"Avantor"

Banded volcanic glass.

Glassy; most specimens float in water.

Light gray, with flow structure.

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

Gray andesite with phenocrysts of felspar and/or hornblende.

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.

Coarse grained and abundant in plagioclase feldspar.

Volcanic glass with snowflakes embedded throughout.