A colorless,white,gray,blue,or lilac mineral of anhydrous calcium sulfate,CaSO4,occurring as layers in gypsum deposits.

• 硬石膏，无水石膏一种无色，白色，灰色，蓝色或淡紫色无水硫酸钙矿物，CaSO4，出现在石膏沉积岩层中