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What is Gabbro?

Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in the deep oceanic crust.

What Minerals are in Gabbro?

Gabbro is composed mainly of calcium-rich plagioclase feldspar (usually labradorite or bytownite) and clinopyroxene (augite). Minor amounts of olivine and orthopyroxene might also be present in the rock. (see composition chart at right)

This mineral composition usually gives gabbro a black to very dark green color. A minor amount of light-colored mineral grains may be present. Unlike many other igneous rocks, gabbro usually contains very little quartz. (see a close-up view of gabbro at right)