Gypsum is a common sulfate mineral of great commercial importance, composed of hydrated calcium sulfate (CaSO4.2H2O). In well-developed crystals, the mineral commonly has been called selenite. The fibrous massive variety has a silky luster and is called satin spar, and the fine-grained massive variety is called alabaster. Gypsum is a non-metallic mineral that is available in various forms. Due to its wide range of variety, it is considered useful in many fields.