Fluorite is one of the most variable of all crystalline minerals, occurring in shades of blue, green, purple, red and many other colors corresponding to their physical makeup and conditions when the mineral was formed. The name fluorite comes from its use as a flux, or chemical cleaning agent, in iron smelting and other metallurgy. Pure fluorite is clear, but most specimens have vivid color due to various impurities and are often fluorescent. With a dazzling array of colors and crystal structures, fluorite specimens have been prized since ancient times and are now among the most popular minerals in the collecting world. Fluorite has long been used as a gemstone and is increasingly popular in the market.