Interview conducted by Cynthia Unninayar

A large segment of the jewellery industry today involves coloured gemstones. Along with the growing use of these gems comes an increasing number of ways to enhance nature’s creations. To learn more about buying gems and gemstone jewellery with confidence, we took the opportunity, on a recent trip to Bangkok, to visit the very modern and well-equipped Gem and Jewelry Institute of Thailand (Public Organization). Established in 1998 under the visionary leadership of Professor Sakda Siripant, the GIT is accredited by the World Jewellery Confederation (CIBJO) and is a member of the Laboratory Manual Harmonization Committee (LMHC), made up of the world’s five leading gem laboratories. Services include the analysis of gemstones and metals with related certificates, as well as research and training, among other gem-related activities. We sat down with the GIT Director, Mrs. Wilawan Atichat, to learn more about issues relating to gemstone treatments.

Professor Sakda Siripant, founder and former director of GIT, and Mrs. Wilawan Atichat, current director.

CIJTC: Not too long ago, a major department store in the USA was called on the carpet for selling jewellery with lead-filled rubies, a treatment that was not disclosed to the consumer. We occasionally hear of other examples of gems that are ‘enhanced’ in some way. How important is gem treatment in the industry today?

Wilawan Atichat: Since time immemorial, gemstones have played a major role in jewellery. And, also since early times, people have come up with ways to change or enhance the quality of gems. More recently, they have created synthetic stones. What is important, however, is not whether a stone has been treated or created, but whether the customer is made aware of this information, and can thus make an informed buying decision.

CIJTC: What is the most common treatment?

WA: Centuries ago, people discovered that by applying heat to a gemstone, they could change its colour and clarity. Using a charcoal fire, for example, they could transform a drab stone into a beautiful one. As with all other fields involving technology, many advances have been made in gem enhancements. Today, ovens and techniques are more sophisticated. Most gemstones are heat-treated, and this is a commonly acceptable practice as long as the treatment is disclosed. For example, less than one in 1,000 sapphires is un-heated, making these gems very rare and thus very valuable.

Faceted Mozambique rubies, showing three unheated stones (back row) and two heated gems (front row).

CIJTC: What are the gemstones that are most commonly heat-treated?

WA: There are many, but among the most common is amethyst. Heating pale amethyst will turn it into the popular yellow-orange citrine [Editor’s Note: see the article In Search of Amethyst and Citrine in the Winter 2012 issue of CIJ Trends & Colours]. Tanzanite is heated to change it into the beautiful purplish-blue shades. Sapphires are heated to lighten or intensify their colour and to improve uniformity. Heat will also improve or change the colours of such gems as rubies, morganite, kunzite, zircon, and tourmaline. Aquamarine is subjected to heat to remove the greenish undertones to obtain a bluer stone. These are but a few examples.

A sample of unheated Paraiba tourmaline (above) and the same sample after heating , showing the change to the prized characteristic neon blue colour.

CIJTC: How can you tell if the stone is heated? WA: Heat modifies the natural inclusions found in gemstones, including gas or fluid inclusions. In the laboratory, our gemmologists examine and study the inclusions, and can tell how the stone has been heat-treated.

CIJTC: If heating is common and acceptable, what are some of other treatments that are less acceptable or not acceptable at all?

WA: People are always coming up with creative ways to modify gems to make them more attractive. These include irradiation, dyeing, fracture filling, and diffusion, among others. Some of these enhancements are stable, but others are not, which is tantamount to cheating the customer. There is also the issue of synthetic stones.

An example of a purported Haüyne gem (left) that turned out to be blue glass, as seen from analysis of the microscopic synthetic Wollastonite crystals (right).

CIJTC: What are some of the major ‘trends’ in gemstone treatment other than heating?

WA: We have all heard lately about labs receiving synthetic diamonds as natural stones, and the same thing happens with coloured stones. One of the ‘hottest’ trends today is synthetic corundum being sold as natural ruby. We are even seeing synthetic rubies that are filled with lead glass! Other concerns involve artificial samples that people attempt to pass off as rare natural gems. Recently, our lab saw two purported samples of Haüyne, a rare and beautiful blue mineral that was discovered in 1807 by René Hauy. As it turned out, they were nothing more than blue glass.

Microscopic view of light reflecting off a fissure filled with lead-glass in a ruby.

CIJTC: You mention rubies filled with lead glass. Can you elaborate?

WA: Rubies that contain fractures or fissures can be ‘repaired’ by filling these fractures and cavities with glass mixed with lead or bismuth to increase the refractive index of glass to make it closer to that of ruby. As a result, fractures or cavities can be disguised, which improves both clarity and colour. This method was invented in about 2004 for improving the low-quality and highly-fractured corundum, especially rubies and orangey-pink sapphires, which come mainly from localities in East Africa. This method is not new, but has been used in diamond treatment, the so-called ‘Yehuda’ treatment, as well as in emeralds treated with resins. A major problem, however, with these types of treatments is that the glass filler is not stable and can easily deteriorate, thus finally ruining the appearance of the stone. It is important therefore that the customer be informed about this treatment and its stability or lack of stability. If customers want to purchase these stones, they must be made aware of this.

Natural sapphires (left) and those heated with beryllium to change their colour (right).

CIJTC: You earlier mentioned diffusion as a treatment. What is beryllium diffusion and how and when is it used?

WA: Diffusion is a controversial treatment. It consists of heating a gemstone in contact with certain chemical elements. The high temperatures allow those elements to penetrate the gem, where they can influence the colour or even produce a star effect. In the case of sapphires treated with beryllium, the result is a yellow colour, or a reduction of blue colour, depending on the makeup of the stone itself. Since beryllium is a tiny atom, it can easily be diffused into the sapphire, sometimes penetrating the entire stone.

Colourful faceted sapphires that have undergone beryllium treatment.

CIJTC: Last year, there was much talk in the industry about irradiation of gemstones, raising fears relating to blue topaz. Is this still a ‘hot’ topic?

WA: Gemstones can be subject to radiation to enhance and deepen their colors. They can be irradiated in a nuclear reactor (neutron bombardment), an accelerator (electron bombardment), or by exposure to gamma rays in a cobalt irradiator. The most commonly treated stone is topaz, which becomes blue as a result of the exposure to radiation plus annealing. There have been some fears among consumers about this treatment, especially in relation to blue topaz. In fact, nearly every blue topaz sold today has been irradiated. In nature, topaz is usually colourless or very light blue. When subjected to radiation, its crystal structure is modified in the way it absorbs the frequencies of light, and this then changes its colour. The U.S. Nuclear Regulatory Commission regulates the initial distribution of gemstones (most notably, blue topaz) that have been irradiated in a nuclear reactor or accelerator to enhance their colours. Confusion still persists in the marketplace about the commission’s role in the regulation of these stones and their safety. The NRC believes that irradiated gemstones currently on the market are safe and it has not requested jewellers to remove them.

Using the world’s most advanced gem instruments, GIT provides a variety of testing and certification services for both consumers and the trade, as well as other related services, including testing the purity of precious metals. The lab’s highly experienced gemmologists also have a strong background in mineralogy and geology. At right front, Mrs. Wilawan Atichat, GIT’s director, examines a gemstone.

CIJTC: What are the most common gems you analyze in the lab, and also some of the more unusual stones?

WA: Being in Thailand, the most common gems the GIT is asked to analyze are rubies and sapphires, but we see really all types. In terms of unusual gems, the lab occasionally receives stones that are claimed to be Pallasitic peridot. They are greenish-yellow gems from outer space that are found in Pallasites, a very rare type of stony-iron meteorite, which contains the semi-precious gemstone peridot (olivine) embedded in an iron-nickel matrix. We are able to distinguish them from terrestrial, and less expensive, peridot by comparing their specific gravity and trace-element content, such as manganese and nickel.

CIJTC: Does GIT ever double-check samples that have been tested by other labs that the owner is still concerned about?

WA: Yes, this happens on occasion. Just a few weeks ago, we received two gems to verify the results, which had previously been certified by another lab as natural rubies. Our analysis, however, showed the two stones to be, in fact, synthetic.

CIJTC: With all the equipment and techniques for analyzing gemstones, how could the other lab have made such a significant error?

WA: I cannot comment on why it happened at the other lab, but to ensure that mistakes don’t happen at GIT, each sample is analyzed independently by at least three technicians, and the results are then compared.

I would like to conclude by saying that most gemstones traded in the market today are enhanced in some fashion. But, without treatment, the world would not have enough beautiful gems to go around. Enhanced gemstones offer a less-expensive alternative for consumers and, in some cases, provide colours that do not exist in nature. There is nothing inherently wrong or illegal about selling enhanced gems as long as the enhancement is fully disclosed to the consumer at the point of sale. As I mentioned, some enhancements are stable and are commonly accepted practices. Others are not stable and should be avoided. It is therefore important that customers, whether retailers or consumers, purchase gems and jewellery from trusted dealers. When in doubt, especially if the stone is valuable, they can always ask for a certificate from a respected laboratory.

www.git.or.th