(also called fluor-spar
or Blue John
) is a mineral
composed of calcium fluoride
. It is an isometric mineral with a cubic habit, though octohedrons and dodecahedrons are not uncommon.
Pig carved in fluorite,|
5 cm (2 inches) long.
Octahedral fluorite crystals.
Fluorite may occur as a vein deposit, especially with metallic minerals, where it often forms a part of the gangue (the worthless `host-rock' in which valuable minerals occur) and may be associated with barite
. It is a common mineral in deposits of pneumatolytic origin and has been noted as a primary mineral in granites and other igneous rocks.
One of the most famous of the older localities of fluorite is Derbyshire
, where under the name of Derbyshire Blue John
beautiful blue fluorite is used for ornamental purposes; its softness, however, has been a bar to general use.
As well as ornamental uses, fluorite is also used as a flux in the manufacture of steel, in the making of opalescent glass, enamels for cooking utensils, and for hydrofluoric acid. The name fluorite is derived from the Latin fluo, flow, in reference to its use as a flux.
*Note on colours
The blue kind is often a delicate violet-blue, sometimes amethystine in tint. Certain specimens appear blue by reflected light and green or yellow by transmitted light. Fluorite sometimes phosphoresces
when heated or scratched. Other varieties fluoresce
beautifully under the influence of X-rays
See also: List of minerals