Fluorite
Fluorite (calcium fluoride, CaF₂) is one of the most beloved mineral species among collectors, prized for its extraordinary range of colors — purple, green, blue, yellow, pink, and colorless — often displaying vivid color zoning within a single crystal. Crystallizing in the isometric system, it typically forms sharp cubes, though octahedral and more complex twinned habits also occur, and many specimens fluoresce strongly under UV light.
Classic localities include the Illinois-Kentucky Fluorspar District in the USA, famous for deep purple cubes; Weardale and the Rogerley Mine in England, source of the collectible green fluorescent fluorite; Yaogangxian in Hunan, China, producing exceptional blue and green crystals on quartz; the Okorusu Mine in Namibia; and Alpine cleft specimens from Switzerland and France with striking pink and colorless habits. Naica in Mexico has also yielded fine amethyst-hued fluorite associated with galena.
Fluorite is frequently found alongside quartz, galena, barite, and sphalerite, making combination pieces especially desirable. Its combination of geometric crystal form, saturated color, and fluorescence makes fluorite a cornerstone species for both systematic mineral collections and aesthetic display specimens.