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Represents a Wide Range of Depositional Environments and Rock Textures

Earthy, porous calcareous tufa.

Buff-colored, coarse, detrital limestone, with cemented shell fragments.

Hematite-cemented quartz; orthoquartzite.

Gray to brown mudstone with abundant silt.

Brownish black, intermediate stage between peat and bituminous coal.

Dense and massive.

Black, fissile; commonly with carbonized fossil plant impressions.

Typical green-gray, fissile, clay-rich.

Black, soft; most widely mined.