Missouri State Gemstone
Fluorite, also called fluorspar, is composed of calcium and fluorine. Although pure fluorite is colorless, this mineral occurs in all colors and can be multicolored. It occurs most commonly as purple, blue, green, yellow, brown, black, reddish-orange, or colorless, and pastels of these colors have also been found. For this reason, fluorite has been called the most colorful mineral in the world.
Specimens are usually a single color but are also found with multicolored bands. "Blue John" is a fluorite variety banded with colors and white found only in Derbyshire, England. The color of fluorite is determined by its impurities, exposure to radiation, and other factors. It is fluorescent in many colors under ultraviolet light and can also be phosphorescent, which means it emits light following radiation, or thermoluminescent, meaning it glows after exposure to heat.
Although Missouri does not have an official state gemstone, fluorite represents the state’s geology well. Fine deposits are located at the Pea Ridge Mine in Sullivan County, Missouri. The mineral is also found at several other mines and quarries throughout the state.
The word fluorite comes from the Latin word fluere, which means "to flow." To help eliminate impurities in steel and other metal smelting, low-grade fluorite can be used as a flux, or added to other liquids to improve flow. Its relatively low melting point makes it an important flux material.
The term fluorescence is derived from fluorite, and the mineral will often exhibit this effect dramatically. The element fluorine also derives its name from fluorite, a major source for the element.
A widely occurring mineral, fluorite is found in large deposits in many areas throughout the world. The United States once produced vast quantities of fluorite, but now produces much less and imports the mineral from other countries.
FORMATION AND OCCURRENCE
Fluorite occurs in low-temperature hydrothermal veins as part of a gangue, a worthless host rock in which valuable minerals are found, especially those containing lead and zinc. It is also an accessory mineral in granite, granite pegmatites, and other igneous rocks. Fluorite can also be a component of marbles and other metamorphic rocks and is found in large deposits in limestone. It typically forms cubical crystals but has other crystals habits as well.
Although first described and named in 1546, there is evidence of fluorite use in prehistoric times. Ancient Romans believed fluorite prevented intoxication, and therefore carved drinking vessels from the mineral. This may have led to the 18th-century practice of mixing fluorite powder with water to treat kidney disease. Migrating American Indians used fluorite from southern Illinois and western Kentucky for ornamental purposes.
Today, the gem is said to have a calming effect, to increase concentration, and to facilitate meditation. Different colors of the mineral are said to have different mental healing properties. Fluorite is also believed to cleanse and purify the body.
Because fluorite provides sharper images than regular glass, even at high power, intermediate-grade fluorite is widely used in the optics field to create high-performance telescope, microscope, and camera lenses. It is also utilized in the production of certain types of glass, enamels, and cooking utensils. The highest-grade fluorite is decomposed with sulfuric acid to make hydrofluoric acid, which is used in the electroplating, stainless steel, refrigerant, and plastics industries. As a source of the element fluorine, fluoride is used in fluorinating water.
A rare gemstone with a glassy luster, fluorite is cut into beads and used in jewelry. However, it should be used only in pendants, brooches, and earrings. At a 4 out of 10 on the Mohs’ scale of hardness, this soft stone with good cleavage is not recommended for use in rings or bracelets. The gem’s trademark purple color is the most popular.
The popularity of fluorite among collectors is second only to quartz. Well-formed crystals are highly prized. A single-cube specimen one meter across was found at the legendary large ore field in Dalnegorsk, Russia. The Ben E. Clement Mineral Museum in Marion, Kentucky, houses a particularly large collection of fluorite specimens from around the world.
SUBSTITUTES / SYNTHETICS
Synthetic crystals are grown to meet the high demand for fluorite in the optics field. A byproduct chemical called fluorosilicic acid is sometimes used to fluorinate public water supplies.
Chemical Formula: CaF2
Crystal Structure: Isometric
Hardness (Mohs): 4
Color: Purple, lilac, golden-yellow, green, colourless, blue, pink, champagne, brown.
Luster: Vitreous, dull
Refractive Index: 1.433–1.435
Some data courtesyof the Mineralogical Society of America
Author: World Trade Press