Ultramafic vs. Mafic

Ultramaficadjective

(geology) Describing igneous rocks that contain magnesium and iron and only a very small amount of silica, such as are found in the Earth’s mantle.

Ultramaficnoun

A rock with such properties.

Maficadjective

(geology) Describing rocks, such as silicate minerals, magmas, and volcanic and intrusive igneous rocks, which contain relatively high concentrations of magnesium and iron.

Maficnoun

A rock with such properties.

Mafic

A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite.