"VWR"

Banded volcanic glass.

Glassy; most specimens float in water.

Light gray, with flow structure.

Gray andesite with phenocrysts of felspar and/or hornblende.

Grayish black trap rock.

Classic, dark; from the Columbia Plateau.

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

Introduce your students to rocks formed from the cooling of magma and lava.