Mineral Identification Chart – LECTURE

Mineral Identification Chart ? 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

7 3.5- White Red, black, or brown; can Dodecahedrons (12- No cleavage.

Dodecahedron form,

X3Y2(SiO4)3 where X and Y are

4.3

be yellow, green, pink. sided polygons)

Brittle. Conchoidal red, glassy, conchoidal

combinations of Ca, Mg, Fe, Al

Glassy. Translucent.

fracture.

fracture, H=7.

Olivine (Mg,Fe)2SiO4

7 3.3- White Pale or dark olive green Short prisms

Conchoidal

3.4

to yellow or brown.

(usually too small to fracture.

Green, conchoidal fracture, glassy, H=7.

Glassy. Transparent.

see).

Brittle.

Usually granular.

Quartz SiO2

7 2.7 White Colorless, white, or gray; Massive; or

can occur in all colors.

hexagonal prisms

Conchoidal fracture.

Glassy, conchoidal fracture, H=7. Hex.

Glassy and/or greasy.

that end in a point.

prism with point end.

Plagioclase Feldspar family:

6 2.6- White Colorless, white, gray, or Tabular crystals or 2 good cleavage

Twinning. 2 cleavages

Anorthite and Labradorite CaAl2Si2O8 to Oligoclase and Albite NaAlSi3O8 Potassium Feldspar family:

2.8

black; can have iridescent thin needles

play of color from within.

Translucent to opaque.

6 2.5- White Pink. Or white, orange, Tabular crystals

planes at nearly right angles.

2 good cleavage

at 90?. Subparallel exsolution

Orthoclase and Microcline

2.6

brown, gray, green.

planes at nearly

lamellae. 2 cleavages

KAlSi3O8 Pyroxene family: Augite

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

Short, 8-sided

right angles. 2 good cleavage

at 90?. Pink color. H=5.5. Dark green or

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

6 3.5 pale grey

prisms (if visible).

planes at nearly right angles.

black. 2 cleavages at 90?. (Looks like HB.)

Amphibole family: Hornblende 5.5 3- Grey- Dark green to black.

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

3.3 green, Opaque.

white

Long, perfect prisms.

2 cleavages planes. Angles: 60? and 120?. Brittle. Splintery fracture.

H=5.5. Dark green or black. 2 cleavages at 60? & 120?. Splintery fracture. Long prisms.

Serpentine Mg6Si4O10(OH)8

2-5 2.2- White Pale or dark green,

2.6

yellow, grey. Opaque.

Dull or silky.

Smooth, rounded masses.

No cleavage.

Mottled green color. Smooth, curved surfaces.

Fluorite CaF2

4 3- White Colorless, purple, blue, Usually cubes or

3.3

grey, green, or yellow.

octahedrons.

4 excellent cleavage Cubic or octahedral directions. Gives form. 4 directions of

Glassy. Opaque to

crystal shape

cleavage. Triangular

transparent. Rainbow

triangular faces.

faces. Rainbow luster

luster in places.

Brittle.

in places.

Mineral Calcite CaCO3

Mica family: Biotite K(Mg,Fe)3AlSi3O10(OH)2 Mica family: Muscovite KAl3Si3O10(OH)2 Halite NaCl

Gypsum CaSO4*2(H20) Talc Mg3Si4O10(OH)2

H SG Streak Color (and/or luster)

Form

3 2.7 White Usually colorless, white, Rhombohedrons.

or yellow, can be green, brown, or pink. Glassy. Opaque to transparent.

2.5- 2.7- Grey- Black, green-black,

Short tablets. Like a

3 3.1 brown brown-black. Transparent tablet of paper.

to opaque.

2- 2.7- White Colorless, yellow, brown, Short tablets. Like a

2.5 3

or red-brown.

tablet of paper.

Transparent to opaque.

2.5 2.1- White Colorless, white, yellow, Cubes.

2.6

blue, brown, or red.

Glassy.

2 2.3 White Colorless, white, or grey. Tabular, prisms,

Translucent to

blades, or needles.

transparent.

1 2.7- White White, grey, pale green, Shapeless masses (if

2.8

or brown. Opaque.

no cleavage visible)

Greasy or silky luster.

or tabular.

Cleavage/Fracture 3 excellent cleavage planes. Angles: < 90? and > 90?.

1 excellent cleavage ? splits easily into thin, flexible sheets. 1 excellent cleavage ? splits easily into thin, flexible sheets. Brittle. 3 excellent cleavage planes: cubes. 1 good cleavage plane.

Distinctive properties

Bubbles in HCL. Double refraction (2 images visible through clear sample). Rhombs, 3 cleavage planes (not 90?), 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.

1 poor cleavage plane (may not be visible).

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 6- 5 6.5

Dark grey Brass yellow; tarnishes brown.

Cubes or octahedrons Brittle. No cleavage.

Cubic form, brassy color, and SG=5.

Magnetite Fe3O4 Hematite Fe2O3

6

5.2 Dark grey Silvery grey to black.

Tarnishes grey. Opaque.

1.5- 2.1- Red to

Silvery grey, black, or brick

6

2.6 red-brown red. Luster can also be

nonmetallic.

Octahedrons

No cleavage.

Thin tabular crystals or No cleavage. shapeless masses.

Attracted to a magnet. SG=5.2. No cleavage. Red streak. Metallic + nonmetallic. Earthy red.

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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