Purple fluorite octahedron
Group: Halide. Chemical formula is CaF2.
Green fluorite cubes
Fluorite is a translucent mineral that covers a rainbow of colors, yet has a clear streak. The crystal structure is cubic to octahedral, often with twinning. Like chalcopyrite, fluorite is found in hydrothermic veins, and hot springs, often alongside sulfides. It is fluorescent under ultraviolet light.
Fluorescent fluorite
The mineral has been used as lenses in telescopes and microscopes, a flux for smelting, and even as a source of fluoride for hydrofluoric acid. It was named in 1797 by Carlo Antonio Geleani Napione, from Latin – “fluor” meaning stream, or to flow – for its use as a flux. Fluorspar is also a common name. Fluorite is also used in carving and jewelry, however with a hardness of 4 on the Mohs scale, heavy wear is not recommended.
Pellant, Chris. Rocks And Minerals. New York, Dorling Kindersley, Inc., 2000. Pg 74.
Central Dakota Gem & Mineral Society 