"PARKWAY PLASTICS, INC."

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.

White, mature, friable.

Dark, waxy, bitumin-rich.

Without Glued-On Grains That Wear Off, Chart Stands up to Repeated use.