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Bicolor Tourmaline

At last count, gemologists had logged in more than 100 tints for tourmaline, making it the gem world’s king of color. Centuries ago, however, when its broad palette meant constant confusion with other stones, tourmaline was one of the gem world’s masters of disguise. Indeed, the gem’s root-name, is turmali, a Sinhalese term used by Ceylonese dealers and means “mixed gemstones of unproven identities.” Today the original name is still apt because it reflects a gemological diversity so great that the gem is classified as a group rather than a family.

Yet, strangely enough, the gem that comes in more colors than any other begins life as colorless, or nearly so. During formation, its crystal structure hungrily absorbs trace elements from its host solution. Some of these chemical impurities -- most notably, manganese for pink and iron for green -- act as coloring agents when they replace atoms normally present.

This susceptibility to color change through chemical substitution makes tourmaline what is called an “allochromatic” gem. Of course, tourmaline is far from alone in this trait. In fact, without such color-susceptibility, many revered gems would be missing from jewelry stores. If, for instance, chromium didn’t replace aluminum in beryl, there would be no emerald.

Nevertheless, tourmaline takes to a wider variety of tinting than any other gem. And because it does, explanations of color causes in tourmaline are still largely theoretical and often conflict with one another. When it comes to color, tourmaline seems to play by lots of rules. “In Brazil, the color chemistry for tourmaline changes from pocket to pocket within an occurrence,” gemologist Joel Arem notes, “while in California it remains fairly uniform throughout the whole San Diego gem belt.”

Many tourmalines provide a visual record of changes in their chemistry by displaying two, sometimes three, areas of different color along their crystals. When cut, these multicolor gems become what Arem calls “history books of tourmaline growth.” Most frequently seen with two large zones of adjoining color, the gem is best known as bicolor tourmaline and usually features combinations of pink and green. Both the pinks and greens run wide gamuts from magenta-purple to brownish-pink and aloe to granny-smith apple green, with numerous intermediate shades.

Occasionally, bicolors depart from pink-green pairings and couple spruce-greens with aqua-blues, aqua-blues with cherry-pinks, and grass-greens with pumpkin-oranges, to name a few of the most beautiful combinations. “No doubt, new finds will give us new color combinations,” Arem adds.

Local Colors

At present, bicolor tourmalines are mined principally in Brazil, Zambia, Madagascar, Nigeria, Afghanistan and California.

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Bicolor Tourmaline