Hydration Of Anhydrite: Gypsum also can variety in the hydration of anhydrite (CaSO₄). Anhydrite can be a calcium sulfate mineral that lacks the h2o molecules existing in gypsum. When exposed to drinking water, anhydrite undergoes a hydration reaction, incorporating water molecules into its construction and reworking into gypsum. Salt Flats: https://www.propanraya.com/id/produk/eco-gypsum-ee-4050