Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate. The chemical formula is CaSO4·2 H2O.

Natural gypsum is gathered from mines. An alternative source is the desulphurization of industrial off-gases like of coal power plants.

Gypsum is used as a fertilizer, as the main constituent in many forms of plaster, finish wallboard (drywall), blackboard, in cement industry (to prevent flash setting of concrete), etc.