Fluorite cubes octahedral

Cubic and octahedral fluorite crystals, a calcium fluoride mineral prized for its fluorescence and wide range of colors.

About this subject

Fluorite (CaF2) is a halide mineral that crystallizes in the cubic system, often forming perfect cubes and, less commonly, octahedra or combinations of both forms. Its perfect octahedral cleavage allows crystals to be easily fractured into octahedrons, a key diagnostic feature. Fluorite exhibits a remarkable range of colors, including purple, green, blue, yellow, pink, and colorless, frequently zoned or in concentric growths. The color is attributed to impurities, lattice defects, or radiation exposure. Under ultraviolet light, many specimens show intense fluorescence, a phenomenon that gave the mineral its name (from Latin 'fluere', to flow). Economically, fluorite is the primary source of fluorine, used to produce hydrofluoric acid, aluminum, and refrigerants. It is also employed as a flux in steelmaking and in the manufacture of high-quality lenses and prisms due to its low dispersion. The most sought-after collector crystals come from localities such as the Weardale region in England (dark blue 'Blue John' fluorite), the Huanggang mines in Inner Mongolia (purple and green fluorite), and Yaogangxian in China (gem-quality crystals). In Brazil, it occurs in pegmatites and hydrothermal veins, notably in Santa Catarina and Minas Gerais.

Frequently Asked Questions

Is fluorite always fluorescent?

No. Although many fluorites fluoresce under ultraviolet light, not all samples exhibit this phenomenon. Fluorescence depends on the presence of specific impurities, such as rare earth elements, and defects in the crystal structure.

What are the main industrial uses of fluorite?

Fluorite is primarily used as a source of fluorine for producing hydrofluoric acid, which is then used in the manufacture of aluminum, refrigerants (hydrofluorocarbons), and in the petrochemical industry. It also serves as a flux in steelmaking and cement production.

Where are the best collector fluorite crystals found?

Famous localities include Weardale (England), with the 'Blue John' variety; Huanggang (Inner Mongolia, China), producing purple and green crystals; and Yaogangxian (China), known for transparent gem-quality crystals. Other notable deposits are in Mexico, the United States, and South Africa.