Mafic rock

According to the IUGS recommendations for igneous rock classification there are no longer any formal "mafic rocks", only ultramafic rocks (>90% dark mafic minerals) and metamafic rocks. They prefer the terms Basic volcanic rock for mafic volcanic rocks, mostly classified as basalt, but the mafic plutonic rocks don't have a formal umbrella term. However the name is still very commonly used by geologists for dark-coloured igneous rocks rich in mafic (ferromagnesian) minerals, particularly basaltic, doleritic and gabbroic rocks. See: basalt, dolerite, gabbro, diorite, etc.

Mafic rocks are sometimes more precisely defined as igneous rocks containinga high proportion of pyroxene and olivine, so that their color index (the volume fraction of mafic minerals) is between 50 and 90 vol.%, or with a silica content between 45 and 55 wt.%.