Contributions to Gemology No.9 - Chemical variations in multicolored "Paraíba"-type tourmalines from Brazil and Mozambique: implications for origin and authenticity determination
Adolf Peretti; Detlef Günther; Eric Reusser; Kathrin Hametner; Willy Peter Bieri
Gemresearch Swisslab AG (2009)
In Collection
#97
10*
Science
Gemology, Tourmaline, Brazil, Mozambique, Nigeria
Hardcover 9783952335994
English
When copper bearing tourmalines were found in the state of Paraíba in Brazil in 1989, they intrigued by their “neon”-blue color and soon became known as “Paraíba” tourmalines in the trade. These tourmalines have become one of the most valuable and sought-after gems, comparable to rubies and sapphires. In the last couple of years an unprecedented tourmaline boom has occurred due to the discovery of new copper-bearing tourmaline deposits. Originally found in the state of Paraíba (Brazil). New mines were subsequently encountered in Rio Grande do Norte in Brazil, as well as in Nigeria and in Mozambique.
The market and the laboratories were divided on whether to call the newly discovered neon-blue colored tourmalines “cuprian-elbaites” or “Paraíba tourmaline” regardless of origin. While this controversy resulted in a lawsuit, currently dropped, the debate on Paraíba tourmalines moved in a new direction. A suggestion emerged on the Internet and in a seminar at the 2009 Tucson Gem & Mineral Show that Paraíba tourmaline may have been the product of diffusion-treatment.
In 2006 GRS has announced it was able to distinguish “Cuprian-Elbaites” from different origins on the basis of chemical compositions. GRS and the laboratory of Inorganic Chemistry and Applied Biochemistry of the ETH Zurich publish the results of this extenive research in this specialized research report. Although some chemical data on the origin of Paraíba tourmalines have been published elsewhere, this study combines the capabilities of several different analytical techniques, concentrating on the analysis of element variations within single crystals of copper-bearing tourmalines, which contain pronounced color zoning and extensive chemical variability. It was possible to solve two different issues at the same time: (1) establish criteria for origin determination of “Paraíba tourmalines” and (2) characterize natural chemical zoning patterns within these tourmalines. This research should prevent confusion between natural “chemical fingerprints” and those resulting from man-made treatment techniques.
Product Details
Edition 2nd
Series Contributions to Gemology
Issue No. 9
No. of Pages 77
Height x Width 305 x 217  mm
Personal Details
Read It Yes
Store Rubin & Son
Location A 3
Purchase Price 42.00 CHF
Purchase Date février 2013
Condition First hand
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