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Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term was derived by contracting "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt and gabbro.

In terms of chemistry, mafic rocks are on the other side of the rock spectrum from the felsic rocks. The term roughly corresponds to the older basic rock class.

Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava, so eruptions of volcanoes made of mafic lavas are less explosively violent than felsic lava eruptions. Most mafic lava volcanoes are oceanic volcanoes, like Hawaii.

Rock Texture	Name of Mafic Rock
Pegmatitic	Gabbro pegmatite
Coarse grained (phaneritic)	Gabbro
Coarse grained and porphyritic	Porphyritic gabbro
Fine grained (aphanitic)	Basalt
Fine grained and porphyritic	Porphyritic basalt
Pyroclastic	Basalt tuff or breccia
Vesicular	Vesicular basalt
Amygdaloidal	Amygdaloidal basalt
Many small vesicles	Scoria
Glassy	Tachylyte, sideromelane, palagonite

[edit] See also

• QAPF diagram
• List of minerals
• List of rock types

v • d • e Igneous rocks by composition Type Ultra-mafic < 45% SiO2 Mafic < 52% SiO2 Intermediate 52-63% SiO2 Intermediate-Felsic 63-69% SiO2 Felsic >69 % SiO2 Volcanic rocks: Dikes & Sills: Plutonic rocks: Komatiite Kimberlite, Lamproite Peridotite Basalt Diabase Gabbro Andesite Diorite Dacite Granodiorite Rhyolite Aplite — Pegmatite Granite