Fluorite

Fluorite (also called fluorspar) is a mineral composed of calcium fluoride, CaF2. It is a common mineral in deposits of hydrothermal origin and has been noted as a primary mineral in granites and other igneous rocks and as a common minor constituent of dolostone and limestone. As well as ornamental uses, fluorite is used in the making of opalescent glass, enamels cooking utensils, hydrofluoric acid, and as a flux in the manufacture of steel. Fluorite is also used in some high performance telescopes and camera lens elements instead of glass. Fluorite is slightly soluble in water, and is decomposed by sulfuric acid to form free hydrofluoric acid, which etches glass.