Fluorite, composition CaF2, is a halide mineral of uncommon occurrence in soils. It has a cubic crystal system with a body-centered structure. Fluorite forms perfect cubes, often with penetration twins. It is commonly translucent to transparent, and has a wide range of colors from colorless to green, yellow, bluish-green, or purple. Single crystals may show bands of varying colors. Fluorescence (hence its name) is often observed.
Fluorite is of no consequence in soils due to its high solubility and comparative rarity. However, it is used mainly as a flux in the making of steel, as an agent in the manufacture of opalescent glass, and as a source of fluorine for the preparation of hydrofluoric acid.
Wyckoff, R.W.G. 1963. Crystal Structures 1:239-241