Place an order for Moon Phase Selenite Circle Round Charging Plate today at Agate Export. Selenite is a crystallized form of gypsum. Chemically, it is a hydrous calcium sulfate. Selenite crystals sometimes form in thin tabular or mica-like sheets and have been used as window panes as at Santa Sabina in Rome. Selenite crystals sometimes will also exhibit bladed rosette habit (usually transparent and like desert roses) often with accompanying transparent, columnar crystals. Selenite, also known as satin spar, desert rose, or gypsum flower are four crystal structure varieties of the mineral gypsum. These four varieties of gypsum may be grouped together and called selenite.