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Fluorite is the mineral form of calcium fluoride, which is noted for its wide range of industrial applications and occasional use as an ornamental material. It produces crystals that are often large in size and flawless, as well as possessing a wide variety of highly-saturated hues. However, due to fluorite’s very low hardness (4.0) and vulnerable directional cleavage, faceted specimens are intended more as a collector’s stone rather than for use within gem-set jewelry.

Attractive microcrystalline forms of fluorite are also encountered, with the most famous example being “Blue John” from Derbyshire, England and, more recently, China’s Zhejiang Province. This material contains contrasting bands of purple, yellow and white, and was especially popular during the nineteenth century when it was primarily used for fashioning into drinking vessels and other receptacles.