Tourmaline has become one of the most popular of all colored gemstones, valued for its enormous range of colors and its vitreous luster. Almost every tourmaline is unique, and large stones are still affordable.
Tourmaline is a family of boron silicate minerals, with many variations on the basic chemical structure. The known history of tourmaline goes back at least to the early 18th century, when traders from the Dutch East India Company brought quantities of tourmaline from Ceylon to Europe. But it is probable that tourmaline was used much earlier as a decorative stone.
The name tourmaline came from the Sinhalese word “turmali”, which was used in Ceylon to refer to mixed gems of unknown identity. Tourmaline was identified as a distinct mineral only in the 19th century. It has a complex chemical composition, with many permutations. Mineralogists recognize 14 different varieties of tourmaline, with the boron silicate compounded with aluminium, iron, magnesium, sodium, lithium or potassium.
The tourmalines containing iron tend to be black or bluish-black or dark brown. The maganese-rich varieties are brown to golden to yellow in color, with the bright yellow known as canary tourmaline. The lithium-rich tourmalines, known as Elbaite tourmalines, are the most popular for gemstones — they can occur in almost any color, especially blue, green, red, yellow and pink.
Bi-colored and multicolored crystals occur frequently in tourmaline, more than in any other gem. This lovely accident of nature is due to variations of fluid chemistry during crystallization. Green and red are often found together in bi-color stones, but yellow, orange and pink are also common.
While mineralogists identify 14 different varieties of tourmaline by chemical composition, the gem trade markets tourmaline by color, and assigns special names to some rare colors. The most popular tourmaline colors have been pink and green. The vivid red tourmaline is known as Rubellite, while the rare neon blue-green is know as Paraiba. The intense green variety colored by chromium and vanadium is called Chrome Tourmaline, while the blue or greenish-blue is known as Indicolite.
Tourmaline is found in many locations in the world. Historically, the most important deposits were in Sri Lanka, Brazil and the USA (California and Maine). More recently, Africa has become an important source of fine tourmaline, with NIGERIA the leading producer. Significant deposits are also found in Mozambique and Afghanistan