Mineral chemical composition Ca[SO 4 ]. The system is rhombic. Dense masses or leafy aggregates are common. Thick tabular, prismatic, and sometimes pseudocubic crystals are rare. Color white, grayish, bluish, reddish. Blue fine-grained anhydrite - vulpinite, or Bergamo marble. The luster is glassy, on the cleavage planes it is pearlescent. Hardness on the mineralogical scale is 3-3.5; density 2800 - 3000 kg/ m3 . In the presence of water in air, it hydrates and turns into gypsum with a volume increase of up to 30%. The bulk of anhydrite is formed by sedimentation. It is found in marls containing gypsum deposits, among deposits of potassium salts, and much less frequently in hydrothermal ore veins. It is used as a fertilizer, in the production of binders (cements) and for crafts. According to TSB.