Dr. Henry H. Hänni, director of the Swiss Gemmological Institute (SSEF) in Basel, Switzerland, has performed the gemological equivalent of a hat trick this month: He’s a three-time newsmaker, having developed a quick beryllium diffusion identification, solved the mystery of the new Sri Lankan blues, and taken top honors with AGA’s Bonanno Award for Excellence.
Beryllium ID. “Due to a new and highly sensitive beryllium detection system,” Hänni claims SSEF now can offer a fast and safe detection of beryllium-diffusion-treated corundum, and at low cost. “We are also prepared to handle large quantities of yellow, and orange sapphires in a very short time,” writes Hänni.
SSEF will demonstrate its new service at jewelry shows in New York, Bangkok, and Tokyo during on-site testing in 2004. Hänni reports that this new testing method will differentiate older yellow sapphires, padparadschas, and rubies from the new diffusion-treated material. For more information, call SSEF at (41-61) 262 06 40 or e-mail: gemlab@ssef.ch.
News on the blues. The new Sri Lankan blue sapphires that recently hit the market have an unusual color concentration and a lack of color zoning, characteristics that led the major gem laboratories to suspect beryllium enhancement. But the labs have yet to find any trace elements of beryllium. “Analyses carried out at SSEF showed that there was no foreign element found with elemental analysis (LA ICPMS – Laser Ablation),” writes Hänni. Instead, what they discovered was more elementary than elemental.
It’s been known since at least the early 1980s that a reducing (oxygen-free) atmosphere is necessary to develop blue in Geuda sapphire, writes Hänni. (See, e.g., Nassau, Gemstone Enhancement, 1982.) A reducing atmosphere in a furnace is created either by burning fuel (a process that removes free oxygen) or by flooding the furnace with a neutral gas such as nitrogen. The oxygen-free atmosphere allows for iron (Fe) and titanium (Ti) as Fe2+ /Ti4+ . This is the main reason for the blue color in Sri Lankan heated sapphires.
But in an oxidizing atmosphere, notes Hänni, the blue color is diminishing: Fe2+ changes to Fe3+, and the iron titanium (Fe/Ti) charge transfer is destroyed.
“We can now imagine a similar process of oxidation at the end of the treatment of the blue sapphires with colorless rim,” writes Hänni. “We think that toward the end of the heating process the pump for protective gas is stopped and some air [containing oxygen] enters the furnace.” This would effectively decolorize a surface-related layer of the stone, as color fading occurs in the last phase of the treatment.
Hänni believes that once this information reaches the Sri Lankan heat treaters, they will alter their operation and avoid the decolorization of surface-related zones.
SSEF will describe these sapphires as “heated,” he says. “We do not see evidence of diffusion of a foreign element as in the case of the beryllium-treated orange and yellow sapphires.”
Other labs are still uncertain. According to the latest GIA and AGTA combined press release, the two labs can’t yet account for the new sapphire’s appearance: “Testing for a number of light elements and for more typical chemical elements that have been diffused into corundum has not, to date, revealed any foreign elements that can be designated as causing the unusual color zoning.”
After instrumental measurement and visual observation of hundreds of stones, they also believe that synthetic overgrowth can be ruled out as the cause of the color zoning. But both labs say that while the exact cause of the unusual zoning is not yet known, aggressive research will provide conclusive answers within the next few months.
Both AGTA and GIA note on their laboratory reports that these stones show indications of heating, but they follow that with a comment that further research is necessary to fully characterize them.
The Bonanno Award. Hänni also received this year’s Antonio C. Bonanno Award for Excellence in Gemology from The Accredited Gemologists Association (AGA).
This year’s nominees included Allan Jobbins, director of the Gemmological Association of Great Britain (Gem-A); Branko Deljanin, EGL-USA’s director of Canadian operations; Kenneth Scarratt, director of the American Gem Trade Association’s Gemological Testing Center in New York; and William Hanneman, of Hanneman Gemological Instruments.
For more information about the AGA, or to submit a candidate for the 2005 Antonio C. Bonanno Award, call Antoinette Bonanno Matlins at (802) 457-5145 or e-mail: amatlins@aol.com.