Editing Fluorite (section)

===Source of fluorine and fluoride===
Fluorite is a major source of [[hydrogen fluoride]], a commodity chemical used to produce a wide range of materials. Hydrogen fluoride is liberated from the mineral by the action of concentrated [[sulfuric acid]]:
:CaF<sub>2</sub>([[solid|s]]) + H<sub>2</sub>SO<sub>4</sub> → [[calcium sulfate|CaSO<sub>4</sub>]](s) + 2 HF([[gas|g]])

The resulting HF is converted into fluorine, [[fluorocarbon]]s, and diverse fluoride materials. As of the late 1990s, five billion kilograms were mined annually.<ref name=Aigueperse>{{Cite book |first= Jean |last= Aigueperse |author2=Paul Mollard |author3=Didier Devilliers |author4=Marius Chemla |author5=Robert Faron |author6=Renée Romano |author7=Jean Pierre Cuer |contribution= Fluorine Compounds, Inorganic |title= Ullmann's Encyclopedia of Industrial Chemistry |year= 2005 |publisher= Wiley-VCH |place= Weinheim|doi= 10.1002/14356007.a11_307 |isbn= 3527306730}}</ref>

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% CaF<sub>2</sub>), the lowest of the three grades, has traditionally been used as a [[flux (metallurgy)|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% CaF<sub>2</sub>) is used in the manufacture of [[opalescence|opalescent]] [[glass]], [[vitreous enamel|enamels]], and cooking utensils. The highest grade, "acid grade fluorite" (97% or more CaF<sub>2</sub>), 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]].<ref name=usgs/>

Internationally, acid-grade fluorite is also used in the production of [[Aluminium fluoride|AlF<sub>3</sub>]] and [[cryolite]] (Na<sub>3</sub>AlF<sub>6</sub>), which are the main fluorine compounds used in aluminium smelting. [[Alumina]] is dissolved in a bath that consists primarily of molten Na<sub>3</sub>AlF<sub>6</sub>, AlF<sub>3</sub>, and fluorite (CaF<sub>2</sub>) to allow electrolytic recovery of aluminium. Fluorine losses are replaced entirely by the addition of AlF<sub>3</sub>, the majority of which react with excess sodium from the alumina to form Na<sub>3</sub>AlF<sub>6</sub>.<ref name=usgs>Miller, M. Michael. [http://minerals.usgs.gov/minerals/pubs/commodity/fluorspar/myb1-2009-fluor.pdf Fluorspar], USGS 2009 Minerals Yearbook</ref>