Fluorites

Fluorite, also called fluorspar, is a mineral composed of calcium fluoride (CaF2). It crystallizes in the isometric (cubic) system and commonly forms euhedral cubes and octahedra with perfect cleavage in four directions. It has a Mohs hardness of 4 and a specific gravity of 3.0–3.2. Fluorite occurs in a wide range of colors, including colorless, green, purple, blue, yellow, brown, and striped varieties. The color is caused by impurities and, in some cases, exposure to radiation. Transparent to translucent specimens are prized as collector’s minerals and as gemstones.

Fluorite forms in hydrothermal veins, often associated with minerals such as quartz, calcite, sphalerite, galena, barite, and dolomite. It occurs in many geologic environments, including sedimentary rocks and granitic pegmatites, and is widely distributed around the world. Major deposits are found in China, Mongolia, Mexico, and several other countries.

Fluorite is well known for its fluorescence under ultraviolet light; many specimens glow blue or purple, with other colors including green and yellow reported. The mineral is also valued as a source of fluorine. Industrially, fluorite is used as a flux to lower the melting point of slag in steelmaking, and as a feedstock for the production of hydrofluoric acid and other fluoride compounds. It is also mined as an ornamental stone and used in carvings and lapidary work.

The name fluorite derives from the Latin fluere, “to flow,” reflecting its historical use as a flux. The mineral’s common name fluorspar has been used in mining and industry.