"Igneous Rock Specimens"

Dark gray, with hornblende as the dominant mafic mineral.

Fine to medium-grained with biotite.

Obsidian is hard black colored, volcanic glass.

Volcanic glass with snowflakes embedded throughout.

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

Shiny black volcanic glass showing conchoidal fracture and some spherulites.

Syenite a light-colored rock consisting of feldspars and hornblende.

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.

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

Grayish black trap rock.

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

Introduce your students to Gray Andesite with large phenocrysts of hornblende.

Rhyolite is a pale, pink felsic rock with lower density than most igneous rocks.