» This article's about the mineral: for other meanings, see Selenite (disambiguation). Selenite, satin spar, desert rose, and gypsum flower are four varieties of gypsum; all four varieties show obvious crystalline structure. The four "crystalline" varieties of gypsum are sometimes grouped together and called selenite. All varieties of gypsum, including selenite and alabaster, are a very soft mineral (hardness: 2 on Mohs Scale) composed of calcium sulfate dihydrate (meaning has two molecules of… (More on Selenite)