calcium fluoride

Calcium fluoride (CaF2) is an insoluble ionic compound of calcium and fluorine. It occurs naturally as the mineral fluorite (also called fluorspar), and 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 the pure material is colourless, the mineral is often deeply coloured due to the presence of F-centers.
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