Gemstones & Pearls/Gemology
Cranking Up the Heat
There's a lot more work to be done before beryllium-diffused sapphires can be easily identified
Its dawn in downtown Bangkok, but Ted Themelis is already conducting heat-treatment experiments on sapphire samples from around the world. His routine: mostly sleepless nights and scorching tropical days that include treating gems, examining them, classifying his findings, exchanging e-mail with colleagues around the world and cataloging his observations.
This type of schedule allowed Themelis to collect the information he needed to publish in February the first major study on changing the color of sapphire through beryllium diffusion. A richly illustrated, detailed book on the process, Beryllium-Treated Rubies and Sapphires is selling briskly in gemological circles. It describes the process and includes a collection of before-and-after photos, photomicrography and other clues to identifying beryllium diffusion. It was in the research stage seven months, then written, photographed, designed by my son Angelo and printed in four days, Themelis says.
Its no surprise the tightly wound Themelis is an authority on corundum, the mineral of which rubies and sapphires are varieties. For decades, he and Angelo have trekked the Far East and Africa, scouring sources and studying, buying trading and treating corundum.
These days, hes anchored to the beryllium issue that has intrigued the gemological community for 17 months. The issue came to light when the trade discovered some corundum that had been sold as natural padparascha sapphires owed their highly valued pink-orange color to treatment rather than nature. The discovery slowed sales of all sapphires because the treatment can affect up to 90% of them, including blues, and because the treatment cant be identified readily. For him, the mystery is just unfolding. Thats why sleeping is just a waste of time, he says.
At the time of writing there are no [standard] gemological tests available that will identify beryllium-treated corundum, only indicative inclusion characteristics, says Themelis (see Corundum Conundrum, Professional Jeweler, March 2002, p. 32, for these inclusion descriptions). In cases where beryllium diffusion is not obvious, sophisticated, time-consuming, expensive and somewhat destructive positive identification is available through two tests: secondary ion mass spectroscopy and laser ablation inductively coupled plasma mass spectroscopy, which detect beryllium content in corundum (natural-color sapphires contain no beryllium).
New studies conducted by the American Gem Trade Association and Dr. John Emmett of Crystal Chemistry, Brush Prairie, WA, in conjunction with the Gemological Institute of America, will result in an article on beryllium diffusion in a future issue of Gems & Gemology, GIAs quarterly publication. Secrets to identifying beryllium-diffused sapphires and rubies inexpensively and quickly might lie in further spectroscopic analysis or in the determination of very faint electrical conductivity present in beryllium-diffused sapphires.
But Emmett believes sophisticated laboratories need to become even more sophisticated. They really need to purchase SIMS testing machines. The price tag is not cheap, ranging from $500,000 to $750,000, depending on whether theyre purchased used or new, he says. But these are great analytical machines because they can detect and measure atoms in parts per million, something most labs technology doesnt allow. Beryllium diffusion is hard to detect because of its infinitesimal quantities as low as 15 parts per million, or one beryllium atom for every 15,000 aluminum atoms.
Emmett notes this kind of detection could help solve other gemological mysteries also, including the exact constitution of fracture fillings in rubies, what happens to geuda sapphires or the recrystallization of Mong-Hsu rubies from Myanmar after heating. He also acknowledges the importance of standard gemological testing in gaining an overall understanding of whats happened to beryllium-diffused sapphires and rubies. I recommend jewelers and gemologists read Ted Themelis new book for that very reason, says Emmett.
Themelis predicts the next frontier for gemologists will be new forms of diffusion using other additives, as well as a variety of other treatments.
For Themelis, thats likely to mean many more steamy days and sleepless nights ahead.
by Robert Weldon, G.G.
|The Name Game
Define diffusion treatment. Corundum expert Ted Themelis says many retailers and consumers misunderstand the term, and he suggests using less technical nomenclature for the commercial end of the trade. He has worked on a description he says represents the product fairly and that dealers, retailers and consumers can all understand. He proposes sapphires treated with any form of diffusion be described as:
Gem Species: Natural Corundum.
Enhancement: Enhanced by heat.
Treatment Classification: Heat treated (with additives).*
*Comments: Additive compounds including beryllium-bearing substances may have been used in the heating process. The resulting color may have been distributed in a non-uniform pattern, and color may be removed if the stone is damaged or after repolishing.
Critics say the word diffusion should never be left out of disclosure. In the U.S., the American Gem Trade Association has steadfastly held onto the description diffusion (bulk/lattice) treatment for the past year. But in recent weeks, there has been a softening over use of the word bulk as part of the definition. Its a generally misunderstood word in this context, so in meeting with lab directors from around the world, there is a leaning toward dropping bulk and just saying lattice diffusion, says Ken Scarratt, director of the AGTA Gemological Testing Center in New York City. Stay tuned.
||Ted Themelis works on a new project with his top/bottom-loading vertical muffle, high-temperature electric furnace in Bangkok, Thailand.