|
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 |
|
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
|
|
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
|
|
Pumice
|
Extrusive, felsic
Vesicular Very light |
|
Scoria
|
Extrusive, mafic
Vesicular Black to reddish brown |
|
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 |
|
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 |
|
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 |
|
Clastic
|
Clasts bound together
|
|
Bioclastic
|
Abundant fossils or fossil fragments
|
|
Crystalline
|
Interlocking crystals
|
|
Fissile
|
Splits into sheets
|
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
