Barite
Barite is a mineral composed of barium sulfate (BaSO4). The high specific gravity of barite makes it suitable for a wide range of industrial, medical, and manufacturing uses. Barite also serves as the principal ore of barium. Barite is also used as a pigment in paints and as weighted filler for paper, cloth and rubber. The paper used to make some playing cards has barite packed between the paper fibers.