Oxygen is the most abundant element in the Earth's crust, making up about 46.6% of its volume. It is found in a wide variety of minerals, including biotite mica and muscovite. Biotite mica is a dark-colored mica that contains a significant amount of potassium, magnesium, and iron. Muscovite is a light-colored mica that contains a significant amount of aluminum and potassium. Oxygen is also found in a variety of other minerals, including quartz, feldspar, and calcite.