Silica is a compound that occurs in rocks and minerals in the form of silicon dioxide, SiO2. It can be found in quartz, flint and sand. It is used to make glass, ceramics and concrete.
Silica is a white or colorless insoluble solid that has characteristics similar to glass. It helps form cristobalite, which is a white mineral found in volcanic rocks. Silicon dioxide forms quartz, which is present in most of Earth’s rocks, but particularly in granite and sandstone. Chert contains a variety of silica in the form of microcrystalline quartz. Flint, once used for arrow and spearheads, contains opaque silica. Lechatelierite is a colorless glass that is made of nearly pure silica. Tridymite is a mineral form of silica, and silex is pure, finely ground silica.