Fluorite

Fluorite or Fluorspar, mineral composed of calcium fluoride (CaF₂), the principal fluorine-bearing mineral. It occurs as cubic, isometric crystals and cleavable masses with a hardness of 4 and sp. gr. of 3-3.3. When pure, fluorite is colorless and transparent, or translucent with a glassy luster. It often occurs with impurities that make it yellow, blue, purple, green, rose, or brown. Several varieties exhibit fluorescence.

The mineral is usually found either in pure veins or associated with lead, silver, or zinc ores. It is common in limestone and dolomites and is occasionally found as an accessory mineral in pegmatites and other igneous rocks. Exceptionally clear crystalline fluorite is mined in Cumberland and Derbyshire, England. Commercially important deposits in the United States occur in a region on the Ohio River that includes parts of Illinois and Kentucky.

Crystalline varieties, such as the fine-colored Derbyshire spar, are often carved into vases and other similar ornaments, and the variety chlorophane is used as a gem. The principal use of fluorite has been for the production of hydrofluoric acid, an essential raw material in the manufacture of synthetic cryolite and aluminum fluoride for the aluminum industry, and in many other applications in the chemical industry. Fluorite is also a standard flux used in the making of steel. Large quantities of fluorite are used in the production of enamel and opal glass, and perfect crystals are used for the manufacture of apochromatic lenses.