Bangkok Gems & Jewellery Magazine


			Old issues	Vol. 18 No. 7 -- February 2005
				GIA ReleasesReport on Diamond Cut
				Reports on Lead Glass Filled Repaired Rubies

AIGS Reports on Lead Glass Filled Repaired Rubies

    In March 2004, the Gemmological Association of All Japan (GAAJ) issued an alert stating that it had encountered a ruby, which showed flash effect from fissures and fractures and that its analysis showed that the stone was impregnated with lead based glass. Following the GAAJ report, the AGTA, ICA, et al also conducted their studies and issued their reports. Thankfully this time, they did not accuse anyone of trying to cheat the consumer, mainly because this treatment is extremely easy to identify.

     The Asian Institute of Gemological Sciences (AIGS) also began its own round of testing and has subsequently released its report. The latest version of the report (version 03) written by AIGS Laboratory Director Vincent Pardieu was released on January 27, 2005. We present here an edited version of the report.

    "In November 2004, a large number of rubies having some uncommon features were brought for testing to the AIGS laboratory in Bangkok. For two months more than 200 of these rubies were analysed in the laboratory. Lead was detected in their fissures and cavities. Between September and December 2004, a total of 244 of these rubies ranging in size from 3-97 carats were examined at the AIGS laboratory including 12 stones over 25 carats.

		3 rubies found with "lead rich foreign substance filling in fissures and cavities" at AIGS laboratory.

Surprised by the large number of stones suddenly appearing on the Bangkok market, AIGS decided to give priority to the study of these stones and began to research this new product. Following several weeks of enquiry we found that the treatment was being performed at Chanthaburi, Thailand. At the end of December 2004, two gemmologists from AIGS visited the company that was applying the treatment. We were very surprised to learn that the treatment expert, Mr. Mahiton Thondisuk had been a student at the AIGS.

Mr. Mahiton Thondisuk explained to the AIGS gemmologists that this treatment was the result of five years of study in association with several Thai scientists from different universities in Thailand. The idea was to develop a glass compound suitable to "repair" fissures in rubies. "Beautiful natural stones for which human intervention is limited to cutting and polishing are very rare and extremely expensive", explained Mr. Mahiton Thondisuk. "There are many more low quality gemstones compared to the tiny amount of real gem quality stones so that if we can find a good way to repair them we can add them to the trade. In the beginning, I was not thinking that people would actually buy this product ...... but some people began to buy these stones...in fact, I don't really like to do this treatment but the market is looking for nice looking cheap stones."

Left to right : Andilamena rough rubies from Madagascar before treatment.

In fact, this treatment is not really a new development. The process was developed in 1982 by diamond cutter Zvi Yehuda from Ramat Gan to produce "Yehuda diamonds". The process used for fracture filling diamonds was quite common in the 1990's. Several companies were producing such stones at that time. Many studies were conducted and many articles about them are found in gemmological literature or on the internet. In the fall 1994 edition of Gems & Gemology an important study of these diamonds was presented. At about this same time, AIGS was developing some special radiographic instruments to detect lead glass filling in diamonds.

The fact is that lead glass filling of fissures is back and this treatment is now known in Thailand as "Paw Mai" (new heat treatment in Thai language). Most of the stones seen these days are believed to be mainly sent to Asian markets like China and India in which the conjunction of important gemstone traditions and the need for cheap gems has created a niche for this product. But these stones are known to have reached the USA and Europe. Mr. Mahiton Thondisuk says, "It is simple, if I give you the choice between two rubies at the same price: one synthetic grown in a factory and one grown in nature but "repaired" by human technology after being mined, which one will you choose? We are selling these stones at very good prices... Imagine how much a 20 carat heat-treated ruby would cost and compare that to one of our stones of equal beauty? We are so much cheaper".

This is an important point and in AIGS' opinion there is nothing wrong about treatments as long as the customer is provided with the correct information about the stone and the price is related to the real quality of the stone. The important thing is the proper disclosure of the nature of the stone. A very good point with these "repaired rubies" is that they don't currently present any real identification problems, which is a big difference when compared to the beryllium treatment issue. Identification of the lead glass "repaired rubies" is very easy for any laboratory that owns an EDXRF (Energy Dispersive X-Ray Fluorescence), but microscopic observation is in most cases enough for a gemmologist that has experience with these stones. Using EDXRF technology fne AfGS laboratory was able to find lead in all the stones studied. It is in our opinion the ideal instrument to provide a diagnostic result for any suspected stone.
		From left to right: Mr. Somkuon Plairahan, Ruby Expert; Mr. Vicent Pardieu, AIGS Laboratory Director; Mr. Mahiton Thondisuk, Master Burner.

An experienced gemmologist using a microscope and dark field illumination will be able to identify correctly the "repaired rubies" without any difficulty: Using dark field illumination, the lead-rich glass filled fissures will display blue/orange flashes. This observation can be easier under fibre optic illumination looking near parallel to the fissure. This is a very typical diagnostic feature that is similar to opticon in emeralds or lead glass in filled diamonds. With careful close up examination of the fissures an observer may also find gas bubbles or "exsolved platelets". Gas bubbles were found in many rubies filled with the simple lead glass. Some observers could be disturbed by the fact that the heat treatment temperature is not high compared with the temperature at which many stones are heated nowadays using gas furnaces. Many inclusions (rutile silk that is not completely dissolved at the lower temperature - Ed.) may still appear as "unheated" which could disturb an inexperienced observer.

Compared to emerald oiling or impregnation using resins, this current ruby treatment is probably more durable. Glass is more stable and its presence in a fissure will probably lower the probability that the fissure will expand. The fact that the fissures are closed with a lead rich glass is also probably improving the durability of the "repaired" gemstone, hut not as much as those fissures fillet with flux additives.

As long as these stones are properly disclosed and priced AIGS feels that these stones should find their place in the gem trade where large size and low prices are of prime importance.

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