Science / Geology / Mafic: A term used to describe an igneous rock that has a large percentage of dark-colored minerals such as amphibole, pyroxene and olivine. Also used in reference to the magmas from which these rocks crystallize. Mafic rocks are generally rich in iron and magnesium. Basalt and gabbro are examples of mafic rocks. (See felsic to contrast.)
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Ultramafic Rock

Science / Geology / Ultramafic Rock: An igneous rock consisting dominantly of mafic minerals, containing less than 10 percent feldspar. Includes dunite, peridotite, amphibolite, and pyroxenite. MORE

Mafic Mineral

Science / Geology / Mafic Mineral: A dark-colored mineral rich in iron and magnesium, especially a pyroxene, amphibole, or olivine. MORE