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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