Although too fragile for most jewelry use, fluorites are often faceted for collectors. They occur in a wide range of attractive colors and can be extremely bright. These gems are also renowned for their fluorescence.
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An extremely wide range is represented: colorless, purple (various shades), green (various shades), blue-green, blue, yellow to orange, brown (various shades), white, pink, red, brownish red, pinkish red, brownish black, black. Crystals are frequently color zoned.
Fluorites come in many colors, including colorless. Most available stones occur in shades of purple, blue, or green. Chrome green material from Colombia and pink gems are rare. Lapidaries can cut multi-colored gems (sometimes called “rainbow fluorites”) from color zoned crystals, too.
Atomic-age inspired sterling silver pendant with a rainbow fluorite stone. Photo by Rhonda. Licensed under CC By-SA 2.0.
For over 1,500 years, English artisans used Blue John or Derbyshire Spar as decorative material in vases, carvings, bowls, and so forth. This fluorite variety has bands of white, blue, violet, and reddish brown.
A craftsman at the Treak Cliff Cavern workshop in Derbyshire, England placed slices of Blue John, too thin for jewelry, on his window. Photo by Andy Mabbett. Licensed under CC By-SA 3.0. (Cropped to show detail).
Some (but not all) fluorites display fluorescence under ultraviolet light (UV). Thus, confirming the presence of this property isn’t diagnostic for identifying fluorite. However, this property is strongly associated with this gem. In fact, in 1852, the physicist Sir George Gabriel Stokes named this effect “fluorescence” after his studies of the mineral fluorite.
Chlorophane, a rare fluorite variety, shows phosphorescence and thermoluminescence, as well as triboluminescence. It luminesces when rubbed or held in your hand.
Chlorophane under normal light (left) and UV shortwave light (right), Buckwheat dump mineral collecting site, Franklin, Franklin Mining District, Sussex Co., New Jersey, USA. Photo by Modris Baum. Public domain.
Currently, high production costs, combined with fluorite’s low hardness and perfect cleavage, make synthetics an improbable choice for jewelry.
How Can You Distinguish Fluorites from Other Similar Gemstones?
Due to their considerable color range, you’ll more likely find natural fluorites misidentified or misrepresented as other gems. For example, fluorites have been offered as amethysts, emeralds, and color change garnets.
Hardness testing, of course, is the easiest way to distinguish fluorites from these more popular and durable jewelry stones. However, conduct scratch testing only as a last resort and never on a finished gem. Fortunately, fluorite’s very low RI and dispersion can help distinguish it from many other gems.
Heating to 100-150° C can lighten dark-colored fluorites, but higher temperatures risk removing all color. On the other hand, radiation treatment can turn colorless and pale green material darker blue, green, or purple.
Decorative objects might receive coating, dyeing, and plastic impregnation treatments.
The most well-known sources of gem-quality material include the following:
Ontario, Canada: banded, violet material in calcite.
Huanzala, Peru: pink crystals.
Chamonix, Switzerland; octahedral pink crystals, on quartz, very rare.
United Kingdom: Cornwall; Cumberland; Derbyshire.
United States: Colorado; Illinois (occurs in many colors, best known, especially violet material from Rosiclare); Michigan; Missouri (purple, blue, yellow, brown, colorless); Westmoreland, New Hampshire (bright green fluorite in crystals up to 8 inches across); New Mexico.
Since suitable rough from a wide range of localities is available, fluorite crystals can be very large. However, large stones totally free of internal flaws are extremely rare. Thus, cut fluorites suitable for jewelry use are usually small.
Los Angeles County Museum: 1031 (yellow, triangle, Cave-in-Rock, Illinois, world’s largest yellow fluorite); 100 (chrome fluorite, Colombia); 30 (chrome fluorite, Azusa Canyon, Los Angeles County, California).
Fluorites contain fluorine (F) as part of their chemical makeup (CaF2). As a gas, fluorine is very toxic. However, fluorites are inert. Wearing or holding fluorite gems or jewelry will pose no health risks. The lapidary processes used to cut fluorites won’t create fluorine gas. (Of course, gem cutters should take basic precautions when working with any gem material).
There are health risks associated with long-term exposure to massive amounts of fluorite in or near mining environments. However, normal gem cutting and handling just won’t result in exposure on that scale.
How to Take Care of Your Fluorite Jewelry
Due to its cleavage, brittleness, and low hardness, fluorite is too fragile for most jewelry use. Ring use isn’t recommended. However, protective settings, occasional wear, and use in pendants and earrings can let you show off these beautiful gems. Some specimens may fade with prolonged exposure to light, so store any fluorite jewelry out of the light. In addition, store them separately from other harder gemstones to prevent contact scratches.