Olivine

Silicate mineral containing iron and magnesium. A green glassy mineral formed at high temperature. Common in basalt, especially ocean-floor basalt, and in ultramafic rocks. Gem-quality olivine is called peridote. Rock made up entirely of olivine is called dunite.

Basalt boulders, a source of olivine, litter Petroglyph National Monument in Albuquerque, NM.