Staff member
Jun 3, 2020
Anhydrite is an evaporite mineral that forms due to the evaporation of sea water and occurs in sedimentary basins. The conditions of occurrence are critical as Anhydrite transforms into Gypsum by the absorption of water. This transformation is reversible with Gypsum forming Anhydrite with around 200 deg. C temperatures under normal atmospheric conditions. It occurs in extensive layered deposits typically interbedded with halite, gypsum and limestone. It can form in shoreline or tidal flat environments, and also occurs as caprock in salt domes. It is rarely found in igneous rocks. Gypsum is abundant in comparison to Anhydrite.


Anhydrite can be used as a substitute for Gypsum. It contains more Calcium than Gypsum due to lack of water. It is used for soil treatment and production of cement, plaster and flooring.

Physical Properties
Crystal SystemOrthorhombic
ColorColorless, white, and light shades of brown, red, gray, pink, blue, violet
LusterVitreous to pearly
CleavagePerfect (results in cubic to pseudocubic fragments)
Mohs Scale Hardness3 to 3.5
DiaphaneityTransparent to translucent
Specific Gravity2.9 to 3
Chemical CompositionCaSO4
Diagnostic PropertiesCubic cleavage, harder than gypsum, no acid reaction


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