Fluorite (often referred to casually as 'Fluorspar' in industrial contexts)

Hardness: 4 on the Mohs scale, relatively soft. Color: Widely variable, including colorless, white, purple, blue, green, yellow, pink, and black. Often exhibits color zoning, as seen in the image with blue and light blue/clear areas. Luster: Vitreous (glassy). Crystal Structure: Isometric (cubic), commonly found in cubes, octahedrons, and dodecahedrons. Cleavage: Perfect octahedral (splits easily into eight-sided forms). Specific Gravity: 3.18. Often fluorescent under UV light (due to rare earth impurities).

Fluorite typically forms in hydrothermal veins, often associated with metallic ores, as a gangue mineral. It can also be found in sedimentary rocks, hot spring deposits, and pegmatites. The specific banding or color zoning seen in the image suggests formation within a fluid-rich environment where mineralizing solutions changed over time. Geological Age: Varies widely depending on the specific deposit, can range from Precambrian to Cenozoic.

Industry: The primary source of fluorine, used in the production of hydrofluoric acid for chemical, ceramics, and optical industries. Flux in steel production (hence 'fluorspar'). Lenses for telescopes and cameras due to its low dispersion. Jewelry: Often cut into cabochons or beads, especially colorful or banded varieties. However, its softness limits its use and durability as a gemstone. Construction: No significant use in construction.

Fluorite is known as 'the most colorful mineral in the world' because of its extensive range of colors. It is also famous for its strong fluorescence under ultraviolet light, a phenomenon for which it gave its name ('fluorescence'). Transparent, flawless fluorite is used for high-performance optical lenses because of its low refractive index and low chromatic dispersion.

How to identify in the field: Look for its distinct perfect octahedral cleavage, its relatively low hardness (can be scratched by a knife), and its vitreous luster. Its common cubic or octahedral crystal habits are also key. Color and fluorescence are often good indicators. Common locations found: Significant deposits are found worldwide, including China, Mexico, Mongolia, South Africa, and the United States (Illinois, Kentucky). Tips for collectors: Due to its softness and perfect cleavage, fluorite specimens should be handled with care to prevent breakage. It is also soluble in strong acids, so cleaning should be gentle.