Gypsum, calcium sulfate dihydrate, CaSO4 . 2H2O This specimen from Essone in France is referred to as selenite. However, selenite varieties of gypsum also includes desert rose, satin spar, and gypsum flower. The crystals of the specimen are clear and tabular with an angled termination. The crystals are relatively minute compared to the cave selenite crystals in the inset picture.