Gypsum is composed of calcium sulfate dehydrate. It is widely mined and used as fertilizer, plaster of paris, and in blackboard chalk. When mined as a natural deposit called alabaster, it is processed to make plaster of paris, which in turn is used to make sculptures. Alabaster is heated and deprived of its moisture and forms fine-grained white or lightly tinted variety of gypsum. It was widely used in Ancient Egypt, Mesopotamia, Ancient Rome, and Byzantine .