A mineral with the chemical composition CaSO₄. Anhydrite occurs commonly in white and greyish granular masses, rarely in large, orthorhombic crystals (see illus.). Fracture is uneven and lustre is pearly to vitreous. Hardness is 3–3.5 on Mohs scale and specific gravity is 2.98. It fuses readily to a white enamel. It is soluble in acids and slightly soluble in water. Anhydrite is an important rock-forming mineral and occurs in association with gypsum, limestone, dolomite, and salt beds. It is deposited directly by evaporation of seawater of high salinity at or above 108°F (42°C). Anhydrite can be produced artificially by dehydration of gypsum at about 390°F (200°C). Under natural conditions anhydrite hydrates slowly, but readily, to gypsum. It is not used as widely as gypsum. Anhydrite is of worldwide distribution. Large deposits occur in the Carlsbad district, Eddy County, New Mexico, and in salt-dome areas in Texas and Louisiana.