Gabbro is a coarse-grained, intrusive igneous rock. It contains interlocking crystals, larger than rice grains, which are randomly oriented. It is dark green to black. It contains mainly mafic (dark coloured) minerals.
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How was it formed?
Gabbro forms deep within the Earth’s crust, often from very large masses of magma that do not reach the surface. Slow cooling produces the large crystals. Gabbro forms under similar conditions to granite and diorite.
But unlike granite, gabbro forms from magma that is rich in iron and magnesium, and poor in quartz (silica).
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