Now, blue sapphires from Sri Lanka are raising more concerns about corundum identification. A statement from the American Gem Trade Association (AGTA) says, “During recent months, we at the AGTA Gemological Testing Center have observed that some blue sapphires reaching the U.S. market show indications that they are being treated by a new technique. Most of the gemstones observed range in size from 2 to 17 cts. Since these gemstones appear to be coming from Sri Lanka, the AGTA and Sri Lanka dealers and associations are working willingly and cooperatively together to determine the exact nature of the treatment.”
Sapphire producers in Sri Lanka have been trying to keep their market isolated from the problems that non-disclosure of beryllium treatments has caused the Thai sapphire industry. These new blues, however, are challenging the capabilities of the professional laboratories and are likely to cause major concerns for the entire blue sapphire industry.
The AGTA announcement describes one stone that showed “indications of heating” and “a pale blue to near-colorless layer closely following the girdle outline.” Other gemstones examined by AGTA showed “a much deeper rim of light blue surrounding a deep blue core. The interface between the core and the rim is undulating and delineated by a white line.”
Such characteristics are “easily observed when the gemstones are viewed immersed in methylene iodide and illuminated through a diffused light source,” says AGTA. “This makes it relatively easy to identify the gemstones when buying or sorting. In addition, similar characteristics have been observed in two rubies.”
Richard Hughes, an expert in sapphires at Pala International, Fallbrook, Calif., reiterates that “the major identifying feature of these stones is a blue core surrounded by a diffuse colorless or near-colorless skin.” He recommends using methylene iodide [di-iodomethane, 3.32 liquid] immersion “with a diffuse white plastic filter between the immersion cell and light source in the microscope.”
Hughes also notes that “all stones placed table down in an immersion cell will show some lightening of color at the girdle, since the stone is thinner at the girdle. But stones treated by this new process show a distinctive colorless rim that penetrates well into the gem, unlike the normal gradual lightening of color towards the girdle in untreated stones.”
If gem treaters recut the gems to remove the outer layer, it will be difficult for the labs to identify any enhancement other than heat. An even bigger worry is that the research testing method that has identified beryllium-treated padparadschas won’t work with the new blues.
“SIMS analyses carried out on several gemstones have not, thus far, revealed a presence of beryllium,” says AGTA. “Further analyses are presently being carried out in an effort to fully characterize the process.
Ken Scarratt, director of the AGTA laboratory, will be adding more detailed information as it becomes available on the organization’s Web site. To see more images of the new blue treated sapphires, and to learn more about this enhancement, visit www.agta.org. If you have information that might be of help, contact AGTA at (800) 972-1162, e-mail: info@agta.org.
In a separate but related article, the Gemological Institute of America’s Summer 2003 issue of Gems & Gemology includes a 50-page report on the new beryllium “lattice diffusion” treatment of corundum. According to the authors, “If we cannot develop a low-cost detection method, gem sapphire will become as common as blue topaz, supply will exceed demand, and prices will fall radically, damaging the entire trade.”
The article covers the original diffusion treatment, how heat affects inclusions, simple visual examinations to uncover evidence of high-temperature treatments, and the most sophisticated SIMS testing results. It’s also a wakeup call to the industry that treaters are using technology to outpace research gemologists’ capabilities to identify these new enhancements.
The paper also warns the trade that identifying enhancements will not get any easier and that if the trade doesn’t receive the cooperation of the people doing the enhancements, the sapphire trade will suffer. “Technology will always advance, and attempting to slow or stop it is as rewarding as trying to sweep back the sea with a broom,” say the authors. “However, as a community we need to come together to understand each new process as it is developed, and bring it to the gem market with full disclosure, allowing an informed marketplace to determine value.”
The study was written by Kenneth Scarratt, AGTA Gem Testing Center; Shane F. McClure and Thomas Moses, GIA Gem Laboratory; Troy R. Douthit, Crystal Chemistry, Los Altos, Calif.; Robert Kane, Fine Gems International, Helena, Mont.; Richard Hughes, Pala International, Fallbrook, Calif.; Owen Bordelon, gemological equipment manufacturer and gemstone supplier, New Orleans; Dr. Steve Novak, Dynamic SIMS Services, East Windsor, N.J.; and Dr. John Emmett, Crystal Chemistry in Brush Prairie, Wash.
An editorial titled “Disclose or Be Disclosed,” written by GIA president Bill Boyajian, calls the lattice diffusion treatment “the most serious threat to corundum and the colored stone market in the past quarter century.”