Mineral Identification Chart – LECTURE

Mineral Identification Chart ¨C LECTURE

NONMETALLIC MINERALS (listed in decreasing hardness) Review mineral formula to connect to family! H=Hardness; SG = specific gravity

Mineral

H

SG Streak Color (and/or luster)

Form

Cleavage/Fracture

Distinctive properties

Garnet

Dodecahedron form,

7

3.5- White Red, black, or brown; can Dodecahedrons (12- No cleavage.

be yellow, green, pink.

sided polygons)

Brittle. Conchoidal

red, glassy, conchoidal

4.3

X3Y2(SiO4)3 where X and Y are

Glassy. Translucent.

fracture.

fracture, H=7.

combinations of Ca, Mg, Fe, Al

Olivine (Mg,Fe)2SiO4

7

3.3- White Pale or dark olive green

Short prisms

Conchoidal

Green, conchoidal

3.4

to yellow or brown.

(usually too small to fracture.

fracture, glassy, H=7.

Glassy. Transparent.

see).

Brittle.

Usually granular.

Quartz SiO2

7

2.7 White Colorless, white, or gray;

Massive; or

Conchoidal

Glassy, conchoidal

can occur in all colors.

hexagonal prisms

fracture.

fracture, H=7. Hex.

Glassy and/or greasy.

that end in a point.

prism with point end.

Tabular crystals or

2 good cleavage

Twinning. 2 cleavages

6

2.6- White Colorless, white, gray, or

Plagioclase Feldspar family:

planes at nearly

2.8

black; can have iridescent thin needles

Anorthite and Labradorite

at 90¡ã.

right angles.

play of color from within.

CaAl2Si2O8 to Oligoclase and

Translucent to opaque.

Albite NaAlSi3O8

Potassium Feldspar family:

6

2.5- White Pink. Or white, orange,

Tabular crystals

2 good cleavage

Subparallel exsolution

Orthoclase and Microcline

2.6

brown, gray, green.

planes at nearly

lamellae. 2 cleavages

KAlSi3O8

Translucent to opaque.

right angles.

at 90¡ã. Pink color.

Pyroxene family: Augite

5.5- 3.2- White, Green to black; opaque.

Short, 8-sided

2 good cleavage

H=5.5. Dark green or

Ca(Mg,Fe,Al)(Al,Si)O6

6

3.5 pale

prisms (if visible).

planes at nearly

black. 2 cleavages at

grey

right angles.

90¡ã. (Looks like HB.)

H=5.5. Dark green or

Amphibole family: Hornblende 5.5 3GreyDark green to black.

Long, perfect

2 cleavages planes.

black. 2 cleavages at

3.3 green, Opaque.

prisms.

Angles: 60¡ã and

Ca(Mg,Fe)4Al(Si7Al)O22(OH) 2

white

120¡ã. Brittle.

60¡ã & 120¡ã. Splintery

Splintery fracture.

fracture. Long prisms.

Serpentine

2-5 2.2- White Pale or dark green,

Smooth, rounded

No cleavage.

Mottled green color.

Mg6Si4O10(OH)8

2.6

yellow, grey. Opaque.

masses.

Smooth, curved

Dull or silky.

surfaces.

Usually cubes or

4 excellent cleavage Cubic or octahedral

Fluorite CaF2

4

3White Colorless, purple, blue,

form. 4 directions of

octahedrons.

directions. Gives

3.3

grey, green, or yellow.

cleavage. Triangular

crystal shape

Glassy. Opaque to

faces. Rainbow luster

triangular faces.

transparent. Rainbow

in places.

Brittle.

luster in places.

Mineral

Calcite CaCO3

H

3

SG

2.7

Streak

White

Color (and/or luster)

Usually colorless, white,

or yellow, can be green,

brown, or pink. Glassy.

Opaque to transparent.

Form

Rhombohedrons.

Cleavage/Fracture

3 excellent cleavage

planes. Angles:

< 90¡ã and > 90¡ã.

Mica family: Biotite

K(Mg,Fe)3AlSi3O10(OH)2

2.53

2.73.1

Greybrown

Short tablets. Like a

tablet of paper.

Mica family: Muscovite

KAl3Si3O10(OH)2

22.5

2.73

White

Halite NaCl

2.5

2.12.6

White

Gypsum

CaSO4*2(H20)

2

2.3

White

Tabular, prisms,

blades, or needles.

1 excellent cleavage

¨C splits easily into

thin, flexible sheets.

1 excellent cleavage

¨C splits easily into

thin, flexible sheets.

Brittle. 3 excellent

cleavage planes:

cubes.

1 good cleavage

plane.

Talc

Mg3Si4O10(OH)2

1

2.72.8

White

Black, green-black,

brown-black. Transparent

to opaque.

Colorless, yellow, brown,

or red-brown.

Transparent to opaque.

Colorless, white, yellow,

blue, brown, or red.

Glassy.

Colorless, white, or grey.

Translucent to

transparent.

White, grey, pale green,

or brown. Opaque.

Greasy or silky luster.

Shapeless masses (if

no cleavage visible)

or tabular.

1 poor cleavage

plane (may not be

visible).

Short tablets. Like a

tablet of paper.

Cubes.

Distinctive properties

Bubbles in HCL.

Double refraction (2

images visible through

clear sample).

Rhombs, 3 cleavage

planes (not 90¡ã), H=3.

1 flexible cleavage

plane (sheet), dark

colored; brown streak.

1 flexible cleavage

plane (sheet), light

colored; white streak.

Salty taste. H=2.5.

Cubic form and

cleavage.

H=2. 1 cleavage plane.

Translucent.

Feels greasy or soapy.

H=1. Opaque.

METALLIC MINERALS (listed in decreasing hardness) Review mineral formula to connect to family! H=Hardness; SG = specific gravity

Mineral

H

SG Streak

Color

Form

Cleavage/Fracture

Distinctive properties

Pyrite FeS2

65

Dark grey Brass yellow; tarnishes

Cubes or octahedrons

Brittle. No cleavage.

Cubic form, brassy color,

6.5

brown.

and SG=5.

Magnetite

6

5.2 Dark grey Silvery grey to black.

Octahedrons

No cleavage.

Attracted to a magnet.

Fe3O4

Tarnishes grey. Opaque.

SG=5.2. No cleavage.

Hematite

1.52.1- Red to

Silvery grey, black, or brick

Thin tabular crystals or No cleavage.

Red streak. Metallic +

Fe2O3

6

2.6 red-brown red. Luster can also be

shapeless masses.

nonmetallic. Earthy red.

nonmetallic.

Galena PbS

2.5

7.6 Grey to

Silvery grey. Tarnishes dull

Cubes and octahedrons Brittle. 3 good cleavage SG=8. Dense! Silver cubes

dark grey

grey.

planes (cubes).

(form and cleavage).

Graphite C

1

2.1- Dark grey Silvery grey to black.

Flakes, short hexagonal 1 excellent cleavage

Dark grey. H=1. Greasy.

2.3

prisms, and masses.

plane.

Dark grey streak.

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