MineralsPotassium Feldspar H = 6 | Salmon pink, white Two cleavages at about 90 degrees | Plagioclase H = 6 | White to dark gray Two cleavages at almost 90 degrees Straight, parallel striations | Quartz H = 7 | Conchoidal fracture Vitreous luster | Muscovite H = 2-2.5 | Colorless, silvery white, brownish silvery white One perfect cleavage Transparent, flexible, and elastic in thin sheets | Biotite H = 2.5-3 | Black to brownish black One perfect cleavage Flexible and elastic in thin sheets | Hornblende (Amphibole) H = 5 | Black Two perfect cleavages at 124 and 56 degrees Splintery | Augite (Pyroxene) H = 5-6 | Black to dark green Two imperfect cleavages at almost 90 degrees | Olivine H = 6.5-7 | Olive green to yellow green Granular | Gypsum H = 2 | Clear, white, light gray Vitreous to pearly | Pyrite H = 6-6.5 | Metallic Brass yellow | Calcite H = 3 | Clear, white, others Three perfect cleavages form rhombic cleavage fragments Reacts strongly with HCl | Dolomite H = 3-3.5 | Reacts slowly or not at all with HCl Three indistinct cleavages | Halite H = 2.5 | Clear to gray to red Three perfect cleavages at 90 degrees Salty taste |
| | Igneous VocabularyPhaneritic | Coarse-grained (>1 mm) | Aphanitic | Fine-grained (<1 mm) | Pegmatitic | Exceptionally large crystals (>3 cm) | Porphyritic | Two crystal sizes | Phenocrysts | Larger crystals | Groundmass | Smaller crystals surrounding phenocrysts | Vesicular | Bubbles | Pyroclastic | Multiple fragments |
Igneous RocksGabbro (phaneritic) | Intrusive, mafic Ca-plagioclase, black pyroxene, olivine | Diorite (phaneritic) | Intrusive, intermediate Na-Ca-plagioclase and hornblende Biotite and quartz | Granite (phaneritic) | Intrusive, felsic Quartz and K-feldspar Na-plagioclase, biotite, and hornblende | Granite (porphyritic) | Intrusive, felsic Coarse-grained Two crystal sizes | Granite pegmatite | Intrusive, felsic Very coarse-grained | Basalt (aphanitic) | Extrusive, mafic Dark gray Ca-plagioclase and olivine | Basalt (vesicular) | Extrusive, mafic Dark gray Ca-plagioclase and olivine | Andesite (porphyritic) | Extrusive, intermediate Fine-grained Gray Plagioclase and hornblende or biotite | Rhyolite | Extrusive, felsic Fine-grained version of granite | Tuff (pyroclastic) | Extrusive Particle size less than 6.4 cm | Obsidian (glassy) | Extrusive, felsic
| Pumice | Extrusive, felsic Vesicular Very light | Scoria | Extrusive, mafic Vesicular Black to reddish brown |
Metamorphic VocabularyFoliated | Parallel or nearly parallel planes | Slaty | Foliation made of minerals to small to see without a microscope | Phyllitic | Foliation composed of minerals visible with handlens to barely visible to naked eye | Schistose | Foliation composed of mineral crystals large enough to see unaided | Gneissic | Coarse foliation Parallel band or layers of light and dark minerals |
Metamorphic RocksFoliated | Slate | Low grade; Very fine grained Generally dark Shale or mudstone | Phyllite | Low grade; Fine grained Silky, shiny Shale or mudstone | Schist | Intermediate Medium to coarse grained Shale or mudstone | Gneiss | High grade Medium to coarse grained Shale, mudstone, or granite | Migmatite | Border between igneous and metamorphic Medium to coarse grained Shale, mudstone, or granite | Nonfoliated | Marble | Grade varies Coarsely crystalline Limestone or dolostone | Quarzite | Grade varies Crystalline Quartz sandstone | Anthracite coal | Low to medium grade Conchoidal fracture Coal | Greenstone | Low to medium grade Greenish gray to black Basalt or gabbro | Amphibolite | Medium to high grade Dark gray to black Medium to coarse grained Basalt or gabbro | Soapstone | Low to medium grade Gray to dark greenish gray Fine grained; Soft Peridotite | Serpentinite | Variable grade Greenish Mottled or streaked Peridotite | Metaconglomerate | Low to medium grade Conglomerate, graywacke, chert | Hornfels | Low grade; Contact Fine grained; Dark Varies |
| | Sedimentary RocksQuartz sandstone | Sand grains of quartz White, rusty brown | Conglomerate | Made of pebbles | Limestone | Calcite Bubbles in acid | Shale | Fissile Black to gray, red, or green | Dolostone | Lesser reaction with acid Crystalline Light gray or buff | Chert | Microcrystalline quartz Conchoidal fracture | Coal | Brown to black Noncrystalline | Mudstone | Not fissile Black to gray, red, or green | Sandstone | Made of sand | Oolite | Limestone Sand-sized spheres | Coquina | Limestone Poorly cemented bioclastic debris | Breccia | Angular particles | Rock Gypsum | White, light gray Crystalline |
Sedimentary VocabularyClastic | Clasts bound together | Bioclastic | Abundant fossils or fossil fragments | Crystalline | Interlocking crystals | Fissile | Splits into sheets |
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