Fluorite

Fluorite (also called fluorspar) is the mineral form of <a href="/facts/Calcium_fluoride/fCKHAvp1">calcium fluoride</a>, CaF2. It belongs to the <a href="/facts/Halide_mineral/4mcEzJtN">halide minerals</a>. It crystallizes in <a href="/facts/Cubic_crystal_system/92Co7BKM">isometric</a> <a href="/facts/Crystal_habit/x2S1HVVY">cubic habit</a>, although octahedral and more complex isometric forms are not uncommon.
The <a href="/facts/Mohs_scale_of_mineral_hardness/wXBMcVIm">Mohs scale of mineral hardness</a>, based on <a href="/facts/Scratch_hardness/5V7xkqar">scratch</a> <a href="/facts/Hardness_comparison/zkwUmdLu">hardness comparison</a>, defines value 4 as fluorite.
Pure fluorite is colourless and transparent, both in visible and ultraviolet light, but impurities usually make it a colorful mineral and the stone has ornamental and <a href="/facts/Lapidary/DAjscsb5">lapidary</a> uses. Industrially, fluorite is used as a <a href="/facts/Flux_(metallurgy)/ruKFTPGD">flux</a> for smelting, and in the production of certain glasses and enamels. The purest grades of fluorite are a source of fluoride for <a href="/facts/Hydrofluoric_acid/wdXqu4bE">hydrofluoric acid</a> manufacture, which is the intermediate source of most fluorine-containing <a href="/facts/Fine_chemical/TuwYNbpp">fine chemicals</a>. Optically clear transparent fluorite has anomalous partial <a href="/facts/Dispersion_(optics)/cUdHnYXz">dispersion</a>, that is, its refractive index varies with the wavelength of light in a manner that differs from that of commonly used glasses, so fluorite is useful in making <a href="/facts/Apochromat/aE1Cho1w">apochromatic lenses</a>, and particularly valuable in photographic optics. Fluorite optics are also usable in the far-ultraviolet and mid-infrared ranges, where conventional glasses are too opaque for use. Fluorite also has low dispersion, and a high refractive index for its density.

Fluorite open-in-new

Fluorite