Selenite is in the Monclinic crystal system and is in the family of sulfates. This clear to white form of Gypsum has a pearly, luster finish. It can be easily scratched and will dissolve if left in water.
Generally it is found in the cavities of limestone deposits. Massive beds of it are found in Utah and India, although the clearest varieties come from a large Sicilian sulfur mine in Italy.