"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.

Obsidian is hard black colored, volcanic glass.

Coarse grained and abundant in plagioclase feldspar.

Coarse-grained plagioclase and pyroxene with some olivine.

Banded volcanic glass.

Pegmatite is igneous rock similar to granite but with larger crystals.

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

Grayish black trap rock.

Scoria is a dark-colored rock formed from lava with a high gas content.

Dark gray, composed mostly of pyroxene and olivine.

Classic, very coarse-grained igneous texture.

Medium-grained with biotite.