What are some examples of ferromagnesian minerals in mafic rock?

Some examples of ferromagnesian minerals in mafic rock include olivine, pyroxene and amphibole. Rocks containing pyroxene and amphibole often also contain feldspar, a non-ferromagnesian mineral.

Olivine is made of fayalite, with a chemical formula of Fe2SiO4, and forsterite, with a chemical formula of Mg2SiO4. Pyroxene can be composed of enstatite (MgSiO3) and ferrosilite (FeSiO3). Igneous amphibole is made of hornblende, which is composed of an iron-magnesium silicate, a calcium-iron-magnesium silicate and an aluminum-iron-magnesium silicate. All of these minerals contain iron and magnesium. Mafic rock is a dark-colored category of igneous rock, the type of rock that forms from solidified magma.