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.
See more at Wikipedia.org...