Selenite Rock Samples

Selenite Rock Samples. 10 specimens of this rock. Call 1-800-411-DINO (3466) for volume discounts. All varieties of gypsum, including selenite and alabaster, are composed of calcium sulfate dihydrate (meaning has two molecules of water), with the chemical formula CaSO42H2O. All varieties of gypsum are very soft minerals (hardness: 2 on Mohs Scale). This is the most important identifying characteristic of gypsum, as any variety of gypsum can be easily scratched with a fingernail. Also because gypsum has natural insulating properties, all varieties feel warm to the touch.