On my site you will find many examples of tourmaline gemstones that have their color influenced by trace amounts of copper in their makeup. With my spectrometer I can see the amount of light that is absorbed by the only oxidation state of copper that has been found in tourmaline as a chromophore. An oxidation state Cu+2 that has been found to be unaffected by heating and not combined in electronic arrangements with any other chromophores, or color centers.
The role that copper can play in coloring tourmaline is spectacular, but limited to a very narrow range, basically one color, in tourmaline. This straight forward role of copper does not begin to match the complex roles of both manganese and iron that are also very important impurities in tourmaline, which affect color. On top of being much more complex, both manganese and iron are much more common in tourmaline than copper.
With the addition of manganese and iron, along with some other minor elements/color centers that might also affect tourmaline’s color, the colorful world of cuprian tourmaline explodes. The limited range of Paraiba/paraiba type/paraiba like tourmaline is the result of marketing and history rather than the color range of cuprian tourmaline found at the original location in Brazil. Heat was used indiscriminately to produce the valuable and marketable range of colors defined by the trade as Paraiba.
Most of the cuprian colors are not unique in tourmaline’s wonderful range of color. I have found that the purples are the most outstanding example of novel color additions to the range of dynamic colors in tourmaline. I use the word dynamic because many of the unheated cuprian tourmaline have colors that are strongly metamatic. This sensitivity of their color to changing light sources is particularly prevalent in unheated specimens. The ultimate example of this is Laurellite. Laurellite is a name that I have given to a unique reverse Alexandrite color changer that is cuprian in nature and has come from Mozambique. To find out more about this fascinating and extremely rare variety of tourmaline please search this site.
To sum up. The relatively recent addition of copper to the important group of coloring agents in tourmaline is a wonderful addition, but many of the colors produced are not unique. Copper, by itself, can produce only a very narrow range of color in tourmaline. But the level of visual impact in cuprian tourmaline/Parabia/paraiba type caused by its purity of color, brightness and sometimes a glow like quality, can be traced to the effect of copper on tourmaline.
Bruce
