"Igneous Rock Specimens"

Diorite is a mix of dark pyroxene and light andesine provides perfect representation of an intermediate igneous rock.

Classic, very coarse-grained igneous texture.

Medium-grained with biotite.

Dark gray, composed mostly of pyroxene and olivine.

Light gray, with flow structure.

Classic, dark; from the Columbia Plateau.

Dark gray with abundant gas pocket vesicles.

Gray-to-brown basaltic, with over 50% vesicles.

Pale pink felsite, with small sanidine phenocrysts.

Gray andesite with phenocrysts of felspar and/or hornblende.

Glassy; most specimens float in water.

Abundant small black phenocrysts in a gray to brown matrix.