An exceptional emerald crystal:
This month’s feature on the R. W. Wise website is an exceptional Colombian emerald crystal. It was found at the La Pita Mine, part of a complex of mines of the same name that I visited during my last buying trip to Colombia.
Historically gems of this quality were found at the old mines like Muzo and El Chivor. Chivor was appropriated by Spanish conquistadors in 1550; Muzo was conquered some five years later. Chivor is closed but Muzo continues to produce, making it one of the world’s oldest productive gem mines. La Pita, located in the same general area, was discovered in the early 1990s and began production soon after (see GemWise Colombian Emerald.
Colombian emeralds range from a slightly yellowish green to slightly bluish medium dark verdant green. This crystal exhibits the pure verdant slightly bluish secondary hue coupled with a high degree of transparency that characterizes the finest Colombian gems. Crystal specimens of this quality are almost never available in the United States. Generally they are cut into high value faceted gems in Bogotá. (pictured right: One of several possible setting designs, a pendant to show off this fabulous crystal)
This crystal has been polished on all faces but is otherwise just as nature made it. The crystal weighs 6.86 carats and its dimensions are 15.5 x 7.3mm. For more information, visit our website: www.rwwise.com.
Copper Diffusion; Is it Gemology’s Worst Nightmare, Part II
This is my second of two posts on Copper diffusion. My first post focused on andesine. This second post will focus on a recent study by Robert James of The International School of Gemology (ISG) alleging that a method has been found to diffuse copper into tourmaline. First a bit of background:
The process, variously called lattice and deep diffusion is commonly used to “inject” Beryllium ions into sapphire was an accidental discovery. It came to world attention in the mid 1990s when a gem burner in Chanthaburi, Thailand experimented with a flux containing Beryllium to facilitate the high temperature heat treatment of pink sapphire and discovered that the flux altered the color to an attractive pink-orange, a rare color known as padparadscha.
Once discovered, this treatment set off a firestorm of controversy within the gem trade. Unlike simple heat treatment, this new process involved the addition of an outside element namely Beryllium. The process has since been used to alter the color of yellow and blue sapphire. The issue is important because gems that are diffused sell for dramatically less than heat enhanced gems and finer qualities of the newly discovered Mozambique cuprian (copper colored) tourmaline sell for thousands of dollars per carat.
The latest ISG study focuses on the analysis of foreign materials found on the surface of rough and in hollow growth tubes that are a characteristic inclusion in tourmaline, specifically cuprian (copper colored) tourmaline from Mozambique. James ran a series of Raman scans on several samples of Mozambique tourmaline both from inside the tubes and “crusted up” on the exterior of the rough and concludes that the scans prove that the material is copper. “How” Mr. James asks, “did this tourmaline get what appear to be multiple tubes filled with solid copper compound?”
The first question, is it really copper? The stains in James’ image closely resemble the typical iron-stained rough that I have seen all over the world. (Pictured left a tourmaline embedded in iron stained quartz, Alta Ligona mining field, Mozambique. (Photo: Farook Hashimi) Note the color of the staining. It certainly resembles the color of the included material shown in James’ images. Pictured right shows the blue-green color of weathered copper ore.)
In Part I of his study James shows a cuprian stone next to an iron skillet and asks: “What do this cast iron skillet and this Mozambique “ Paraiba ” Tourmaline have in common? Answer: They share an exact match Raman Scan as seen below. Why? The answer may surprise you. Don’t miss the continuation of this report in next week’s edition.”
In Part II he does not provide the promised answer. Like a new penny, polished copper does have a color similar to the material shown in the growth tubes but consider that same penny after it has been left out in the rain, what color is it, blue-green! This raises an obvious question. If this is copper and it has been exposed to air why isn’t it green? Dr. Lore Kieffert, Director of the AGTA lab makes a similar point. She believes that the stains may be iron. In a 2006 study of cuprian tourmaline published in Gems & Gemology, the authors note the same stains and speculate that the material is iron though unfortunately they did not test the material.
At the Chicago World of Gems Conference I had an opportunity to speak with John Koivula, Chief Gemologist with GIA. I asked Koivula about James’ conclusions. Koivula expressed doubt that copper could be successfully defused into tourmaline. The problem, Koivula pointed out has to do with the host material. Sapphire melts at a very high temperature (2,000C), andesine at over 1400C, however, “ at about 1,000C tourmaline breaks down and turns into a rather ugly crusty material that when tested with x-ray diffraction closely resembled mullite.” It is no longer tourmaline. “I won’t say”, Koivula said with an ironic smile, “that it (copper diffusion in tourmaline) is impossible. I have been proven wrong in the past, I just think it unlikely.”
I had previously received reports that gem alchemists in Thailand had perfected a method to diffuse copper into non-cuprian material and that some of this material had been mis-identified as cuprian by an unnamed Asian lab. I asked Koivula if non-cuprian tourmaline could be misidentified as cuprian by advanced instruments. Surprisingly, Koivula’s answer was “yes”! He too mentioned the growth tubes that are characteristic of Mozambique cuprian tourmaline, he said. “If a stone were polished on a copper lap, which is fairly common, sufficient copper residues could be forced down these tubes to mimic a copper reaction sufficient to fool an EDXRF which is the least sensitive test.” Laser Ablation, SIMS or LIBS are far more sensitive, he noted. Apparently it does not take much to adulterate the samples: “You can rub a copper penny across a tourmaline and produce the same result.” Koivula said. This provides one possible explanation of how non-cuprian tourmaline could be mistaken for cuprian and is one obvious explanation for James’ finding native copper in the hollow tubes of his samples.
Bear Williams a dealer (Bear Essentials) and a certified gemologist raised another issue: According to Williams the diffusion of Beryllium, an element with a relatively small atomic mass (9.012182 amu) is one thing, diffusing copper an element with a relatively large mass (63.546 amu) is quite another. “It would have to be done atom by atom.” Williams said. Koivula concurs describing the time that would be necessary to copper diffuse tourmaline at temperatures below the melting point of copper (1084.62 °C) as “glacial.” I got a similar answer from Christopher Smith, Chief Gemologist at The American Gemological Lab (AGL) who points out that it is not necessary to melt copper but he did characterize the time required to diffuse copper into tourmaline below the point where tourmaline turns into aquarium gravel, as requiring a “geological time frame”?
Another simple and obvious explanation for Mr. James findings suggests itself. Cuprian equals copper, so cuprian tourmaline obviously formed in an environment with copper. Although the area currently being mined in Mozambique is a secondary deposit, the presence of copper on the surface of the rough and inside inclusions should not be surprising. Koivula, who has seen James’ images, is not persuaded by his conclusions. “Copper in growth tubes does not prove diffusion” he said.
I put some of these questions to Robert James. In an email he responded that the copper scan in the tourmaline is identical to that of the andesine and that proves copper diffusion. Further, “If that much copper were present as syngenetic inclusions, the entire tourmaline would be bursting with copper, not as a trace element. And you cannot get that much copper to 100% permeate the stone without some kind of artificial diffusion.”
This argument is not persuasive. How much copper? Is James talking about the copper in the inclusions or the percentage of copper present in the crystal? If the former, as discussed, the mere presence of copper outside the crystal structure does not prove diffusion into the crystal structure. His conclusion is, at best, pure speculation and hardly proves his point. If the latter, where has he demonstrated that a tourmaline crystal will absorb elements relative to the concentration of those elements in the growth environment? This too is quite a speculative leap.
Tourmaline has a complex chemical structure and cuprian tourmaline regardless of source (Brazil, Nigeria and Mozambique) contains barely more than trace amounts of copper. In a previous report James states that Brazilian Paraiba tourmaline is 4% copper. This fact, he says, is very important. Where does this figure come from? In a comprehensive study of cuprian tourmaline from known sources published (Spring 2006) in Gems & Gemology, the authors tested samples from all sources and report a widely variable percentage of copper in Brazilian Paraiba cuprian tourmaline (0.21-2.01wt%) and similar variations in the Mozambique material: (0.26-1.19w%). In no case does it approach 4%. Were tourmaline to absorb high levels of copper it would no longer be tourmaline. Crystals take from the environment they need to form.
Rush to Judgment:
James has promised another installment soon once more “advanced” Laser Ablation and SEM scans on the material is completed. Both Koivula and Emmett concur that these tests are necessary. The question is why didn’t he have these “advanced” tests performed before he made his charges public? In the words of Richard Hughes; “Before you break somebody’s rice bowl you better make sure you have the facts.”
Some applaud James’ work and point out that he was right about andesine. However, tourmaline is a separate issue and after interviewing a number of prominent researchers, I can find a couple who admire James’ luck, but not one who will endorse his science. Chris Smith of American Gemological Labs puts it succinctly: “James raises interesting points, but the way in which he reaches his conclusions don’t add up.”
Initially I congratulated James on his research. I am, like many professionals, frustrated that the time taken to research these issues tends to work to the benefit of the scam artists. By the time science proves what’s been done, honest dealers are left with the unenviable task of explaining the whole mess to their clients. Unfortunately, good research does take time. I have had conversations with some of the world’s leading research gemologists. Most have read the latest ISG report and some applaud James’ willingness to take on the issue, but I could not find one who supports his methodology or the quality of his research. After examining his arguments and speaking to a number of experts, it seems to me that James’ conclusions simply do not follow from his premises. He may be right, as he was, at least in part, on andesine, but his claim to have proved copper diffusion in tourmaline from the evidence he presents is overblown and making his charges before he completes his own advanced testing is irresponsible.
This is not, as one of James supporter has suggested; simply a “squabble over research methods.” Poor methods produce incorrect results. I have distilled out all I have learned and raised some basic questions and presented an alternate scenario that explains some of James’ findings. I have not disproved James’ claims; only questioned them and pointed out that the evidence he has thus far is a beginning, but it is a long way from proof. James has promised Part III as soon as advanced tests on his samples are completed. Perhaps he will provide all the answers at that time.
Some see James’ lack of support from the gemological community as evidence of a deep, dark conspiracy, of the gemology trade closing ranks. There is no question that James is out there all alone. None of the established gem labs seem to be taking these allegations seriously. He has offered to work with at least one established laboratory and his offer was ignored. Still, I do not believe that there is any sort of conspiracy. Most of these researchers work for separate competing organizations. As Dr. Emmett pointed out in the last post, no one is paying for basic research.
It does trouble me that anyone with the temerity to question (and some who agree) with James claims is required to run a gauntlet of personal attacks, initiated either by James or by one of his chorus of surrogates.
“…criticism is a mode of autobiography.” Oscar Wilde
In response to my first post on this topic Mr. James made the following statement:
“Dr. John L. Emmett is doing nothing but riding the ISG coat tails. We had the truth on this andesine issue back in April. And suddenly Dr. Emmett has an epiphany on andesine in September? Please!”
I find James’ unprovoked attack on Dr. Emmett inexplicable. A distinguished scientist agrees with his findings (though not necessarily his research) and James attacks him. I suggest that Dr. Emmett’s conclusions are not an epiphany; rather they are the result of months of careful and tedious research. James further states:
“Dr. Emmett is simply trying to cash in on our work.”
Cash in”? Is Robert James talking about research or publicity? Dr Emmett is retired. He is unpaid. He works in his basement. He has no business to “cash in” on. Others have since added to the din.
I understand that some of the members of the chorus are former true believers who bought the overblown claims of TV pitchmen. The lesson that should have been learned from that experience is to cast a critical eye over everything you are told, not blindly exchange one set of beliefs for another. There are good people and bad people in the gem business. Don’t judge us all by a single standard. None of us are heroes; we all have feet of clay. Stay tuned.
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