Tourmaline: October’s Colorful Birthstone

Posted on Oct 1, 2013 in Birthstones, Gemstones,

Tourmaline has one of the widest color ranges of any gemstone. While October’s birthstone can be found in virtually every hue of the rainbow, the most popular varieties range from rich reds and pinks, to greens and yellows, to blues and violets. Some tourmalines are bi-colored and parti-colored, exhibiting two or more colors in a single gem – a feature known as color zoning.

Colorful tourmalines. From the Dr. Eduard J. Gubelin Collection.

Historically, tourmalines were often mistaken for other gemstones due to its vast range of colors. One of the “rubies” in the Russian crown jewels, the “Caesar’s Ruby” pendant, is actually rubellite tourmaline. A Spanish conquistador found a green tourmaline crystal in Brazil in the 1500s and confused the gem with an emerald. These types of mistaken identities continued for centuries, until scientists recognized tourmaline as a distinct mineral species in the 1800s.

6.72 carat pink cushion-cut tourmaline and diamond ring. Image courtesy of Omi Prive.

When shopping for this gemstone, color is the most important quality factor to look for. Highly saturated colors without dark areas are the most valuable, but less saturated tones have recently become popular as well. The pink/red variety, known by the trade name rubellite, is one of the most sought-after and readily available tourmaline colors. High-quality tourmalines mined from Paraíba, a famed Brazilian source of the gemstone, command a premium.

Tourmaline, diamond and gold flower brooch. Image courtesy of Christie’s Images / The Bridgeman Art Library.

These gemstones often grows in environments rich in liquids, which can capture inclusions during crystal formation. The most typical inclusions resemble thread-like cavities parallel to the length of the crystal. If cut as a cabochon, these inclusions can appear as a striking a cat’s eye effect.

Cut is also an important factor when selecting a tourmaline. Many gem cutters orient a tourmaline based on its depth of color. They are often cut in long rectangles to accentuate the gemstone’s pleochroism, meaning it shows different colors when viewed from different directions.

While tourmalines can reach extraordinary sizes, fine-quality stones are very rare, so large-sized gems rise considerably in per-carat price. Availability drops and prices rise sharply for facet-quality rough material.

The Hamlin necklace. Courtesy of the Harvard Mineralogical Museum.

Tourmaline is rated 7 to 7.5 in hardness on the Mohs scale and is suitable for everyday wear. These colorful gems are generally stable enough to withstand light and most chemicals, but heat can be damaging. Warm soapy water and a soft toothbrush is the best method for cleaning tourmaline. The use of ultrasonic and steam cleaners is not recommended.

With such a wide variety of colors and color combinations available, which color of tourmaline are you most drawn to?