The blue variety of the anhydrite mineral became known as angelite. It is an anhydrous calcium sulfate. It cleaves perfectly in three directions. The name of anhydrite origins from the greek anhydros (without water) word (Hall in Tirol A.G.Werner 1804), because anhydrite forms from gypsum, during it is loosing water. With the suitable conditions this process works backwards with adding water. This mineral usually issues in evaporites with sedimentary origin (dolomstone, gypsum, halite, etc.), rarer in hydrothermal streamlets, but formats in tidal zones. Its columnar crystals are rare, it is mostly massive, grainy, thick, fibrous. Localities: China, Peru, Mexico, Italy etc.