Barite (ground barium sulphate (BaSO4)) in its pure form is chemically inert in fresh water and oil based drilling fluids. It can be used to increase mud densities to as high as 2400 kg/m³.
Barite increases the hydrostatic pressure of the drilling mud allowing it to compensate for high-pressure zones experienced during drilling. The softness of the mineral also prevents it from damaging drilling tools during drilling and enables it to serve as a lubricant.