Minerals Quiz

Quartz

Fracture (no cleavage), hexagonal prismatic crystal form, hardness 7

Potassium Feldspar

zigzag striations, 2 planes of cleavage at nearly 90, lighter in color (pink, off-white, red)

Muscovite Mica

flaky, one plane of cleavage, soft - can be scratched by fingernail, white/gray

Biotite Mica

black/brown, one plane of perfect cleavage, soft - can be scratched by fingernail

Garnet

high density, dodecahedral crystal form, fracture, redish=brown color

Magnetite

Magnetic, metallic, black

Pyrite

Greenish-black streak, metallic luster (“fool’s gold”), made up of little cubes

Galena

Super metallic, high density, 3 planes of cleavage, cubic crystal form

Gypsum

Striations on the sides, light gray/white, extremely soft (hardness of 2), perfect cleavage in one direction, common use = drywall

Calcite

Reacts with acid, white/clear, 3 planes of cleavage, common uses = TUMS, cement

Flourite

Octahedron/dodecahedron crystal form, can be many different colors, common use = toothpaste

Halite

Salty taste, plastic-y exterior, translucent, glassy luster, 3 planes of cleavage, common use = table salt

Talc

Soapy texture, hardness of 1, chalky streak, one direction of cleavage, common use = baby powder

Plagioclase Feldspar

parallel (straight) striations, 2 planes of cleavage at nearly 90, gray, white streak

Amphibole

Black/green, dull but glassy luster, 2 planes of cleavage at 60 and 120,

Olivine

Looks like a pistachio, crystal-like exterior (orthorhombic crystal form), green, glassy

Hematite

Red color, red streak, slightly metallic

Pyroxene

2 planes of cleavage at 90, dark color, glassy