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Traditionally a place for the meeting of the world's foremost gemological minds, Tucson this year played host to a number of conferences presenting the latest data on beryllium-diffused sapphire.

Currently, beryllium diffusion is only detectable in a standard gemological laboratory if the treatment caused color zoning — i.e., the rim of the stone is a different color from the core, which happens when the beryllium is not diffused all the way through the stone.

If the beryllium is diffused all the way through the stone, the whole gem will be a single color. In that case, labs need to test for the presence of beryllium in the molecular structure of the stone. Because it's such a light element, that requires advanced techniques like Secondary Ion Mass Spectrometry (SIMS), which can only be done in a specialized research laboratory. (Click here to learn more about SIMS). SIMS analysis is expensive — costing $500 to $600 to test a single spot on the stone — and the time and expense make it impractical for testing all but the priciest gems.

Current research is focused on finding more practical ways of identifying beryllium diffusion. Although beryllium diffusion produces some very distinctive yellow, orange, and orange-pink colors, gemologists warn that color alone is not enough to determine whether a stone has been treated.

"[Color] isn't an absolute," said Shane McClure, Vice-President of West Coast Identification Services at the Gemological Institute of America (GIA). He recounted the story of a sapphire that was sent in for testing that was a "brilliant orange-yellow," a color that looked like the result of beryllium diffusion. But when they sent it for SIMS testing, it came back beryllium-free.

Perhaps one of the most promising ways to spot the treatment is to look at inclusions in the gem.

"One of the results of this treatment is that the inclusions are obliterated totally," said Kenneth Scarratt of the American Gem Trade Association Gem Trade Laboratory. Gem treaters are now using furnaces that can heat stones to very high temperatures, which destroys many of the minerals or other inclusions in the stone. One example is zircon, which gemologists at the GIA have found actually melts and then recrystallizes inside the sapphire, forming a distinctive pattern.

John Emmett of Crystal Chemistry, an expert on heat-treatment of corundum, said that the process involves heating the stones to temperatures of 1750 to 1850 C for anywhere from 25 to 300 hours. The longer the stone is heated, the farther the beryllium will be diffused into the stone. A heating time of 300 hours will diffuse the beryllium 6.2 mm into the stone, enough to completely change the color of a 12.4-mm sapphire.

The treatment produces a wide range of results in different types of sapphire. Ted Themelis of Gemlab Inc., also an expert on heat-treating corundum, conducted beryllium-diffusion experiments on approximately 30,000 stones from various localities, as well as synthetics. In his book Beryllium-Treated Rubies and Sapphires, he described the results as follows:

Madagascan sapphire — Light yellowish turn to intense yellow-to-orange color; light pinkish turn to various shades of orange; light pinkish-yellow turn to pink-orange. Many other colors are produced, including yellow-green, blue, purple, and multi-colored varieties.

Songea (Tanzania) ruby and sapphire — Dark-red rubies turn red-orange; most blue, pink, and yellow-green sapphires turned yellow to yellow-orange.

Umba (Tanzania) ruby and sapphire — Lilac-purplish stones turn dark purple; bluish-green sapphires turn light yellow or lilac-purple. Orange-red rubies got a purplish tinge.

Tunduru (Tanzania) sapphire — Results were unpredictable. Generally, light purple to pink-purple stones turned a darker purple; colorless or light pink stones turned orange-pink; blue stones turned colorless, yellow-blue, or coppery orange.

Thai ruby and sapphire — Blue to blue-green sapphires showed little or no color improvement. Brown-red or purple-red rubies got redder, although that may have been due to the heat alone.

Montana sapphire — Pale blue-green sapphires turned yellow, yellow-orange, or orange.

Australian sapphire — Green-blue, yellow-blue, green-yellow, and colorless stones produced either yellow-green or medium to intense yellow stones. "By comparison, blue-green Australian sapphires produce better results than their Tanzanian counterparts."

Sri Lankan sapphire — Some milky-white stones turned blue with beryllium treatment; others turned intense orange. "The real impact of the beryllium process in treating geuda [white sapphire rough] is unknown, and additional experimentation is clearly needed. It is expected that most Sri Lankan sapphires will respond favorably to the beryllium treatment."

Mong Hsu (Myanmar, formerly Burma) ruby — Reddish-purple rubies took on a more purplish hue, and no clarity improvement was noted.

In Tucson, researchers also discussed the health risks of beryllium diffusion. Beryllium by itself and in powdery compounds is highly toxic, and is a controlled substance in many countries.

"There's quite a risk to treaters, and quite a high risk to people who recut the stones," said Emmett. Because the outer rim of the stone will contain the highest concentration of beryllium, repolishing the stones may release dust that is toxic when inhaled. People who wear the finished gems, however, are not at risk.

"Any time you have a beryllium compound, once it's in its solid form it's not hazardous," Emmett continued. "Once that gemstone is polished, it presents no hazard to the wearer."

Research into the identification of beryllium-diffused sapphires is continuing, and gemologists are hopeful that they will find a less expensive — and therefore more practical — way of identifying it soon. Until then, dealers remain wary of any stone that seems too good to be true.