"Specimens"

Grayish black trap rock.

Gray, fine, friable, with abundant small sanidine crystal fragments.

Dark gray, composed mostly of pyroxene and olivine.

Fine to medium-grained with biotite.

Classic, dark; from the Columbia Plateau.

Medium-grained with biotite.

Coarse, 'salt and pepper': dark pyroxene and light andesine. Provides perfect representation of an intermediate igneous rock.

Abundant small black phenocrysts in a gray to brown matrix.

Gray andesite with phenocrysts of felspar and/or hornblende.

Light gray, with flow structure.