MINERAL IDENTIFICATION printable PDF file

PHYSICAL GEOLOGY ROCK IDENTIFICATION

IGNEOUS ROCKS
GRANITE pink to white/gray color, light colored minerals dominant, - mostly orthoclase, phaneritic or porphyritic
DIORITE equal amounts of light and dark minerals, "salt and pepper texture" phaneritic or porphyritic
GABBRO mostly dark colored minerals, phaneritic, rarely porphyritic
DUNITE mostly olivine, usually phaneritic
RHYOLITE light colored (light gray, white, pinkish), aphanitic, can be porphyritic
ANDESITE intermediate colored (gray, medium gray); aphanitic, can be porphyritic
BASALT dark colored (black) aphanitic, commonly porphyritic
PUMICE light colored, vesicular texture (bubbly rock), light weight
SCORIA dark colored vesicular texture bubbly rock), light weight
OBSIDIAN dark volcanic glass, has sharper edges and is more vitreous than chert

SEDIMENTARY ROCKS

CONGLOMERATE has rounded pebbles, pebbles may be loose, inorganic
BRECCIA same as above but with sharp edged pebbles, inorganic
QUARTZ SANDSTONE sandstone with only quartz, light colored (white or tan) well sorted, inorganic
ARKOSE sandstone with orthoclase, reddish color, inorganic
SILTSTONE very fine grained, will feels gritty, inorganic
SHALE very fine grained, feels smooth, inorganic
MICRITIC LIMESTONE (MICRITE) fizzes in acid, massive looking, looks like cement, organic
CHALK limestone, light weight, fizzes in acid, writes on things, organic
OOLITIC LIMESTONE fizzes in acid, made of sand sizes carbonate spherical particles (oolites) organ
FOSSILIFEROUS LIMESTONE has visible fossil fragments, fizzes in acid, organic
COQUINA limestone, fizzes in acid, made entirely of shell fragments, organic
CHERT does not fizz in acid , generally light color, dull luster compared to obsidian, microcrystalline silica (SiO₂) organic, Harder than glass
COAL black, light weight, crumbly, made out of plant debris, organic
GYPSUM fibrous, silky feel, monominerallic, soft, non clastic (chemical)

METAMORPHIC ROCKS
SLATE foliated, break into flat slabs, harder than shale, protolith=shale
PHYLLITE foliated, breaks into slabs that may be contorted, lustrous sheen, shinier than slate, protolith=shale
MICA SCHIST foliated, has lots of mica flakes that are visible on flat surfaces only,
GARNET SCHIST foliated, same as above but also contains lots of "little" garnets (red mineral)
BLUESCHIST foliated but, doesn't look very foliated, "denim" blue in color
GNEISS foliated, alternating bands of light and dark colored minerals, "tiger stripes"
QUARTZITE non foliated, crystalline, sugary texture, light colored, rougher surface than chert, harder than glass, protolith=quartz sandstone
MARBLE non foliated crystalline, sugary texture, usually light, but may be colored, softer than glass, fizzes in acid, protolith=limestone
AMPHIBOLITE non foliated but may be foliated, black color, flakes easily, made of mostly hornblende crystals
METACONGLOMERATE non foliated, visible pebbles that are welded into the rock, and wont fall out, protolith=conglomerate

TERMS YOU NEED TO KNOW

phaneritic, aphanitic, porphyritic, glassy, vesicular, felsic, mafic, intrusive, extrusive, clastic, nonclastic, organic, inorganic, grain size, foliated, non foliated, rock mineralogy

Updated February 6, 2003