The Major Rock-Forming Minerals in Hand Sample

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Alkali Feldspar occurrence

Felsic igneous; metamorphics (sometimes clastic sed)

Alkali Feldspar identification

Pink (less often white), perthitic, 2-directional cleavage

Quartz occurrence

Felsic igneous; metamorphics; clastic sedimentary

Quartz identification

Usually clear /white, translucent, conchoidal fracture, no cleavage

Calcite occurrence

Chemical sedimentary; some metamorphics

Calcite identification

Rhombohedral cleavage, usually light-colored, fizzes in acid

Amphibole occurrence

Felsic/mafic igneous; metamorphics

Amphibole identification

Dark color, long/thin habit, 60/120 cleavage

Pyroxene occurrence

Mafic/ultramafic igneous; high-grade metamorphics

Pyroxene identification

Dark color, short/stumpy habit, 90 degree cleavage

Mica occurrence

Felsic igneous; metamorphics

Mica identification

Platy cleavage, shiny; can be dark (biotite) or light (muscovite

Garnet occurrence

Felsic igneous; metamorphics

Garnet identification

Red/purple ball-shaped; no cleavage

Olivine occurence

mafic/ultramafic, igenous

Olivine identification

Olive-green ball-shaped; no cleavage