Fluorite

Fluorite, also known as fluorspar, is often called 'The Most Colorful Mineral in the World' because it occurs in every color of the rainbow. It is the defining mineral for a hardness of 4 on the Mohs scale. It is famous for its perfect octahedral cleavage and its ability to glow under ultraviolet light—a phenomenon that was actually named 'fluorescence' after this mineral.

Formation & Geology

Fluorite typically forms as a hydrothermal mineral in veins, often in association with metallic ores like lead, silver, and zinc. It can also be found in the cavities of sedimentary rocks like limestone. It is a halide mineral composed of calcium fluoride. The vast array of colors is caused by various impurities (like rare earth elements) and radiation damage to the crystal lattice.

Physical Characteristics

Fluorite is beloved by collectors for its beautiful crystals, which usually form as cubes or octahedrons. It has perfect cleavage in four directions, meaning it can be easily split into perfect pyramids. While beautiful, its low hardness (4) and perfect cleavage make it too fragile for most jewelry use, although it is sometimes used for pendants or beads. It has a vitreous luster and is often very transparent.

Industrial & Scientific Use

Beyond its beauty, fluorite is a critical industrial mineral. It is the primary source of fluorine, which is used in everything from toothpaste to Teflon. In the steel industry, it is used as a 'flux' to lower the melting point of raw materials (the name comes from the Latin 'fluere', meaning 'to flow'). In optics, special high-purity fluorite is used to make lenses for high-end cameras and microscopes because it has very low dispersion and eliminates chromatic aberration.

The Fluorescence Phenomenon

Fluorite is the mineral that gave the phenomenon of "fluorescence" its name. In 1852, George Gabriel Stokes coined the term after observing that some fluorite specimens glowed with a blue light when illuminated. This glow is caused by trace amounts of rare earth elements like Europium within the crystal lattice displacing atoms and reacting to UV radiation.