Selenite, also known as satin, desert rose or gypsum flower, are four varieties of mineral gypsum with a crystalline structure. These four varieties of gypsum can be grouped and called selenite.
All gypsum varieties, including selenine and alabaster, consist of calcium sulphate dihydrate (which means it has two molecules of water) with the chemical formula CaSO4 · 2H2O. Selenite does not contain significant selenium, the similarity of names of substances from the ancient Greek word to the moon.
Some of the largest crystals ever found are selenite, the largest specimen found in the Naica mine's cave with a length of 12 meters and a weight of 55 tons.