The combination of quartz and feldspar form a large mineral group called felsic minerals . The felsic minerals are usually light in color. The next three silicate minerals are mica, amphibole, and pyroxene , and are silicates that contain aluminum, magnesium, iron, and potassium or calcium. Finally, we have the seventh silicate mineral called olivine , which contains magnesium and iron, but no aluminum, along with the silicate minerals. These last four silicate mineral groups are called mafic minerals because they all contains magnesium and iron.
Mafic minerals are usually dark in color.
Common igneous rocks Igneous rocks form when molten rock known as magma solidifies. When magma solidifies, it is made up of all seven silicate minerals previously discussed, which combine to form igneous rocks. Because most of these minerals are felsic, granite is classified as a felsic igneous rock . Granite usually has white, pink, gray , or black grains, and is commonly used in tombstones and decorative landscaping. Diorite is a felsic igneous rock.