Calcium fluoride is the inorganic compound with the formula CaF2. This ionic compound of calcium and fluorine occurs naturally as the mineral fluorite (also called fluorspar). It is the source of most of the world's fluorine. This insoluble solid adopts a cubic structure wherein calcium is coordinated to eight fluoride anions and each F− ion is surrounded by four Ca2+ ions. Although perfectly packed crystalline samples are colorless, the mineral is often deeply colored due to the presence of F-centers.