Known for its dazzling saturated hues, tourmaline is a colorful and trendy gemstone. October born stone is tough and durable enough for the wear and tear sustained in everyday use. Most tourmalines undergo heat and radiation treatment to achieve their hues. However, these procedures have solid results. With so much color variety, you can always add more tourmalines to your collection.
The 4 C's
Colour (color): Tourmaline can be found in every color of the rainbow. When purchasing a tourmaline of any color, look at it under different types of lighting, as most gemstones exhibit some change in color or reduction in saturation under incandescent light.
BLUE
In tourmaline, blue and blue-green tones arise from the presence of iron or copper in the crystalline structure. Although rare, shades of blue are also the most popular color of this gemstone.
Indicolites is the gemological name for blue tourmalines. Generally, this term refers to iron-colored tourmalines. Indicolites can be blue-gray, blue or blue-green. More expensive gemstones exhibit medium tones and saturated colors. As they receive thermal and radiation treatment, before buying, ask about the treatments.
Paraíba: In 1989, a new variety of tourmaline appeared in Brazil. This material, called “paraíba tourmaline” after the Brazilian state where it was found, exhibits a vibrant blue and blue-green hue due to the presence of copper. Prior to this discovery, tourmaline colors were prized primarily for the way they simulated the best-known colors such as rubies, emeralds and blue sapphires. Now more people recognize and appreciate tourmalines because of their dazzling saturation.
Although this variety was named for its original location, mines in other countries produced copper tourmalines and eventually entered the market as “paraiba tourmaline”. The main gemological laboratories can determine the origin of the stone, a test recommended for any stone sold as of Brazilian origin. While quality Paraiba tourmalines are also found in other locations such as Nigeria and Mozambique, Brazilian stones are priced much higher.
Like indicolite, midtones and saturated color are the hallmarks of a quality Paraiba tourmaline. The tone should be blue, sometimes with very light green tones. Significant green tones will lower its value. Dark-toned specimens are often subjected to heat treatment to lighten them.
Green
Verdelita, or green tourmaline, is a variety of elbaite with primary green tones. The most common color of quality tourmaline, green tourmalines occur in yellowish-green, green, and blue-green hues. Of these, the stones that are closest in color to emerald, with medium dark tones and slight secondary blue tones, and those that imitate blue-green Paraiba tourmalines, with intense saturation and medium tones, have the highest value. Lighter shades like mint also enjoy some popularity.
Chrome: Some green tourmalines contain chromium and/or vanadium, which gives them a beautiful green hue. The same elements color tsavorite and emerald garnet, so it's no surprise that chrome tourmaline's color resembles high-quality emerald. These gems tend to be heavily saturated and have pure green to slightly bluish tones.
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Rubellite is a broad term that refers to tourmaline gemstones in the dark pink to red range. While the ruby comparison is tempting, it is not entirely accurate. Considering how tourmaline's color can vary under different light sources, a rubellite with a very red hue, similar to a ruby, may dull or turn purple under incandescent light. Although undesirable in ruby, the shift to purplish tones is much more attractive in rubellite than a shift to muddy red.
Perhaps the most beautiful colors of rubellite are raspberry shades. These gems feature light to moderate secondary purple tones and attractive saturation that make tourmaline a prized gemstone.
Other colours
Yellow, orange and purple are very rare shades. When evaluating the price of these colors, keep in mind that purer tones generally have higher values. For example: a lemon yellow gem is more valuable than a discolored stone.
Affordable brown tourmalines occur in a variety of shades including chocolate and cognac.
Despite not being very expensive, black tourmaline adds sophistication to a piece of jewelry.
Bicolor and multicolor tourmalines
Changes in chemical composition during tourmaline formation create different hues within the gem. As a result, many crystals feature two or more shades. Often, the combination between green and pink is present. The best gems have equal amounts of each color.
Clarity (transparency): The transparency in tourmaline changes based on color. Verdelites – the most common color – with a high degree of transparency are the easiest to find, something common for chrome tourmalines. On the other hand, rubellites with the same degree of transparency are uncommon. Indicolites and transparent paraiba tourmalines are rare and have a high value.
Tourmalines with multiple colors are more likely to show inclusions and cracks due to changes in their chemical composition during their formation process.
Some tourmalines have a cat's eye effect due to the hollow tube type inclusion. When cut correctly, they are a charm!
Cut (cut): Dark, highly saturated rough gemstones can benefit from shiny or checkerboard type cuts. For slightly jagged buds, any cut will work. In any case, make sure the cut is symmetrical and harmonic.
Due to their crystalline structure, many tourmalines are cut long and narrow to conserve weight or to show off the colors in a bicolor or multicolor stone.
Carat (weight): Easier sizes to be found are related to the color of the tourmaline. However, you can find tourmalines of any color in any size. For example, verdelite and rubellite are easily found in sizes up to 6 carats. However, anything over 15 carats will require a certain degree of investigation.
Chrome tourmalines tend to be smaller, with sizes under 2 carats – the most common, with any over 8 carats being very rare.
For indicolite, any size is rare and will fetch a good price. Paraíba tourmalines from Brazil are rare in any size, but most of the rough stones from this locality produce gems with less than 2 carats. On the other hand, the material from Mozambique is much larger – around 20 carats.
Dichroism: the multicolored effect
Tourmalines are highly dichroic, changing their hue according to the viewing angle, creating a spectacular effect with adjacent facets, which present totally different hues. Although undesirable in emeralds, rubies and sapphires, this effect can be very attractive in tourmalines, giving the gem a unique sparkle.
Treatments
Most tourmalines are heat treated, although some are subjected to radiation. Unfortunately, as they create solid colors, sellers often don't reveal it to consumers. Always ask about treatments before purchasing a tourmaline and assume that any tourmaline has been heat treated.
Pink, red and blue tourmalines usually receive heat and radiation treatment. Green tourmalines are sometimes heated to lighten their color. However, this treatment does not usually produce a desirable color. Still, it's best to assume that the tourmaline has been heat treated.
This text is a translation of the original Tourmaline Buying Guide.
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