muthmannite, (Ag,Au)Te. Pyroxmangite, Mn,Fe, pyroxene. Nagyagite,Au,Pb, sulpho-telluride. Babingtonite, (Ca,Fe,Mn)SiO3, with IRON Fe2(SiO3)3. Native Iron, Fe. ANTHOPHYLLITE, (Mg,Fe)SiO3. GLAticopHANE, NaAl(SiO3)2. Awaruite, FeNi2. (Fe,Mg)SiO3. Josephinite,FeNi3. RIEBECKITE, 2NaFe(SiO3)2.FeSiO3. Chalmersite,Cu2S.Fe4S5. CROCIDOLITE, NaFe(SiO3)2.FeSiO3. Sternbergite,Ag2S.Fe4S6. ARFVEDSONITE, Na,Ca,Fe, silicate. (Fe,Ni)S. Peritlandite, ^Enigmatite,Fe,Na,Ti-sihcate. Pyrrhotite,FeS. FeS. Weinbergerite,NaAlSiO4.3FeSiO3. Troilite, Astrolite,(Na,K)2Fe(Al,Fe)2(SiO3)6.H20? Daubreelite,FeS.Cr2S3. H2(Mg,Fe)4Al8Si10O37. lolite, Badenite, (Co,Ni,Fe)2(As,Bi)3. 0O31. Taramellite,Ba4Fe 'Fe4 'Sii Chalcopyrite,CuFeS2. Helvite, (Be,Mn,Fe)7Si3Oi2S. Pyrite,FeS2. Almandite, Fe3Al2(SiO4)3. Bravoite,(Fe,Ni)S2. Andradite,Ca3Fe2(SiO4)3. Cobaltnickelpyrite,(Fe,Co,Ni)S2. Partschinite,(Mn,Fe)3Al2Si3Oi2. FeAs2. Arsenoferrite, Fayalite,Fe2SiO4. Marcasite, FeS2. Knebelite,(Fe,Mn)2SiO4. FeAs2. Lollingite, H7((Fe,Mn)Cl)(Fe,Mn)4Si4O,6. Pyrosmalite, Arsenopyrite,FeAsS. Homilite, (Ca,Fe)3B2Si2O10. Eichbergite,(Cu,Fe)2S.3(Bi,Sb)2S3. Allanite,(Ca,Fe)2(AlOH)(Al,Ce,Fe)2(SiO4)3. 5CuFeS2.2Sb2S3.7Bi2S3. Histrixite, ILVAITE, CaFe2(FeOH)(SiO4)2. FeS.Sb2S3. Berthierite, Melanotekite, 3PbO.2Fe2O3.3SiO2. Stylotypite,3(Cu2,Ag2,Fe)S.Sb2S3. 2(Ca,Mg)O.5(Al,Fe)2O3.6Si02. Angaralite, Molysite, FeCl3. (AlO)4(AlOH)Fe(SiO4)2. STAUROLITE, Lawrencite, FeCl2. Grandidierite,Al,Fe,Mg, silicate. Rinneite,FeCl2.3KCl.NaCl. Fe,Ca,Mg,Na, silicate. Aloisite, Kremersite, KCl2.NH4Cl.FeCl2.H2O. Pochite, Hi6Fe8Mn2Si3O29. 2KCl.FeCl3.H2O. Erythrosiderite, Lotrite,3(Ca,Mg)0.2(Al,Fe)208.4Si02.2H2 Hematite, Fe2O3. Zinnwaldite,Li-Fe mica. ILMENITE, FeTiO3. Biotite,Mg-Fe mica. Senaite,(Fe,Mn,Pb)O.TiO2. Lepidomelane, Iron mica. Arizonite,Fe2O3.3TiO2. H2(Fe,Mg)Al2Si07. Chloritoid, 9 Mn2O3.4Fe2O3.MnO2.3CaO. Sitaparite, '

'

'

APPENDIX

670

B

Pharmacosiderite,6FeAs04.2Fe(OH)3.

Prochlorite,Fe,Mg,chlonte.

12H20. Moravite, 2Fe0.2(Al,Fe)203.7Si02.2H20.

2Fe3P2O8.Fe(OH)2.8H2O.

Ludlamite, Cronstedtite, 4FeO.2Fe2O3.3SiO2.4H2O. Cacoxenite, FePO4.Fe(OH)3.4^H2O. 8FeO.4(Al,Fe)2O3.6SiO2.9H2O. Thuringite,

Beraunite, 2FePO4.Fe(OH)3.2|H2O. Brunsvigite, 2AlPO4.2Fe(OH)2.2H2O. Childrenite, 4(Mg,Fe,Ca)0.(Al,Fe)203.5Si02. Griffithite, Mazapilite,Ca3Fe2(AsO4)4.2FeO(OH).5H2O. 7H2O. (AsO4)2.2Fe(OH)3. Yukonite, (Ca3,Fe2'/') Chamosite, Fe,Mg, silicate.

9(FeM^O.2A\f)^O2m,O.

Stilpnomelane\ Fe /

5H2O.

silicates.

Mmgu6tite H4Fe2(Al,Fe)2Si2Oii. Strigovite,

Calciof errite, Ca3Fe2 (PO4)4. Fe (OH )3. 8H2O.

Borickite,Ca3Fe2(PO4)4.12Fe(OH)3.6H2O.

Egueiite,Hydrous Fe,Al,Ca, phosphate. (Na2,K2)2(Mg,Fe)3(Fe,Al)2 Spodiophyllite, Richelite,4FeP2O8.Fe2OF2(OH)2.36H2O. (SiO3)8. Chenevixite,Cu2(FeO)2As2O8.3H2O. silicate. Celadonite,Fe,Mg,K, CuO.3Fe2O3.2P2O5.8H2O. Chalcosiderite, Glauconite,Hydrous Fe,K, silicate. (PO4)2. Roscherite, (Mn,Fe,Ca)2Al(OH) K20.12(Fe,Mg)O.A}203.13Si02. Pholidolite, 2H20.

5H2O.

(Al,Fe)2O3.2Si02.2H2O. Faratsihite, Melite,2(Al,Fe)203.Si02.8H20. Chloropal,H6Fe2(SiO4)2.2H2O. Mullerite,Fe2Si3O9.2H2O. Hisingerite\ Hydrous ferric silicates. / J Morencite

Astrophyllite,Na, K, Fe, Mn,

titano-sil-

icate.

Narsarsukite,Fe,Na, titaim-silicate. Neptunite, Fe,Mn,Na,K, titano-silicate. Joaquinite,Ca,Fe, titano-silicate. Dysanalyte,Ca,Fe, titano-niobate. (Mg,Fe)Ti03. Geikielite, Delorenzite,Fe,U,Y, titanate. Neotantalite,Fe tantalate. (Fe,Mn) COLUMBITE, TANTALITE, (Nb,Ta)206. Tapiolite,Fe(Ta,Nb)2O6. Fe,Ca,Y,Er,Ce, tantalate. Yttrotantalite, Samarskite,Fe,U,Y, etc.,niobate-tantalate. Hielmite,Y,Fe,Mn,Ca, stanno-tantalate. Monimolite, Pb,Fe, antimonate. TRIPHYLITE, Li(Fe,Mn)PO4. Graftonite,(Fe,Mn,Ca)3P2O8. Triplite. (RF)RPO4; R Fe,Mn. Triploidite(ROH)RPO4; R Fe,Mn. Dufrenite,FePO4.Fe(OH)3. LazuUte, 2AlPO4.(Fe,Mg)(OH)2. Arseniosiderite, Ca3Fe(AsO4)3.3Fe(OH)3. Dickinsonite i Hydrous Mn,Fe,Na, / Fillowite phosphate. Messelite (Ca,Fe)3P2O8.2"H2O. Anapaite, (Ca,Fe)3P2O8.4H2O. Vivianite,Fe3P2O8.8H2O. Symplesite,Fe3As-"O8.8H2O. Scorodite,FeAsO4.2H2O. Vilateite, Hydrous Fe, Mn, phosphate. Purpurite,2(Fe,Mn)PO4.H2O. =

=

FePO4.2H2O. Strengite, Phosphosiderite, 2FePO4.3^H2O. Barrandite, (Al,Fe)PO4.2H2O. FePO4.3H2O. Koninckite, Sicklerite, Fe2O3.6MnO.4P2O5.3(Li,H)2O. Salmonsite, Fe2O3.9MnO.4P2O5. 14H,O. Liskeardite, (Al,Fe)AsO4.2(Al,Fe) (OH)3. 5H2O.

Tripuhyite,2FeO.Sb2O5. 4FeSbO4.3H2O. Flajolotite, Catoptrite, 14(Mn,Fe)O.2(Al,Fe)2O3.2SiO2. Derbylite,Fe antimo-titanate. Fe Diadochite, Hydrous phosphate and sulphate. and phate. sulPitticite,Hydrous Fe arsenate Beudantite, 3Fe2O3.2PbO.2SO3.As2O8.6H2O. Hinsdalite,3Fe2O3.2PbO.2SO3.P2O5.6H2O. and Lossenite, Hydrous Fe,Pb, arsenate sulphate. Ludwigite, 3MgO.B2O3.FeO.Fe2O3. Vonsenite,3(Fe,Mg)O.B2O3.FeO.Fe2O3. Magnesioludwigite,3MgO.B2O3.MgO.Fe2O3. Warwickite, (Mg,Fe)3TiB2O8.

Lagonite,Fe2O3.3B2O3.3H2O. Hulsite,12(Fe,Mg)O.2Fe2O3.lSnO2.3B2O3. (Fe,Al)2(SO4)3. Millosevichite,

Szomolnokite,FeSO4.H2O. (Mn,Zn,Fe)SO4.4H2O. Ilesite, FeSO4.7H2O. Melanterite, (Fe,Cu)SO4.7H2O. Pisanite; Halotrichite,FeSO4.Al2(SO4)3.24H2O. FeSO4.Fe2(SO4)3.24H2O. Bilinite, Dietrichite,(Zn,Fe,Mn)SO4.Al2(SO4)3. 22H2O.

Coquimbite,Fe2(SO4)3.9H2O. Quenstedtite, Fe2(SO4)8.10H2O. Ihleite, Fe2(SO4)3.12H2O. CuSO4.Fe2(SO4)3.nH2O. Phillipite,

Ferronatrite,3Na2SO4.Fe2(SO4)3.6H2O. Romerite, FeSO4.Fe2(SO4)3.14H2O. CuO.PbO.Fe2O3.2SO3.4H2O. Beaverite, Vegasite, PbO.3Fe2O3.3SO3.6H2O.

Copiapite,2Fe2O3.5SO3.18H2O. Fe2O3.2SO3.8H2O. Castanite, Utahite,3Fe2O3.2SO3.7H2O. Amaranthite,Fe2O3.2SO3.7H2O. Fibrof errite, Fe2O3.2SO3.10H2O.

Raimondite,2Fe2O3.3SO3.7H2O. Carphosiderite, 3Fe2O3.4SO3.7H2O. Planoferrite, Fe2O3.SO3.15H2O. Glockerite, 2Fe2O3.SO3.6H2O. Knoxvillite, Hydrous Fe,Al,Cr,sulphate.

APPENDIX

672 3PbO.2Cr03. Phcenicochroite,

2(Pb,Cu)CrO4.(Pb,Cu)3P2Os Vauquelinite, Pb arseno-chromate. Bellite, PbSO4.2PbCO3.Pb(OH)2. Leadhillite, Caracolite,Pb(OH)Cl.Na2SO4. Lanarkite,Pb2SO6. (Pb,Cu) (OH)2. Caledonite,(Pb,Cu)S04. Linarite,(Pb,Cu)SO4.(Pb,Cu) (OH)2. Beaverite,CuO.PbO.Fe2O3.2SO3.4H2O. Vegasite,PbO.3Fe2O3.3SO3.6H2O. Plumbojarosite,PbFe6(OH)i2(SO4)4. Palmierite,3(K,Na)2SO4.4PbSO4.

B

HYPERSTHENE, (Fe,Mg)Si03. Pyroxene, Ca,Mg, etc.,silicate. ANTHOPHYLLITE, (Mg,Fe)SiO3. Amphibole, Ca,Mg, etc.,silicate. GLAUCOPHANE, NaAl (SiO3)2. (Fe,Mg)SiO8 IOLITE,H2(Mg,Fe)4Al8SiioO37. Molybdophyllite, (Pb,Mg)SiO4.H2O. Pyrope, Mg3Al2(SiO4)3. Chrysolite,(Mg,Fe)2SiO4. Monticellite, CaMgSiO4. Fosterite,Mg2SiO4. Hortonolite,(Fe,Mg,Mn)2SiO4. ,

CHONDRODITE, [Mg(F,OH)]2Mg3(SiO4)2. Humite, [Mg(F,OH)]2Mg5(Si04)3. 3PbW04.PbMo04. Chillagite, WULFENITE, PbMoO4. LITHIUM

LiAl(Si2O5)2. Petalite, Spodumene, LiAl(SiO3)2. Eucryptite,LiAlSiO4. LEPIDOLITE, Lithium mica. Zinnwaldite,Lithium-iron mica. Manandonite, H24Li4Ali4B4Si6()53. TRIPHYLITE, Li(Fe,Mn)PO4. Lithiophilite, Li(Mn,Fe)PO. AMBLYGGNITE, Li(AlF)PO4. Fremontite, (Na,Li)Al(OH,F)PO4. Sicklerite, Fe2O3.6MnO.4P2O5.3(Li,H)2O. MAGNESIUM

MgCl2. Chloromagnesite, Sellaite, MgF2. Nocerite,2(Ca,Mg)F2(Ca,Mg)O. Koenenite, Al,Mg, oxy chloride. Carnallite, KCl.MgCl2.6H2O. Bischofite,Mi _.-0Jl2.6H20. Tachhydrite, CaCl2.2MgCl2.12HoO Ralstonite,(Na2,Mg)F2.3Al(F.OH)3.2H2O. Periclase, MgO. Spinel,MgO.Al2O3. Magnesioferrite, MgO.Fe2O3. Jacobsite,(Mn,Mg)O.(Fe,Mn)2O3. BRUCITE, Mg(OH)2. "

,

Hydrotalcite, Al(OH)3.3Mg(OH)2.3H2O. Pyroaurite, Fe(OH)3.3Mg(OH)2.3H20. Dolomite, CaCO3.MgCO3. Ankerite,CaCO3.(Mg,Fe,Mn)CO3. Magnesite, MgCO3. Mesitite, 2MgCO3.FeCO3. Pistomesite, MgCO3.FeCO3. Northupite, MgCO3.Na2CO3.NaCl.

Tychite,2MgCO3.2Na2CO3.Na2SO4.

Nesquehonite, MgCO3.3H2O. Hydromagnesite, 3MgCO3.Mg(OH)2.3H2O.

Clinohumite,[Mg(F,OH)]2Mg7(SiO4)4. Kornerupine,MgAl2SiO6. Sapphirine, Mg5Ali2Si2O27. Serendibite, 10(Ca,Mg)O.5Al2O3.B2O3.6SiO2. Silicomagnesiofluorite, H2Ca4Mg3Si2O7Fi0

Lptrite,3(Ca,Mg)O.2(Al,Fe)2O3.4SiO2. Biotite,Magnesium-iron mica. Phlogopite,Magnesium mica. K, Mg, silicate. Ta3niolite,

Seybertite, H3(Mg,Ca)6Al5Si2Oi8. Xanthophyllite, H8(Mg,Ca)14Al16Si6O52. Chloritoid, H2(Fe,Mg)Al2SiO7. Clinochlore,Penninite,H8Mg5Al,Si3O18. Prochlorite, Fe,Mg, chlorite. Brunsvigite, 9(Fe,Mg)O.2Al2O3.6SiO2.8H2O. Griffithite, 4(Mg,Fe,Ca)O.(Al,Fe)2O3.5SiO2. 7H2O.

Spodiophyllite, (Na2,K2)2(Mg,Fe)3(Fe,Al) .

Serpentine, H4Mg3Si2O9. Deweylite,4MgO.3SiO2.6H2O. Genthite, 2NiO.2MgO.3SiO2.6H2O. Nepouite,3(Ni,Mg)O.2SiO2.2H2O. Garnierite, H2(Ni,Mg)SiO4 + water. Talc, H2Mg3(Si03)4. SEPIOLITE,H4Mg2Si3Oi0. Spadaite,5MgO.6SiO2.4H2O. Saponite,Hydrous Mg,Al, silicate. Celadonite, Fe,Mg,K, silicate. K20. 12(Fe,Mg)0.A1203.13SiO2 Pholidolite, 5H2O.

Colerainite, 4MgO.Al2O3.2SiO2.5H2O. Tartarkaite, Al,Mg, hydrous silicate. Geikielite, (Mg,Fe)TiO3. Berzeliite, (Ca,Mg,Mn,Na2)3As2O8. Wagnerite,(MgF)MgPO4. Adelite,(MgOH)CaAsO4. Tilasite, (MgF)CaAs04. Lazulite, 2AlPO4.(Fe,Mg)(OH)2 Struvite, Hydrous, NH4,Mg, phosphate. Pyrophosphorite, Mg2P2O7.4(Ca3P2O8.

Hydrogiobertite,MgC03.Mg(OH)2.2H20. Ca2P2O7).

Artimte,MgCO3.Mg(OH)2.3H2O.

Roselite, (Ca,Co,Mg)3As2O8.2H2O. Lansfordite, 3MgC03.Mg(OH)2.21H20. Bobierrite, Mg3P2O8.8H2O. Brugnatelhte, MgCO3.5Mg(OH)2.Fe(OH)3.Hcernesite,

Mg3As2O8.8H2O. Cabrerite, ( Ni,Mg)3As2O8.8H2O. Gajite basic,hydrous Ca,Mg, carbonate. Newberyite,HMgPO4.3H2O. Stichtite,2MgC03.5Mg(OH)2.2Cr(OH)3. Hannayite i Hydrous, NH4,Mg, ENSTATITE,MgSiOs. 4ji2v-J"

Schertelite /

phosphates.

APPENDIX

Liineburgite,3MgO.B2O3.P2O6.8H2O. Nitromagnesite, Mg(NO3)2.nH2O. Sussexite,H(Mn,Zn,Mg)BO3. Ludwigite. 3MgO.B2O3.FeO.Fe2O3. Vonsenite, 3(Fe,Mg)O.B2O3.FeO.Fe2O3. Magnesioludwigite, 3MgO.B2O3.MgO.Fe2O3. Pinakiolite, 3MgO.B2O3.MnO.Mn2O3. Szaibelyite,2Mg5B4Oi,.3H2O. BORACITE, Mg7Cl2Bi6O30. Ascharite,Hydrous Mg, borate. Warwickite, (Mg,Fe)3TiB2O8. Pinnoite,MgB2O4.3H2O. Heintzite,Hydrous Mg,K, borate. Hulsite,12(Fe,Mg)O.2Fe2O3. !SnO2.3B2O3. 2H2O.

Hydroboracite,CaMgB6On.6H2O. Sulphoborite,2MgSO4.4MgHBO3.7H2O. Langbeinite,K2Mg2(SO4)3. Vanthoffite,3Na2SQ4.MgSO4. Kainite,MgSO4.KC1.3H2O. Kieserite,MgSO4.H2O. Epsomite, MgSO4.7H2O. Cupromagnesite,(Cu,Mg)SO4.7H2O. Loweite, MgSO4.Na2SO4.2"H2O. Blodite,MgSO4.Na2SO4.4H2O. Leonite,MgSO4.K2SO4.4H2O. Boussingaulite,(NH4)2SO4.MgSO4.6H2O. Picromerite,MgSO4.K2SO4.6H2O. Polyhalite,2CaSO4.MgSO4.K2SO4.2H2O. Hexahydrite,MgSO4.6H2O. Pickeringite,MgSO4.Al2(SO4)3.22H2O. Botryogen, MgO.FeO.Fe2O3.4SO3. 18H,O. Quetenite, MgO.Fe2O3.3SO3.13H2O. MANGANESE .

Alabandite,MnS. Hauerite, MnS2. Samsonite, 2Ag2S.MnS.Sb2S3.

Sacchite,MnCl2. Chlormanganokalite, 4KCl.MnCl2. Manganosite, MnO. Senaite,(Fe,Mn,Pb)O.TiO2. Pyrophanite, MhTiO3. Sitaparite,9Mn2O3.4Fe2O3.MnO2.3CaO. Vredenburgite, 3Mn3O4.2Fe2O3. FRANKLINITE, (Fe,Zn,Mn)O. (Fe,Mn)2O3. Jacobsite,(Mn,Mg)O.(Fe, Mn)2O3. Hausmannite, MnO.Mn2O3. Coronadite, (Mn,Pb)Mn3O7. Crednerite,3CuO.2Mn2O3. BRAUNITE, 3Mn2O3.MnSiO3.

Bixbyite,FeO.MnO2. Polianite,MnO2. Pyrolusite,MnO2. Manganite, Mn2O3.H2O. Pyrochroite,Mn(OH)2. Backstromite, Mn(OH)2. Chalcophanite, (Mn,Zn)O.2MnO2.2H2O Heta3roHte,2ZnO.2Mn2O3.lH2O. manganate. Psilomelane,Hydrous Mn Wad, Mn oxides. Skemmatite, 3MnO2.2Fe2O3.6H2O. Beldongrite,6Mn3O5.Fe2O8.8H2O.

673

B

Rhodochrosite,MnCO3. Schizolite, HNa(Ca,Mn)2(SiO3)3 Lavenite,Zr-silicate of Mn, Ca. Rhodonite, MnSiO3. Pyroxmangite,Mn,Fe pyroxene. Babingtonite, (Ca,Fe,Mn)SiO3 with Fe2(SiO3)3. Margarosanite,Pb(Ca,Mn)2(SiO3)3.

Helvite,(Be,Mn,Fe)7Si3O12S. Danalite, (Be,Fe,Zn,Mn)7Si3O12S. Spessartite,Mn3Al2(SiO4)3. Partschinite,(Mn,Fe)3Al2Si3Oi2. CaMnSiO4. Glaucochroite,

Knebelite, (Fe,Mn)2SiO4. Tephrdite, Mn2SiO4. Trimerite,(Mn,Ca)2SiO4.Be2SiO4. Friedelite, H7(MnCl)Mn4Si4Oi6. Pyrosmahte, H7((Fe,Mn)Cl)(Fe,Mn)4Si4Oi6 Piedmontite, Mn epidote. Hancockite, Pb,Mn,Ca,Al, etc.,silicate. Harstigite,Mn,Ca, silicate. Leucophoenicite,Mn5(MnOH)2(SiO4)3. Ardennite, Al,Mn,V, silicate. Langbanite, Mn silicatewith Fe antimonate.

Kentrolite,3PbO.2Mn2O3.3SiO2. Carpholite,H4MnAl2Si2O10. Pochite, Hi6Fe8Mn2Si3O29. Inesite,H2(Mn,Ca)6Si6Oi9.3H2O. Ganophyllite,7MnO.Al2O3.8SiO2.6H2O. Alurgite,Manganese mica. Dixenite,MnSiO3.2Mn2(OH)AsO3. Bementite, H6Mn5(SiO4)4. Ectropite,Mn2Si8O28.7H2O. Agnolite,H2Mn3(SiO3)4.H2O. Hodgkinsonite, 3(Zn,Mn)O.SiO2.H2O. Gageite,Hydrous, Mn,Mg,Zn, silicate. Caryopilite,4MnO.3SiO2.3H2O. Neotocite,Hydrous, Mn, Fe, silicate. Astrophyllite,Na,K,Fe,Mn,Ti-silicate. Neptunite, Fe,Mn,K,Na, titano-silicate. COLUMBITE-TANTALITE, (Fe,Mn) (Nb,Ta)2O6. Hielmite,Y,Fe,Mn,Ca, stanno-tantalate. Berzeliite, (Ca,Mg,Mn,Na2)3As2O8. Li(Mn,Fe)PO4. Lithiophilite, Natrophilite,NaMnPO4. Graftonite,(Fe,Mn,Ca)3P2O8. Fe,Mn. Triplite,(RF)RPO4; R R Mn.Fe. Triploidite(ROH)RPO4; Sarkinite,(MnOH)MnAsO4. Trigonite,Pb3MnH(AsO3)3. Lacroixite,Na4(Ca,Mn)4Al3(F,OH)4P3Oi0. =

=

2H20.

Pyrobelonite,4PbO.7MnO.2V2O6.3H2O. Mn3As2O8.4Mn(OH)2. Allactite, Synadelphite,2(Al,Mn)AsO4.5Mn(OH)2. Flinkite,MnAsO4.2Mn(OH)2. HematoHte, (Al,Mn)AsO4.4Mn(OH)2. Retzian, Y,Mn,Ca, phosphate. (Mn,Ca)9(Mn,Fe)2(OH)" Arseniopleite, (AsO4)6. Manganostibiite,Mn antimonate.

674

APPENDIX

Dickinsonite Fillowite

Hydrous Mn,Fe,Na,

l

phosphates. Brandite,Ca2MnAs2O8.2H2O. Ca3MnP2O8.2H2O. Fairfieldite, Reddingite,Mn3P2O8.3H2O. Palaite,5MnO.2P2O6.4H2O. Stewartite,3MnO.P2O5.4H2O. Purpurite,2(Fe,Mn)PO4.H2O. Fe2O3.6MnO.4P2O5.3(Li,H)2O. Sicklerite, Salmonsite,Fe2O3.9MnO.4P2O6. 14H2O. Hureaulite,H2Mn6(PO4)4.4H2O. Hemafibrite,Mn3As2O8.3Mn (OH)2.2H2O. Eosphorite,2AlPO4.2(Mn,Fe) (OH)2.2H2O. (Mn,Fe,Ca)2Al(OH) (PO4)o.2H,O Rosche-rite, Catoptrite, 14(Mn,Fe)O.2(Al,Fe)2O3.2SiO2. I

Sussexite, H(Mn,Zn,Mg)BO3. Pinakiolite, 3MgO.B2O3.MnO.Mn2O3. Szmikite,MnSO4.H2O. Ilesite, (Mn,Zn,Fe)SOi.4H2O. Mallardite,MnSO4.7H2O. Apjohnite,MnSO4.Al2(SO4)3.24H2O. Dietrichite,(Zn,Fe,Mn)S04.Al2(SO4)3.

B

Bravoite, (Fe,Ni)S2. Cobaltnickelpyrite, (Co,Ni,Fe)S2. CHLOANTHITE, NiAs2. NiAsS. Gersdorffite, Willyamite, CoS2.NiS2.CoSb2.NiSb2. Villamaninite,Cu,Ni,Co,Fe,sulphide. Ullmanite, NiSbS. Ni(Sb,Bi)S. Kallilite, Rammelsbergite, NiAs2. Wolfachite,Ni(As,Sb)S. Melonite, NiTe2. Bunsenite, NiO. Zaratite,NiCO3.2Ni(OH)2.4H2O. Genthite,2NiO.2MgO.3SiO2.6H2O. Nepouite, 3(Ni,Mg)O.2SiO2.2H2O. Garnierite,H2(Ni,Mg)SiO4 + water.

Connarite,H4Ni2Si3Oi0. Annabergite, Ni3As2O8.8H2O. Cabrerite,(Ni,Mg)3As2O8.8H2O. Forbesite,H2(Ni,Co)2As2O8.8H2O. Lindackerite, 3NiO.6CuO.SO3.2As2O6. 7H20.

Morenosite,NiSO4.7H2O. PLATINUM

22H.O. MnWO4. Hiibnerite, MERCURY Native

Native

Platinum, Pt.

PtAs2. Sperrylite, POTASSIUM

Mercury, Hg.

Amalgam,

(Ag,Hg). Metacinnabarite, HgS. Tiemannite, HgSe. Onofrite, Hg(S,Se). Cotoradoite, HgTe. Cinnabar, HgS. Livingstonite, HgS.2Sb2S3. Calomel,HgCl.

Kleinite, Hg,NH4, chloride. Eglestonite, Hg4Cl2O. Terlinguaite, HgClO. Mosesite,Hydrous Hg,NH4, chloride. HgO. Montroydite,

Ammiolite,Hg

antimonite.

MOLYBDENUM

Molybdenite,MoS2. Molybdite,MoO3. Powellite, Ca(Mo,W)O4. Chillagite, 3PbWO4.PbMoO4. WULFENITE, PbMoO4. Koechlinite, Bi2O3.Mo03. NICKEL

Awaruite,FeNi2. FeNi3. Jbsephinite, Maucherite, Ni3As2. PENTLANDITE,(Fe,Ni)S.

Millerite,NiS NiS. Beyrichite, Hauchecornite, Ni(Bi,Sb,S)? NiAs. Niccolite, NiSb Breithauptite,

Ni4S6. Polydymite,

Badenite, (Co,Ni,Fe)2(As,Bi)8.

SYLVITE, KC1.

Chlormanganokalite, 4KCl.MnCl2. Rinneite,FeCl2.3KCl.NaCl. Hieratite,K,Si, fluoride. CARNALLITE, KCl.MgCl2.6HoO. Kremersite,KCl,NH4Cl.FeCl2.H2O. 2KCl.FeCl3.H2O. Erythrosiderite,

Milarite,HKCa2Al2(Si2O5)6. Orthoclase,Microcline,KAlSi3O8.

Hyalophane, (K2,Ba)Al2(SiO3)4. Anorthoclase,(Na,K)AlSi3O8. Leucite,KAl(SiO3)2. KAlSiO4. Kaliophilite, ApophylUte,H7KCa4(SiO3)8.4|H2O. PtiloHte, (Ca,K2,Na2)Al2Si10O24.5H2O. Mordenite,(Ca,K2,Na2)Al2SiioO24.20H20. Wellsite,(Ba,Ca,K2)Al2Si3O10.3H20. Phillipsite, (K2,Ca)Al2Si4O,2.4iH2O. Harmotone, (K2,Ba) Al2Si6Oi4. 5H2O Potash zeolite. Offretite, Muscovite,H2KAl3(SiO4)3. TaBniolite, K,Mg, silicate. -

.

(Na2K2)2(Mg,Fe)3(Fe,Al)2 Sppdiophyllite, (SiO3)8.

Celadonite, Fe,Mg,K, silicate. Glauconite,Hydrous Fe, K, silicate. Astrophyllite, Na,K,Mn,Fe, titano-sih'cate. Palmerite, HK2Al2(PO4)3.7HoO. Carnotite, K2O.2U2O3.V2O5.3H2O. Niter,KNOs. Rhpdizite, A1,K, borate. Heintzite, Hydrous Mg,K, borate. 5K2SO4. (NH4)2S04. Taylorite, Aphthitalite, (K,Na)2SO4. Langbeinite, K2Mg2(SO4)3.

APPENDIX

675

B

Kainite,MgSO4.KC1.3H2O.

lodobromite, 2AgCl.2AgBr.AgI. Hanksite, 9Na2SO4.2Na2CO3.KCl. Miersite,4AgI.CuI. Misenite, HKSO4. lodyrite,Agl. Lecontite,(Na,NH4,K)SO4.2H2O. SODIUM Syngenite, CaSO4.K2SO4.H2O. Leonite,MgSO4.K2SO4.4H2O. Halite,NaCl. NaF. Picromerite,MgSO4.K2SO4.6H2O. Villiaumite, Polyhalite,2CaSO4.MgSO4.K2SO4.2H2O. Huantajayite, 20NaCl.AgCl. Rinneite,FeCl3.3KCl.NaCl. Kalinite,KA1(SO4)2.12H2O. Voltaite,3(K2,Fe)O.2(Al,Fe)2O3.6SO3.9H2O.CRYOLITE, Na3AlF6. ChioUte, 5NaF.3AlF3. Metavoltine, 5(K2,Na2,Fe)O.3Fe2O3.12SO8. 18H2O. Ralstonite,(Na2,Mg)F2.3Al(F,OH)3.2H2O. Northupite, MgCO3.Na2CO3.NaCl. ALUNITE, K2A16(OH)12(SO4)4. Tychite, 2MgCO3.2Na2CO3.Na2SO4. Jarosite,K2Fe6(OH)12(SO4)4. Dawsonite, Na3Al(CO3)3.2Al(OH)3. Palmierite,3(K,Na)2SO4.4PbSO4, Thermonatrite, Na2CO3.H2O. Lowigite, K2O.3A12O3.4SO3.9H2O. Natron, Na2CO3. 10H2O. SILVER CaCO3.Na2CO3.2H2O. Pirssonite, Gay-Lussite, CaCO3.Na2CO3.5H2O. Native Silver,Ag. Trona, Na2CO3.HNaCO3.2H2O. Amalgam, (Ag,Hg). Eudidymite, Epididymite, HNaBeSi3O8. Dyscrasite,Ag3Sb. Rivaite,(Ca,Na2)Si2O6. Chilenite,Ag6Bi. Anorthoclase,(Na,K)AlSi3O8. Cocinerite,Cu4AgS. Albite,NaAlSi3O8. Stutzite,Ag4Te. Oligoclase Naumannite, (Ag2,Pb)Se and Mixtures of Argentite,Ag2S. Hessite,Ag2Te. Petzite,(Ag,Au)2Te. Aquilarite,Ag2(S,Se). Eucairite,Cu2Se.Ag"Se. : Crookesite,(Cu,Tl,Ag)2Se. (Ag,Cu)2S. Stromeyrite, Acanthite, Ag2S. Sternbergite,Ag2S.Fe4S5. Sylvanite,(Au,Ag)Te2. Krennerite, (Au,Ag)Te2. Muthmannite, (Ag,Au)Te. Andorite, Ag2S.2PbS.3Sb2S3. Matildite,Ag2S.Bi2S3. Miargyrite, Ag2S.Sb2S3. Smithite,Ag2S.Sb2S3. Trechmanite, Ag2S.As2S3. + PbS. Hutchinsonite, (Tl,Ag,Cu)2S.As2S3 As2S3(?). Schirmerite,3(Ag2.Pb)S.2Bi2S3. 5(Pb,Ag2)S.2Sb2S3. Freieslebenite, Diaphorite, 5(Pb,Ag2)S.2Sb2S3. Stylotypite,3(Cu2,Ag2,Fe)S.Sb2S3. Lengenbachite,7[Pb,(Ag,Cu)2]S.2As2S8. ",

3Ag2S.Sb2S3. PYRARGYRITE, PROUSTITE, 3Ag2S.As2S3. 3Ag2S.Sb2S3. Pyrostilpnite, Samsonite, 2Ag2S.MnS.Sb2S3. STEPHANITE, 5Ag2S.Sb2S3. POLYBASITE, 9Ag2S.Sb2S3. Pearceite,9Ag2S.As2S3. 12Ag2S.Sb2S3. Polyargyrite, Xanthoconite, 3Ag2S.As2Ss. Argyrodite,4Ag2S.GeS2. 4Ag2S.SnS2. Canfieldite, Cerargyrite,AgCl. Embolite, Ag(Br,Cl). Bromyrite,AgBr.

Andesine

Labradorite

CaAl2Si2O8,

Anemousite, NaO.2CaO.3Al2O3.9SiO2. Ussingite,HNa2Al'(SiO3)3. ACMITE, NaFe(SiO3)2. JADEITE, NaAl(SiO3)2. PECTOLITE, HNaCa2(SiO3)3. Schizolite, HNa(Ca,Mn)2(SiO3)3. Rosenbuschite, near pectolitewith Zr. Wohlerite,Zr-silicate and niobate of Ca,Na. Hiortdahlite,(Na2.Ca)(Si,Zr)O3. GLAUCOPHANE, NaAl(SiO3)2.(Fe,Mg) Si03.

RIEBECKITE, 2NaFe(SiO3)o.FeSiO3. CROCIDOLITE, NaFe(SiO3)2.FeSiO3.

Na^a^e" Arfyedsonite,

silicate.

Fe,Na,Ti-silicate. jiEnigmatite, Weinbergerite,NaAlSiO4.3FeSiO3. Elpidite,Na2O.ZrO2.6SiO2.3H2O. H4 (Na2,Ca) ZrSi3On Catapleiite, .

Nephelite,NaAlSiO4. H6Na6Ca(NaCO3)2Al8 CANCRINITE, (Si04)9. Microsommite, Davyne, near cancrimte. SODALITE, Na4(AlCl)Al2(SiO4)3 Hackmanite, near sodalite. HAITTNITE, (Na2,Ca)2(NaSO4.Al)Al2 (SiO4)3. Noselite,Na4(NaSO4.Al)Al2(SiO4)3. LAZURITE, Na4(NaS3.Al)Al2(SiO4)3. of SCAPOLITE GROUP, Mixtures Ca4Al6Si6O26 and Na4Al3Si9O24Cl. Sarcolite,(Ca,Na2)3Al2(SiO4)3. Melilite,Na2(Ca,Mg)n(Al,Fe)4(SiO4)9. Mordenite, (Ca,K2,Na2)Al2Si,0O24.20H2O. Stilbite,(Na2,Ca)Al2Si6Oi6.6H2O.

676

APPENDIX

H8(Ca,Na2)Al2Si9O26.2H2O. Flokite, (Ca,Na2)Al2Si4Oi2.6H2O. Gmelinite,(Na2Ca)Al2Si4OI2.6H2O. CHABAZITE,

Analcite, NaAlSi2O6.H2O. Faujasite,H4Na2CaAl4Si10O38. Na2Al2Si3Oi0.2H2O. Natrolite, Mesolite, Na2Al2Si3Oi0.2H2O + 2[CaAl2Si3 Oi0.3H2O].

Gonnardite, (Ca,Na2)2Al2Si6O,5.5|H2O. Thomsomte, (Na2,Ca)Al2Si2O8.2"H2O. Hydrothomsonite, (H2,Na2,Ca)Al2Si2O8.

5H2q.

B

3(K,Na)2SO4.4PbSO4. Palmierite, Almeriite, Na2SO4.Al2(SO4)3.5Al(OH)3.H2O. STRONTIUM

SrCO3. Strontianite,

Ancylite,4Ce(OH)CO3.3SrCO3.3H2O. Rare earths,Sr, carbonate.

Ambatoarinite.

Brewsterite, H4(Sr,Ba,Ca)Al2(SiO3)6.3H2O. Fermorite,(Ca,Sr)4[Ca(OH,F)][(P,As)O4]3 Hamlinite,Sr,Al,phosphate. Harttite,Sr.Al. phosphate and sulphate. SrSO4. Celestite,

Arduinite,Ca,Na, zeolite. THORIUM Echellite, (Ca,Na2)O.2Al2O3.3SiO2.4H2O. " Epidesmine, (Na2,Ca)Al2Si6Oi6.6H2O. fluo-silicates. /Ca,Ce,Y,Th, Erionite,H2CaK2Na2Al2Si6O17.5H2O. Thorite,ThSiO4. Hydronephelite,HNa2Al3Si3Oi2.3H2O. Auerlite,Th silico-phosphate. Paragonite,H2NaAl3(SiO4)3. Th,Y, silicate. Spodiophyllite,(Na2,K2)2(Mg,Fe)3(Fe,Al)2 Yttrialite, Mackintoshite, U,Th,Ce, silicate. (Si03)8. Yttrocrasite, Hydrous Y,Th, titanate. Searlesite, NaB(SiO3)2.H2O. Pyrochlore,RNb2O6.R(Ti,Th)O3. Molengraafite,Ca,Na, titano-silicate. Astrophyllite, Na,K,Mn,Fe,titano-silicate. MONAZITE, (Ce,La,Di)PO4with ThO2. Th and U oxides. Thorianite, Narsarsukite, Fe,Na,titano-silicate. Na4Ba(TiO)2(Si2O5)5. Leucosphenite, TIN Lorenzenite,Na2(TiO)2Si2O7. Cu2S.FeS.SnS2. n iobate. Stannite, Epistolite, Ti,Na,etc., Canfieldite, 4Ag2"S.SnS2. Berzeliite, (Ca,Mg,Mn,Na2)3As2O8. PbSnS2. Teallite, NaMnPO4. Natrophilite, NaBePO4. Franckeite, Pb5Sn3FeSb2S14. Beryllonite, Jezekite,Na4CaAl(AlO) (F,OH)4(PO4)2. Cylindrite, Pb3Sn4FeSb2Si4. Lacroixite,Na4(Ca,Mn)4Al3(F,OH)4P3O16. Cassiterite, SnO2. 2H2O. Stokesite, H.CaSnSisOu. Durangite,Na(AlF)AsO4. Hielmite,Y,Fe,Mn,Ca, stanno-niobate.

Trftomfte

Fremontite,(Na,Li)Al(OH,F)PO4.

Nordenskioldine, CaSn(BO3)2. Hulsite, 12(Fe,Mg)0.2Fe203. !SnO2.3B2O3. }3(Mn,Fe,Na2)3P208.H20.

raiowite11^

2H2O.

Stercorite, HNa(NH4)PO4.4H2O. Soumansite,Hydrous Al,Na,fluophosphate. SODA

NITER, NaNO3.

Darapskite, NaNO3.Na2SO4.H2O. Nitroglauberite, 6NaNO3.2Na2SO4.3H2O Borax, Na2B4O7.10H2O. Ulexite, NaCaB5O9.8H2O.

TITANIUM

ILMENITE, FeTiO3. Senaite,(Fe,Mn,Pb)O.TiO2. Arizonite, Fe2O3.3TiO2. Pyrophanite,MnTiO3. Pseudobrookite, Fe4(TiO4)3. Rutite,Ti02.

Na2SO4. Thenardite, Aphthitalite, (K,Na)2SO4. GLAUBERITE,Na2SO4.CaSO4. Vanthoffite, 3Na2SO4.MgSO4.

Octahedrite, Brookite,TiO2. Uhligite, Ca(Ti,Zr)O5.Al(Ti,Al)O6.

Sulphohalite, 3Na2SO4.NaCl.NaF. Caracolite, Pb(OH)Cl.Na2SO4.

Molengraafite, Ca,Na, titano-silicate. Keilhauite, titano-silicate. Ca,Al,Fe,Y, Ischeffkmite, Ce, etc.,titano-silicate

Hanksite,9Na2SO4.2Na2CO3.KCl Lecontite, (Na,NH4,K)2SO4.2H2O. Mirabikte,Na2SO4.10H2O. Loweite,MgSO4.Na2SO4.2iH2O. Blodite, MgSO4.Na2SO4.4H2O. Mendozite, NaAI(SO4)2.12H2O.

Astrophyllite, Na,K,Fe,Mn, titano-silicate. Johnstrupite Mosandrite

Ce, etc.,titano-silicates

Rmkite

Narsarsukite, Fe,Na, titano-silicate. Neptunite, Fe,Mn,Na,K, titano-silicate. NatrochalciteCu4(OH)2(S04)2.Na2S04.2H20. Benitoite, BaTiSi3O9. Ferronatnte, 3Na2S04.Fe2(S04)3.6H26 Leucosphenite, Na4Ba(TiO)2(Si2O6)6. Sideronatrite, 2Na20.Fe203.4S03.7H20 Lorenzenite, Na2(TiO)2Si2O7. Krohnkite, CuSO4.Na2SO4.2H2O.

3.

12S03.

Natrojarosite, Na2Fe6(OH)12(S04)4

Joaquinite, Ca,Fe, titano-sih'cate.

PEROVSKITE,CaTiO3. Knopite,Ca,Ce, titanate.

APPENDIX

Dysanalyte, Ca,Fe, titano-silicate. Geikielite, Mg,Fe, titanate. Delorenzite,Fe,U,Y, titanate. Yttrocrasite,Hydrous Y, Th, titanate. (UO,TiO,UO2)TiO3. Brannerite, Pyrochlore, RNb2p6.R(Ti,Th)O3. Aeschynite, Ce, niobate-titanate. Polymignite, Ce,Fe,Ca,niobate-titanate. 1 ^r ^ TT Y Ce,U mobatePolvcrase tltanatesBlomstrandine-Priorite j Betafite,U, etc.,niobate-titanate. Euxenite

"

i_

j

Epistolite, Na,Ti, Lewisite,5CaO.2Tiq2.3Sb2O5. Mauzeliite,Pb,Ca, titano-antimonate. Warwickite, (Mg,Fe)3TiB2O8. etc.,mobate.

677

B

Phosphuranylite, (UO2)3P2O8.6H2O. Trogerite, (UO2)3As2O8.12H2O. Walpurgite,Bi10(UO2)3(OH)24(AsO4)4. .URANINITE, Uranyl,etc.,uranate. Gummite, alteration of uraninite. Th and U oxides. Thorianite, Uranosphaerite, (BiO)2U2O7.3H2O. Johannite,Hydrous Cu,U, sulphate. Gilpinite,(Cu,Fe,Na2)O.UO3.SO3.4H2O. CaU8S2O3i.25H2O. Uranopilite, fcS

VANADIUM

PATRONITE, VS4. 3Cu2S.V2S5. Sulvanite, Alaite,V2O5.H2O. Ardennite, Al,Mn,V, silicate. Vanadium Roscoelite,

TUNGSTEN

mica.

Pucherite,BiVO4. Vanadinite, Pb4(PbCl)(VO4)3. Descloizite,(Pb,Zn)2(OH)VO4. Pyrobelonite,4PbO.7MnO.2V2O5.3H2O. Dechenite, PbV2O6. Calciovolborthite, (Cu,Ca)3V2O8.(Cu,Ca) (OH)2. Turanite, 5CuO.V2O5.2HoO.

Tungstenite, WS2. Tungstite, WO3. (Fe,Mn)WO4. WOLFRAMITE, Hubnerite, MnWO4. SCHEELITE, CaWO4. Cuprotungstite, CuWO4. Powellite,Ca(Mo,W)O4.

}Pb,Cu,"nadates. 3PbWO4.PbMoO4. Chillagite, Reinite,FeWO4. Fe2O3.WO3.6H2O. Ferritungstite,

Uvanite, 2UO3.3V2O5.15H2O. Ferganite,U3(VO4)2.6H2O. Fernandinite,CaO. V2O4.5V2O5. 14H2O. Pascoite,2CaO.3V2O5.llH2O. Pintadoite,2CaO.V2O6.9H2O.

URANIUM

Rutherfordine, UO2CO3. Uranothallite,2CaCO3.U(CO3)2.10H2O. Liebigite,Hydrous, U,Ca, carbonate. Voglite,Hydrous, U, Ca, Cu, carbonate. Mackintoshite, U,Th,Ce, silicate. Uranophane, CaO.2UO3.2SiO2.6H2O. Delorenzite,Fe,U,Y, titanate. Brannerite,(UO,TiO,UO2)TiO3. Hatchettolite,U, tantalo-niobate. Samiresite,U, etc.,niobate. Fergusonite,Y,Er;U, niobate. Samarskite, Fe,Ca,U,Ce,Y, niobate. Ampangabeite, U, etc.,niobate. Annerodite, U,Y, niobate. Euxenite

Polvcrase

1v

MeUhewettite

Volborthite,Hydrous, Cu,Ba,Ca, vanadate. Hydrous, Pb,Zn, vanadate. Hiigelite, CARNOTITE, K2O.2U2O3.V2O5.3H2O. Tyuyamunite, CaO.2UO3.V2O5.4H2O. 15H2O. Minasragrite, (V2O2)H2(SO4)3.

TT

\Y"Ce"U'

"

u

mobate^

tltanates-

Blomstrandine-Priorite j Betafite,U, niobate-titanate. Plumboniobite, Y,U,Pb, niobate.

Uvanite, 2UO3.3V2O6.15H2O. Ferganite,U3(VO4)2.6H2O. Torbernite,Cu(UO2)2P2O8.8H3O. Zeunerite,Cu(UO2)2As2O8.8H2O.

Bas'sTtfte }Ca(UO2)2P2O8.8H2O. Uranospinite,Ca(UO2)2As2O8.8H2O. Uranocircite,Ba(UO2)2P2O8.8H2O. CARNOTITE, K2O.2U2O.V2O6.3H2O. Tyuyamunite, CaO.2UO3.V2O5.4H2O. Uranospathite, Hydrous uranyl phosphate.

Etc.

YTTRIUM,

(Ca3,Y2)F6. Yttrofluorite, Yttrocerite,(Y,Er,Ce)F3.5CaF2.H2O. Tengerite,Y carbonate. Cappelenite,Y,Ba, boro-silicate. Melanocerite

n^

}CaO.3V!O,9H2O.

\

fluo-silicates. [Ca,Y,Ce, Caryocerite Steenstrupine J Tritomite,Th,Ce,Y,Ca, fluo-silicate. Gadolinite,Be2FeY2Si2Oi0. Th,Y, silicate. Yttriah'te, Rowlandite, Y sih'cate. Thalenite,Y silicate Thortveitite,(Sc,Y)2Si2O7. Cenosite,H4Ca2(Y,Er)2CSiOi7. Keilhauite,Ca,Al,Fe,Y, titano-silicate. Delorenzite,Fe,U,Y, titanate. Yttrocrasite,Hydrous Y,Th, titanate. Risorite,Y niobate. Fergusonite,Y,Err niobate. Sipylite,Er niobate. Yttrotantalite, Y, etc.,tantalate-niobate. .

B

APPENDIX

678

niobate-tanta-

Fe,Ca,U,Ce,Y,

Samarskite,

Zn2(OH)AsO4.

Adamite,

(Pb,Zn)2(OH)VO4.

Descloizite,

late.

niobate.

U,Y,

Annerodite,

stanno-tantalate.

Y,Fe,Mn,Ca,

Hielmite,

Par^peite }^P2O8.4H!O. Zn3As2O8.8H2O.

Kottigite, !

Euxenite

niobate-

Y,Ce,U,

Barthite,

3ZnO.CuO.3As2O5.2H2O.

Hugelite,

Hydrous,

YPO4.

Retzian,

Y,Mn,Ca,

Zn,

vanadate

(OH)2.3H2O.

niobate.

Y,U,Pb,Fe,

Plumboniobite, XENOTIME,

Pb,

Zn3(PO4)2.Zn

Spencerite,

2Zn3(PO4)2.Zn(OH)2.6iH2O.

Hibbenite,

Hydrous,

Veszelyite,

Cu,

Zn,

phospho-

arsenate. arsenate.

Ce,Y,

Hydrous

Rhabdophanite,

phosphate. Kehoeite,

Hydrous,

Sussexite,

H(Mn,Zn,Mg)BO3.

Al,

Zn,

phosphate.

ZINC

ZnSO4.

Zinkosite, ZnS.

Sphalerite,

Ilesite,

Wurtzite,

ZnS.

Voltzite,

Zn^O.

ZINCITE,

ZnO.

Gahnite,

ZnO.A]2O3.

FRANKLINITE,

(Mn,Zn,Fe)SO4.4H2O.

Goslarite,

ZnSO4.7H2O.

Dietrichite,

(Zn,Fe,Mn)SO4.Al2(SO4)3.

22H2O.

Serpierite, (Fe,Mn)203.

(Fe,Zn,Mn)O.

Chalcophanite,

(Mn,Zn)O.2MnO2.2H2O.

Hydrous,

Zincaluminite,

Cu,

Zn,

sulphate.

2ZnSO4.4Zn(OH)2.6Al(OH)3.

5H2O.

2ZnO.2Mn2O3.lH2O.

Hetserolite,

ZIRCONIUM

ZnCO3.

Smithsonite,

Baddeleyite,

2CuO.CuCO3.5ZnCO3?

Rosasite,

ZrO2.

Aurichalcite,

2(Zn,Cu)CO3,3(Zn,Cu)(OH)2.

Uhligite,

Hydrozincite,

ZnCO3.2Zn(OH)2.

Rosenbuschite,

Hardystonite,

Ca2ZnSi2O7.

Wohlerite,

Danalite,

(Be,Fe,Zn,Mn)7Si3Oi2S.

Ca(Ti,Zr)O6.Al(Ti,Al)O6.

Lavenite,

Zn2SiO4.

Hiortdahlite,

Calamine,

H2ZnSiO5.

Eudialyte,

Clinohedrite,

H2CaZnSiO5.

Gageite,

Tarbuttite,

Hydrous,

Mn,

Zn3P2O8.Zn(OH)2.

MR,

Zn,

(Na2,

Zircon,

Ca)

(Si, Zr)

O3.

silicate.

Na2O.ZrO2.6SiO2.3H2O.

Catapleiite, silicate.

and

silicate.

Zr,Fe,Ca,Na,

Elpidite,

3(Zn,Mn)O.SiO2.H20.

silicate.

silicate

Mn,Ca,Zr,

Willemite,

Hodgkinsonite,

Na,Ca,Zr, Na,Ca,Zr,

Zr

H4(Na2,Ca)ZrSi3On. SiO4.

Chalcolamprite,

R

'

'Nb

.O6. R

'

'SiO3.

niobate.

B

APPENDIX

680

B.

LUSTER

METALLIC

(AND

SUBMETALLIC) .

APPENDIX

II.

CRYSTALLIZATION A.

B.

LUSTER

LUSTER

METALLIC

681

B

TETRAGONAL. NONMETALLIC.

(AND

SUBMETALLIC).

APPENDIX

682

III. CRYSTALLIZATION

HEXAGONAL.*

by speciesare distinguished

Rhombohedral A.

Some

B

LUSTER

NONMETALLIC.

pseudo-hexagonalspecies are included.

a

letter R.

APPENDIX

B.

IV.

METALLIC

LUSTER

CRYSTALLIZATION A.

LUSTER

B

(AND SUB METALLIC).

ORTHORHOMBIC. NONMETALLIC.

683

A.

B.

Brookite (p.429)

538) IlvaiteKp.

B

APPENDIX

684

.

Gothite (p.431)

.

.

...

(p.367) Sternbergite Manganite (p.432)

LUSTER

METALLIC

3-87-4-07 4-0-4-05 4-0-44 4-1-4-2

5-5-6 5-5-6 5-5-5

4-2-44

4-43-4-45 Enargite(p.393)...:

Wittichenite(p.388)

NONMETALLIC

LUSTER

4-5

1-1-5 4 3

(AND SUBMETALLIC). Stibnite (p.358)

4-5^-6 .

2

.

Famatinite (p.393) Klaprotholite(p.386) Hutchinsonite (p.386) .

.

4-57

3-5

.

4-6

2-5

4-6

1-5-2

.

Euxenite

4-6-5 47 4-75-5

(p.591)

Chalmersite (p.366) Chalcostibite (p.386)

.

6-5 3-5 3-4

APPENDIX B.

LUSTER

METALLIC

B

685

(AND SUBMETALLIC) .

686

APPENDIX

A.

LUSTER

B

NONMETALLIC.

APPENDIX

688

VI.

B

TRICLINIC.

CRYSTALLIZATION

A.

LUSTER

NONMETALLIC.

APPENDIX

TABLE

III. I.

689

B

CRYSTALLINE

ISOMETRIC

HABIT.

SYSTEM.

the followinglists some whose crystalline speciesare enumerated habit is often so marked as to be a distinctive character. LUSTER: METALLIC ! Cubes. Pyrite. LUSTER: FluonTe : Cuprite NONMETALLIC (at times elongated into capillaryforms) Sylvite;Boracite;Pharmacosiderite. Also Percy lite; Cerargyrite; Halitej Perovskite. with Cube-like forms occur the following: Apophyllite (tetragonal); Cryolite (monoclinic). Also with the rhombohedral species: Chabazite: Alunite;Calcite;rarelyQuartz and Hematite. Octahedrons. SUBMETALLIC METALLIC LUSTER: AND Magnetite: Franklinite; ChroAlso sometimes, Galena; Pvrite; Linnaeite; mite; Uraninite. Dysanalyte. NONMETALLIC LUSTER: and Gahnite) ; Cuprite;Diamond; PyroSpinel(incl."Hercynite chlore and Microlite;Ralstonite;Periclase; Alum. Forms somewhat with some resembling regularoctahedrons occur tetragonalspecies,as Braunite; Hausmannite; Chalcopyrite; rhombohedral species, Zircon,etc.; also with some as Dolomite. Dodecahedrons. METALLIC LUSTER: Magnetite; Amslgam. NONMETALLIC LUSTER: Garnet; Cuprite;SoH^lif^ Tetrahexahedrons. Native Copper; Fluorite. NONMETALLIC LUSTER: Trapezohedrons. Garnet; Leucite; Analcite. (Jobaltite.Also Gersdorffite; LUSTER: Gersd Pyritohedrons. METALLIC Hauerite JPyrite^ In

Galem^

"

"

"

"

"

"

(submetallic). Tetrahedrons. NONMETALLIC

The

METALLIC LUSTER: Tetrahedrite. LUSTER: Sphalerite;Boracite;Helvite;Eulytite;Diamond; Zunyite. tetragonalsphenoids of Chalcopyritesometimes closelyresemble tetrahedrons. "

II.

SYSTEM.

TETRAGONAL

SUBMETALLIC LUSTER: Square Pyramids. Braunite; Hausmannite. NONMETALLIC LUSTER: Zircon; Wulfenite; Vesuvianite; Octahedrite;Xenotime. NONMETALLIC vesuvianite.: Scapolites;Apophyllite; LUSTER: zircon: Square Prisms. "

"

Phosgenite. with Apophyllite; Wulfenite; Torbernite. Square tabular crystalsoccur Prisms of orthorhombic species,e.g., Topaz; nearly square are noted with a itiuritDer monoclinic also (100 A 010 with the Andalusite; Danburite: 90", Pyroxene 110 A 110 87") """"

=

=

III.

SYSTEM.

HEXAGONAL

Apatite: Bervl: VanadiNONMETALLIC LUSTER: Hexagonal Prisms. Pyromprphite; nite; Mimetite (usuallyindistinct rounded forms). Also Nephelite; Milarite: Tysonite, "

and

others.

Hexagonal prisms Tourmaline

L

also

are

common

with

the

Willemite; Phenacite; Dioptass, etc.

rhombohedral species: Quartz;Calcitej Again, with the Micas, efc. Numef^

could be included here. orthorhombic (or monoclinic) specieshaving a prismaticangle of about 60" (and the result of twinning. as and stillmore 120") simulate this form both in simple crystals lolite. It is also to be noted that the isometric Thus, Aragonite;Strontianite; Leadhillite; dodecahedron, e.g., of Garnet, has often the form of a hexagonalpyramid with trihedral terminations (cf.Fig. 470, p. 175). LUSTER: Tabular hexagonal prisms are noted with various species. Thus, METALLIC LUSTER: Tri^ Graphite; Molybdenite; Hematite; Ilmenjte; Pyrrhotite. NONMETALLIC ous

rare

specit

-

Many

Hexagonal Pyramids. Apatite: Corundum, (rhombohedral);Quartz (rhombohedraltrapezohedral): Hanksite. This form is often simulated by various orthorhombic species,in part as the result of LUSTER: Chalcocite; Stephanite; Polybasite;Jortwinning. For example, METALLIC "

danite;etc.

Also Brookite. LUSTER: Witherite;Bromlite; Cerussite;lolite. Tourmaline. Trigonal Prisms. Siderite : PJiodochrosite. Rhombohedrons. Angle ?5u(and 105"): Calcite ;:JDolomitej. Quartz ; Hematite. Angle not far from 90": Chabazite; Alunite ;Talciter'also Scalenohedrons. Calcite and allied Carbonates^ProustifE7~~ NONMETALLIC

"

"

"

B

APPENDIX

690

"

SYSTEMS.

Stibnite;Arsenopyrite;Bournonite;Manga-

LUSTER:

METALLIC

Prismatic Crystals.

TRICLINIC

AND

MONOCLINIC

ORTHORHOMBIC,

IV.

m

Andalusite;"arite: Celes(orthorhombic) Tojmz; Sj^ijrolite;

LUSTER:

NONMETALLIC

and many Pyroxene; Amphibole; Qrthoclase, others. Also (monoclinic) tite;Danburite. in aspect (Fig.894, p. 531JT often prismatic are Epidote crystals Wollastonite;4lhl'te, Tabular Crystals. Barite; Cerussite;Calamine; Diasppre; LUSTER: Stibnite;BismutEimtej Miflente;JameAcicular Crystals. METALLIC sonite;Aikinite,and other species. Natrolite: Scolecite; Thomsonite, and other Zeolites. NONMETALLIC LUSTER: gectolite; lesd 6f ten Calcite. Also many other species. Also Aragonjie;Strontianite; istic. speciesis very characterTwinTrystals. The habit of the twins occurringwith many Reference is made to pp. 165 to 172 and the accompanying figuresfor a presentation of this subject. "

"

'

"

STRUCTURE

IV.

TABLE

OF

MASSIVE

MINERALS

Fibers separable: Asbestus (amphibole);also the similar asbestiform variety serpentine(chrysotile) ; Crocidolite (colorblue). Fibers not separable, Also Aragonite; Anthophyllite;Calcite; Gypsum. chieflystraight: Barite; Celestite;Anhydrite; Brucite; Enstatite; Wollastonite;Dufrenite; Vivianite.

Fibrous.

"

of

See also Columnar below. Fibrous-Radiated. Wavellite; Pectolite;Thomsonite; Natrolite;Stilbite, Scolecite; and other Zeolites;Gothite;Malachit Columnar. METALLIC LUSTER: Stibnite;Hematite; Jamesonite;Zinkenite, etc. NONMETALLIC LUSTER: Limonite; Gothite; Aragonite;Amphibole (tremolite, actinolite, Natrolite and other Zeolites: Stronetc.);Epidote; Zoisite;Tourmaline; Sillimanite; tianite; "

.

"

Witherite;Topaz. Cyanite has often a bladed Fibrous and columnar Lamellar-Stellate. Foliated. METALLIC "

"

,

tructure.

varieties pass

into

one

another.

Gypsum; Pyrophyllite;Talc. LUSTER: Graphite; Molybdenite; Tetradymite; Sternbergite-

Nagyagite. NONMETALLIC LUSTER: Talc; Orpiment; Gypsum; Pyrophyllite; Serpentine;Gypsum Micaceous. The Micas,p. 559: also the Brittle Micas, p. 566, and the Chlorites, 568 p. Also Brucite; Orpiment; Talc; Torber^ite; Autunite. Granular. METALLIC LUSTER: Galena; Hematite; Magnetite. Many sulphides, sulpharsemtes;etc.,have varieties which are fine-granular to compact and impalpable NONMETALLIC LUSTER: Pyroxene (coccolite); Garnet;Calcite; etc "

"

Botryoidal,Mammillary, Reniform,

Barite,

etc.

"

METALLIC

LUSTER:

Allemontite.

Hematite; Arsenic-

Malachite; Prehnite; Smithsonite;Calamine; Chalcedony; Stalactitic.

METALLIC

"

LUSTER:

Limonite; Psilomelane;Marcasite.

LUSTER: Calcite; NONMETALLIC Aragonite;Gibbsite;Chalcedony. Granular

Cleavable." METALLIC LUSTER: Galena. NONMETALLIC LUSTER: Calcite;Dolomite;Sphalerite; Fluorite. Oolitic. Calcite; Aragonite;Hematite. "

fcartny. "

NONMETALLIC

LUSTER:

TABLE

V.

Magnesite; piolite

PHYSICAL

CHARACTERS.

I. CLEAVAGE. Cubic.

"

METALLIC

LUSTER:

Galena. Halite: Sylvite. The

STER:

Ui.

also

Corundum,

Diamond.

l

75

"alcite "dral'~ 105!

Square Prismatic(90"). -

and^

other

cleavageof Anhydrite (alsoof Cyro-

p. 413.

Magnetite

(also Franklinite)has

often distinct

Sodalite; Hauynite. wine group (pp. 437-445) angles

sPecies of th^

Scapolite; Rutile;Xenotime.

APPENDIX

Prismatic. Basal.

"

691

B

Barite METALLIC

(78"i, 101"^);Celestite; Amphibole (54" and 126"),etc. LUSTER: Graphite; Molybdenite. LUSTER: Apophyllitej Topaz; Talc; the Micas and Chlorites; ChalcoPyroxene often shows marked basal parting.

"

NONMETALLIC etc. phyllite,

Pinacoidal.

METALLIC LUSTER:

"

NONMETALLIC

LUSTER:

Stibnite.

Gypsum;

Orpiment; Euclase;Diaspore;Sillimanite; Cyanite;

Feldspars. II. 1.

Soft

Minerals.

The

"

less;they hence have

HARDNESS.

followingminerals feel.

are

conspicuouslySoft,that is,H

(See further the Tables, pp. 679

2

=

688.) METALLIC LUSTER: Graphite; Molybdenite; Tetradymite; Sternbergite; Argentite; of the Native Metals (Lead, etc.). Nagyagite; some NONMETALLIC LUSTER: Talc; Pyrophyllite; Brucite;Tyrolite;Orpiment; Cerargyrite; Cinnabar; Sulphur; Gypsum. Also Calomel, Arsenolite,and many hydrous sulphates,phosphats, etc. Minerals. Minerals whose hardness is equal to or greater than 7 (Quartz 2. Hard 7). The followingminerals are here included:

or

a

greasy

to

"

=

LUSTER

QUARTZ (p.403) Tridymite (p.407) Barylite (p.498).Dumortierite (p.543) Danburite (p.522) BORACITE (p.620) Zunyite (p.505) CYANITE (p.526) TOURMALINE (p.540) GARNET (p.505) IOLITE (p.497) STAUROLITE (p.543) (p.510) Schorlpmite Sapphirine (p.544) Euclase (p.529)

NONMETALLIC

7 7 7 7

7-7'25 7 7

5-7'25 7-7*5 6'5-7'5 7-7-5

7-7 "5 7-7*5 7'5 7'5

Hambergite (p.620) ZIRCON (p.520) ANDALUSITE (p.524) BERYL (p.495) Lawsonite (p.540) Phenacite (p.514) Gahnite (p. 420) Hercynite (p.420) SPINEL (p.419) TOPAZ (p.523) Rhodizite (p.621) CHRYSOBERYL (p.423) CORUNDUM (p.413) DIAMOND (p.345)

7'5 7'5 7'5 7'5-8 7'5-8 7'5-8

7'5-8 7 '5-8 8 8 8 8'5 9 10

7. The followingminerals have hardness equal to 6 to 7, or 6 '5 METALLIC: Iridosmine LUSTER (p. 355); Iridium (p. 355); Sperrylite(p. 379). Ardennite NONMETALLIC: LUSTER (p. 534); Bertrandite (p. 539); (p. 539); Axinite Cassiterite (p. 425); Chrysolite (p. 511); Diaspore (p. 431); Elpidite (p. 496); Epidote (p. 531);Forsterite (p. 513); Gadolinite (p. 529); Jadeite (p.479); Partschinite (p. 510); Sillimanite (p.526);Spodumene (p.480); Trimerite (p.515). "

III.

SPECIFIC

GRAVITY.

gravityto Attention is called to the remarks in Art. 302 (p.199),on the relation of specific in Art. 303 as to the average specific gravity chemical composition. Also to the statements The speciesin each of the minerals of metallic and norimetallic luster respectively. among are arranged separate lists of Table II of minerals classifiedwith reference to crystallization tinguished gravities.Hence the lists give at a glance minerals disaccording to ascending specific by both low and high density. IV. Metallic.

"

Native

LUSTER.

metals;

most

(See Art. 364, p. 249) Sulphides; some

ganese, Oxides, those containingiron,man-

lead,etc. Here belong chieflycertain iron and manganese compounds, as Ilmenite; Submetallic. Ilvaite;Columbite; Tantalite (and allied species);Wolframite; Braunite; Hausmannite. Also Brookite;Uraninite,etc. Here Adamantine. belong minerals of high refractive index: (a)Some hard minerals: Zircon; Rutile. (6) Many speciesof high density,as Diamond; Corundum; Cassiterite; also of of Thus, Cerussite,Anglesite,Phossilver, lead, mercury. copper, compounds erite, Cinnabar, etc. (c)Also certain varieties of Sphalgenite,etc.; Cerargyrite;Cuprite; some "

"

Tjtanite and Octahedrite.

APPENDIX

(592

B

varieties of the following: Cuprite, some Pyrargyrite; Metallic-Adamantine. Octahedrite, Rutile,Brookite. Phosphates. Sphalerite;Sulphur; Elseohte; Serpentine; many Resinous or Waxy. Garnet, Beryl, etc. as Silicates, Vitreous. Quartz and many site, Cerus-

"

"

"

(on cleavage surfaces) foliated species: Talc, Brucite, Pyrpphylhte.Also Also, less prominent: conspicuouslythe following: Apophyllite,Stilbite,Heulandite. Feldspar,and others. Diaspore; some Barite;Celestite; fibrous minerals,as Gypsum, Calcite;also Asbestus; Malachite. Some

Pearly "The

Silky. "

V.

COLOR.

ever, of suggestion. It is to be noted, howin the way use followinglists may be of some especiallyin the case of metallic minerals a slightsurface change may alter the luster particularly,no minerals of nonmetallic sharp effect of color. Further, among variations of shade occur and many between colors slightlydifferent, be drawn line can unless inconvenientlyextended, no lists, in the case of a singlespecies. For these reasons could make any claim to completeness. The

that

(a)

METALLIC

LUSTER.

and Native silver;Native Antimony, Arsenic Tellurium; Silver-white,Tin-white. Amalgam; Arsenopyrite and Lollingite;several sulphides,arsenides,etc., of cobalt or Tellurides;(Bismuth (reddish).) No sharp line can nickel,as Cobaltite (reddish);some these and the followinggroup. be drawn between Steel-gray. Platinum; Manganite; Chalcocite; Sylvanite; Bournonite. Blue-gray. Molybdenite; Galena. Galena (bluish); as Stibnite; many Sulpharsenites, etc., Lead-gray. Many sulphides, as Jamesonite,Dufrenoysite,etc. Iron-black. Graphite; Tetrahedrite; Polybasite; Stephanite; Enargite; Pyrolusite; Magnetite; Hematite; Franklinite. Black (with submetallic luster). Ilmenite; Limonite; Columbite; Tantalite, etc.; Wolframite;Ilvaite;Uraninite,etc. The followingare usually brownish black: Braunite; "

"

"

"

"

"

Hausmannite.

Copper-red.

Native copper. Bornite (quicklytarnished givingpurplishtints) ; Niccolite.

"

Bronze-red.

"

Bronze-yellow. Pyrrhotite; Pentlandite;Breithauptite. Brass-yellow. Chalcopyrite;Millerite (bronze). Pale brass-yellow: Pyrite; Marcasite (whiterthan Pyrite). Gold-yellow. Native gold; chalcopyriteand pyrite sometimes are mistaken for gold. "

"

"

Streak.

The

"

followingminerals

of metallic luster

are

notable

for the color of their

streak:

Cochineal-red:

Pyrargyrite. Cherry-red:Miargyrite. Dull Red: cinnabar. Hematite;Cuprite;some Scarlet: Cinnabar (usually nonmetallic). Dark Brown: Chromite. Manganite; Franklinite; Yellow: Limonite. Tarnish. The following are conspicuous for their bright or variegated tarnish: Bornite (purplish Limonite. tints); Tetrahedrite;some "

(6) NONMETALLIC Colorless.

IN

CRYSTALS:

copyrite; Chal-

LUSTER.

Quartz; Calcite;Aragonite;Gypsum; Cerussite;AnglesApophyllite;Natrolite and other Zeolites; Celestite; Diaspore;Nephelite;Meionite;Calamine; Cryolite;Phenacite, etc MASSIVE: Quartz;Calcite; Gypsum; Hyalite (botryoidal) White. CRYSTALS: Amphibole (tremolite); Pyroxene (diopside,usually greenish). Quartz5 Felspars, especiallyAlbite;Barite;Cerussite, lit^T i^; Mllk7 l IVEiCr Scapolite;Talc; Meerschaum;Magnesite;Kaolinite; Amblygonite, etc. Blue. BLACKISH BLUE: Azurite;Crocidolite. INDIGO-BLUE: Indicolite (Tourmaline);Vivianite. AZURE-BLUE: Lazulite; Azurite;Lapis Lazuli;Turquois Sapphire; Cyanite; Mite; Azurite;Chalcanthite and many mIN"BLUE: copper "

ite; Albite; Barite; Adulana; Topaz;

-

"

693

APPENDIX

MOUNTAIN-BLUE:

Beryl; Celestite. Amethyst; Fluorite. BLUE: Amazon-stone; Chrysocolla;Calamine; Smithsonite;some

SKY-BLUE, VIOLET-BLUE: GREENISH

Turquois;

Beryl. Green.

BLACKISH

"

GREEN:

Epidote; Serpentine;Pyroxene; Amphibole.

Beryl (Emerald); Malachite; Dioptase; Atacamite; and many other compounds; Spodumene (hiddenite);Pyroxene (rare);Gahnite; Jadeite and Jade. copper GREEN: BLUISH Beryl; Apatite; Fluorite;Amazon-stone; Prehnite;Calamine; Smithsonite; Chrysocolla; Chlorite; some Turquois. MOUNTAIN GREEN: Beryl (aquamarine); Euclase. APPLE-GREEN: Talc; Garnet; Chrysoprase; Willemite;Garnierite;Pyrophyllite:some Muscovite; Jadeite and Jade, Pyrophyllite. PISTACHIO-GREEN: Epidote. GRASS-GREEN: Pyromorphite; Wavellite;Variscite;Chrysoberyl. GREEN: GRAYISH Amphibole and Pyroxene, many common kinds; Jasper; Jade. OLIVE-GREEN: YELLOW-GREEN to Beryl; Apatite; Chrysoberyl; Chrysolite (olivegreen); Chlorite; Serpentine;Titanite Datolite; Olivenite;Vesuvianite. Yellow. SULPHUR-YELLOW: Vesuvianite. Sulphur; some ORANGE-YELLOW: Orpiment; Wulfenite; Mimetite. also WINE-YELLOW, WAXYELLOW: STRAW-YELLOW, Topaz; Sulphur; Fluorite; Cancrinite; Wulfenite; Vanadinite; Willemite; Calcite; Barite; Chrysolite;Chondrodite; Titanite; Datolite, etc. BROWNISH YELLOW: Much Sphalerite;Siderite;Gothite. Gothite: OCHERYellow ocher (limonite). YELLOW: dinite; Red. RUBY-RED: Garnet; Proustite;VanaRuby (corundum); Ruby spinel; much Sphalerite;Chondrodite. EMERALD-GREEN:

"

"

Cuprite; Cinnabar.

COCHINEAL-RED:

Zircon; Crocoite. ORANGE-RED. Zincite;Realgar; Wulfenite. Tourmaline CRIMSON-RED: (rubellite);Spinel,Fluorite. Cinnabar. SCARLET-RED: BRICK-RED: Some Hematite (red ocher). to PINK: Rose ROSE-RED quartz; Rhodonite; Rhodochrosite; lite. Apophyllite and Zoisite;Eudialyte; Petalite;Margarite. PEACH-BLOSSOM RED to LILAC: Lepidolite;Rubellite. HYACINTH-RED.

"

"

FLESH-RED:

Stilbite and BROWNISH Brown.

"

Erythrite;some

Scapo-

some Chabazite; Some (the variety troostite); Orthoclase; Willemite Heulandite; Apatite; rarely Calcite;Polyhalite.. RED: Jasper; Limonite; Garnet; Sphalerite;Siderite;Rutile. Some Sphalerite;S aurolite; Cassiterite; BROWN: REDDISH Garnet; some

Rutile. CLOVE-BROWN: YELLOWISH

Axinite; Zircon; Pyromorphite. related carbonates; Sphalerite;Jasper; Limonite; Siderite and Staurolite. Chrondrodite; Vesuvianite; Gothite; Tourmaline; BLACKISH BROWN: Siderite; Sphalerite. Titanite; some SMOKY BROWN: Quartz. Mica biotite):also (especially Black: (melanite); some Tourmaline; black Garnet back); some Amphibole, Pyroxene and Epidote (these are mos'ly greenish or brownish to black); smoky brown kinds of Quartz (varying from further,some Sphalerite and some mentioned luster are with submetalhc black minerals also Allanite; Samarskite. Some on

p. 692. Streak.

BROWN:

minerals with nonmetallic of some The streak is to be noted in the case the mass in (e.g.Tourmaline), colored far the when deeply By majority have, even be mentioned: The following may but little from white. differing ORANGE-YELLOW: Zincite,Crocoite. COCHINEAL-RED: Pyrargyriteand Proustite.

luster.

"

a

streak

SCARLET

Cinnabar. RED: BROWNISH RED: Cuprite; Hematite. BROWN: Limonite. , A Azunte, and blue minerals, as Malachite, The streak of the various green copper, little often a paler. though is about the same the color of the mineral itself, as ,.

,

.,

etc.,

GENERAL

696

aggregate,8, 182 Crystalline

Carlsbad twin, 170 Center

INDEX

structure, 8

of symmetry, 12

Charcoal tests,334 Chemical compound, 318

composition and

acters, optical char-

180 Crystallites, systems of, 15 Crystallization, 7 Crystallography,

literature of,2

298

Cube,

elements, 311, 312 formula,312

54

Cubic system, 52 Curved and crystals

mineralogy,311

faces,177

317 radicals,

reactions,317

D

symbol,312 Decrepitation, 332, 333

tests,328, 338

Chlorides,tests for,338 Chromium, tests for,339 Circular polarization, 240, 270

Deltoid dodecahedron, 69 Dendritic structure, 173, 183 .

imitated by mica 300

Classification of minerals,343

Cleavage, 186 basal,187 cubic,187 dodecahedral,187 octahedral,187

Diaphaneity,247

187 prismatic,

134 Clinopinacoid,

Clinoprism,135 Clinopyramid, 135 Closed tube tests,333

Cobalt,tests for,339 use nitrate, of,332 Cohesion, 186

Diploid,65 Dispersion,221 crossed,294 horizontal,293 inclined,292 of bisectrices, 293, 294 of optic axes, 289 Distorted crystals, 13, 174 Ditetragonalbipyramidalclass,77 Ditetragonalprism, 79

Colloid structure,183 Colloidal minerals,324

Color,204, 247, 248 complementary, 205 structure,182

Complementary colors, 205 Composition-plane,161 160 Compound crystals, Concentric Conchoidal

pyramid, 82

structure,182

fracture,191

for electricity, Conductivity, 306 for heat,304 Conical

276 refraction,

Conoscope,243 Contact "goniometer 162 Contact-twin, Coolingtaste,310 Copper,tests for,389^

Density, 195 Descriptionof species,343 Determination of minerals,341 Diamagnetic minerals,309 Diamagnetism, 309 Diametral prism, monoclinic system, 134 orthorhombic system, 122 Diathermancy, 305 Dibasic acid,318 Dichroism, 247, 268 Dichroscope,269 223 Diffration, Dihexagonal bipyramidalclass,95 Dihexagonal pyrism, 96 Dihexagonal pyramid, 98 Dihexagonal pyramidal class,98 Dimorphism, 325

rhombohedral, 187 133 Clino-axis, Clinodome, 135 Clinohedral class, 138

Columnar

tions, sec-

,,

-

Ditetragonalpyramidal class,84 Ditrigonalbipyramidalclass,103 Ditrigonalprism, 103 pyramid, 103 Ditrigonalpyramidal class,109 Ditrigonalscalenohedral class,104 structure, 182 Divergent

J.

Dodecahedron,54 deltoid,69 dyakis,65

Coralloidal struetur Corrosion forms, 191^.

pentagonal,64 72 tetrahedral,

Cotangentrelation,; Jlffi Critical angle,210 h Crossed dispersion,

H Crypto-crystalline, H Crystal, definition, distorted

form, 30

Domatic

rhombic, class,138

Domes, 31, 123, 135, Double

54

145

223 refraction,

Drusy, 183 Dyakis-dodecahedron, 65 Dyakisdodecahedral class,63

GENERAL

E

Earthy

191 fracture,

Effervescence,328 Eightling,164 186, 194 Elasticity, Elastic minerals,194 Electrical conductivityin minerals, 306 Electro-negativeelements,313 -positiveelements,313 Elements, angular, 128, 139, 148 axial,128, 139, 148 chemical,312 polarizedlight,240 Elliptically Elongation,negative or positive,280 Enantimorphous forms, 71, 113 288 Epoptic figures, Etching figures,189 332 Exfoliation, Expansion by heat, 304 Exterior conical refraction, 276 Extinction,230 character of,239 directions, inclined, 260, 278 parallel, 260, 278 278 Extinction-angle, Extraordinary ray, 254

Feel,310 Fetid odor, 310 Fibrous

structure, 182

Filiform,183 First order prisms,79, 95 pyramids,80, 97 Fiveling,164 332 Flame coloration, oxidizing,331 reducing,331 Flexible,194 Fluorescence,251 Fluorides,test for,339 Fluxes,336 Foliated structure, 182

Forceps, 330 Form, 30 Formula, chemical,312, 320 calculation of,321 Fracture, 191 in minerals,306 Frictional electricity Fundamental form, 30 304, 332 Fusibility, scale of,332

Gels, 324 General mineralogy, literature of,3 Gladstone law, 210 Glass,opticalcharacters of,252, 300 Glass tubes,331, use of,333

Gliding planes,187 Glimmering luster,250

697

INDEX

250 Glistening luster,

Globular

structure,183

180 Globulites, Glowing,332, 333

Gnomonic

Gnomonic

40 projection, projectionof isometric forms, 62 hexagonal forms,99, 109

tetragonalforms, 84 triclinic forms, 147 monoclinic forms,

"

137

orthorhombic

forms,

127

Goniometer,contact

or hand, horizontal,155 154 reflecting, 157 theodolite, 157 two-circle,

Granular

152

structure, 182

Greasy luster,249 Grouping,molecular,22 parallel, 172, 173

Gyroidalforms, 71 H

Habit, crystal,10 Hackly fracture,191 Hand goniometer, 152 Hard minerals,193 Hardness, 191 Heat, 303 effect on opticalproperties,296 Heavy solutions,198 Hemihedral forms, 21 Hemimorphic class,hexagonal system, monoclinic

98

system,

138

orthorhombic

system,

126

tetragonal system, Hexagonal

axes,

94

bipyramidalclass,100 prisms,95, 96 prism of third order,111 pyramidalclass,101 pyramids,97, 98 symmetry, 11 system, 17, 94

class,102 trapezohedral trapezohedron,102 Hexakistetrahedron,70 Hexoctahedral class,52 Hexoctahedron, 59 66 Hextetrahedral class, Hextetrahedron, 70 Holohedral forms, 21 292 Horizontal dispersion, goniometer, 155 Horse-radish odor, 310, 334 Houppes, 288 Hour-glass structure, 478

Hydroxides,318

84

GENERAL

698

INDEX

202 Light-waves,

Icosahedron,65, 67 58 Icositetrahedron, Impalpable structure, 182 274 biaxial, Indicatrix, 257 uniaxial, Dana, 29 Indices,crystallographic, Goldschmidt, 29 Naumann, 29 Weiss, 29 29 rational, 207 refractive,

determination

of,280,

213, 216 angle of,206 Incidence, 292 Inclined dispersion, hemihedrons,67 179 Inclusions, Inelastic minerals,194 Insoluble minerals,329

224, 230 Interferenceof light, 236 colors, 260 biaxial crystals, uniaxial crystals, 278 281 biaxial, figures,

inclined, 267, 283 260 uniaxial, Interior conical

276 refraction,

332 Intumescence, 250 Iridescence,

213 Liquids with high refractive indices, 339 test for, Lithium, Lorentz law, 210 Lorenz law, 210

Luster,249 M

Macro-axis,121, 144 Macrodome, 123, 145 Macropinacoid,122, 145 Macroprism,123 Macropyramid, 124 Magnesium, test for,339 Magnetic minerals,308

Magnetism, 308 Magnets, natural,308 193 Malleable minerals, 183 structure, Mammillary Manganese, test for,339 180 Margarites, of crystalangles, 152 Mercury, test for,339 325 Meta-colloids, Metagenetictwins, 163 249 Metallic-adamantineluster, 249 Metallic luster, 249 Metallic pearly luster, 313 Metals, Mica plate, of,264 use

Measurement

Mica

Iron,test for,339 Iron cross, 166 252 Isodiametric crystals,

325 Isodimorphism,

Isometric crystals, opticalproperties 252 52 16, system, 322 Isomorphism,

Isomorphousgroup, 322 323 mixtures, 252 Isotropic crystals,

twin, 171, 457

Manebach

sections superposed,300

Micaceous structure,182 326 Microchemical analysis, Microcosmic salt,v. Salt of Phosporus,336 180 Microlites, 245 Microscope,

Miller hexagonalaxes, 117 117 indices, 28 indices, 14 Mimetic crystals, 326 Mineral,artificial,

literatureof,4 definitionof, 1

Jollybalance,196

326 synthesis, kingdom, 1 4 journals, Mineralogical

Mineral K

chemical Mineralogy, Klein

198 solution,

and

determinative,

literatureof,4 science of,1, 2 21 Models of crystals, Mohs scale of hardness,191

Lamellar

302 polarization,

Molecular networks,22, 25

182 structure,

structure,7

.

Lamp Law

for blowpipe, 330 of rational indices, 29

Lead, test for,339 Left-handed crystal, 114,403 241 polarization,

Light,nature of,200 204 Light-ray,

Light velocity, relationto refractive index,

weight,316 311 Molecule,

Molybdenum,test for,339 Monobasic

acid,318 Monoclinic axes, 133 134 crystals, 291 opticalcharacters, system, 17, 133 183 Mossy structure,

GENERAL

N Natural

Oscillatory combination, 176 Oxides,318 Oxidizingflame,331

magnets, 308

Naumann's

indices,29 277, 286 Negative crystal,biaxial, uniaxial,254, 258, element, 313 elongation,280 Network, molecular,22 Neutral salt,319 Newton's rings,225 Nickel,test for,339 Nicol prism, 228 Niobium, test for,339 Nitrates,test for,339

264

Nodular structure, 183 249 Non-metallic luster,

Non-metals, 313 angles,44 class,isometric system, 52 hexagonal system, 95

Normal

monoclinic

system, 133 system, 121 tetragonalsystem, 77 triclinicsystem, 144 orthorhombic

salt,319

Oblique system, 133 Octahedron, 54 Ocular, Bertrand, 279 Odor, 310 Opalescence,250 Opaque, 247 Open tube tests,334 form, 30 Optic axes, 273, 276 axial angle,277 axis,254 Opticalanomalies,301 characters of crystalline aggregates, 300 twin crystals, 298

effectof heat upon,

296 on, 300 pressure relation to chemical composition,298

tests,methods

and

699

INDEX

order of,295

Paragenetictwins,163 Parallel extinction, 260, 278 grouping, 172 hemihedrons, 64 Paramagnetic minerals,309 Paramagnetism, 309 Parameter, 27

Paramorph, 27' Paramorphism, 27 Parting,188 249 Pearly luster, Penetration-twin,162 Penfield beam balance,197 Pentagonal dodecahedron, 64 72 tetrahedral, hemihedral class,63 71 icositetrahedral class, 71 icositetrahedron, Pentavalent element,317 Percussion figure,188 Pericline law (twinning),172,462 Periodic law, 314, 315 Phanero-crystaUine,182 Phosphates, test for,339 Phosphorescence,251 Phosphoric acid,test for,339 307 Photo-electricity, Physicalcharacters,185 mineralogy,literature of,2 307 Piezo-electricity, Pinacoid,31 Pinacoidal class,144 Plagiohedralclass,71 Plagiohedralhemihedral class,71 Plane-polarized light,226 226 Plane of polarization, Planes of symmetry, 10 Platinum wire,330, 336 Play of colors,250 Pleochroic halos,288

Pleochroism,247, 287 Pleomorphism, 325 Point

system, 23

229, 243 Polariscope, 226 Polarization, 288 Polarization-brushes, Orthodome, 135 -microscope,245 Orthopinacoid,134 226 Polarized light, Orthoprism, 135 229 Orthopyramid, 135 Polarizer, Orthorhombi ombic axes, 121 Polysynthetictwinning, 163 Positive crvstal, biaxial, 277, 286 bipyramidalclass,121 254, 258, 264 uniaxial, bisphenoidalclass,128 121 element,313 crystals, elongation,280 optical characters, 288 Potassium, test for,340 optical characters, 289 Pressure, effect upon dispersion, 300 pyramidal class,126 189 figures, system, 17, 121

Ordinary ray,

254 Ortho-axis,133

GENERAL

700

INDEX

Reflectinggoniometer, 154

Primary opticaxes, 276 Prism, 30

Reflection of light,205

96 hexagonalsystem, dihexagonal, first order,95

second order,96 third order,100 monoclinic system, 135 orthorhombic system, 123 79 tetragonalsystem, ditetragonal, first order,79

angle of,205 Refraction,206 double, 223 strength of,224 Refractive index,207 determination of, 213. 216, 180 relation to lightvelocitv,

second order, 79 third order,85

241 Refractometer,

triclinicsystem, 145 133 Prismatic class,

Regular system, 52 Relief,high or low, 212

gnomonic, 40 Projection,

Reniform structure, 183 Resinous luster, 249 Reticulated structure, 182 Rhombic section,462

literature of,44 31 horizontal, 31 spherical, 32 stereographic,

literature of,44 14, 169,437 Pseudo-hexagonalcrystals, -isometric

301 crystals,

Pseudomorph, 183,326 Pseudomorphism, 326 Pseudosymmetry, 14, 60, 164, 174,297 Pycnometer, 197 Pyramid, 31 hexagonalsystem, dihexagonal,98 firstorder,97 second order,97 third order,100 monoclinic system, 135 orthorhombic

system, 124 79 tetragonal system, ditetragonal, first order, 79 second order,79 third order,85 triclinicsystem, 145

Pyramidal hemihedral

208

indices,principal, 209

hemimorphic

class,

101

Pyramidal-hemimorphic class, hexagonal system, 101

tetragonal system, 86 63 Pyritohedralclass, Pyritohedron,64 306 Pyro-electricity, 338 Pyrognostics,

Q Quarter-undulationmica plate, 264 Quartz wedge, 231 use of,286

sphenoid, 128 class,104, 110

Rhombohedral Rhombohedral Rhombohedral

103 division,

hemihedral

class,104

hemimorphic class,109 tetartohedral class,110

Rhombohedron, positive and

negative, 104, 105 second order, 110 third order,110 Right-handed crystal,114, 403 241 polarization,

Roasting,334 Rontgen rays,

25

Saccharoidal structure,182 Saline taste,310 Salt of phosporus, 337

Salts,319 106 Scalenohedron, 88 tetragonal,

Scalenohedral class, 87 Scale of fusibility, 332 Scale of hardness,191 251 Schiller, 251 Schillerization, 192 Sclerometer,

Second

order prism, hexagonalsystem, 96

tetragonal system, 79 pyramid, hexagonal system, 97

tetragonal system, 79-

rhombohedron, 110 Radiated structure, 182

Radical, 317 chemical, Rational indices, law of,29 Reaction, 317 chemical, Reagents,chemical, 328 Reducingflame,331 Reduction of metals,334

Secondaryoptic axes, 276 twinning,165, 188 193 Sectile,

Selenite-plate, 236, 266 Selenium,test for,340 313 Semi-metals, 247 Semi-transparent,

Sensitive tint,236 use

of,266

GENERAL

Separable,182

Symmetry,

250 Shining luster, test for,340 Silica, Silkyluster,249 Silver,test for,340 Soda, use of,330, 336 Sodium, test for,340 Soft minerals,193 Solid solution, 323 in minerals,328 Solubility Solution planes,189 Sonstadt solution,198

Sound

701

INDEX

of, 12 15 classes, exhibited by Stereographicprojection, center

45

of systems, 18, 19 planes of, 10

Synthesis, mineral,326 System, hexagonal,94 52 isometric, monoclinic,133

201

waves,

.

Specificgravity,195 determination

orthorhombic,121

tetragonal,77 143 triclinic, 15 Systems of crystallization,

of, 196

221 Spectroscope, Sphenoid,87

rhombic,

128

Sphenoidalclass,monoclinic system, orthorhombic

138

system,

128

tetragonalsystem, 87 class,87 89 tetartohedrajclass, 31 projections, Spherical Spherulites, 300, 459 250 Splendent luster, hemihedral

191 Splintery fracture,

Stalactitic structure, 183 Stellated structure, 182 circles and scales, 36 Stereographic 32 projection,

literature of,44

hexagonal forms, 99, 108 isometric forms,

Tangent relation 49 Tarnish,250 Taste, 310 Tautozonal faces,45 Tellurium,test for,340 Tenacity, 193 ,

Test paper, 330 Tetartohedral class, isometric system, 72

tetragonalsystem, forms, 22 85 Tetragonal bipyramidal class, 89 bisphenoidalclass, 77 crystals, 86 pyramidal class, scalenohedron,88 87 sphenoidalclass,

tetragonal forms, 83

triclinic

forms,

146

monoclinic

forms,

137

orthorhombic

forms,126 protractor, 35, 39

Streak,247 224 Strengthof double refraction, 176 Striations, 188 v. Percussion-figure, Strike-figure, Strontium,test for,340 of

minerals,182

Sublimate,333, 334 247 Subtranslucent, 247 Subtransparent, 249 Subvitreous, test for,340 Sulphates, test for,340 Sulphides, 320 Sulpho-salts, Sulphur, test for,340 Sulphurous odor, 310 Swellingup, 332 Symbol, chemical,312 27 crystallographic,

89

symmetry, 11 system, 16, 77

61

Structure

10

axis of, 11

89 trapezohedralclass, trapezohedron,89 58 trisoctahedron, 69 tristetrahedron, 66 Tetrahedral class, 66 hemihedral class, pentagonal dodecahedral class,72 pentagonaldodecahedron, 72 s/ Tetrahedron, 67 Tetrahexahedron, 56 Tetravalent element,317 Theodolite goniometer,157 307 Thermo-electricity, Third-order prism,hexagonal system, 100 tetragonalsystem, 85 pyramid, hexagonal system, TOO tetragonalsystem 85 rhombohedron, 110 198 Thoulet solution, Tin, test for,340 Titanium, test for,340 210 Total reflection, 219, 241 refractometer,

Tourmaline

tongs, 243

Translucent,247 Transparency, 247

GENERAL

702

Transparent, 247 Trapezohedral class, hexagonal system, 102, 112 system, tetragonal

89

hemihedral class,102 tetratohedral class,112

INDEX

U

Ultra-blue,521 Uneven fracture,191 253 Uniaxial crystals, of

behavior

light in,

253

Trapezohedron,58

determination

hexagonal, 102 tetragonal,89 trigonal,113

of

tive refrac-

254 indices, in

examination

gent conver-

polarized light,

Tribasic acid,318 Trichite,180 Triclinic axes, 143

examination interference

opticalcharacters of, 295

254

Trigonalbipyramidal class,114 class,103 division,103 class,103 hemimorphic class,109

prism, 103 pyramid, 103 pyramidal class,114

260 colors,

270 opticalcharacters, positive and negative,

system, 17, 143 symmetry, 115

hemihedral

in polarized

light,259

143 crystals,

257 indicatrix, surface,255 wave Unit form, 30 Univalent element, 317 Uranium, test for,340 490 Uralitization,

symmetry, 11 system, 103

class,114 114 hemimorphic class, trapezohedralclass,112 trapezohedron,113 57 trisoctahedron, 69 trictetrahedron, Trigondodecahedron, 69 Trigonotype class,103 164 Trilling, tetartohedral

Valence,317 Vanadium, test for,340 Velocityof light,203 relation to 208 Vicinal forms, 24 Vitreous luster, 209 W

Trimorphous,325 Tripyramidal class,hexagonal system, 100 tetragonal system, 85 57 Trisoctahedron, Trirhombohedral

class,110

69 Tristetrahedrons,

Trivalent element, 317

Truncate,truncation,56 Tungsten,test for,340 Twin

160 crystals,

opticalcharacters of,298 188 Twinning,artificial,

axis,161 plane, 161

refractive

Water

of crystallization, 320 Water-waves, 201 Wave-front,203 Wave-length,204 Wave-motion, 201 biaxial crystals, 273 Wave-surface, uniaxial crystals, 255 249 Waxy luster, Westphal balance,199 White light, 204

Widmanstatten

lines,356

163 polysynthetic,

repeated,163

secondary,165 symmetrical,163 165 Twins, isometric, hexagonal,167 170 monoclinic, 169 orthorhombic,

spinel,419 tetragonal,166

'

172 triclinic, Two-circlegoniometer,157

X-rays and crystalstructure,25

Zinc,test for,340 test for,341 Zirconium, 82 Zirconoid, Zonal

equations,46

Zone, 31 31 Zone-axis,

dex, in-

Kermesite

Antimony,Red, White, 409 Antimony oxides,409 oxysulphide,383 sulphide,358 Antimony glance,358 632 Antlerite, 595 Apatite, 604 Aphanese,Aphanesite, 440 Aphrite, 542 Aphrizite, v.

SPECIES

TO

INDEX

704

Ascharite,621 Asmanite, 408 596 Asparagus-stone, 498 Aspasiolite, Asphaltum, 647 Asteria,413

571

Aphrosiderite, 624 Aphthalose,

Asteriated quartz, 405

sapphire,413 637 Astrakanite, 496 Astrolite, 585 Astrophyllite, Atacamite,400 606 Atelestite,

I 1

Bassanite,630

1Bassetite,617 474, 573 Bastite, 449 Bastnasite, 579 IBatchelorite, 646 Bathvillite, 512 Batrachite, Baumhauerite,386 Bauxite,433

Bavenite,558 612 Bayldonite, 540 Bazzite,

618 Atopite, 614 Attacolite,

624 Aphthitalite, Apjohnite,637 Aplome, 508 546 Apophyllite, Apotome, 627

549 Beaumontite,

522 Auerlite, Augelite,614 Augite,477 498 Auralite, 451 Aurichalcite, Auripigmentum,357 420 Automolite, 616 Autunite, 465 Aventurine feldspar,

Aquamarine,495 604 Araeoxene, Aragonite,446 Arcanite,624 539 Ardennite, 558 Arduinite, 531 Arendalite, 494 Arfvedsonite, 440 Argentine,

quartz. 405 482 Ax-stone,

v.

Argentobismutite,

Matil-

Bergblau,v.

B

v. Bergsalz,

485 Babingtonite, 435 Backstromite, 562 Saddeckite, 428 v. Aragonite, Jaddeleyite, Arragonite, 374 Jadenite, 44 O 533 Sagrationite, ARSENATES,592 477 Saikalite, 348 Arsenic, 581 Jakerite, White,409 Salas ruby, 419 Arsenical antimony,349

361 ARSENIDES, v. ArsenopyArsenikalkies, nte

606 Arseniosiderite, v. Arsenopyrite Arsenkies,

617 Arsenobismite, 378 Arsenoferrite, 409 Arsenolite, 381 Arsenopyrite,

ProusArsensilberblende, tite 453 Artinite, v.

Asbestos,Asbestus,489, Blue,493 Asbolan,436 436 Asbolite, ,

Beryl,495 423 Berylliumaluminate, 620 borate, 601 phosphate,

495, 496, 514, silicate, 529, 539 595 Beryllonite, 365 Berzelianite,

carbonate, 447,

593 Berzeliite, 591 Betafite,

619 nitrate,

606 Arseniopleite,

573

539 Bertrandite,

449

rite

Halite

386 Berthierite,

526 Samlite, 458 Sarbierite, 440 3aricalcite, 625 iarite,

y. Arsenopy- Barium Arsenikkies,

Azurite

579 Bergseife, v. Pittasphalt Bergtheer, 614 |Berlinite, v. Amber Bernstein,

573 Saltimorite,

Arsenic oxide,409" 357 sulphide,

394

v. Quartz Bergkrystall, 556 Bergmannite,

493 Bababudanite,

418 Arizonite, 430 Arkansite, 354 Arquerite, Armangite,594

631 Bellite,

|Bell-metal ore,

491 Bergamaskite,

dite

Arite,372

v. Nephrite |Beilstein, 436 Beldongrite,

Bementite,582 585 IBenitoite, Beraunite,615

Awaruite,356 451 Azurite,

394 Argyrodite,

Beauxite,433 638 Beaverite, 623 Bechilite, 540 Beckelite, 392 Beegerite,

399 Belonesite,

Axinite,534

364 Argentite,

449 Barytocalcite, 617 Baryturanit, 406 Basanite,

403 460, 498, 549, Beta-quartz, silicate,

550, 555, etc. 625 sulphate,

617 ariumuranit, 494 arkevikite, 610 Barrandite,

618 Beudantite, '

372 Beyrichite, 636 Bieberite, v. Agalmatolite Bildstein,

637 Bilinite, 617 Bindheimite, 391 Binnite, 468 Biotine, Biotina,

523 Barsowite, 612 Barthite, 498 Barylite, 498 Barysilite,

625 Baryt,Barytes, Baryta,v. Barium 460 460

Baryta-feldspar, Baryta-orthoclase,

563 Biotite, 581 Bisbeeite, 402 Bischofite,

Bismite,410 IBismuth,349

INDEX

Bismuth

arsenate, 606

TO

705

SPECIES

BORATES, 619 Borax, 622 Borickite,615 Boric acid,435 Bomite, 374 Boron hydrate, 435 silicate, 522, 527

Bunsenite, 411

641 tellurate, 360 telluride,

622 Boronatrocalcite,

490 Byssolite, Bytownite,467

uranate, 617

575 Bostonite,

carbonate,449, 454 oxide,410 oxychloride,401 selenide,359 504 silicate, 359 sulphide,

vanadate, 594 glance,359 gold,350 ocher,410 Bismuthinite,359 Bismutite,454 Bismutoplagionite,387 Bismutosmaltite,380 Bismutosphaerite,449 v. Epsomite Bittersalz, Bismuth Bismuth Bismuth

Bitter spar, Dolomite

Bitterspath,v.

Bitumen, 646, 647 Bituminous coal,648 Bityite,558

Bixbyite,425 387 Bjelkite, Black jack,367 Black lead,347 Blanfordite,477 Blatter tellur, v. Nagyagite Blaueisenerde,v. Vivianite Bleiantimonglanz,v. Zinkenite

Bleiglanz,v. Galena v. BindBleinierite, Bleiniere, heimite

Bleischweif,363 v. Anglesite Bleivitrol, Blende, 367 Blodite, 637

Bloedite,Bloedite,637 Blomstrandine, 591

Bloodstone,405 Blue asbestus. 493 iron earth,608

John, 398 malachite,v. Azurite 636 vitriol, Bobierrite,608

Bccumlerite,399 Boghead cannel,648 Bog-iron ore, 433 manganese, Bole, 579

436

Boleite,401

Bologna stone, 626 Boltonite,513 Bone-phosphate, 597 turquoise,613 498 Bonsdorffite, Boort, 345

Bort, 345

v. Bornite Buntkupfererz, 406 Burrstone, Bushmanite,637 Bustamite,484 v. Buttermilcherz, Cerargy-

rite

Botryogen, 639 Botryolite,528 Boulangerite,387 Bournonite, 388 637 Boussingaultite, Bowenite, 572 Bowmannite, 601 Brackebuschite,604 Bragite,588 Brandisite,566 Brandtite,607

Cabrerite,609 Cacholong, 408 Cacoxenite,614 Cadmia, 540 Cadmium sulphide,371 Cadmium blende, v. Greenockite,371 Cadmium oxide,411 Caesium silicate, 470 v. Cenosite,580 Brannerite, 586 Cainosite, Brauneisenstein, v. LimonCairngorm stone, 405 ite Caking coal,648 Calamine, 539, 445 Braunile,425 383 Braunstein,Grauer, v. Pyro- Calaverite, 440 Calc sinter, lusite Bravoite,378 spar, 438 Brazilian pebble,325 tufa,440 615 Calcioferrite, emerald, 542 448 Calciostrontianite, sapphire,542 604 428 Calciovolborthite, Brazilite, 438 Calcite, Bredbergite,508 Calcium arsenate, 610, etc. 490 Breislakite, 372 antimonate, 618 Breithauptite, borate,620, 621, etc. Breunerite,443 carbonate,438, 446 Breunnerite,443 399 chloride, Brevicite,556 398 flouride, Brewsterite, 549 iodate,619 Britholite,580 Brittle silver ore, 392 molybdate, 643 niobate,587, etc. Brochantite, 632 nitrate,619 Broggerite,623 oxalate,644 Bromargyrite, 397 401 oxyfluoride, BROMIDES, 397 phosphate, 595, 606, Bromlite, 447 611, etc. Bromyrite, 397 483, 467, etc. silicate, Brongnartine,632 sulphate,629, 633, etc. Brongniardite,387 sulphide,369 Bronzite,472 587 Calcium tantalate, Brookite, 429 titanate,583, 586 Brown coal,648 '

iron ore, 432 iron stone, 432 hematite, 432 ocher,432 spar, 443 Brucite, 434 453 Brugnatellite, Brunsvigite,572

Brushite, 611

Boothite, 636

Bucholzitef526 Bucklandite,532, 533

Boracite,620

Buhrstone, 406

tungstate, 642

Caledonite,632 520 Californite, Callainite,610 Calomel, 395

Campylite, 598 Canaanite, 476 Cancrinite, 501

sulphatic,501 Canfieldite,394 Cannel coal,648 Caoutchouc, Mineral, 647

372 pyrites, Capillary 552 Caporcianite, 496 Cappelenite, 631 Caracolite, Carbon, 345 Carbonado, 345

CARBONATES,

436

585 Carlosite,

Carminite, 594 Carnallite,401 468 Carnegieite, Carnelian,405 Carneol,v. Carhelian

Caraotite,617 540 Carpholite, 639 Carphosiderite, 374 Carrollite, Caryinite,593 496 Caryocerite, 582 Caryopilite, 425 Cassiterite, Castanite,639

Castor,CastorHe, 455 565 Caswellite, 496 Catapleiite, 498 Cataspilite, 580 Catlinite, 618 Catoptrite, Cat's eye, 405, 424 Cauk, Cawk, 626 518 Cebollite, Celadonite,577 627 Celestine, 627 Celestite, Celsian,460 Cenosite,580 397 Cerargyrite, Cerite,540 Cerium carbonate,449 399 fluoride, niobates,587 phosphates,593,609,etc. silicates, 533,540,585,etc. 616 Ceruleite, 448 Cerussite, 410 Cervantite, 424 Cesarolite, 410 Ceylanite, Ceylonite, 552 Chabazite, 636 Chalcanthite, Chalcedony,405 366 Chalcocite, 572 Chalcodite, 587 Chalcolamprite, 641 Chalcomenite, 435 Chalcophanite, 612 Chalcophyllite, 374 Chalcopyrite, 616 Chalcosiderite, 366 Chalcosine, 386 Chalcostibite, 411 Chalcotrichite,

Cfcalk,440

French,575

SPECIES

TO

INDEX

706

Chalmersite, 366

Chalybite,443 Chamoisite,Chamosite, 572 Chathamite, 378 Chemawinite, 645 Chenevixite, 616

Chert, 406 Chessy copper, 451 Chessylite, 461 Chesterlite, 525 Chiastolite,

451

Childrenite,615 362 Chilenite, 643 Chillagite,

Chiolite,400 385 Chiviatite, Chladnite,472

Chloanthite,378 399 Chloralluminite, 595 Chlor-apatite, 397 Chlorargyrite, v. Cotunnite Chlorblei, CHLORIDES, 395 Chlorite,568 CHLORITE Group, 568 567 Chloritoid, v. Chloritoid Chloritspath, Chlormanganokalite,399 399 Chlorocalcite, Chloromagnesite,399 Chloromelanite,482 Chloropal,582 571 Chlorophseite, Chlorophane, 398 498 Chlorophyllite, mel CaloChlorquecksilber, v '

419 Chlorospinel, Chlorsilber v. Cerargyrite Chondrarsenite,601 Chondrodite,536 Chrismatine, Chrismatite, 645 468 Christianite, 408 Christobalite, 368 Christophite, CHROMATES, 630, etc.

Chrome Chrome

diopside,476 spinel,419 Chromeisenstein, v. Chromite Chromic

iron,423 Chromite, 423

423 Chromitite,

Chromium

oxide,423

639 sulphate, 374 sulphide, 423 Chrysoberyl, 581 Chrysocolla, 511 Chrysolite, CHRYSOLITE Group, 510 405 Chrysoprase, 573 Chrysotile, 609 Churchite,

Cimolite,579 Cinnabar, 370 Inflammable, 646 Cinnamon-stone, 507 606 Cirrolite, Citrine,405 Clarite,393 Claudetite,409 364 Clausthalite, Clay, et seq. 578 416 Clay iron-stone, Brown, 433 Cleavlandite,465 Cleiophane,368 Cleveite,623 434 Cliachite, 347 Cliftonite, Clinochlore,569 604 Ch'noclase, 604 Clinoclasite, 477 Clinoenstatite, 540 Clinohedrite, Clinohumite,536 532 Clinozoisite, 566 Clintonite, CLINTONITE Group, 566 Coal, Mineral, 647, 648 Cobalt arsenate, 607, 608 carbonate,446, 453 arsenide,378, 379, 380, 381 641 selenite, 378 sulph-arsenide, sulphate,636 sulphide,378 Cobalt bloom, 608 Cobalt glance,v. Cobaltite Cobaltine,379 379 Cobaltite, 378 Cobaltnickelpyrite, Cobaltoadamite, 604 441 Cobaltocalcite, Cobaltomenite, 641 Coccolite,477 Cocinerite,362 Cockscomb Pyrite,380 627 Crelestine, 614 Coeruleolactite, Cohenite, 356 Coke, 648 Colemanite, 621 583 Colerainite, v. Celestite Cb'lestine, 620 Collbranite, 606 Collophanite, 580 Collyrite, Colophonite,508, 520

Coloradoite, 369 COLUMBATES

V.

587

Columbite, 588

Comptonite,558 579 Confolensite, 612 Conichalcite,

NlOBATES.

INDEX

TO

Connarite,577

517 Couseranite,

Connellite,631

371 Covellite, 601 Crandallite, Creedite,402 Crednerite,424 Crestmoreite,546 417 Crichtonite,

Cookeite,563 Copal, Fossil,645 Copaline,Copalite,645 Copiapite,638 Copper, 353 Emerald, v. Dioptase 515

Gray, 390 Indigo, v.

Covellite,

371

Native, 353 Red, v. Cuprite,410 Copper, Vitreous,v. Chalcocite,366 Yellow, 374 Copper arsenate, 603, 604, 612, etc. arsenide,362 carbonate,450, 451 395, 400 chloride, manganate,

424

iodide,395 nitrate,619 oxides,410,

Cristobalite,408 Crocalite,556 493 Crocidolite, Crocoite,630 Cromfordite,v. Phosgenite 571 Cronstedtite,

et seq.

et seq.

386 sulpho-bismuthites,

tungstate, 643

vanadates, 604 Copper glance,366 Copper mica, 616 Copper nickel,372 Copper pyrites,374 Copper uranite,616 636 Copper vitriol, Copperas, 636 Coprolites,597 Coquimbite, 637 497 Cordierite, Cordylite,449 Gorkite, 618 Cornwallite,612 Coronadite, 424 571 Corundophilite,

508 Derbylite,618

Derbyshire spar, 398 604 Descioizite,

Cube ore, ite Cube spar,

Pharmacosider-

v.

Anhydrite

v.

Custerite,497

Cyanite,526 Cyanochroite,637 638 Cyanotrichite, Cyclopite,468 394 Cylindrite, Cymatolite,481

Cymophane,

423

Cyprine, 519 Cyprusite,639 522 Cyrtolite, D

Dahllite, 597

Damourite, 561 Danaite, 382 Danalite, 504 Danburite, 522

Dannemorite, 489 Darapskite,619 Datholite,527

Desmine, 551 618 Destinezite, Dewalquite, 539 Deweylite,575 Diabantite,571 Diadochite,618 Diallage,477 Dialogite,444 Diamant, 345 Diamond, 345 Bristol, Lake Diamond, George, 405 Dianite,589 Diaphorite,387 Diaspore,431 434 Diasporogelite, Diatomite, 409 Dichroite,.497 Dickinsonite,607 Didymolite,497 637 Dietrichite, 619 Dietzeite, Dihydrite,605 Diopside,476 Dioptase,515 Dipyre, 517 566 Disterrite, Disthene,526 Dixenite, 581

Dog-tooth spar, 439 Dolerophanite,632 Dolomite, 442 Domeykite, 362 Domingite, 387 Doppelspath, v. Calcite Dopplerite,646 Double-refracting spar, Doughtyite, 638 Douglasite,402 Dreelite,626

Dry-bone, 445 Dudleyite,572 Dufreniberaunite,605 Dufrenite, 605

Dufrenoysite,387

413 Corynite,379 Cosalite,387 494 Cossyri'te,

Datolite,527 Daubreeite, Daubreite,401 Daubreelite, 374

Durangite, 601

Cotunnite,399

Davidsonite,496

Durdenite, 641

Corundum,

345

Demantoid,

Crossite,493 399 Cryolite, 400 Cryolithionite, Cryophyllite,363 Cryptolite,593 Cryptoperthite,460 Cuban, 374 Cubanite, 374

572 Culsageeite, Cumengite, 401 Cummingtonite, 489 phosphates,603, 612, etc. Cuprite,410 365 Cuproadamite, 604 selenides, 641 Cuprobismutite,385 selenite, 604 Cuprodescloizite, silicates, 515, 581 635 Cuprogoslarite, sulphantimonate,393 sulphantimonites,386 et Cupromagnesite, 636 Cuproplumbite, 364 seq. 643 393 Cuproscheelite, sulpharsenates, 643 Cuprotungstite, sulpharsemte,386 Cuspidine,535 drous, sulphates,630, 632; hy636

Daviesite,401 Davyne, 501 Dawsonite, 452 Dechenite,604 Deeckeite,518 571 Delessite, Delatynite,645 Delorenzite,586 Delphinite,531 Delvauxite,615 Demant, v. Diamond,

Crookesite, 365

412 400 oxychlorides,

sulphides,366, 371, 374

707

SPECIES

Dumortierite, 543 Dundasite, 452

Dysanalyte,586 361 Dyscrasite, 420 Dysluite, Dysodile,646 Dyssnite,485 500, 562 Dysyntribite,

SPECIES

TO

INDEX

708

394 Epiboulangerite, 571

Epichlorite, Epidesmine,558 455 Epididymite,

et seq.

499 Eleolite,

EPIDOTE

Emerald,495 413 Oriental, 508 Uralian, v.

515

nickel,453

Emery, 410 Emmonsite, 641 386 Emplectite, 383 Empressite, 393 Enargite, 587 Endeiolite,

Soda, 464

Felsobanyite,639 Felspar,v. Feldspar Ferganite,609 Fergusonite,588 Fermorite, 597 Fernandinite, 609

FERRATES, 418 Ferrazite,611 644 Ferritungstite, 487 Ferroanthophyllite,

Ferrobrucite,434 441 Ferrocalcite, 379 Ferrocobaltite, 635 Ferrogoslarite, Ferronatrite,638 633 Ferropallidite, v. Pyrostilpnite,

Feuerblende

639 Fibroferrite, 526 Fibrolite, 645 Fichtelite, 401 Fiedlerite, 607 Fillowite, 409 Fiorite, Fire opal,408 marble, 356 Fireblende, v. Pyrostilpnite, 390

Fischerite,613 646 Flagstaffite, 618 Flajolotite,

Fleches d'amour,

Euxenite,591 Evansite,614

Flint,406 409 Float-stone,

Dioptase,False Galena.

427

Flos

446 ferri,

402 Fluellite, 399 Fluocerite, Fluor v. Fluorite, 595 Fluor-apatite,

Fluor spar, 398

367

393 Famatinite, 578 Faratsihite, 556 ?argite, v. Fibrolite ?aserkiesel, v. Natrolite ?aserzeolith,

FLUORIDES, 398

et seq.

Fluorite,398 Fluorite tellurium v.

Flusspath,v. Foliated

Pontainebleau

"ava,

?orbesite,611

439 limestone,

631 Footeite,

428

513 ?orstereite,

Halotrich-

387 feather-ore, v. Jamesonite ^edererz,

Nag-

yagite,383

477 ?assaite, 555 Faujasite,

513 v. Bournonite Fayalite, Endellionite, 388 v. ^eather-alum, 598 ite Endlichite, 472 Enstatite, 615 Eosphorite,

Lime, 467 Potash, 457, 460

Flinkite,606

501 Facellite, 390 Fahlerz, 498 Fahlunite, 607 Fairfieldite, 390 Palkenhaynite,

387 Embrithite,

Emerald

Lazulite

Flokite,552 Florencite,601

496 Elpidite, Embolite,397

copper,

v.

Common, 457 Glassy,458 Labrador,466

604 Eusynchite,

615 Eleonorite,

Emerald

Group, 456

Feldspar,Baryta,460 Blue

Group, 530 Epidote,531 Epigenite,394 549 Epistilbite, E 592 Epistolite, Epsom salt,635 Ecdemite, 618 635 Epsomite, 558 Echellite, 588, 591 niobate,, Erbium 582 Ectropite, Pisolite v. Erbsenstein, ficume de Mer, 576 Erdkobalt, v. Asbolite Edelite,535 580 Erikite, 490 Edenite, 605 Erinite, Edingtonite,555 558 Erionite, 520 Egeran, 374 Erubescite, 401 Eglestonite, 608 Erythrite, 615 Egueiite, 402 Erythrosiderite, Ehrenwerthite,432 498 Esmarkite, 605 Ehlite, Esmeraldaite,433 385 Eichbergite, Essonite,507 620 Eichwaldite, 640 Ettringite, Eisen,v. Iron 365 Eucairite, Vivianite Eisenblau,v. Euchroite,611 v. Flos ferri Eisenbliithe, Euclase,529 Hematite v. Eiaenglanz, Eucolite,496 Eisenglimmer,v. Hematite 584 Eucolite-titanite, v. Pyrite Eisenkies, 500 PentlandEucryptite, v. Eisenniekelkies, Eudialyte,496 ite Eudidymite, 455 Eisenrahm, v. Hematite Eudyalite,496 Hematite Eisenrosen,v. Eugenglanz, v. Polvbasite Eisenspath,v. Siderite 365 621 Eukairite, Eisenstassfurtite, Euklas, 529 Eisspath,v. Rhyacolite Eulytine,504 Eisstein. v. Cryolite 504 Eulytite, Ekdemite, 618 596 499 Eupyrchroite, Elseolite, 571 647 Euralite, Elaterite,

Electrum,350 Elements,344

FELDSPAR

Fossil copal,645

wood, 405, 408 615 ^oucherite,

Fouqueite. 532

INDEX

Fowlerite,484 Franckeite,394 Francolite,596 420 Franklinite, Fraueneis,v. Selenite Frauenglas,v. Mica 391 Fredricite, 390 Freibergite, 387 Freieslebenite, Fremontite, 602 French chalk,576 359 Frenzelite,

Friedelite,515 367 Frieseite, Fuchsite,561 Fuggerite,518 Furaacite,604

TO

GERMANATES, 394 379 Gersdorffite, Geyerite,381 409 Geyserite,

Gibbsite,435 Gieseckite,500, 562 Gigantolite, 498, 562 561 Gilbertite, 640 Gilpinite, 647 Gilsonite, 453 Giorgiosite," Gips, v. Gypsum Girasol,408 Gismondine, 552 Gismondite, 552

Glance

coal, 648

Cobalt, v. Colbaltite Copper, v. Chalcocite Glanzeisenerz,v. Hematite Glaserite,v. Aphthitalite Glaskopf,Brauner, v. Limon-

Gadolinite,529 Gageite, 582

709

SPECIES

507 Grossular, Grossularite,

Grothine,545 Grothite,584 Griinbleierz,v. phite

Griineisenerde, v, Dufrenite Griinerite,490 360 Griinlingite, Guadalcazarite,369 Guanajuatite,359 Guano, 597 Guarinite,525 Guejarite,386 Guitermanite,388

Gummierz,

v.

Gummite

Gummite, 624 Gymnite, 575 Gypsum, 633 Gyrolite,546

ite

Rother,

Gahnite, 420

Gajite,453 Galactite,556 Galapectite,579 Galena, Galenite,363 Galena, False,367 Galenobismutite,386 Galmei, v. Calamine Ganomalite, 498 Ganophyllite,546 Garnet, 505 Cinnamon, 507 Chrome, 417 Grossalur,507 Oriental,507 Precious,507 Tetrahedral,v. Helvite White, v. Leucite Garni erite,575

Gastaldite,493 Gavite, 576 Gay-Lussite,452

v.

Hematite

Glassy Feldspar,458 Glauber salt,632 Glauberite,625 Glaucochroite,513 Glaucodot, 382 Glaucolite,517 Glauconite,577 Glaucophane, 492 Glaukodot, 382 645 Glessite, Glimmer, v. Mica Globosite,615 Glockerite,639 Glucinum, v. Beryllium

Gekrosstein,v. Tripe stone v. Wulfenite Gelbbleierz,

Hamartite, 449 Hambergite, 620 Hamlinite, 601 Hancockite, 533

Goethite,431

Hannaite,

611

Gold, 350 391 Goldfieldite, Gold tellurides, 382, 383 Gonnardite, 557 Goshenite,496

Graftonite, 594

Gehlenite, 518 Geikielite,586

Halotrichite,637

Hanks!

Gothite,431 Goyazite,616

Gedanite, 645 Gedrite,487

Haarkies,v. Millerite Haarsalz,v. Epsomite Hackmanite, 502 Hematite, v. Hematite Haidingerite,610 Hair salt, 635 Halite,395 562 Hallerite, Hallite,572 Halloysite,578

Gmelinite, 554

Goslarite, 635

Gearksutite, 402

Grahamite, 647 Gramenite, Graminite, 582 Grammatite, 489 Granat, v. Garnet

HaMfouite,

498

Harl. Harmotomc 535 Harstigite, Hartite,645 Harttite,601 491 Hastingsite, Hatchettine, Hatchettite, 645

Hatchettolite,587

Hauchecornite,372 Hauerite, 378

Grandiderite, 544

Haughtonite, 564 Hausmannite,

Genthite, 575

Graphic tellurium. 382 Graphite,347 Gray antimony, 358

646 Geocerellite, Geocerite,646

Greenalite,577

Gelbeisenerz, v. Jarosite

Gelbeisenstein,v. siderite

Georceixite, 601 Geocronite, 392

Geomyricite,646 Georgiadesite,594 Geraesite,601 Gerhardtite, 619**

Pyromor-

Xantho-

424

Greenockite,371 Greenovite,584 Grenat, v. Garnet

608 Hautefeuillite, Hauyne, 503 Haiiynite,503 Haydenite, 552 Heavy spar, 625 Hebronite, 602 Hedenbergite, 476 Hedyphane, 598

572 Griffithite,

622 Heiiitzite,

Griphite,500

Heliodor,495

copper, Green

390

lead ore, 597

710 618 Heliophyllite,

Heliotrope,405 Hellandite,540 Helvite,Helvine,504 Hemafibrite,611 Hematite, 415 Brown, 432

Hematogel,434 Hematolite,606 606 Hematostibiite, Hemimorphite,539 Henwoodite,616 Hepaticcinnabar, 370 420 Hercynite,

Herderite,601 638 Herrengrundite, 552 Herschelite,

Hessite,365 Hessonite,507 435 Hetaerolite, 425 Heterocline, 387 Heteromorphite,

Heulandite,548 Hewattite,611 Hexahydrite,637

Hibbenite,612 Hibschite,540

Hielmite,Hjelmit,591 400 Hieratite, 481 Hiddenite, 645 Highgateresin, Hipgensite,604 546 Hillebrandite, Himbeerspath,v. Rhodochrosite 618 Hinsdalite, 622 ^jabzeitc, Hiortdah'.u

SPECIES

TO

INDEX

396 Huantajayite,

546 Inesite,

Hiibnerite,642

Inflammable cinnabar, 646 Infusorial earth,409

612 Hiigelite,

Hudsonite,492 571 Hullite, Hulsite,622

622 Inyoite,

lodate of

619 calcium, 397 lodembolite,

'

Humboltine, 645 518 Humboldtilite, Humboldtite,528

Humite, 536 362 Huntilite, 386 Hutchinsonite,

Hureaulite,611

Hussakite,592 Hyacinth,521,507 Hyalite,409 Hyalophane,460 511 Hyalosiderite, 498 Hyalotekite, 435 Hydrargillite, 440 Hydrauliclimestone, 623 Hydroboracite,

HYDROCARBONS,

645

452 Hydrocerussite, 538 Hydroclinohumite, Hydrocyanite,630 435 Hydrofranklinite, 433 Hydrogothite, 453 Hydrogiobertite, Hydrohematite,433 Hydromagnesite,452 Hydromica, 561 Hydromuscovite,561 558 Hydronephelite, Hydrophane, 408 399 Hydrophilite, 435 Hydrotalcite, Hydrothomsonite,558 '

sulphides,369,373,377,

498 Iberite, Ice,411

493 Holmquistite,

Ice spar,

v. Wood-opal Holzopal, v. Woodtin Holzzinnerz, 529 Homilite,

Iceland spar, 439

v.

Rhyacolite

512 Iddingsite, 519 Idocrase,

Honey-stone, 646 v. Honigstein, Idrialite,

v. Phosgenite Hornblei, 490 Hornblende, 397 Hornesit, Hornsilber, 406 Hornstone,

Horse-flesh ore, 374 362 Horsfordite, 513 Hortonolite,

Howlite,621

572 386 sulphantimonite,

451 Hydrozincite, Hypersthene,473

Hohmannite, 639 630 Hokutolite, 424 Hollandite,

Horn quicksilver, 395 Horn silver, 397

610 etc.

silicates, 513, 538, 571, 381 sulpharsenide, sulphates,636,637,638,

Hoernesite,608

Mellite

"

596 Hydroxyapatite,

551 Hypostiibite,

Hopeite,607

IODIDES,397 lodobromite,397 397 lodyrite, 497 lolite, Hydrous, 498 Iridium,355 Iridosmine,355 Iron,Chromic,v. Chromite Magnetic, 420 Meteoric,356 Native,356 v. Hematite Oligist, Iron aluminate,420 arsenates,608,609, etc. 381 arsenides, carbide,356 carbonate,443 399 chlorides, chromate,423 columbate,588 420 ferrate, hydrates,431,432 niobate,588 oxalate,528 oxide, 415, 420; hydrated,431, 432 phosphates, 605, 608,

435 Igelstromite, 638 Ihleite, 634 Ilesite, 417 Illmenite,

427 Ilmenorutile,

Hvaite,538 490 Imerinite, 647 Impsonite, 579 Indianaite,

Indianite.467 542 Indicolite, .542 Indigolite.

etc.

381

magnetic,373 588 tantalates, tellurite,.641 titanates, 417, 424 tungstates,641, 644 Iron alum, 637 Iron natrolite, 556 Iron pyrites, 377 Magnetic,373 White, 380 563 Irvingite, 427 Iserine, 611 Isoclasite, 458 Isothose, 417 Itabirite, 406 Itacolumite,

Ixiolitc

J

Jacobsite, Jade,482: 489 B

"

643 Lead tungstate,

vanadates, 598, 604 Lead glance,363 v. Anglesite Lead vitriol, 631 Leadhillite, Lecontite,632 Ledererite,554 584 Lederite, Ledouxite,362

Lehrbachite,365

Lengenbachite,388 572 Lennilite, Leonhardite, 552 Leonite,637

397 Leopoldite, 432 Lepidocrocite, Lepidolite,.562 Lepidomelane,565 468 Lepolite, 638 Lettsomite,, Leucaugite,477 569 Leuchtenbergite,

Leucite,469 Leucochalcite,612

Leucomanganite, 607 646 Leucopetrite, Leucophanite,496 538 Leucophoenicite, Leucopyrite,381 Leucosphenite,585 Leucoxene, 418 Levynite,554 Lewisite, 618 Libethenite,603

500, 562 Liebenerite, 454 Liebigite, 538 Lievrite, Lignite,648 584 Ligurite, 388 Lillianite, Lime, v. Calcium Lime-mesotype, 557 Lime uranite,515 Limestone,440 Hydraulic,440 Magnesian, 442 Limonite,432 632 Linarite, 618 Lindackerite, 374 Linnaeite,

SPECIES

TO

INDEX

712

385 Livingstonite,

Lodestone, 421 Loeweite, 637

Loewigite,640 381 Lollingite, Lorandite, 386 Loranskite, 591

Lorenzenite,586 Lorettoite,401 Lossenite, 619 Lotrite,546 Loweite, 637

Manandonite, 563 MANGANATES, 418 Manganandalusite, 524 Manganapatite, 596 Manganblende, v. Alabandite Manganbrucite, 434 Manganchlorite, 569 Manganepidote, v. Piedmontite

Manganese antimonate, 606 arsenates, 601, 606 carbonate, 444 378 disulphide, hydrates,432, 435

Lowigite,640 Loxoclase,458 Lublinite,439 Lucinite, 610

Luckite,636 Ludlamite, 614 Ludwigite,620 Luigite,545 Lumachelle, 440 619 Liineburgite, 405 Lussatite, Lutecite,407 Luzonite,393 Lydian stone, 406 M

Mackintoshite,529 Made, 525 Maconite, 572 Magnesioferrite,420 Magnesioludwigite,620 Magnesite, 443 Magnesium aluminate,419 arsenate, 608

borate,621, 622 carbonates, 443, 452, 453 420 ferrate, 399 fluoride, hydrate,434

oxides,411, 434 phosphates, 600,

v

niobate,588 oxides, 411, 424, 425, 427, 430, 432, 435 phosphates, 594, 600, 484, 513, 582, silicates, etc.

633, 636 sulphates, sulphide,369, 378 tantalate,588 titanate,418 tungstate, 642

Manganfayalite, 513 Manganglanz v. Alabandite v. SpessarMangangranat, tite

Manganhedenbergite,476 Manganite, 432 Manganmagnetite, 420 Manganocalcite, 441, 444 Manganocolumbite, 589 Manganophyllite, 564 Manganosiderite, 444 Manganosite, 411 Manganospherite, 444 Manganostibiite,606 Manganotantalite, 589 Manganpectolite, 483 Manganspath) v. Rhodochrc site

608, Mangantantalite, 588 611 Mangan-vesuvianite, 520 473, Marble, 440 etc.; 472, silicates, Verd-antique,573 513, 536, 573, 576 Marcasite, 380' sulphates,633, 635 Marceline,425, 485 titanate,586 iron 420 Margarite, 566 Liroconite ore, v. Magnetic Linsenkupfer, Margarodite, 561 557 Magnetic pyrites,373 Lintonite, Margarosanite, 498 615 Magnetite, 420 Liroconite, Marialite,518 v. 614 Magnetkies, Pyrrhotite Liskeardite, 420 Lithia mica, 562 Marignacite,587 Magnoferrite, 565 450 v. Mariposite, Lithionglimmer, Lepido- Malachite, lite Marmatite, 368 Blue,v. Azurite 594 Marmolite, 573 Green,450 Lithiophilite, Lithium 476 Marshite, 395 phosphates,594. Malacolite, 602 522 Marsjakskite,577 Malacon, 611 Martinite, silicates480, 500, 562 Maldonite,350 391 Martite, 417 Lithographic stone,440 Malinowskite, 578 636 Mascagnite, 624 Lithomarge, Mallardite, 387 Liveingite,

Maltha, 646

Maskelynite,467

INDEX

Masonite, 567 Massicot, 412 Matildite,386 Matlockite,401 Maucherite, 362 Mauzeliite,618

TO

713

SPECIES

Mica, Magnesia, 563, 565 Potash, 560 Soda, 562 Vanadium, 565

Monite, 606 Monrolite,526 Montanite, 641 513 Monticellite,

Micaceous

579 Montmorillonite,

iron ore, 415

Michei-levyte,626 Maxite, 631 Microcline,460 Microcosmic Mazapilite,615. salt,611 Meerschaum, 576 Microlite,587 Meionite, 516 Microsonunite,501 Melaconite, 412 Microperthite,460 Melanglanz, v. Stephanite Microphyllite,467 Melanite, 508 Microplakite,467 Melanocerite,496 Miersite,397 Melanophlogite,408 Miesite,598 Melanotekite, 539 Mikroklin,460 Melanterite, 636 Milarite,455 Milky quartz, 405 Melilite,518 372 Melinophane, v. Meliphan- Millerite, 630 ite Millosevichite, Mimetene, Mimetesite, 598 Meliphanite,496 Melite, 580 Mimetite, 598 Mellate of aluminium, 645 Minasite,614 Minasragrite,641 Mellite,645 Mineral caoutchouc, 647 Meionite, 382 Mineral coal,647 Menaccanite, 417 oil,646 Mendipite, 401 pitch,647Mendozite, 637 resin,645 Meneghinite, 391 tallow,645 Menilite,408 tar, v. Pittasphalt Mennige, v. Minium 645 Mercurammonite, 395 wax, Minguetite, 572 Mercury, 354 Minium, 424 Horn, 395 632 Mirabilite, Native, 354 Misenite, 631 Mercury antimonite,618 Mispickel,381 chloride,3Q5 369 Misy, 638 selenides, 423 Mitchellite, sulphides,369, 370 369 Mixite, 617 sulpho-selenide, 369 Mizzonite,517 telluride, Mocha stone, v. Moss agate Mercury amalgam, 354 Mock lead,291 Meroxene, 564 Moissanite, 356 Mesitite,443 Mohawkite, 362 Mesitinspath,v. Mesitite Molengraaffite,585 Mesole, v. Thorn sonite

Molybdanbleispath,v,

Mesolite, 557

Molybdanglanz,

Metabrushite, 611 Metachinabarite, 369 Metahewettite, 611 Metastibnite, 359

I, 616

Meta-torbernite

Metavoltine, 639

Metaxite, 575 Meteoric iron,356 Mexican

onyx,

Wul-

fenite

556 Messelite, 607

Mesotype,

440

Montroydite, 412 Moonstone, 458, 465 Moravite, 571 Mordenite, 548 Morencite, 582 Morenosite, 635 Morganite, 495 Morion, 405 Moroxite, 596 Mosandrite, 585 Mosesite, 402 Moss

agate, 405

Mossite,590 Mottramite, 604 Mountain cork,490 490 leather, 578

soap,

tallow,645 wood, 490 582 Miillerite, Mullanite,388 Muller's glass,409 608 Mullicite, Mundic, v. Pyrite Murchisonite,458 Muscovite, 560

Muscovy glass,562 Mussite, 478 Muthmannite, 383 N

"

Nadeleisenerz,v. Gothite Nadelerz,v. Aikinite Nadelzeolith,v. Natrolite Nadorite,618 Naegite,522 Nagyagite, 383 Nailhead

spar, 439

Nantokite,395 Napalite,645 Naphtha, 646 Narsarsukite, 585

v.

denite Molyb-

MOLYBDATES, 641 360 Molybdenum sulphide, 410 trioxide, Molybdenite, 360 Molybdic ocher,410 Molybdite, 410 Molybdomenite, 641 Molybdophyllite,498

Nasonite, 498 NATIVE ELEMENTS, 344 Natramblygonite, 602 Natrium, v. Sodium 622 Natroborocalcite, Natrochalcite, 638 Natrolite,556 640 Natrojarosite, Natromontebrasite,602

Natron, 452

Meyerhofferite,622

502 Molybdosodalite,

594 Natrophilite,

Miargyrite,386 MICA Group, 559 Mica, Iron, 563, 565 Lime, 566 Lithia,562

Molysite,399

Naumannite, 364 Needle ironstone, 432

Monazite, 593

Monetite, 606 Monheimite, 445 Monimolite, 593

Needle Needle 556

ore,

v.

Aikinite

zeolite,v.

Natrolite,

714

TO

INDEX

Nemalite,434 Neocolemanite,621 Neotantalite,587 Neotocite,485, 582 499 Nepheline,

Nephelite,499 Nephrite,489 Nepouite,575 Neptunite,585 Nesquehonite,452 Nevyanskite,355 Newberyite, 611 Newtonite, 579 Niccolite,372 446 Nicholsonite, Nickel antimonide,372

arsenates,609

arsenides, 372,378, 382 carbonate,453 oxides,411 575 silicate, sulphantimonide,379 sulpharsenide, 379, 382 sulphate,635 sulphides, 369,372,373 382 telluride, Nickelantimonglanz, v. Ullmaimite GersNickelarsenikglanz, v. dorffite 575 Nickel-gymnite, 380 Nickel-skutterudite, 427 Nigrine,

Oisanite,532

Paposite,639

Okenite, 546 Oldhamite, 369

Paracelsian, 460

Oligistiron

v.

Hematite

Oligoclase,466 444 Oligonite, Olivenerz,v. Olivenite Olivenite,603

Olivine,511 Omphacite, 477 Oncosin, 561 Onofrite,369 Onyx, 406 Mexican, 440 Onyx marble, 440 Oolite,440 Opal, 408 Opal jasper,409 573 Ophicalcite, 573 Ophiolite, Ophite, 575 Orangite,522 Oriental alabaster, 440 amethyst, 413 emerald, 413 ruby, 413 topaz, 413 582 Orientite, Orpiment, 357 Orthite,533 Orthoclase,457 Orthose,v. Orthoclase Oruetite,360

Nigrite,647

Osannite, 494

NIOBATES,587

Osmelite,483 Osmiridium, 355

Niter,619 Niter,Soda, 619

NITRATES,619

SPECIES

Osmium

379 sulphide,

582 Nontronite,

596 Osteolite, Otavite,452 567 Ottrelite, Ouvarovite,508 Owenite, 572 3XALATES, 644 Oxammite, 644 3xiDEs, 402

620 Nordenskipldine,

3XYCHLORJDES,400

619 Nitrobarite, 619 Nitrocalcite, 619 Nitroglauberite,

Nitromagnesite,619 623 Nivenite,

Nocerite,401

Nordmarkite,544 450 Northupite, 503 Nosean,' 503 Noselite, Noumeite,575 Nussierite, 598

3XYFLUORIDES,

400

61 Dxykertschenite, DXYSULPHIDES,383

Paraffin,645 Paragonite,562 Parahopeite,607 401 Paralaurionite, Paraluminite,639 Paramelaconite, 412 Parasite,621 Paravivianite,608 "

428 Paredrite,

Pargasite,490 Parisite,449 Parophite,562 Parrot coal,648 510 Partschinite, Pascoite,609 Passauite,517 Paternoite. 621

Patronite,361 Peacock Ore, 374 Pearceite,393 Pearl sinter, 409 Pearl-spar,441 Peat, 648 405 Pebble, Brazilian, Pechblende, Percherz, v. Uraninite

Peckhamite, 474 483 Pectolite, Peganite,613 579 Pencil-stone, 401 Penfieldite, Pennine, 570 Penninite,570 Pentlandite,369 498 Peplolite, 401 Percylite, 411 Periclase, 465 Pericline, Peridot,511 465 Peristerite, 460 Perthite, Perofskite,586 Perovskite,586 Perowskit, 586 Petalite,455 Petrified wood, 406

Petroleum,646

3zarkite,557

Petzite,365

645 Ozocerite,

501 Phacelite, Phacellite, 553 hacolite,

Pharmacolite,610 614 Pharmacosiderite,

Ocher, Brown, 432 Red, 415 Ochrolite, 618 428 Octahedrite,

Odontolite 613 (Eilde

chat,424

561 (Ellacherite, 554 Offretite,

Oil,Mineral

646

Pachnolite,402 Pagodite,562 622 Paigeite, 484 Paisbergite, Palaite,607 Palladium, 355 Palmerite,610 640 Palmierite, Panabase,v. Tetrahedrite

Pandermite,621

Phenacite,514

Phengite,561 572 Philadelphite, 491 Philipstadite, 638 Phillipite, 550 Phillipsite, Phlogopite,565 630 3hoenicite, 630 Phcenicochroite,

Pholerite,578

INDEX

Pholidolite

577

Phosgenite,450 PHOSPHATES, 592 Phosphoferrite,601 Phosphorite,596 Phosphophyllite,618 v. Phosphorsalz,

Stercorite

Phosphosiderite,610 Phosphuranylite,617 Photicite,485 Phyllite,567 Physalite,523 Picite,615 637 Pickeringite, 419 Picotite, 532 Picroepidote,

573 Picrolite, Picromerite,637 Picropharmacolite,607 417 Picrotitanite,

Piedmontite, 532

Pigeonite,479 620 Pinakiolite, Pinguite,582 Pinite,562, 498 Pinnoite,622 Pintadoite,609 Piotine,576 Pirssonite,452

Pisanite,636 440 Pisolite, 531 Pistacite, Pistomesite,443 Pitchblende,623 646 Pittasphalt, 618 Pitticite,

TO

508 Polyadelphite,

Pyrargyrite,389

Polyargite,562

508 Pyreneite, Pyrgom, 477

393 Polyargyrite, 601 Polyarsenite, 392 Polybasite,

Polycrase,591

372 Capillary, Cockscomb, 380 Copper, 374

Polymignite,591

Magnetic,373 Radiated,380 Spear,380

598 Polysphaerite,

Ponite,445 Poonahlite,v. Scolecite Porpezite,350

Proustite, 389 Prussian

blue,Native, 608 Przibramite,432 Pseudoboleite, 401

Platinum, arsenide,379

Pseudobrookite,424 Pseudocampylite, 598 Pseudoleucite,470 Pseudomalachite, 605 Pseudomeionite,516

Plattnerite,428

557 Pseudomesqlite,

Platynite,385

550 Pseudophillipsite, Pseudophite, 570 579 Pseudosteatite, 483 Pseudowollastonite,

Platinum, 35

Plazolite,580 386 Plenargyrite, Pleonaste,419 356 Plessite, Plumbago, 347 Plumbogummite, 601 Plombocalcite,441 Plumbojarosite,640

Psilomelane, 436 548 Ptilolite,

Pochite,545 Polianite,427 Pollucite,470

571 Pycnochlorite, 498 Pyrargillite,

Plumbostib, 387 Plumosite,387 Podolite, 618

White

Q Quartz, 403 Quartzine,407 Quartzite,406 Quecksilber, Gediegen,

v.

Cinnabar mel Quecksilberhornerz,v. Calo-

(uenstedtite,637 luetenite,640 354 uicksilver, 347 uisqueite,

R

604 Psittacimite,

Pucherite,594 551 Puflerite, Punamu, 482 Purple copper ore, 374 Purpurite,610 Puschkinite,532 Pycnite,523

Plumboniobite, 592

Iron,377

Tin, 394 iron,380 Posepnyte,646 Pyroaurite,435 Potash alum, 637 Pyrobelonite,604 Potassium borate,622 Pyrochlore,587 396 chloride, Pyrochroite,435 nitrate,619 430 Pyrolusite, silicate, 457, 460, 469, Pyromorphite, 597 560, etc. Pyrope, 507 624 sulphate, Pyrophanite,418 606 Potstone,576 Pyrophosphorite, Powellite,643 579 Pyrophyllite, 523 Prase, 405 Pyrophysalite, 498 646 Praseolite, Pyroretinite, 572 Prehnite,534 Pyrosclerite, 604 Preslite, Pyrosmalite,515 368 390 Pfibramite, Pyrostilpnite, 621 Priceite, Pyroxene, 474 591 PYROXENE Priorite, Group, 470 Prismatine,544 Pyroxmangite, 485 593 Przibramite,368 Pyrrharsenite, 571 Prochlorite, Pyrrhite,588 538 Pyrrhotine,373 Prolectite, 373 Prosopite,402 Pyrrhotite, 473 Protobastite,

Plancheite, 515

r

Pyrite,377 .Pyrites, v. ArsenoArsenical, pyrite,381

498 Polychroilite, Polydymite,373 637 Polyhalite, 563 Polylithionite,

Placodine,3r"2 374 Plagioclase, 38T7 Plagionite, 639 Planoferrite, Plasma, 405 Plaster of Paris,634 Platina,355 355 Platiniridium,

715

SPECIES

Radelerz,v. Bournonite Radiated pyrite,380 Radiotine,573 401 Rafaelite, Raimondite, 639 402 Ralstonite, Ramirite,604 Rammelsbergite, 382 Ranite, 558 Raspite,643

716

INDEX

Rathite, 386

Romanzovite,

Rauchquarz, v. Smoky Quartz Raumite, 498 Realgar,357 Red antimony, v. Kermesite chalk,416

Romeite, 618

copper

ore, 410

hematite,415 iron ore, 416

lead ore, 630

ocher,416 silver ore, 389 zinc ore, 411

Reddingite,607 Reddle, 416 Redingtonite,639 Redruthite,366 Reinite,644 549 Reissite, Remingtonite,453 576 Rensselaerite, Resin,Mineral,645 573 Retinalite, Retinite,645 Retzbanyite,385 Retzian,606 Rezbanyite,385 Rhabdophanite, 609 527 Rhaetizite, Rhagite,617 Rhodalose, v. Bieberite Rhodizite,621 Rhodochrome, 570 Rhodochrosite,444 Rhodolite, 507

Rhodonite,484 570 Rhodophyllite, 546 Rhodotilite, Rhodusite,493 Rhonite,494 Rhomboclase, 641

SPECIES

TO

507

Romerite, 638 Rosasite,449 Roscherite, 616 Roscoelite, 565 Rose quartz, 405 Roselite, 607 Rosenbuschite, 483 Rosieresite,610

Rosite,562 Saussurite, 350 Rosolite,509 Scacchite,399 Rothbleierz,v. Crocoite Rotheisenerz,Rotheisenstein,Scapolite,516 SCAPOLITE Group, v. Hematite 618 Rothgiiltigerz,v. Pyrargy- Schafarzikite, 368 Schalenblende,

rite

v. Stolzite Scheelbleispath,

Rothzinkerz,v. Zincite Rowlandite, 529 Rubellite,542 Rubicelle,419 Rubin, 419 Ruby, Almandine, 419 Balas,419 Oriental,413 Spinel,419 Ruby blende,368 Ruby copper, 410 389 Ruby silver, Ruby zinc,368 Ruin marble, 440 Rumanite, 645 Rumpfite, 572 Ruthenium 302 sulphide, 449 Rutherfordine,

Rutile,427

361 Rizopatronite,

Rock

405 crystal, meal, 440 milk,440 salt,395

498 Roeblingite, Romerite,638

513 Roepperite,

Scheelite,642 v. Scheelite Scheelspath, 645 Scheererite,

477 Schefferite, 611 Schertelite, 474 Schiller-spar,

Schirmerite,386 483 Schizolite, v. TripeSchlangenalabaster,

stone v. Emery Schmirgel, 552 Schneiderite, 637 Schoenite,

Schorlomite,510

Schorza,531 356 Schreibersite, v. Schrifterz,Schrifttellur, Sylvanite 580 Schrotterite, v. Lepidolite Schuppenstein, 401 Schwartzembergite, 391 Schwatzite,

Riband

569 Ripidolite, 588 Risorite, 393 Rittingerite, 455 Rivaite, 546 Riversideite,

515

Schapbachite,387 Rothkupfererz,v. Cuprite Niccolite v. Schaumerde, v. Aphrite Rothnickelkies, 508 Rothoffite, Schaumopal, 409 mesite Schaumspath, v. Aphrite Rothspiessglanzerz,v. Ker-

458 Rhyacolite,

jasper,406 615 Richellite, 489 Richterite, 362 Rickardite, 573 Ricolite, Riebeckite,493 Rinkite,585 Rinneite,399

Saponite,576, 579 Sapphire, 413 Sapphirine,544 518 Sarcolite, Sard, 405 Sardonyx, 406 Sarkinite,601 385 Sartorite, Sassolite,435 Satin spar, 439, 634 Saualpite,530

Schwefel

v.

Sulphur

382 Safflorite, Sagenite, 405, 427 Sahlite,477

v. Pyrite Schwefelkies, v. Schwefelquecksilber,

Sal

v. Plattnerite Schwerbleierz, Barite v. "Jchwerspath, v. Sartorite Scleroclase, 557 Scolezite, Scolecite, 609 Scorodite, Scorza,531 609 Scovillite, 583 Searlesite, 552 Seebachite, SELENIDES,364, 365 634 Selenite, SELENITES,641 Selenium,344 TiemanSelenquecksilber, v.

Ammoniac,

397

477 Salite, Salmiak, 397

Salmite,567 Salmonsite,610 Salt,Rock, 395 v. Niter Saltpeter, 636 Salvadorite, Samarskite,590

Samiresite,587

Sammetblende,432 390 Samsonite, 391 Sandbergerite, 390 Sanguinite, 458 Sanidine, Saphird'eau,498

nite 348 Selensulphur,

nabar Cin-

SPECIES

717

Skemmatite, 436 Skleroklas,v. Sartorite Skogbolite,590 Skutterudite,380 Smaltite,378. Smaragd, v. Emerald Smaragdite, 490 Smectite,579, 580 Smegmatite, 579 Smirgel,v. Emery Smithite,386 Smithsonite,445, 539 Smoky quartz, 405 Soapstone, 576 Sobralite,485 Soda alum, 637

Spodumene, 480 434 Sporogelite, 556 Spreustein, v. Polybasite Sprodglanzerz, v. Polybasite Sprodglaserz, 446 Sprudelstein,

Soda-mesotype,557

576 Steatite, 496 Steenstrupine, 498 Steinheilite, 363 Steinmannite, Steinmark,v. Lithomarge

INDEX

Selenwismuthglanz, v. Guanjuatite Seligmannite,388 399 Sellaite, Semeline, 584 Semi-opal,408 Semseyite, 387 Senaite,418 Senarmontite, 409 576 Sepiolite, Serendibite, 545 561 Sericite, Serpentine,573 638 Serpeirite, Seybertite,566 Shanyavskite, 436 Shattuckite,581 Shepardite,472 Sheridanite,571 Shell marble, 440 542 Siberite, 610 Sicklerite, Siderite,443 639 Sideronatrite, 564 Siderophyllite, Siegenite,374 Silber,v. Silver Silberamalgam, v. Amalgam v. Argentite Silberglanz, Silberhornerz, v. Cerargyrite 403 Silex,Silica, SILICATES,454 409 Siliceous sinter, Silicifiedwood, 404 545 Silicomagnesiofluorite, Silicon oxido,403, 407, 408 526 Sillimanite, Silver,352 Silver antimonide, 361 arsenide,362 bismuthide,362 bromide, 397 397 chlorides, iodide,397

selenide,364 .

sulphantimonites, 386, 389 389 sulpharsenite,

sulphide,364, 367 386 sulpho-bismuthite,

sulpho-germanate,394 telluride, 362, 365, 382 Silver glance,364 Simetite,645 Simonyite, 637 Sinopite,580 Sinter,Siliceous,409 588 Sipylite, 355 Siserskite, Sismondine, Sismondite, 567 355 Sisserskite, 418 Sitaparite, Skapolith,516

TO

Soda

microcline,461 Soda niter,619 Soda orthoclase, 458 518 Soda-sarcolite,

Sodalite,502 borate,622 carbonate,452, 453

Sodium

Spurrite,581

Staffelite, 596, 597 440 Stalactite, 440 Stalagmite, Stannite,394 621 Stassfurtite, 405 Star-quartz,

sapphire,410 543 Staurolite, Staurotide,543

v. Halite Steinsalz, 558 Stellerite,

632 Stelznerite,

395 hloride,

Stephanite,392 611 Stercorite, 367 Sternbergite, Stewartite,607 410 Stibiconite, 556 590 Stibiotantalite, 358 sulphate, 625: hydrous Stibnite, 453 Stichtite, 632, etc. 518 Somervillite, Stilbite, 551, 548 572 Stilpnochloran, Sonnenstein,v. Sunstone Soretite,491 Stilpnomelane,572 611 Stoffertite, Souesite,356 Soumansite, 614 Stokesite,540 Stolpenite,579 Spadaite,577 446 643 Spaerocobaltite, Stolzite, v. Clinoclasite Spangolite,631 Strahlerz, v. Marcasite Spargelstein, v. Asparagus Strahlkies, 489 stone Strahlstein, 485 Stratopeite, Spathic iron,443 Stream v. Siderite Spatheisenstein, tin,426 Spear pyrites,380 Strengite,610 572 Speckstein,v. Steatite Strigovite, Specular iron,415 Stromeyerite,366 Strontianite,447 Speerkies,v. Marcasite 440 Strontianocalcite, Speiskobalt,v. Smaltite Strontium carbonate,447 Spencerite,612 549 silicate, Spessartine,Spessartite,507 491 sulphate,627 Speziaite, 379 Struvite,606 Sperrylite, 427 Striiverite, Sphaerite,614 362 446 Stiitzite, Sphaerocobaltite, 388 Stylotypite, Sphalerite,367 Succinic acid,645 Sphene, 583 Succinite,645, 507 Sphenomanganite, 432 Sulfoborite,623 v. Wurtzite Spiauterite, 393 SULPHANTIMONATES, Spinel,419 383 SULPHANTIMONITES, Spinelruby, 419 393 SULPHARSENATES, Spinthere,584 572 SULPHARSENITES, 383 Spodiophyllite, SULPHATES, 624 Spodiosite,600 fluoride, 399, etc. nitrate,619 phosphate, 594, etc. silicate, 464, 502, 554,

"

.

INDEX

718

SPECIES

oxide,410 Melonite v. Tellurnickel, Hessite v. Tellursilber, Tellurwismuth, v. Tetrady

Tellurium

SULPHIDES, 357 383

SULPHOBISMUTHITES, 623 Sulphoborite, 631 Sulphohalite,

SULPHOSTANNATES,

TO

315

Sulphur,347 Sulvanite,393 Sundtite,385 Sunstone,466 Susannite,631 Sussexite, 619

Svabite,598 Svanbergite,618 Sychnodymite, 373 382 Sylvanite, 396 Sylvite, Symplesite,608 Synadelphite,606

Tridymite,407 Trigonite,601 Trimerite,515

v. Skutterudite Tesseralkies,

601 Triploidite, 409 Triploite, 618 Trippkeite, 618 Tripuhyite, 604 Tritochorite, 496 Tritomite, 617 Trogerite, 373 Troilite, 614 Trolleite,

Tetradymite,360 390 Tetrahedrite, Thalenite,529 531 Thallite, 365 selenide,

Syngenite,636

Thaumasite, 581 Thenardite,624 Thennonatrite,452

633 Szomolnokite, T

ThermophyUite,575 441 Thinolite, 468 Thiorsauite, 402 Thomsenplite,

Thomsonite,

557

Thonerde,v.

Aluminium

Tabular

spar, 482 Tachhydrite,402

Thorianite,624 Thorite,522

Tachyhydrite, Tachydrite,

Thorium

402 565 Taeniolite, 356 Taenite, v. Wollastonite Tafelspath,

612 Tagilite, Talc,575 v. Magnetite Talkeisenerz, 600 Talktriplite, 402 Tallingite, Tallow,Mineral,645 Tamanite,607

silicate, 522, 540 529 Thortveitite, Thorogummite, 624 530 Thulite, 571 Thuringite, Tiemannite,369 405 Tiger-eye, 601 Tilasite,

Tile ore, 410 364 Tilkerodite, Tin, Native,354 Tin borate, 620

TANTALATES,587

oxide,425

588 Tantalite, Tantalum,349 389 Tapalpite, 590 Tapiolite, 498 Taramellite, 604 Tarbuttite,

394 sulphide,

446 Tarnowitzite, 583 Tartarkaite, 646 Tasmanite, 606 Tavistockite, Tawmanite,532 624 Taylorite, 394 Teallite, v. Tellurium Tellur,

TELLURATES,641 360 Tellurbismuth,

Tellurblei, v. Altaite 364 et sea TELLURIDES, 410 Tellurite, 641 TELLURITES,

349 Tellurium,

Tremolite,489

Temiskamite, 372 Tengerite,454 Tennantite,391 Tenorite,412 Tephroite,513 401 Terlinguaite, Termierite,579 Teschemacherite, 450

Thallium

Szaboite,474 620 Szaibelyite, 489 Szechenyiite, Szmikite,633

Travertine,440

Trechmanite,386 607 Trichalcite,

mite

449 Synchisite, 489 Syntagmatite,

476 Traversellite,

629 Tripestone, Triphane,480 594 Triphyline, 594 Triphylite, 600 Triplite,

Trona, 453 514 Troostite, Tschewkinit, Tscheffkinite, 585

637 Tschermigite, Tsumebite,604 440 Tufa,Calcareous, 410 Tungsten trioxide, 361 Tungstenite, 410 Tungstite, Turanite,604

Turgite,433 613 Tiirkis, Turmalin,540 593 Turnerite, Turquois, Turquoise,613

Tychite,450 Tyrite,588 Tyrolite,612 Tysonite,399

Tyuyamunite, 617

Tin ore, Tin stone,425 Tin

pyrites,394

Tincal,622 Tinkal,622 612 Tirolite,

TlTANATES,583 v. Ilmenite Titaneisen, Titanic iron ore, 417

583 Titanite,

Titaniumoxide, 427, 428, 429 584 ritanomorphite, 540 Toernebohnite, Topaz,523 False,405 413 Oriental, 508 Topazolite, 648 Porbanite, 616 Torberaite,

406 Touchstone,

Tourmaline. 540

U 428 Uhligite, 647 Uintahite, Uintaite,

Ulexite,622

Ullmannite,379 392 Jltrabasite, 503 Jltramarine, Umangite,365 530 Jnionite, 641 Jraconite, 490 Jralite, JRANATES, 623 623 Jraninite, 616 Jranite, Jranium

arsenate, 617

454 carbonates, niobates, 590, 591 phosphates,616 581 silicates, sulphate,641

720 630, 635 Zinc,sulphates, sulphides, 367,371 vanadate,604 Zinc blende,367 Zinc ore, Red, 441 445 Zincorodochrosite,

INDEX

TO

SPECIES

Zinkblende,v. Sphalerite Zinkenite,385. 630 Zinkosite, Zinkspath,v. Smithsonite Zinnerz,425 Zinnkies,v, Stannite Zinnober,v. Cinnabar

Zincaluminite,640 Zincite,411

Zinnstein,425

385 Zinckenite, 441 Zincocalcite,

Zinnwaldite,563 641 Zippeite,

Zircon,520 Zirconium

428 dioxide, silicate, 520, 484

428 Zirkelite, 530 Zoisite, Zorgite,365 Zunyite,505 518 Zurlite,

500 Zwieselite,

c