Myanmar's Other Ruby
This is part of an article on heat treatment of ruby taken from a scientific publication published by the Gemological Institute of America.

Mogok is not the only active ruby mining area in Burma. Stones from the Mong Hsu (pronounced "Maing Shu") deposit, located northeast of Taunggyi in myanmar's Shan State, first began appearing in Bangkok in mid-1992. Since then they have completely dominated the world's ruby trade in sizes of less than 3 carats. While Myanmar has taken steps to control the trade of Mong Hsu ruby, much of it manages, nevertheless, to make its way straight to the northern Thai border town of Mae Sai.

The Mae Sai ruby market is located in Ruby Lane, where upwards of 500 people engage in selling Mong Hsu ruby, mostly rough with a few cut stones making an appearance. Perhaps 50 kilograms of rough on a given day is displayed in the market; no doubt much more is stored and viewed under guard behind closed doors.

Before heat treatment, the Mong Hsu ruby is certainly an ugly duckling; most pieces look like sub-cabochon-grade rhodolite garnet. This is mainly due to the crystal's unusual blue cores. Heat treatment removes the blue, as well as any silk, leaving the final product a rich, clear red.

The Mong Hsu ruby's biggest liability is the practice of glass infilling in surface cavities and fractures. Kenneth Scarratt, Lab Director at the Asian Institute for geological Sciences, confirms that virtually every stone over one carat that is sent for testing comes back with the objectionable comments that evidence of glass filling has been found. Some dealers lose so much money due to glass filling that they stop buying Mong Hsu ruby altogether.

It is common practice to use borax (borosilicate) during burning. Many Thai oven use fossil fuels, such as diesel, or even charcoal. Such fuels create a reducing atmosphere that adds, rather than subtracts, blue. Borax is said to help neutralize the atmosphere created by fossil fuels.

A simple solution is to use an electric oven- addition of certain gases can produce the desired atmosphere even with the stones burned dry and without chemicals such as borax added to the crucible. But electric oven are more expensive and old habits die hard; thus the prevalence of cheap oven and glass-filled rubies.

There are a few treaters who burn dry, but if the quantity of glass-filled rubies is any indication, they are the exception. Thus traders are left to their own devices - either trying to remove the glass by soaking the gems in hydrofluoric acid (HF), or, when that fails, trying to convince gemologists and jewelers that glass infilling is an "acceptable trade practice."

Meanwhile, consumer demand continues to fuel the trade in Mong Hsu ruby. According to Bangkok dealer Mark Smith, most Mong Hsu ruby weighs less than half a carat. Stones in the 1-1.5 carat retch up to $1,500 per carat.

In Thailand's Chanthaburi market, Mong Hsu rubies as large as five carats are occasionally seen, and Smith himself has purchased a couple of stones over three carats for $2,500-$3000 per carat.

This is from November/December 1996 Trade Journal Colored Stone

As they undergo enhancement, rubies are heated at temperatures as high as 2000 degrees Celsius and packing silica, aluminum, or borax. The first two substances have been widely rejected, but borax, used as a cleansing agent in glass manufacturing, has gained general market acceptance, primarily because it enhances the clarity of the stone by entering fissures and either masking or partially mending them.

An example of heated-treated ruby.
The dark violet color on the left
is the natural ruby.The light red
color on the right is the side that
has been heated.

The crux of the problem lies in the amount of residue contained in the stone. A lack of clear-cut classifications in the enhancement process has resulted in increasing dissatisfaction over the last two to three years among Japanese buyers, who were unwilling to purchase heat-treated gems that had undergone fracture filling. This dissatisfaction has snowballed into a growing lack of consumer confidence in Thai products in a market that commands 20 per cent of Thai gem exports.

Discussion of this matter at the most recent meeting between a delegation from the Japan Jewelry Association (JJA) and the Thai Gem and Jewelry Traders Association (TGJTA) in March 1996 failed to produce any real progress and instead left both sides adamantly defend their positions. "[The Japanese] don't want borax used, but we believe it helps the stone," said Thanan Maleesriprasert, manager of the TGJTA. "exports to Japan have fallen, but consumers must understand that all stones must be treated or there are no good colors. The Japanese are creating a problem because they want a stone that they cannot find, and when they realize this they'll come back to us," said Thanan at the meeting, championing the opinions of heat-treatment facility owners in Chanthaburi.

In contrast to the Japanese market, the report will probably not make a big difference to traders from the United States. According to Banker, the U>S> market is generally characterized by mass quantity and prices that the consumer assumes reflect the type of treatments that the stone has undergone.

The report from AIGS is considered by many the most positive step in the last three years to clarify market requirements. But although agreement on classification of heat treatments has been reached, the use of borax still pits the dealers against the buyers. Chanthaburi heat-treatment facilities owners, with vested interests in maintaining strong business ties with Japan, claim that even if borax were not used, they would have to use other chemicals which would produce other residues., and the issue would start again from square one.