One of the USA's largest and most respected Gem Testing Laboratory releases a statement explaining their postion on the Paraiba vs Cuprian controversy!
Because we are unable to post photos to the list I have included the link to the original article as it was accompanied by several amazing shots of Tourmaline in every color!
Reprint from: AGTA Gemological Testing Center's Laboratory Update - February 2007A major item of controversy in the gem world over the past year has been the definition of paraíba tourmaline. When this gem variety was first discovered in Brazil, the unusually intense "neon" or "electric" colors set it apart from any other tourmaline previously known. The color of this gem ranges from intense emerald green through "windex" blue-green to a rich sapphire blue and continuing along the spectrum to intense violet or even purple (similar to fine amethyst). Apart from the intense colors, another remarkable feature of these gems is their relative lack of extinction.
Because the colors were so unusual, traders immediately began marketing the gems under the moniker "paraíba" tourmaline, after the Brazilian state where they were first found. Later, traders asked gemological labs to describe the gems on lab documents as "paraíba" tourmaline. This forced labs to come up with a definition for this variety.
One proposal was to determine the coloring agent(s) for these unusual varieties. Quickly it was determined that copper played a major role, along with manganese. But building a variety definition based on composition alone is fraught with danger.
First, our knowledge of what creates color is fluid, constantly changing as new discoveries are made. Once upon a time, chromium was considered the only cause of color in emerald. We now know that vanadium also plays a role, sometimes the dominant one. Similarly, until quite recently, iron was thought to be a major cause of color in yellow sapphire; today we understand that color centers are more important.
Second, the color of finished gems is dramatically affected by all manner of things unrelated to composition, such as variations in size, cutting, inclusions and color zoning. Thus composition alone is problematic.
The LMHC has attempted to address these issues by building a definition that is both independent of origin and that incorporates color and composition (see LMHC Information Sheet #6). While the LMHC definition does not currently encompass stones in the violet-to-purple range, this could be a topic for future discussion. Currently, the AGTA GTC follows the LMHC definition.
Does every tourmaline that contains a certain amount of copper/manganese qualify as a paraíba? In a word, no. The most important feature of a paraíba tourmaline is exactly that which made the gem famous in the first place – intensity of color. Thus if a gem submitted for testing lacks the necessary degree of color saturation, it will not meet the AGTA GTC's paraíba criteria, no matter what its chemistry. In such a case, color trumps chemistry.
Another issue is that of origin. While paraíba tourmalines were first found in Brazil's Paraíba State, stones of similar color and composition have now been found in Rio Grande do Norte State (Brazil), Nigeria and Mozambique. Some purists have argued that the paraíba variety should be limited to Brazilian stones, but the decision of the LMHC was that this variety will be defined by color and composition, not country-of-origin. Upon request, member labs of the LMHC will identify the country-of-origin on their documents, thus satisfying all clients.
For more info from AGTA GTC Lab:
http://www.agta-gtc.org/2006-05-16_paraiba.htm
