"Specimens"

Dark gray with abundant gas pocket vesicles.

Pale pink felsite, with small sanidine phenocrysts.

Red, medium, to coarse-grained iron oxide cement; shows hematite bands.

Feldspar group; white to gray, sodium plagioclase cleavages; some faces may show twinning.

Feldspar group; greenish gray alkali feldspar, coarse crystalline, some iridescence.

Spinel group; iron-black, massive; natural magnet.

Pyroxene group; dark green, pure cleaved fragments.

Deep purple crystal clusters.

Deep blue, massive, with nepheline; key feldspathoid.

Dark brown to black; polycrystalline zinc ore.

Exemplary display of hexoctahedral crystal shape.

Light gray, fine small clasts.

Brownish black, intermediate stage between peat and bituminous coal.

Classic, very coarse-grained igneous texture.

Gray, fine-grained, massive contact rock.

Fine crystalline, pure calcite.