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Imitation tourmaline is occasionally seen. The popular watermelon tourmaline and other parti-colored tourmalines are a common target of the imitators. Some assembled imitation stones consist of a thin wafer of colored glass or plastic, glued between two pieces of colorless glass. These imitations are easy to detect with a microscope or loupe. If the stones…

Heat and irradiation are common treatments used to improve the color of tourmaline. Both of these treatments are commonly done after the stones have been cut and polished. They can be undetectable when viewed with a gemological microscope. Heat treatment can lighten an undesirable tone in some materials and give some brownish stones a brighter,…

Tourmaline is a pleochroic mineral. That means its apparent color can change with different directions of observation. The color is usually darkest looking down the c-axis of the crystal (down the long axis). It is usually lightest when viewing perpendicular to the long axis of the crystal. Cutting pleochroic gem materials requires skill and knowledge.…

Tourmaline is one of many minerals that can be chatoyant when cut into a gem. “Chatoyant” is a gemological adjective used to describe minerals that exhibit a “cat’s-eye”. Chatoyant tourmalines contain thousands of tiny parallel tubes that have the ability to reflect light. When a tourmaline crystal filled with these tubes is properly cut as…

Changing conditions during tourmaline crystal growth often result in single crystals that contain two or more different colors of tourmaline. The earlier color is usually overgrown by the later color. These bicolor crystals are known as “zoned crystals.” Cut gemstones with distinctly different color zones are known as parti-color gems. In many gems, color zoning…

The name “Paraiba” perks up the ears of people who like tourmaline. In 1989 and 1990, spectacular bright blue to bright green elbaite tourmaline, colored by trace amounts of copper, was found in pegmatite pockets at mines in the states of Paraiba and Rio Grande do Norte, Brazil. Later, violet specimens containing traces of both copper and manganese were found. The…

A table above lists the names and chemical compositions for 32 different members of the tourmaline mineral group. These names are based upon the chemical composition of the mineral. Because it can be impossible or impractical to determine the chemical composition of a large number of specimens or even a single specimen, the generic name…

Tourmaline is a complex boron silicate mineral with a generalized chemical composition of:XY3Z6(T6O18)(BO3)3V3W Letters in the formula above represent positions in the atomic structure of tourmaline that can be occupied by ions listed below.  X = Ca, Na, K, [] ([] = vacancy) Y = Li, Mg, Fe+2, Fe+3, Mn+2, Al, Cr+3, V+3 Z = Mg, Al,…

Tourmaline has a few properties that can aid in its identification. If you have a tourmaline crystal, identification should be easy. Don’t despair if your suspected tourmaline is an accessory mineral in an igneous or metamorphic rock. It often occurs in these rocks as tiny prismatic crystals. Get a hand lens and look for striations and rounded…

Brazil has been the world’s leading source of tourmaline for nearly 500 years. In the 1500s Portuguese explorers obtained green and blue tourmaline from indigenous people and from panning streams in search of gold. They thought that these colorful stones were emeralds and sapphires and sent them back to Portugal, where they were cut into gems and used to make jewelry…