 varieties and the one that naturally makes up the enamel layer of our teeth is called hydroxyapatite. If fluorine is present in your saliva, which it is after using fluoride toothpaste or drinking fluoridated water, then the apatite of the tooth enamel can alter to fluorapatite. Fluorapatite crystals are larger than hydroxyapatite crystals, so their relative surface area is less and they do not dissolve as easily as hydroxyapatite crystals. Hence teeth with enamel composed largely of fluorapatite will have far fewer cavities!
Fluorite is too soft to be used as jewelry, but the Romans mined a massive crystalline variety of fluorite, later known as Blue John or Derbyshire spar, that exhibited a distinctive color banding of blues, violets and purples. This banded fluorite was carved to create bowls, vases and ornamental objects that were extensively traded across Europe and the Mediterranean area. Although the Derbyshire deposits are now largely mined out, other varieties of fluorite are still among the most actively traded and collected mineral samples, as they occur in a wide range of colors and forms. As an example, for centuries the Chinese mined a green variety of fluorite, erroneously called ‘green quartz’, for carvings and figurines.
Clear fluorite is among the rarest of the many fluorite varieties and was once used in the manufacture of optical lenses. Modern fluorite lenses, though, are usually from commercially manufactured fluorite, rather than natural clear crystals.
In Our Future: The Environmental Implications of Fluorite Use
Fluorine taken from fluorite is an extremely reactive chemical. In small quantities it can provide medical benefits such as reduced dental cavities, but in larger quantities fluorine can be quite dangerous. Fluorine gas is a deadly poison. Combined with hydrogen, fluorine makes hydrofluoric acid, an acid so powerful that it is used to etch glass.
Perhaps fluorine’s most potent threat though, comes from its use in compounds that can be handled with little to no risk. Fluorine is used to create chlorofluorocarbons, known as CFC’s. CFC’s were once widely used as the cooling fluid of refrigerators and air-conditioners, as well as the propellant for aerosol cans of paint and hairspray. They are inert compounds that do not react with other substances, are non-toxic and initially appeared to pose little risk to human populations. Consequently they were widely used before researchers realized that CFC’s released into the atmosphere pose a serious threat to the atmospheric ozone layer that protects the Earth’s land life from harmful ultraviolet radiation that can cause cancer and mutations. As ozone naturally forms and breaks apart, it absorbs ultraviolet radiation from the sun, thus shielding the Earth’s surface (and much of its life) from this harmful radiation. However, CFC’s in the high atmosphere help to speed up the process of ozone breaking down, so that much less ultraviolet radiation is absorbed. The radiation that is no longer absorbed can reach the Earth’s surface and poses a particular threat to populations living in high latitude areas, where this process of ‘ozone depletion’ is the most effective. International agreements have now banned the manufacture and use of CFC’s in many nations, but unfortunately this ban is not global so CFC’s still pose a potent, long-term environmental risk.
Fluorite in the Upper Midwest:
Thick widespread carbonate rock units of the Upper Mississippi River Valley once hosted large amounts of fluorite. These deposits formed as hydrothermal fluids moved along fractures in the carbonate rock, altering or dissolving the carbonate minerals and precipitating a wide variety of metallic ores and pore-filling minerals, including fluorite. Most of the richest fluorite deposits have now been mined out, but some fluorite can still be found, especially in Illinois’ Hardin and Pope Counties.