Diffusion Confusion: More on Treated ‘Padparadschas’

Last month we reported on a study conducted by the American Gem Trade Association Gem Testing Center that found that certain sapphires coming out of Bangkok had been diffusion-treated to make them look like padparadschas. The lab reports that "the orange component of the apparent overall color of this stone is due to artificial surface diffusion." AGTA also notes that repolishing may remove the diffused orange color. (See " 'Padparadschas' Are Diffusion Treated," JCK March 2002, p. 24.) The Gemological Institute of America's Gem Trade Laboratory, with help from Richard Hughes at Pala International, examined close to 50 of these gems. According to this study, while researchers could not confirm introduction of a trace element, they did find a color layer that takes on the shape of the faceted or preformed gem. Dr. John Emmett, president of Crystal Chemistry in Brush Prairie, Wash., su

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