"Specimens"

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.

Chlorite-mica with perfect slaty cleavage.

White, very dark green, and very dark red to light red granoblastic intergrowth of wollastonite, diopside, and andradite.

Cross section of a Pennsylvanian fusulinid in chert that shows random orientations of structural features, including the proloculus and chamber walls.