Compared to felsic igneous rocks, mafic igneous rocks contain greater amounts of what?

Compared to felsic igneous rocks, mafic igneous rocks often contain far more iron in them. Malfic igneous rocks are rich in both magnesium and iron as well as lots of pyroxene and calcium filled plagioclase feldspar. they are often much darker in color, sometimes black.

English , i don't understand spanish.

Self-ionizes to form an equilibruium system in which [ h_{3} o^{+} ]=[ oh^{-} ]=10^{-7} m