Feldspar
One of the most common minerals found in rocks, feldspar is one of the main components in granite, and is the mineral that gives granite its color. This mineral can be white, blue, green or red and it always contains both silica and aluminum.
Quartz
Quartz is also very common in different kinds of rocks and it is the other mineral which largely composes granite. Quartz is a very hard mineral, the hardest of the common minerals, and because it's chemically stable it takes a long time for it to weather.
Biotite Mica
Mica comes in many colors from clear to black, green, brown, yellow or red. It is also sometimes called "muscovite" because it's commonly found near Moscow and in the past was used as glass in windows in homes there. Biotite Mica contains iron and magnesium, which make it dark green to black.
Hornblende
Hornblende occurs often in the crystal of different kinds of igneous rocks, including some granite. Because it contains iron, silica, magnesium and aluminum, it is most often green, brown or black in color.
Augite
Sometimes found in granite, augite can be brown-green, green or light brown to black. It's found in many different kinds of igneous rocks. The word "augite" comes from the Greek "auge" which means "luster." This is because augite has a luster similar to dull hematite.
Magnetite
With a high iron content, magnetite is black or brown-red in color. Magnetite is one of only two minerals in the world that are naturally magnetic. It's sometimes called lodestone and occurs in many kinds of igneous rock, including some granite. It's also an important source of iron ore.