Fluorspar

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Infobox on Fluorspar
Example of Fluorspar
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Fluorspar

Description

Fluorite is a mineral with a veritable bouquet of brilliant colours. Fluorite is well known and prized for its glassy luster and rich variety of colours. The range of common colours for fluorite starting from the hallmark colour purple, then blue, green, yellow, colourless, brown, pink, black and reddish orange is amazing and is only rivaled in colour range by quartz. Intermediate pastels between the previously mentioned colours are also possible. It is easy to see why fluorite earns the reputation as "The Most Colourful Mineral in the World".

The many colours of fluorite are truly wonderful. The rich purple colour is by far fluorite's most famous and popular colour. It easily competes with the beautiful purple of amethyst. Often specimens of fluorite and amethyst with similar shades of purple are used in mineral identification classes to illustrate the folly of using colour as the sole means to identify minerals.

The blue, green and yellow varieties of fluorite are also deeply coloured, popular and attractive. The colourless variety is not as well received as the coloured varieties, but their rarity still makes them sought after by collectors.

Fluorite (also called fluorspar) is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Crystal twinning is common and adds complexity to the observed crystal habits.

The word fluorite is derived from the Latin root fluo, meaning "to flow" because the mineral is used as a flux in iron smelting to decrease the viscosity of slags at a given temperature. This increase in fluidity is the result of the ionic nature of the mineral.

Fluorite is a colourful mineral, both in visible and ultraviolet light, and the stone has ornamental and lapidary uses. Industrially, fluorite is used as a flux for smelting, and in the production of certain glasses and enamels. The purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, which is the intermediate source of most fluorine-containing fine chemicals. Optically clear transparent fluorite lenses have low dispersion, so lenses made from it exhibit less chromatic aberration, making them valuable in microscopes and telescopes. Fluorite optics are also usable in the far-ultraviolet range where conventional glasses are too absorbent for use.

There are three principal types of industrial use for natural fluorite, commonly referred to as "fluorspar" in these industries, corresponding to different grades of purity. Metallurgical grade fluorite (60–85% CaF2), the lowest of the three grades, has traditionally been used as a flux to lower the melting point of raw materials in steel production to aid the removal of impurities, and later in the production of aluminium. Ceramic grade fluorite (85–95% CaF2) is used in the manufacture of opalescent glass, enamels and cooking utensils. The highest grade, "acid grade fluorite" (97% or more CaF2), accounts for about 95% of fluorite consumption in the US where it is used to make hydrogen fluoride and hydrofluoric acid by reacting the fluorite with sulfuric acid.

Internationally, acid-grade fluorite is also used in the production of AlF3 and cryolite (Na3AlF6), which are the main fluorine compounds used in aluminium smelting. Alumina is dissolved in a bath that consists primarily of molten Na3AlF6, AlF3, and fluorite (CaF2) to allow electrolytic recovery of aluminium. Fluorine losses are replaced entirely by the addition of AlF3, the majority of which will react with excess sodium from the alumina to form Na3AlF6.