Gabbro is a mafic, intrusive igneous rock.  It has the same chemistry & mineralogy as basalt, but is coarsely crystalline (phaneritic texture; all crystals between 1 mm and 1 cm in size) due to relatively slow cooling of magma deep underground.  Gabbros are dominated by the minerals plagioclase feldspar (grayish) and pyroxene (black).





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