Fluorite (mineral)
Fluorite, also known as fluorspar, is a common mineral with the chemical formula CaF₂, notable for its vibrant colors and perfect cleavage that typically forms octahedral crystals. It is primarily found in hydrothermal veins alongside minerals such as lead, silver, and zinc, and can also occur in sedimentary rock cavities, hot-water deposits, and water-rich igneous pegmatites. Globally, significant deposits are located in countries like China, Mexico, and South Africa, with major sources in the United States including Illinois and Kentucky.
Fluorite serves several important industrial functions; it is a critical flux in the production of iron, steel, and aluminum and is essential for producing hydrofluoric acid, a key ingredient in various fluorine-bearing chemicals. The mineral is also utilized in the manufacturing of glass, ceramics, and enamels. Historically, fluorite has been valued for its ornamental properties, with notable uses in art and decoration dating back to ancient civilizations. Additionally, fluorine compounds derived from fluorite have played a controversial role in dental health, particularly in the fluoridation of drinking water, which has been shown to help reduce tooth decay. Overall, fluorspar's unique properties and diverse applications make it a significant mineral in both industry and public health.
Fluorite (mineral)
Where Found
Fluorite is a common mineral that is found worldwide. It occurs in hydrothermal veins associated with the oreminerals of lead, silver, and zinc. It commonly is the most abundant mineral in the vein and can occur as the only mineral in some veins. Fluorite is also found in cavities of sedimentary rocks, in hot-water deposits near springs, and in water-rich igneouspegmatites. Fluorite is associated with many different minerals, including calcite, dolomite, gypsum, barite, quartz, galena, sphalerite, topaz, and apatite. In the United States, the most important sources are in Illinois, Kentucky, Ohio, New Mexico, and Colorado. Worldwide, fluorite is found in China, Kenya, Mexico, Mongolia, Morocco, Namibia, Russia, South Africa, and Spain.
Primary Uses
Fluorite is an excellent flux and is used extensively in the production of iron, steel, and aluminum. Fluorite is the chief ore for elemental fluorine gas and related fluorine chemicals. It is used in the chemical industry in the production of hydrofluoric acid (HF). This acid is the primary ingredient used to produce almost all organic and inorganic fluorine-bearing chemicals. Fluorite is also used in manufacturing of glass, fiberglass, pottery, and enamel.
Technical Definition
The mineral fluorite, called fluorspar in the mining industry, has a formula of CaF2 and is the index mineral on the Mohs hardness scale at 4.0. Fluorite displays a glassy luster and a perfect cleavage that yields octahedral fragments. Fluorite crystallizes in the isometric system and commonly forms perfect to near-perfect cubes.
Description, Distribution, and Forms
Fluorite has a structural defect in its atomic arrangement called a “color center,” where an electron fills a “hole” from a missing ion. This defect causes fluorite to display a wide variety of colors, including deep purple, light green, bluish green, yellow, and less commonly colors of rose, blue, or brown. A single slab or crystal can show distinct color banding, commonly with four or more different colors being present. Fluorite can also be colorless and perfectly transparent. The property of “fluorescence,” a luminescence caused by exposure to ultraviolet light, is common and pronounced in fluorite to the point that fluorite is the namesake of this spectacular property.
History
The name fluorite comes from the Latin word fluere, which means “to flow,” referring to its ancient use as a flux in smelting iron. Fluorite has a long history of use as an ornamental material; fluorite carvings are among the earliest Chinese works of art. A red-blue-colorless-dark purple sequentially banded variety of fluorite from Derbyshire, England, known as “Blue John,” was used by the Romans for cups and dishes. Early American Indians carved artifacts from purple fluorite from southern Illinois.
In the early 1940’s, scientists determined that in drinking water a sodium fluoride concentration of 1 part per million was high enough to cause a decrease in dental cavity formation but low enough not to cause the mottling of teeth that higher levels were known to cause. Early fluoridation programs were instituted in Michigan and Wisconsin in 1945. Fluoridation was controversial from the beginning, with its more radical opponents deeming it a communist plot against the United States. Nonetheless, as tests seemed to validate fluoride’s effectiveness as an antidecay agent, its use spread throughout municipal water districts in the United States. In the past, some debated whether fluoridation was truly effective or whether other factors (such as better nutrition and oral hygiene) might be responsible for the decrease in tooth decay seen beginning in late 1940’s. However, the scientific community widely accepts that fluoridation does indeed reduce decay.
Obtaining Fluorite
Mining of fluorite for industrial and chemical applications began in the eighteenth century in the United States. There are three principal market grades of fluorite: acid, ceramic, and metallurgical. The specifications are in regard to purity. Acid grade is 97 percent pure, ceramic grade is about 94 percent pure, and metallurgical grade is between 60 and 90 percent pure.
Uses of Fluorite
Chlorofluorocarbons (CFCs) were made from acid-grade fluorite by having the hydrofluoric acid react with chloroform or carbon tetrachloride. These fluorocarbons performed outstandingly as refrigerants, aerosol propellants, and solvents. However, the diffusion of CFCs into the upper atmosphere is believed to be responsible for damage to the ozone layer, and production of these fluorine-based chemicals was banned by the Montreal Protocol in 1987.
Artificial fluoridation of drinking water and toothpaste is another widespread use of fluorine compounds, or fluorides. In the 1930’s, researchers discovered that the presence of sufficient amounts of fluorine occurring naturally in drinking water could lead to a low level of tooth decay and dental cavities.
Bibliography
U.S. Geological Survey.