Light gray, earthy.
Gray to buff, with numerous ooliths and fossil fragments.
Dense and massive.
Gray, fine to medium-grained “Berea grit”.
Hematite-cemented quartz; orthoquartzite.
Typical green-gray, fissile, clay-rich.
Brownish gray, kerogen-rich; commercial oil source.
Well-cemented, medium-grained orthoquartzite.
Black, soft; most widely mined.
Cemented glacial gravel.
Small, rounded pebbles and tightly cemented granules.
Introduce your students to rocks formed from deposition of sediment.
