"Igneous Rock Specimens"

Dark gray, with hornblende as the dominant mafic mineral.

Fine to medium-grained with biotite.

Volcanic glass with snowflakes embedded throughout.

Coarse-grained, with microcline, biotite and horblende phenocrysts.

Shiny black volcanic glass showing conchoidal fracture and some spherulites.

Coarse grained and abundant in plagioclase feldspar.

Coarse-grained plagioclase and pyroxene with some olivine.

Banded volcanic glass.

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

Grayish black trap rock.

Classic, very coarse-grained igneous texture.

Medium-grained with biotite.

Dark gray, composed mostly of pyroxene and olivine.

Light gray, with flow structure.

Dark gray with abundant gas pocket vesicles.

Classic, dark; from the Columbia Plateau.