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Coarse, 'salt and pepper': dark pyroxene and light andesine. Provides perfect representation of an intermediate igneous rock.

Volcanic glass with snowflakes embedded throughout.

Hematite-cemented quartz; orthoquartzite.

Gray to brown mudstone with abundant silt.

Classic, dark; from the Columbia Plateau.

Gray, fine, friable, with abundant small sanidine crystal fragments.

Dense and massive.

Chlorite-mica with perfect slaty cleavage.

Brownish black, intermediate stage between peat and bituminous coal.

Typical green-gray, fissile, clay-rich.