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Grain Size |
Description or Comments |
Rock Name |
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Gravel |
rounded rock fragments |
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angular rock fragments |
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Sand |
predominantly quartz grains |
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quartz with considerable feldspar |
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dark with feldspar, clay, and rock fragments |
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Silt |
Mud |
fissile (splits along planes into thin layers) |
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Clay |
breaks into chunks or blocks |
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Group |
Composition |
Description or comments |
Rock Name |
| Inorganic | Calcite | made of small spherical grains or ooids | |
| made from chemical precipitation such as in dripstones in caves | |||
| Dolomite | commonly altered from limestone | ||
| Halite | made by the evaporation of water | ||
| Gypsum | made by the evaporation of water | ||
| Microcrystalline Quartz | very compact, hard rock made from silica deposited directly from water | ||
| Biochemical | Microcrystalline Quartz | very compact, hard rock made of hard parts of microscopic marine organisms | |
| Calcite | coarse rock of poorly cemented shell fragments | ||
| soft, light-colored porous rock made of hard parts of microscopic marine organisms | |||
| Organic plant material | soft, brown, porous, obvious plant remains | ||
| black, soft, nonporous, some with conchoidal fracture | |||