Minerals
Potassium 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 |
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Igneous Vocabulary
Phaneritic |
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 Rocks
Gabbro (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
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Pumice |
Extrusive, felsic
Vesicular
Very light |
Scoria |
Extrusive, mafic
Vesicular
Black to reddish brown |
Metamorphic Vocabulary
Foliated |
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 Rocks
Foliated |
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 |
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Sedimentary Rocks
Quartz 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 Vocabulary
Clastic |
Clasts bound together |
Bioclastic |
Abundant fossils or fossil fragments |
Crystalline |
Interlocking crystals |
Fissile |
Splits into sheets |
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