Light gray, earthy.
Gray to buff, with numerous ooliths and fossil fragments.
Dense and massive.
Gray to white, coarse crystalline, carbonate rock.
Pink/gray coarse carbonate rock.
Shiny black volcanic glass showing conchoidal fracture and some spherulites.
Banded volcanic glass.
Glassy; most specimens float in water.
Fightly cemented, medium-to-coarse quartz grains.
Light gray, with flow structure.
Gray, fine to medium-grained “Berea grit”.
Hematite-cemented quartz; orthoquartzite.
Foliated biotite, coarse, silvery gray with quartz-feldspar bands.
Typical green-gray, fissile, clay-rich.
Brownish gray, kerogen-rich; commercial oil source.
Slaty cleavage; contains hematite.
