Barite is a mineral consisting of barium sulfate. It is generally white or colorless, and is the main source of barium. Barite occurs in a large number of depositional environments, and is deposited through a large number of processes including biogenic, hydrothermal, and evaporation, among others. Baryte commonly occurs in lead-zinc veins in limestones, in hot spring deposits, and with hematite ore. It is often associated with the minerals anglesite and celestine. It has also been identified in meteorites. 77% of barite worldwide is used as a weighting agent for drilling fluids in oil and gas exploration to suppress high formation pressures and prevent blowouts. Other uses are in added-value applications which include filler in paint and plastics, sound reduction in engine compartments, coat of automobile finishes for smoothness and corrosion resistance, friction products for automobiles and trucks, radiation-shielding cement, glass ceramics and medical applications (for example, a barium meal before a contrast CAT scan). Historically baryte was used for the production of barium hydroxide for sugar refining, and as a white pigment for textiles, paper, and paint. Although baryte contains a "heavy" metal (barium), it is not a toxic chemical because of its extreme insolubility. It is also sometimes used as gemstone.