By Richard W. Hughes (Palagems.Com)
In 1997, a colleague and I submitted a paper to a gem industry trade association for publication in their newsletter. The article discussed a specialized heating technique used to treat over 95% of the ruby traded in the world market. To our great surprise, the editor rejected the article, deeming it “too controversial.” In the words of the official, “many mainstream journalists read our publication and if they got hold of this story it could mean big trouble.”
Just what treatment could possibly be so nefarious that it could not even be discussed in the polite pages of an industry publication? I speak of the use of fluxes to “heal” open fractures in ruby. Since that time, the process has been a point of discussion at dozens of meetings between both traders and gemologists. While some today have a solid knowledge of flux healing, it is surprising that so many traders and even gemologists do not grasp the treatment method and its impact on a gem. The following is designed to shine a bit of light into this dark industry corner.
The use of fluxes during heat treatment is not a recent invention. In the early 1980’s, while I was directing Bangkok’s Asian Institute of Gemological Sciences (AIGS), a number of Burmese rubies with unusual characteristics were brought into our lab for testing. Based on the inclusions, it was clear they originated from the Mogok mines. But unlike the classic Mogok stones, these rubies showed numerous thick wispy fingerprints. There was also evidence of high-temperature heat treatment.
Someone had apparently been cooking Mogok ruby. It was equally clear that the heat-treatment process was healing fractures, either pre-existing, or those produced by the stresses of the heat treatment itself.
For a brief period, we saw many such stones. Then, just as suddenly as they appeared, they were gone.
Fill ‘er up - Surface repair (glass infilling)
A year later a group of rubies came into the AIGS lab with suspicious characteristics. In this case, large surface cavities had been filled with glass (Hughes, 1984). One of these stones is shown in Figure 3. This process became known as “surface repair” or “glass-infilling.” Its purpose was to fill unsightly surface cavities, thus allowing larger stones to be cut. The first of these stones had huge glass-filled cavities. When customers balked, the gems largely disappeared from the market. But the idea was now in the minds of both dealers and gemologists - glass might be used to fill surface cavities.
Desperately seeking glass
In the years that followed, gemologists were zealous in seeking out glass-filled surface cavities, often to the point of flagging tiny amounts resulting from inclusions that had melted during heat treatment, fillings that had absolutely no impact on the weight or appearance of a gem. This situation left dealers scratching their heads. Stones with “accidental” glass fillings of no consequence were being lumped together with other stones featuring surface cavities deliberately filled with glass to add weight or hide naturals. Eventually at AIGS, we came to an arrangement. When we found accidental fillings, if the owner was agreeable we simply removed the glass with hydrofluoric acid, thus allowing us to issue a cer twithout the nasty “glass filling” comments.
As for the gems with deliberate glass fillings, owners wanted no part in removing them since gaping cavities would remain. Such stones were clearly flagged on ID reports and buyers rejected them. Thus it was not long before they mostly disappeared from the market.
Enter Mong Hsu
In the early 1990’s, a major discovery of ruby was made in Burma’s Shan State, at Mong Hsu (pronounced ‘Maing Shu’ by the Shan; ‘Mong Shu’ by the Burmese), northeast of the provincial capital of Taunggyi. So important were these discoveries that - within just a few years - Mong Hsu rubies constituted over 95% of the faceted ruby entering world markets. This remains true to this day.
Mong Hsu ruby before (left) and after HPHT treatment
There are two major problems. The first is dense silk/particle clouds and a strong purplish color, making most stones look like low-grade, cloudy rhodolite garnet. This is mainly due to the crystal’s unusual blue cores. Ordinary heat-treatment removes the blue, as well as removing silk, making the final product a rich, clear red. The market generally accepts such heated stones without a quibble.
Most Mong Hsu stones come out of the ground in a heavily fractured state. But Thai burners are nothing if not ingenious. For years some had used fluxes in conjunction with their burning. This pow chemie (‘heating with chemicals’) was supposedly done for a variety of reasons. According to some, fluxes produced a shine on the surface of the rough after cooking, making the color look better. Others said it helped create a desired furnace atmosphere. Some even believed that it helped prevent thermal shock during heating (an idea which has since been discredited).
When I examined my first parcel of Mong Hsu ruby, the coin dropped. Those Mogok rubies with their twisted drippy fingerprints from so many years before were early examples of flux-assisted fracture healing. And with Mong Hsu rubies, burners were taking that treatment to the next level. Unfortunately, this information never quite filtered down to the dealer on the street. Small bits of glassy flux residue were often found on the surfaces of finished stones. Since the amounts involved were tiny, many assumed the glass to be an accidental by-product of heat treatment. The reality was far different - the tiny flux remnants were but droppings on the trail of a massive treatment beast - one the gem trade has yet to fully confront. It was this secret that the gem industry was so afraid to bring out in the open.
These are strong words, but carefully chosen. In the late 1990s, the emerald trade was rocked by non-disclosure of clarity enhancements. Incredibly, what has been done to ruby over the past decade is far more radical, and yet has completely slipped under the radar.
One major factor that separates fine gems from inferior is clarity. Heavily fractured stones are common in nature, but clean gems are decidedly not. What is being done today with Mong Hsu rubies is the removal of fractures. How often is this treatment applied with respect to Mong Hsu rubies? So often that over the past decade I can recall seeing only a handful of stones from that deposit which had open fractures. And yet virtually every piece of Mong Hsu rough is riddled with open fractures prior to treatment.
Dealing with it
With the explosion of Mong Hsu ruby onto the market, it became obvious that traditional lab nomenclature was not equipped to deal with this treatment. Thus in 1997, while directing the colored stone identification department of the Los Angeles office of European Gem Labs (EGL), I developed terminology to honestly describe this treatment. The idea was to provide the customer with an estimate of how this treatment had impacted the gem. A number of labs (AGTA, GIA, Gubelin, SSEF, GIT, and GAAJ) have now adopted elements of this nomenclature and refined its application. The author’s suggested nomenclature is as follows and it can (and should) be applied to other treatments:
• Treatment type: Indications of heating + flux healing of fractures
• Extent: Minor/moderate/significant number of flux-healed fractures
• Stability: Stable/unstable under normal wearing conditions
• Prevalence: Never/rarely/commonly/usually/always found in the market
We have a superior treatment for Mong Hsu ruby, one that is actually more stable than ordinary oiling. So why worry?
First, purchasers of ruby are not accustomed to buying heavily fractured stones. Unlike emerald, clean rubies do exist in nature. Second, the process can also be accomplished with heat alone. If such stones are deemed acceptable without further comment, what happens when only heat is used?
In the end, the flux-healing treatment should be looked at for what it is, a radical reconfiguration of the clarity characteristics of a gemstone. If lumped together with simple heat treatment, it will completely redraw the map not just for ruby, but also potentially for the entire gemstone industry.
We must stop kidding ourselves. In the eyes of the consumer, the high-temperature heating and flux healing/impregnation of a ruby is not the same as simply cutting and polishing it. No amount of explaining will make it so. A gem that only requires polishing to reveal its beauty is far more rare than something that needs both polishing and ordinary heating. And that is rarer than the Mong Hsu ruby, which needs polishing, high-temperature heating and flux-fracture healing. The market should reflect these realities in its descriptions of goods and, most importantly, in it’s pricing. Gems and jewelry are luxuries. They compete against a number of different goods and services. If we don’t start getting our act together, that retail customer may stop buying more than just Mong Hsu rubies.