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GIA Issues Lab Alert on Pink Tubes in Tourmaline

Jan 28, 2009 5:41 PM   By Press Release
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PRESS RELEASE


CARLSBAD, Calif. Jan. 28, 2009 – Samples of blue to blue-green, copper-bearing tourmaline containing surface-reaching growth tubes surrounded by intense pink “sleeves” have recently been seen in the trade. In response to rumors of possible diffusion treatment, John I. Koivula, Kevin Nagle, Andy Shen and Philip Owens, GIA Laboratory staff members, carefully examined several of these tourmalines over the past year. Based on this examination, the GIA team determined that the pink zones were produced by fluids containing naturally occurring radioactive material.

In all instances where pink coloration was observed, the growth features surrounded by the pink color reached the surface of the stones. In cases where growth tubes did not reach the surface, no pink color was seen. When these pink zones were viewed down their length, the color was observed to bleed out into the surrounding tourmaline host, becoming weaker until it gradually faded away. If post-growth matter in the tube created a blockage, coloration occurred only to that point. Additionally, any cracks extending from or between the growth tubes also showed a pink color.

Radiation is known to produce a pink-to-red color in tourmaline. The coloration of surface-reaching features in tourmaline by invading radioactive fluids has not been reported in the literature; however, there have been reports of both smoky quartz and green diamonds with coloration that was caused by exposure to naturally occurring radioactive fluids. This mechanism explains all the observations of pink and red in these tourmalines. “Since radiation is the cause of pink color in tourmaline, the presence of these features should not be attributed to any type of intentional diffusion, but rather to the influx of radioactive fluids in their post-growth environment,” said John I. Koivula, GIA Laboratory chief gemologist and one of the study’s authors.

All the copper-bearing tourmaline samples with this feature observed thus far have come from Mozambique. This suggests that this type of inclusion feature may be characteristic of that locality.

The presence of the pink zones in these otherwise blue to blue-green gems also provides proof that the host tourmalines were not heat treated, since the temperature needed to treat copper-bearing Mozambique material exceeds the published stable temperature for pink-to-red color in tourmaline.

An article by Koivula and his colleagues detailing these observations will appear in the Spring 2009 issue of GIA’s Gems & Gemology, due out in April. To subscribe, visit www.gia.edu/gemsandgemology or call toll-free 800.421.7250, ext. 7142. Outside the U.S. and Canada, call 760.603.4000, ext. 7142.


About GIA:
 
An independent nonprofit organization, the Gemological Institute of America (GIA) is recognized as the world's foremost authority in gemology. Established in 1931, GIA has translated its expert knowledge into the most respected gemological education available. Early in the 1950s, GIA invented the famous Four Cs of Color, Cut, Clarity and Carat Weight.  In 1953, the Institute created the International Diamond Grading System™ which, today, is recognized by virtually every professional jeweler in the world.

Through research, education, gemological laboratory services, and instrument development, the Institute is dedicated to ensuring the public trust in gems and jewelry by upholding the highest standards of integrity, academics, science, and professionalism. GIA can be found on the web at www.gia.edu . Media queries contact: Laura Simanton 760.603.4112 or Jessica Sachariason, 760.603.4197.

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