Mineral Identification: Properties and Characteristics for Geology Students

Galena

Color: lead gray; Streak: gray; Hardness: 2.5; Cleavage: perfect cubic; Luster: metallic; Density: ~7.4 g/cm³

Garnet

Color: red, green, orange, etc.; Streak: white; Hardness: 6.5-7.5; Cleavage: none; Fracture: conchoidal; Luster: vitreous; Density: ~3.5-4.3 g/cm³

Graphite

Color: steel gray to black; Streak: gray to black; Hardness: 1-2; Cleavage: perfect basal; Luster: metallic to dull; Density: ~2.1-2.3 g/cm³

Gypsum

Color: colorless, white, or gray; Streak: white; Hardness: 2; Cleavage: perfect; Luster: vitreous; Density: ~2.3 g/cm³

Halite

Color: colorless, white, or gray; Streak: white; Hardness: 2.5; Cleavage: perfect cubic; Luster: vitreous; salty

Hematite

Color: steel gray to reddish-brown; Streak: reddish-brown; Hardness: 5-6.5; Cleavage: none; Fracture: uneven; Luster: metallic to earthy; Density: ~5.3 g/cm³

Kaolinite

Color: white, gray, or cream; Streak: white; Hardness: 2-2.5; Cleavage: perfect; Luster: earthy to dull; Chalky

Magnetite

Color: black; Streak: black; Hardness: 5.5-6.5; Cleavage: none; Fracture: uneven; Luster: metallic; Magnetic

Muscovite

Color: silvery white, gray, or pale; Streak: white; Hardness: 2-2.5; Cleavage: perfect basal; Luster: vitreous to pearly; Density: ~2.8 g/cm³

Olivine

Color: olive green; Streak: white to colorless; Hardness: 6.5-7; Cleavage: poor; Fracture: uneven; Luster: vitreous; Density: ~3.2-4.4 g/cm³

Plagioclase Feldspar

Color: white to gray; Streak: white; Hardness: 6-6.5; Cleavage: good in 2 directions at ~90°; Luster: vitreous to pearly; Density: ~2.6-2.8 g/cm³

Potassium Feldspar

Color: pink, white, or flesh-colored; Streak: white; Hardness: 6; Cleavage: good in 2 directions at ~90°; Luster: vitreous to pearly; Density: ~2.5-2.6 g/cm³

Pyrite

Color: Gold; Streak: greenish-black; Hardness: 6-6.5; Cleavage: poor; Fracture: cubic; Luster: metallic; Density: ~5.0 g/cm³

Quartz

Color: colorless or varies; Streak: white; Hardness: 7; Cleavage: none; Fracture: conchoidal; Luster: vitreous; Density: ~2.6 g/cm³

Sulfur

Color: yellow; Streak: yellow; Hardness: 1.5-2; Cleavage: poor; Fracture: uneven to conchoidal; Luster: resinous to greasy; Density: ~2.1 g/cm³, smells bad

Talc

Color: white, gray, or greenish; Streak: white; Hardness: 1; Softest known mineral

Augite

Color: Dark green-Black, Streak: green-gray, Luster: glassy, 5-6 hardness

Biotite Mica

Color: dark brown/green, Luster: glassy, Hardness: 2.5, Thin sheets

Calcite

white/translucent, Dull glass luster, White streak, 3 hardness

Copper

Reddish Brown, metallic, 2.5 hardness

Corrundum

Colorless/can be any color, Diamond like luster, Very hard(9), doesn't easily scratch off on plate

Gneiss

Coarse-grained; alternating light and dark bands; hard and dense; visible mineral grains; often looks striped or layered. Think: "banded."

Marble

Usually white, gray, pink, or other colors; crystalline and sugary-looking; hard but can be scratched by a knife; no visible layers or foliation. Think: "sparkly limestone."

Quartzite

Very hard and dense; usually white, gray, pink, or reddish; granular/sugary appearance; quartz grains; does NOT easily break around individual grains. Think: "super-hard sandstone."

Phyllite

Fine-grained; shiny or silky surface; usually gray, green, or black; thin layers/foliation; slightly wavy appearance. Think: "shiny slate."

Schist

Medium- to coarse-grained; very obvious shiny mineral flakes, especially mica; strongly foliated; flakes can often be seen and felt. Think: "flaky."

Slate

Very fine-grained; dull to slightly shiny; usually gray, black, green, or purple; splits easily into thin, flat sheets. Think: "roof tile."

Basalt

Dark black or dark gray; fine-grained; dense and relatively heavy; crystals usually too small to see; may have small holes (vesicles). Think: "dark, fine-grained lava rock."

Andesite

Gray to medium gray; fine-grained; fairly dense; crystals usually difficult to see; intermediate color between basalt and rhyolite. Think: "gray volcanic rock."

Rhyolite

Light-colored, usually pink, tan, or light gray; fine-grained; crystals usually difficult to see; may have small dark crystals. Think: "light volcanic rock."

Granite

Light-colored, usually white, pink, or gray; coarse-grained; individual crystals easily visible; quartz and feldspar commonly present; hard and dense. Think: "speckled kitchen countertop."

Gabbro

Dark black or dark gray; coarse-grained; individual crystals easily visible; dense and heavy; looks like coarse-grained basalt. Think: "dark, chunky basalt."

Diorite

Salt-and-pepper appearance; coarse-grained; black/dark minerals mixed with white/light minerals; crystals easily visible. Think: "salt and pepper."

Scoria

Dark red, brown, or black; very vesicular with many holes; lightweight compared with solid lava; rough and often jagged. Think: "heavy-looking lava rock full of holes."

Pumice

Very light-colored, usually white, tan, or light gray; extremely porous with many tiny holes; very lightweight; may float in water. Think: "foamy rock."

Obsidian

Usually black, dark brown, or dark gray; glassy and shiny; smooth surfaces; very fine-grained with no visible crystals; breaks with sharp, curved edges. Think: "volcanic glass."