Silica is the chemical compound silicon dioxide, also known as silica (from the Latin silex). It is an oxide of silicon with a chemical formula of SiO2 and has been known for its hardness since antiquity. Silica is most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms. It is a principal component of most types of glass and substances such as concrete. Silica is the most abundant mineral in the Earth’s crust. It is a raw material for many white ware ceramics such as earthenware, stoneware and porcelain.