Gypsum is an evaporite mineral most commonly found in layered sedimentary deposits in association with halite, anhydrite, sulfur, calcite, and dolomite. Gypsum (CaSO4.2H2O) is very similar to Anhydrite (CaSO4). The chemical difference is that gypsum contains two waters and anhydrite is without water. Gypsum is the most common sulfate mineral

Uses of Gypsum

Gypsum uses include: manufacture of wallboard, cement, plaster of Paris, soil conditioning, a hardening retarder in portland cement. Varieties of gypsum known as “satin spar” and “alabaster” are used for a variety of ornamental purposes; however, their low hardness limits their durability.




Physical Properties of Gypsum
Chemical Classification Sulfate
Color Clear, colorless, white, gray, yellow, red, brown
Streak White
Luster Vitreous, silky, sugary
Diaphaneity Transparent to translucent
Cleavage Perfect
Mohs Hardness 2
Specific Gravity 2.3
Diagnostic Properties Cleavage, specific gravity, low hardness
Chemical Composition Hydrous calcium sulfate, CaSO4.2H2O
Crystal System Monoclinic
Uses Used to manufacture dry wall, plaster, joint compound. An agricultural soil treatment.