Gypsum

Gypsum is a mineral composed of hydrated calcium sulfate (CaSO₄·2H₂O), recognizable by its wide variety of crystalline forms and its low hardness. It can be colorless, white, gray, yellow, pink, or brown and comes in different varieties, including selenite (transparent crystals), satin spar (fibrous gypsum with a silky luster), alabaster (massive variety), and desert rose, formed of crystals enclosing sand grains. Primarily formed by the evaporation of saline waters, gypsum is one of the most widespread evaporitic minerals in the world.