Buy Selenite Spiral Wand With One Side Point today. Selenite is a variety of gypsum occurring in transparent crystals or crystalline masses. The salt was formed by the repeated flooding of seawater millions of years ago. It is the concentrated saline solution combining with the gypsum that promotes the selenite crystal growth in a portion of the salt flats. Selenite is a crystallized form of gypsum. Chemically, it is a hydrous calcium sulfate. elenite crystals sometimes form in thin tabular or mica-like sheets and have been used as window panes as at Santa Sabina in Rome.