"The Mystery of Lyle and Louise"

Pure, large, transparent-to-translucent cleavages, Mohs’ hardness of 4.

Chlorite-bearing.

Spinel group; black, dull metallic luster; common iron oxide.

Black, soft; most widely mined.

Slaty cleavage; contains hematite.

Pale pink felsite, with small sanidine phenocrysts.

Gray, fine-grained, massive contact rock.

Gray to buff, with numerous ooliths and fossil fragments.

Shiny black volcanic glass showing conchoidal fracture and some spherulites.

Brownish black, intermediate stage between peat and bituminous coal.