Fluorite

Hardness: 4 on the Mohs scale, relatively soft. Color: Highly variable; common colors include purple, blue, green, yellow, colorless, pink, and brown. The specimen appears to have blue and green hues. Luster: Vitreous (glassy). Crystal structure: Isometric (cubic), commonly forms cubes or octahedra, or massive habits. Cleavage: Perfect octahedral cleavage (breaks into eight-sided forms). Specific Gravity: 3.18.

Fluorite is a hydrothermal mineral, typically forming in veins with metallic ores, as a gangue mineral. It can also be found in sedimentary rocks, granites, and some metamorphic rocks. It forms at relatively low temperatures and pressures. Geological age varies depending on the specific deposit.

A significant industrial mineral, fluorite is primarily used as a flux in steelmaking to lower the melting point of raw materials. It's also used in the production of hydrofluoric acid for various chemical industries (e.g., refrigerants, aerosols, plastics like Teflon). High-quality, clear fluorite is used in optics for lenses and prisms due to its low dispersion. Gem-quality fluorite is occasionally cut into cabochons or faceted stones for jewelry, but its softness and perfect cleavage make it less suitable for everyday wear. Collectors value well-formed crystals and unusual color combinations.

Fluorite is known for its wide range of colors, which are often caused by impurities or radiation exposure. It is also famous for its fluorescence (glowing under ultraviolet light), a property from which the term 'fluorescence' itself is derived. The name 'fluorite' comes from the Latin word 'fluere,' meaning "to flow," referring to its use as a flux. Different colors of fluorite can sometimes be found within the same crystal.

To identify fluorite in the field, look for its characteristic octahedral cleavage, which often results in smooth, flat faces when broken. Its relatively low hardness (you can scratch it with a knife) is also a key indicator. The wide array of vibrant colors is a strong clue, especially the violet-blue and green varieties. It's commonly found alongside minerals like quartz, calcite, barite, and various sulfide minerals in hydrothermal veins. Major sources include China, Mexico, Mongolia, and South Africa, as well as several localities in the United States. Collectors often seek out well-crystallized specimens, especially those exhibiting zoning or color changes.