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Questions About Treated Sapphires, Thailand

Questions About Treated
Sapphires from Thailand
(updated 18 September 2003)

Note: Since late in 2001, treated sapphires from Thailand have created a great deal of controversy (see ‘The Skin Game’ and ‘Understanding the New Treated Pink-Orange Sapphires’ for full details).

As of the current writing, the evidence is overwhelming that such stones owe their color to a form of outside-in diffusion of coloring agents.

In the summer of 2003, the GIA published a major new study on beryllium diffusion of ruby and sapphire. This is currently the most complete study to date on these stones, and is a landmark paper for the cause of color in corundum and gems in general.

  • Beryllium diffusion of ruby and sapphire by John L. Emmett, Kenneth Scarratt, Shane F. McClure, Thomas Moses, Troy R. Douthit, Richard Hughes, Steven Novak, James E. Shigley, Wuyi Wang, Owen Bordelon and Robert E. Kane, Gems & Gemology, Summer 2003, pp. 84–135.

The above paper confirms what has been strongly suspected since late January of 2002, namely that the outside-in diffusion of light elements (primarily beryllium) produces the color changes seen in these treated stones.

This process is basically the same as that used with surface diffusion treated blue sapphires in the past, but with different chemicals. Both the AGTA and GIA labs are now labeling this treatment process “lattice diffusion” (previously termed ‘bulk’ diffusion) and that information will be clearly listed on their identification reports.

Over the past years, a number of questions have arisen regarding this treatment. The following are answers to many of these questions.

What is the color range of goods produced by this process?
This treatment involves outside-in diffusion of light-element coloring agents to create trapped-hole color centers. These color centers produce a yellow color. Applying this treatment to a near-colorless or green stone turns it yellow. The same treatment applied to a pink stone turns it orange, while a purplish red stone (ruby) becomes a purer red.

It has also been demonstrated that the process may produce a lightening of the color of dark blue sapphires. Such stones have blue cores with colorless rims and are being encountered more and more frequently. Elements beyond beryllium may be involved and intensive investigations are currently underway at major gem labs.


It was reported in early 2002 that such stones owe their color to a change in the valence state of iron already in the stone. Is this true?
Reports to this effect were issued by a couple labs. It is now generally understood that these reports were flawed.

Subtraction of before and after spectra suggest that Fe is not playing a major part in the coloration of these stones. This fact has been confirmed in laboratory experiments by John Emmett and Swarovski, both of which independently found that diffusion of beryllium produced colors identical to what we have seen in these gems.

It has been reported that “internal migration” of elements already in the gem is responsible for the color changes. Is this true?
This theory was proposed by one gemologist (Bangkok Post, 2 July, 2002 and 18 Sept. 2002). To the best of our knowledge, no gemological laboratory outside of Thailand has adopted this nomenclature.

While the elements originally in the gem no doubt affect the success of the treatment, even dealers and gemologists in Thailand now admit that the color of these stones results from outside-in (‘lattice’) diffusion of beryllium. In other words, the external migration of beryllium into the gem is the key to this treatment, rather than the internal movement of atoms already there. Beryllium is an element not normally found in corundum in the amounts detected in these treated stones.
bulk diffusion, beryllium diffusion, treated sapphire, diffusion-treated sapphireThe latest study of John Emmett and Troy Douthit (5 Sept. 2002) involved diffusion of beryllium into high-purity synthetic colorless sapphire. The result was a brown to orange color, with absorption features identical to those found in the treated stones from Thailand. What this shows is that diffused beryllium is mainly responsible for these color changes, rather than any internal migration, as suggested by Perreti. These experiments also discredit the “catalyst” theory recently proposed by another gemologist. To put it succinctly, beryllium has been proven to be the main colorant, not a modifier, not a catalyst.


Thai burners claim they add nothing to these stones during the cooking. Is this true?
Statements in this regard are quite contradictory. In one breath Thai burners have been quoted as saying that they add nothing, but in the next some admit to adding fluxes and even chrysoberyl (Colored Stone, July/Aug. 2002). It is our belief that both fluxes and chrysoberyl would qualify as “additives.” The chemical formula of chrysoberyl is BeAl2O4. Be is the chemical symbol for beryllium. Chemical analyses of these treated stones have now proven beyond doubt that beryllium is being added to these stones from outside.



Thai burners/dealers point to the fact that stones react differently even when burned together as proof that nothing is added. Is this true?
In our opinion, no. The current theories on cause of color in these gems suggest the light element (usually beryllium) added during the treatment reacts with elements already in the gem to produce the final color. Different combinations of internal chemistry will thus react differently. But the light element added is key to success. Without the outside-in “lattice” diffusion of this light element, this treatment would not produce the results it does.


It has been suggested that, since the added color of some of these stones penetrates the gems entirely, they do not meet the traditional definition of “surface (‘lattice’ or ‘bulk’) diffusion.” Is this true?
Again, in our opinion, no. The traditional meaning of surface diffusion had more to do with the fact that colorants are being introduced through the surface of a gem, rather than simply that the color layer is restricted to the surface regions. The important difference between lattice diffusion (surface diffusion) and other forms of heat treatment is not that the color lies at the surface, but that coloring agents are artificially introduced into the gem from outside. This outside-in diffusion of coloring agents is the key distinguishing characteristic of the lattice-diffusion process.


It has been suggested that, since “traditional” corundum heat treatment involves diffusion, that these stones should be considered the same. Is this true?
Again, in our opinion, no. “Traditional” in terms of corundum heat treatment was previously defined and agreed to by the world's gemological labs and trade associations as “heat only.” These agreements included Thai gem trade associations and labs. Scientifically speaking, such “heat only” actually involved diffusion of hydrogen. This is not a new discovery, and has been understood for well over a decade. But when these stones first entered the market in the late-1970’s, this was not understood, and so dealers were sold these goods unknowingly. Thus a special exemption was made for them.

Certain parties in Thailand now ask that a special exemption also be made for their beryllium-diffused goods. But if special nomenclature exemptions are possible every time a new treatment appears, the current system, which has taken years of tedious meetings to put together, will quickly become a useless swamp of special interests. The world gem trade/gemological community has been hostile to the idea of a beryllium exemption, in large part because the warnings went out so quickly that most dealers abroad did not get stuck with the goods. Thus they were free to make an unbiased judgment because they did not have a stake in the outcome. In other words, they were free to choose between doing the right thing and the selfish thing.

After January 2001, beryllium diffused goods have mostly been “buyer beware,” an idea that is well understood in Thailand. The fact that some dealers in Thailand have continued to trade these goods, knowing the potential risks, is their business. But ignorance is no longer a valid defense.


It has been suggested that there are vast differences between the blue (titanium-based) lattice diffusion of the past and the new yellow (beryllium-based) lattice diffusion of today. Is this true?
Not really. Both treatments involve diffusion of a foreign element into the gem to produce changes in color. Whether or not a gem is considered lattice diffusion treated has nothing to do with the type of element being diffused into a material, nor the efficiency of the process.


How can gems treated by this process be identified?
In many cases, gems treated by this process can be identified by immersion in 3.32 liquid, which reveals a yellow-orange layer at and just beneath the surface of the gem. But in other cases, the color may penetrate entirely through the gem. Gemologists around the world are currently working to develop detection methods for all stones treated by this process.


beryllium treated sapphire
No, this gem does not come from the “trillion” mine, but is a Madagascar pink sapphire with an orange color rim created by beryllium lattice diffusion. The gem is immersed in di-iodomethane. Note that recutting such stones will produce a loss of the orange color. Photo: R.W. Hughes

Some treaters/dealers claim that these treatments are stable and merely finish the job that nature started. Is this true?
While color stability is an important issue, it is not the only issue. Synthetic corundums all have completely stable color, but no one would suggest that they could be sold as natural on that basis. Similarly, the basic ingredients of sapphire (aluminum and oxygen) all have the potential to become sapphire. There is no question that humans have the ability to improve upon nature. That is not an issue.

Virtually any gem can today be produced in a laboratory in bigger and better qualities than that found in nature. Buyers today willingly pay more for natural stones because they value the rarity and “naturalness” of natural stones. If this were not the case, then treaters should have no fear about full disclosure of treatments. The fact that treaters are often shy to fully disclose such treatments is clear evidence that such disclosures are important in the decision-making process of consumers.


It has been suggested that because some of these stones are unidentifiable except by advanced techniques, that they should be allowed to be sold as "enhanced,” rather than “treated.” Is this true?
The fact that something is difficult to identify has nothing to do with how it is categorized. We expect identification techniques to improve as gemologists become more familiar with the material. But even if identification remains difficult, it would not change the disclosure requirements.


It has been suggested in the Thai press that foreign dealers’ objections to these stones are merely an attempt to steal Thai trade secrets. Is this true?
This has nothing to do with trade secrets. In much of the world, it is considered fraud to sell a product without fully disclosing any information that might affect the value of the product. For example, in Thailand and elsewhere, it is considered fraud to sell a Rolex watch that is not made by Rolex. It doesn't matter that in the copy the parts are all the same, or even that the copy keeps time just as well as the Rolex. When a buyer buys a Rolex, they expect it to be a genuine Rolex and not a copy.

Foreign buyers are not asking to know the exact recipes for such treatments, but only the general methods. If chemicals are being inserted (‘lattice diffused’) into a gem to produce color changes that mimic nature, buyers must be informed of this. If sellers wish to sell into most foreign markets, they will have to disclose this to buyers. If they do not wish to disclose such information, they must realize that many buyers will simply stop doing business with them.


It has been suggested in anonymous e-mails and press articles from Thailand that the AGTA has attempted to extort $500,000 from the Thai gem trade as a result of this treatment. Is this true?
No, it is not. AGTA president Richard Greenwood has called that statement: “…a complete misrepresentation.

Greenwood says that the $500,000 in question was actually an AGTA fundraising effort to pay for research into these gems. A letter requesting funds for the research on lattice diffusion-treated sapphires was sent to all AGTA members in the spring of 2002, he said. In addition, AGTA vice president Jeffrey Bilgore met with members of the Thai Gem and Jewelry Trade Association, presenting them with the letter written in English and Thai along with an outline of a three-step plan for assistance.

“It [the fundraising letter] was not directed at the Thai gem and jewelry community. It went to the entire AGTA membership. There has never been correspondence that strong-armed anybody,” Greenwood says. “We created a research fund. It would be helpful if the Thai Gem and Jewelry Trade Association helped with that effort.”

Discussions between board members of the AGTA and members of Thailand’s trade were held and it was suggested that, since this problem was one of Thailand’s making, that foreign labs and trade associations should not have to bear the cost of research alone. While it is difficult to put an exact dollar figure on that cost, there is no question that it is substantial, and as of this writing probably reaches into the hundreds of thousands of dollars when one factors in lost time, outside chemical analysis fees, travel costs, sample stone purchases, etc.

Unfortunately, there is a history of improper treatment disclosure from Thailand. During the late 1970’s, large quantities of heated sapphires were sold by Thai treaters without any disclosure that they had been high-temperature heat treated. In the 1980’s, rubies from Thailand were sold as simply heated, but it was later proven that they contained glass-filled surface cavities. Again, in the 1990’s, rubies from Thai ovens were sold as simply heated, and we now know that they have had their fractures artificially healed with fluxes. Unmasking all of the above takes time and money. It is unfair to expect the rest of the world to have to spend money time and time again to deal with problems created by improper disclosure by some treaters and traders in Thailand.


Did some labs originally issue “heat only” certificates on these stones?
It is possible and not even surprising that stones might be initially misidentified. As with any undertaking, mistakes are possible and there is a learning process. Since the labs are not treating the gems themselves, and since most gemologists do not have paranormal abilities, they cannot know everything immediately. Scientific work is based on careful weighing of evidence and open publication of the findings. If others have problems with the determinations, they are welcome to voice these opinions. But such opinions should stick to the evidence and also be openly published.


It has been reported that some stones contain recrystallized (synthetic) corundum on their surfaces. Is this true?
Yes, it is. Kenneth Scarratt of the AGTA lab has published a preliminary report on this question, and the GIA has added a further report. Such synthetic regrowths have been found most often in yellow stones treated by this lattice diffusion process. We should add that such melting and redeposition is also found in treated rubies from Möng Hsu, Burma. For more on this topic, see ‘Foreign Affairs’ by Richard Hughes.


It has been reported that the GIA's data is wrong. Is this true?
In the GIA's original report, an aluminum (Al) column was mistakenly included in one table, but that mistake in no way invalidated the other data obtained. Our current understanding is that all the data suggests that the yellow color of these stones is a result of outside-in diffusion of coloring agents (particularly beryllium). The latest data from the GIA (Summer 2003) can be downloaded at this link. Due to a lack of calibration standards, the initial numbers were slightly off. The fundamental supposition put forward by the AGTA and GIA labs has remained unchanged – namely that these stones were treated by a lattice-diffusion process involving outside-in diffusion of light elements. This fundamental information has been correct since January 2002, when the first SIMS analyses revealed elevated beryllium levels in the skins of treated stones. At the end of January 2002, these findings were presented to a major meeting of gemologists and traders from around the world, including many from Thailand.


It has been suggested that certain groups in the US are prejudiced against treated gems and that the AGTA/GIA labs are working on their behalf. Is this true?
The AGTA and GIA labs do not take any stand on such a question. Their mission is simply to provide accurate information regarding the presence or absence of any treatments on a given stone. In cases where a gem is found to be treated, they try to describe the type of treatment to the best of their abilities. It is up to the buyer/marketplace to determine what is or is not acceptable.

According to the AGTA enhancement guidelines, which AGTA members must follow and which have been in place for many years, all enhancements must be disclosed to the buyer at the time of sale. It is not enough to simply say a stone has been heated when something more has been done. The evidence in the case of these stones is clearly that something beyond ordinary heat treatment has taken place.


Some have suggested that terms like “lattice” or “bulk” diffusion are too technical to use with consumers. What would be a simple way to describe these stones?
Jewelers can simply tell their customers that these stones are artificially colored with beryllium. Such language is short, sweet and – most importantly – honest.


Further reading
Below we list in chronological order the major online references that discuss this treatment.

Note: Many of the articles that have appeared in the Bangkok Post on this subject are filled with inaccuracies and half-truths. We list them only for the record.


Related reading
Below are articles that discuss previous cases of diffusion treatment in Thailand, as well as other controversial Thai gem treatments.

  • Coldham, T. (2002) Orange sapphires or just lemons? Australian Gemmologist, Vol. 21, No. 7, pp. 288–293.
  • Coldham, T. (2003) The history and importance of heat treatment of Australian sapphire. Australian Gemmologist, Vol 21, No. 11, September.
  • Emmett, John L. and Douthit, Troy R. (1993) Heat treating the sapphires of Rock Creek, Montana. Gems & Gemology, Vol. 29, No. 4, pp. 250–272.
  • Hänni, Henry A. (2001) Beobachtungen an hitzegehandeltem Rubin mit künstlicher Rissheilung (Observations on heat-treated ruby with artificially healed fissures). Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 50, No. 3, pp. 123–136.
  • Hänni, H.A. and Pettke, T. (2002) Eine neue Diffusionsbehandlung liefert orangefarbene und gelbe Saphire (A new diffusion treatment supplies orange and yellow sapphires). Gemmologie: Zeitschrift der Deutschen Gemmolgigischen Gesellshaft, Vol. 51, No. 4, 2002, pp. 137–152.
  • Hughes, R.W. (1984) Surface repaired rubies. The Australian Gemmologist, Vol. 15, No. 8, pp. 279–280.
  • Hughes, R.W. (1987) Gem treatments: to disclose or not to disclose. Gemological Digest, Vol. 1, No. 1, pp. 1–2.
  • Hughes, R.W. (1988) Reappearance of surface-diffusion treated sapphires in Bangkok. ICA Lab Alert, No. 12, 2 pp.
  • Hughes, R.W. (1991) There’s a Rumble in the Jungle: The sapphire face-lift face-off saga. Gemological Digest, Vol. 3, No. 2, pp. 17–31.
  • Hughes, R.W. (1992) Devil’s Advocate: Vampire blues: deep-diffusion treated sapphires. JewelSiam, No. 3, May-June, pp. 83–86.
  • Hughes, R.W. and Galibert, O. (1998) Foreign affairs: Fracture healing/filling of Möng Hsu ruby. Australian Gemmologist, Vol. 20, No. 2, April–June, pp. 70–74.
  • Kane, R.E., Kammerling, R.C. et al. (1990) The identification of blue diffusion-treated sapphires. Gems & Gemology, Vol. 26, No. 2, Summer, pp. 115–133.
  • Schmetzer, K., Bosshart, G., Hänni, H. (1983) Naturally-colored and treated yellow and orange-brown sapphires. Journal of Gemmology, Vol. 18, No. 7, July, pp. 607–622.