Mafic

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Mafic minerals are usually dark in color and have a specific gravity greater than 3. Common rock-forming mafic minerals include olivine, pyroxene, amphibole, biotite and other micas, augite and the calcium-rich plagioclase feldspars. Common mafic rocks include basalt and gabbro.

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

Mafic lava, before cooling, has a lower viscosity than felsic lava due to its lower silica content. 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