Gypsum is a very common Calcium Sulphate mineral that is found in a wide variety of forms as well as in large beds of rock. These include alabaster and selenite, as well as several remarkable structure types, such as "desert rose" and large striated satin spars. It occurs in most parts of the world, being formed from the precipitation of salt water, and is mined on a large scale in places like Mexico, Sicily, and the United States. It is a soft mineral that has transparent to transluscent crystalsthat can be anywhere from colorless to white, tinged with any one of a number of pale red, brown, or yellow colors.