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A Dark Hour for Gemology: The Diffusion Debacle

by David Federman

A Mozambique “Paraiba” Tourmaline in the immersion cell.

A close-up showing the red-filled tubes with color diffusing into the stone.

If he were charging for his lecture at the Hotel Arizona on Friday, February 6th on the use of “grain boundary diffusion” with feldspar, tourmaline, garnet and topaz, it would be the hottest ticket in town at Tucson 2009. Robert James, founder of the International School of Gemology, San Antonio, Texas, has spent tens of thousands of dollars and 14 months conclusively proving that variations of the chemical process once known as “bulk diffusion” used to turn plentiful Madagascar corundum into so-called “padparadscha” sapphire are now being used on numerous other gems—most of them, sadly, subject to intensive TV and Internet marketing. In their defense, sellers of these gems can produce reams of identification reports from leading gem labs stating the color of their artificially beautified gems is natural or produced by acceptable enhancement methods.

The establishment goofed. Nothing could be farther from the truth. Tragically, these altered gems defy categorization as natural or even legitimately enhanced. They fall outside all existing gemological classifications into a new order of mutant minerals that have less authenticity as gems than synthetics. We say this because these mutant minerals owe their color and appearance to the forced infusion of foreign trace elements and transition metals not normally associated in any meaningful way with these gems. In some cases where high-temperature heating isn’t enough, irradiation is performed to molest the molecular structure of the rough and create openings that allow for insertion of colorizing atoms.

In other words, bulk diffusion allows treaters to reduce all gems to mere substrate matter than can be manipulated for any ends they want.

But, wait, the crisis deepens. What is called “bulk diffusion” is used not simply to alter appearance and produce desirable hues. It is done to fool gemologists into thinking that stones possess certain trace elements in enough quantities to allow them to be misrepresented and sold under prestigious value-adding names such as “sunstone” and “Paraiba tourmaline.”

Besides creating a nomenclature nightmare that has befuddled the colored stone industry, rampant bulk diffusion has embarrassed the gemological community—first, for failing to detect the degree to which it is practiced and, second, for ridiculing those who voiced suspicions about the magnitude of the problem. No wonder Robert James, who first voiced and then proved the awful truth, finds himself in the far too familiar persona non grata position of the whistle-blower who is shunned by the industry he exposes and who, by dint of being the messenger, becomes the fall guy for his message. Colored Stone conducted a lengthy interview with James to get a preview of what he would say in Tucson, its implications for the industry and his recommendations for reform.

A pink tourmaline that did not take well to treatment. Consequently it was cut it en-cabochon. About the innards: the lighter grey material is polish compound; the pink is true color, with remnants of the diffusion material that filled pre-existing fissures which bulged out during heating.

Colored Stone: Robert, there are plenty of dart boards around these days with your face on it. People tell us you are scandalizing the colored stone industry at the very worst possible time—during a recession when everyone is down on their luck. Do you see yourself as the publicity-seeking avenging angel you are made out to be?

Robert James: You make it seem like we’re in a Batman movie and I’m a diabolical gemologist out to wreck the jewelry industry. People forget that we began our investigations when times were good and there were fortunes to be made selling diffused andesine as natural and diffused African tourmaline as “Paraiba.” Believe me when I say that ISG had no intention of hurting the industry; we just wanted to see if there was deception and, if so, try to stop it.

CS: Look, we’re not accusing you of anything except, maybe, due diligence. We’ve had our own long-simmering suspicions about the expanded use of diffusion to lots of gems beyond corundum. As bad, we’ve had equally long-simmering suspicions about Thailand’s role as a culprit country in what we now call “the diffusion debacle.” Just what have you discovered, how did you do so, and what does it mean for gemologists and gem dealers alike?

RJ: Once we proved that diffusion had been performed on mostly yellow feldspars to turn them red and green to resemble Oregon sunstone, we turned our attention to blue-green tourmalines which were allowed to be called ‘Paraiba’ if they showed the presence of copper—no matter how miniscule the traces of that metal.

A Mozambique “Paraiba” tourmaline that did not treat properly. Notice that the deep blue color is in the center of the stone.	The same stone from the side. Note that the blue color is splotchy and zoned. Also the red material that we have been seeing.

CS: Excuse my interruption. But are you suggesting that diffusion was used to insert copper into stones in order to earn them labeling as ‘Paraiba’?

RJ: We are now, but we weren’t when we began our investigation 14 months ago. We have tested bona fide African tourmaline that is supposedly non-Cuprian [copper-bearing] and found that it has been force-fed enough copper to make it artificially Cuprian. This finding showed us what diffusion can do. It can be used to create chemical forgeries of natural stones. That is why this new alchemical capability must be revealed and steps taken to either curb its import or correctly label it.

Calling in the Heavy Artillery of Lab Analysis

CS: You have been accused of shooting from the mouth and hip, drawing correct conclusions from incorrect assumptions. Will your research into tourmaline satisfy your critics who say your science is faulty?

RJ: You know, we offered to work with all the major labs and some of the most renowned scientists in this industry. But no one accepted our invitation. So we went to one of the best material science research labs in America and performed—at our own expense—the very same kinds of advanced analytical tests that GIA or AGTA would have used if they followed in our footsteps: Raman microscope scans, X-Ray fluorescence [XRF], secondary ion mass spectrometry [SIMS] and laser ablation inductively coupled mass spectrometry [LA-ICP-MS]. What’s more, we had every PH.D. who conducted these tests write reports on their methods, findings and test results. All of that research has been combed through and combined into our Tucson presentation.

An immersion cell shows how the diffusion material did not permeate uniformly, leaving a tell-tale color zone pattern in each stone. This is a classic signature for diffusion-treated gemstones.

CS: Where did you get the rough and polished stones used for testing?

RJ: ISG has students in most of the tourmaline-producing countries. So we arranged through them to buy bona fide rough direct from the mines as well as stones cut in their countries. Then we bought tourmalines from Thailand where we have long suspected diffusion has become part of gem-processing. Sure enough, our tests proved that virtually all tourmalines from Thailand had been reduced to a common denominator material regardless of origin.

CS: Your many on-line articles about your research suggest you cast a wider dragnet than just tourmaline. What other stones did you work with and why?

RJ: We started out buying material sold as Paraiba tourmaline from TV networks and Internet sellers. But when we were sold liddicoatite tourmaline as elbaite tourmaline, and these stones exhibited tell-tale signs of diffusion, we broadened our investigation to other gems that seemed likely candidates for this process. Among the most likely were tsavorite garnets that we were seeing in colors and sizes not seen in years. To our amazement and horror, we found plenty of grossular garnets were being converted into tsavorites. Again, the identity change was produced using diffusion. Eventually, we found diffusion in topaz, also—colorless material turned gloriously imperial.

Blue color zoning in a Mozambique “Paraiba” tourmaline showing where the diffusion material permeated the stone in mottled fashion.	Another blue tourmaline rough crystal showing grain boundary diffusion.

Diffusion: Routine Chemical Assault

CS: Just how does diffusion work its dark art?

RJ: The process is generally called “grain-boundary diffusion,” although some object to this term. Imagine the molecular structure of a gem. In the case of andesine, the first stone we investigated, atoms don’t create a perfect mesh. So it is into those tubular spaces in the lattice that diffusion can force colorizing trace elements. If you use irradiation, those pathways can be widened even further, thus permitting infusion of even more trace elements. In the case of Mozambique tourmaline, we have found amounts of copper and manganese in the interior of stones twice as great as the amounts at the surface. This is due to the crystals being treated in the rough as well as the fact that the orientation changes with each faceted stone. In some gems we have routinely found chemical impurities so concentrated that they form a kind of clay.

CS: Why didn’t any of the labs that have been identifying this material find this?

RJ: The history of treatment detection is a series of lucky breaks—nothing more systematic than that. Strangely, we see lots of references to “grain boundary diffusion” in the gemological literature, but the discussion is always confined to corundum. I don’t know why people didn’t realize the multi-species applicability of diffusion early on. Maybe they did. I can’t speculate. All I can say is that once you understand the process, as well as the people who developed it, you would conclude no species is safe from tampering—and take the appropriate steps.

Look carefully at the photo on the left taken from the side of the crystal. The center and right photos are taken from the top. You can see the blue diffusion material used on the stone. We are finding that the diffusion is done down the “C” axis, which you can see in these images.

No Need for Panic

CS: If experienced labs missed the extent to which diffusion is practiced, how can dealers or jewelers feel safe selling colored stones?

RJ: Once labs catch on, they usually do a very good job of catching up. From then on, ferreting out suspect stones from suspect species is fairly easy. In addition, we believe there are simple in-store gemological tests that can be devised to help jewelers make reliable identifications of diffusion.

CS: Will you be introducing them at your seminar in Tucson?

RJ: We hope to. But at the very least, we’ll be able to sketch out the identification techniques we’re pursuing.

CS: Diffusion creates a whole new category of gemstone beyond natural, enhanced and synthetic. Do we need to overhaul the industry’s gemstone enhancement manual to accommodate what we call “X-gems?”

RJ: That’s only the beginning. We need to better define what is meant by disclosure and get the trade to adopt strict, greatly expanded disclosure rules for dealers, jewelers and even appraisers—anyone who interfaces with the public. One purpose of our seminar is to get gemological and ethical reform going—and going strong. They say the future is now, but in this case the future arrived a decade ago, maybe sooner. Diffusion is now so widespread that we’ve been living in the past without even knowing it.

Robert James is the founder of the International School of Gemology (ISG) in San Antonio, Texas. His seminar on diffusion will be held during the Tucson Show at the Hotel Arizona on Friday, February 6th, starting at 3:00pm (no registration necessary). For more details, contact ISG at 210-877-5816 or by email at ISG@SchoolofGemology.com.

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