November 18, 2003
More Treated Blue Sapphires Showing Up Daily
Dealers' inventories contain more treated blue sapphires exhibiting an unusual color distribution than once thought, according to preliminary research. The treatment itself is still a mystery. "The number of stones that show these characteristics increases daily," says a research team comprised of American Gem Trade Association Gemological Testing Center and Gemological Institute of America staffers and advisors. "During searches through small and selected portions of stocks held by five dealers, 35 stones were identified." The stones examined so far have ranged from 2-17 carats.
AGTA GTC says it will not issue reports on the new sapphires, which show a colorless or near-colorless outer rim, until the process used to treat them has been fully described by the investigators. Instead, clients who submit stones will receive an interim letter describing the problem and stating that a report will be issued at a later date.
The team investigating the new treatment has found these sapphires exhibit an unusual blue core surrounded by colorless to near-colorless outer rims. This identification feature is easily visible when the stone is immersed in methylene iodide and viewed against a white diffused light source. The outer rims of these stones fluoresce a red color when exposed to long-wave ultraviolet light and viewed in a dark room. Additionally, the researchers found the cores of color do not necessarily conform to the faceted stone, leading them to believe these stones are treated in the rough.
AGTA GTC will handle reports for other sapphires with a business-as-usual-approach: "Clearly, sapphires that show no indications of heating are not treated by this process and we will continue to issue reports on these gemstones," says the lab. "We shall also continue to issue reports on those sapphires that have been heated, but do not show these easily observable unique characteristics."
AGTA GTC says it's implementing a batch-testing service for dealers to help them separate these stones from natural and other heat-treated stones. The fee for the batch testing will be $300 per hour, and a 30-minute minimum is required.
The team researching the new treatment is composed of John Emmett, George Rossman, Kenneth Scarratt, Garry DuToit, Donna Beaton, Tom Moses, Shane McClure, John Koivula, Christopher Smith, Mary Johnson, Matthew Hall, Wuyi Wang and James Shigley.
by Robert Weldon, G.G.