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Laboratory Manual for Introductory Geology 4e

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APPENDIX 3.1

Mineral Identification Flowcharts

C. Minerals with Nonmetallic Luster, Light Colored

Hardness Breakage Color

Other diagnostic

properties

Possible minerals

(see Appendix 3.3 for

additional properties)

Softer than

a fingernail

Prominent

cleavage in one

direction

Cleavage in one

direction rarely

seen

Colorless

White, gray

White, colorless

White

Splits into thin, transparent sheets

Feels greasy

Splits into slabs; massive variety

is fine grained, granular

Typically powdery masses;

sticks to the tongue

Muscovite

Talc

Gypsum

Kaolinite

Softer than

a penny,

harder than

a fingernail

Cleavage in three

directions at 90°

Cleavage in three

directions

not at 90°

Colorless

Usually white

or gray

Cube-shaped crystals;

tastes salty

Cube-shaped crystals;

tastes bitter

Flat, stubby crystals;

unusually high specific gravity

Halite

Sylvite

Barite

Harder than

a penny,

softer than

glass

Cleavage in three

directions

not at 90°

Colorless,

gray, white,

pink

Reacts vigorously with

hydrochloric acid

Powder reacts weakly with

hydrochloric acid

Calcite

Dolomite

Cleavage in

four directions

Colorless,

purple, green

Cube-shaped crystals

Fluorite

Conchoidal

fracture

Highly

varied

Commonly in elongate

6-sided crystals

Quartz

Harder

than glass

Cleavage in two

directions

at 90°

Cleavage in two

directions

not at 90°

White,

gray, black

White,

gray, pink

White, gray

Blue, gray

Striations (fine lines) on one

cleavage direction; may be iridescent

No striations; may have narrow

ribbon-like exsolution lamellae

Elongate 4-sided crystals;

transverse sections may show

cross-like pattern of inclusions

Flat, bladed crystals; H = 5.5 parallel to

long side, H = 7 parallel to short side

Plagioclase

feldspar

Potassium

feldspar

Andalusite

Kyanite

One direction

White, gray

Slender, elongate crystals;

sometimes fibrous

Sillimanite

None (may show

smooth, flat

breakage)

Gray, brown

(gem varieties

red, blue)

H = 9; commonly in 6-sided

prismatic crystals with flat

breakage planes at end

Corundum

APPENDIX 77

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