Tourmaline Buying Guide
Known for stunning, saturated hues, tourmaline is a colorful and modern gemstone. This October birthstone is hard enough and durable enough for everyday jewelry wear. Most tourmalines undergo heat and radiation treatments to achieve these hues. However, these procedures have stable results. With so many varieties and colors, you can always add more tourmalines to your collection.
Tourmaline Buying and the Four Cs
The IGS tourmaline value listing has price guidelines for Paraíba tourmalines, indicolite, rubellite, chrome tourmalines, and other colors of faceted stones, as well as cat’s eye and non-phenomenal cabochons.
Tourmalines come in all the colors of the rainbow. When buying tourmaline of any color, view it under several different types of lighting, as most gems will exhibit some alteration in color or decreased saturation in incandescent light.
In tourmalines, blue and blue-green hues arise from iron or copper in the crystal structure. While rare, blue hues are also the most popular color of this gemstone.
Indicolite is the gemological name for blue tourmalines. Generally, this term refers to tourmalines colored by iron. Indicolites can be greyish blue, blue, or blue-green. The most costly gems exhibit medium tones and saturated color. Since indicolites commonly receive heat and radiation treatments, ask about treatments before purchasing. If you’re interested in indicolites, read the indicolite buying guide.
In 1989, a new variety of tourmaline came out of Brazil. This material, called “Paraíba tourmaline” for the Brazilian state of Paraíba, displays an electric blue to blue-green hue due to the presence of copper. Before the discovery of this variety, tourmaline colors were valued primarily on how well they simulated better-known rubies, emeralds, and blue sapphires. Now, more people recognize and appreciate tourmalines for their eye-popping saturation.
While this variety was named for its original locality, mines in other countries have produced copper-bearing tourmalines. These have entered the market as “Paraíba tourmaline.” Major gem laboratories can determine the origin of the stone, and this testing is recommended for any stone sold as Brazilian in origin. While quality Paraíba tourmalines also occur in other localities, such as Nigeria and Mozambique, Brazilian stones hold much higher value.
Like indicolite, medium tones and saturated color are the hallmarks of a top-quality Paraíba tourmaline. Hue should be blue, sometimes with very slight green hues. Significant green hues will detract from the price. Dark-toned specimens often undergo heat treatment to lighten them.
Verdelite, or green tourmaline, is a variety of elbaite that has primary green hues. The most common color of gem-quality tourmaline, green tourmalines occur in yellow-green, green, and blue-green hues. Of these, the stones that come closest in color to fine emerald, with medium-dark tones and slight secondary blue hues, and those that imitate blue-green Paraíba tourmalines, with intense saturation and medium tones, hold the highest value. Light tones, such as mint greens, also enjoy some popularity. The verdelite buying guide has more information on what to look for in green tourmalines.
Some green tourmalines contain chromium and/or vanadium, which imparts a lovely green hue. The same elements color tsavorite garnets and emeralds, so, unsurprisingly, fine chrome tourmaline color resembles high-quality emerald green. These gems tend to have strong saturation and pure green to slightly bluish green hues. Yellow hues hold less value. For more information, look at the chrome tourmaline buying guide.
Rubellite is a loose term that refers to tourmaline gems in the deep pink to red range. Although the comparison to ruby is tempting, it’s not entirely accurate. Considering how tourmaline color can alter under different lighting sources, a rubellite with a fine red, ruby-like day hue may dull in incandescent light, or this lighting will bring out secondary purple hues. While undesirable in ruby, the shift to purplish hues is much more attractive in rubellite than a shift to a muddied red.
Perhaps the finest rubellite colors are the raspberry hues. These gems show slight to moderate secondary purple hues and the eye-catching saturation that make tourmaline a prized stone. The rubellite buying guide has more information on these gems.
Pale pink hues of elbaite, though not rubellite, can have beautiful shades for more reserved jewelry pieces.
Yellow, orange, and purple hues of tourmaline are very rare. When evaluating the price of these colors, keep in mind that purer hues generally hold higher prices. For example, a lemon-yellow gem without a greenish tinge or slight orange hue is more valuable than an off-color stone.
Affordable brown tourmalines occur in a range of hues, including chocolate and cognac.
Although inexpensive, black tourmaline can add a sophisticated look to a jewelry piece.
Bi-colored and Parti-colored Tourmalines
Changes in chemical composition during tourmaline formation create differences in hue within the gem. As a result, many tourmaline crystals exhibit two or more chromatic hues along the crystal. Most commonly, a combination of green and pink is present. A gem that exhibits intense hues with a drastic transition between colors will fetch a better price than one with a slower or muddied transition. The relative sizes of the colors also affect the prices of these gems. The best gems have even amounts of each color.
Generally, tourmaline color changes along the length of the crystal. However, for watermelon tourmalines, the color changes radially outward. Here, the inside of the crystal is pink and the outside green, resembling a watermelon. These gems are often cut in slices to mimic the fruit.
Tourmaline clarity expectations differ based on color. For verdelites, the most common color, eye-clean gems are readily available, and loupe-clean verdelites are not difficult to obtain. Clarity for chrome tourmalines is similar to verdelites. However, eye-clean rubellites are less common. For indicolites and Paraíba tourmalines, eye-clean specimens are rare and hold very high value.
Tourmalines that exhibit multiple chromatic hues are more likely to have inclusions and fractures. This is due to changes in their chemical composition during their formation.
Due to their crystal structure, many tourmalines are cut into long, narrow posts to retain weight or to exhibit the colors in a bi-color or parti-color stone.
Easily available sizes differ by the color of tourmaline. Nevertheless, you can find tourmalines of any color in any size. For example, verdelites and rubellites are readily available in sizes up to six carats. However, anything over 15 carats in these gems will require some searching.
Chrome tourmalines tend to be smaller, with sizes under two carats the most common and anything above eight carats much rarer.
For indicolite, any size is rare and will fetch a good price. Paraíba tourmalines from Brazil are rare in any size, but most rough from this locality produced gems under two carats. On the other hand, Paraíba material from Mozambique is much larger, up to 20 carats.
Dichroism: The Multicolor Effect
Tourmalines are highly dichroic, shifting hue depending on the viewing angle. This creates a spectacular effect where adjacent facets may show entirely different hues. While undesirable in traditional emeralds, rubies, and sapphires, this effect can be very attractive in tourmalines. It can give the stone a unique sparkle.
This gem has strong dichroism, with bright pink and peach tones visible. © JL White Fine Gemstones. Used with permission.
Most tourmalines receive heat treatment. Some also undergo radiation treatment. Unfortunately, since these create stable colors, vendors often don’t disclose them to consumers. Always ask about treatments before purchasing a tourmaline, and assume that any tourmaline has been heat-treated.
Pink, red, and blue tourmalines commonly receive heat and radiation treatments. Green tourmalines are sometimes heated to lighten their color. However, this treatment often doesn’t produce a desirable color. Still, it’s best to assume that a tourmaline was heat treated.
Synthetic tourmalines are expensive and difficult to manufacture, even in very small sizes. Thus, they aren’t commercially available. Dyed quartz, glass, or other synthetic stones, such as synthetic spinel, are sometimes presented as simulants for tourmaline.