Barium sulphate is an inorganic compound with the chemical formula BaSO4. It is a white crystalline solid that is odourless and insoluble in water. It occurs as the mineral barite, which is the main commercial source of barium and materials prepared from it. The white opaque appearance and its high density are exploited in its main applications, chief among which is as a component of white pigment for paints, especially heat-reflecting paint, as well as a paper brightener, plastics filler and a component of oil well drilling fluid.