GIA and AGTA Update Wording for New Corundum Treatment


May 30, 2002

GIA and AGTA Update Wording for New Corundum Treatment

The Gemological Institute of America Gem Trade Laboratory and American Gem Trade Association Gem Testing Center are changing their reporting policies for the new corundum treatments involving diffusion. The changes are based on the discussions and recommendations of May 4 and 5 meetings among labs and scientists, as well as on the research conducted to date by GIA and AGTA. These policies pertain mainly to yellow, orange, orange-pink and orange-red corundum. Blue sapphires are not significantly affected.

The new wording reflects two significant determinations regarding these treatments: they involve bulk diffusion, and an overgrowth of synthetic material has been observed on several stones. Each is explained below, and the new wording is in the group, variety and treatment comments as seen below.

GIA's statement says:
"The induced color, whether present as a rim close to the surface or continuing throughout the stone, is caused by a process known as bulk diffusion. As a result of discussions and a review of the technical literature, it is clear that 'bulk diffusion' is scientifically correct and should replace the terms 'surface diffusion' and 'diffusion treated' as they were previously used gemologically. GIA and AGTA reports on such stones will include wording similar to the following (to be adjusted per the specific format of each lab's report):

Group/Species: natural corundum
Variety: sapphire/ruby
Treatment comments: indications of heating and of surface-related color created by bulk diffusion.

Overgrowth of synthetic material occurs during the new treatment process. If such a synthetic overgrowth is still present on the finished stone, it will be addressed in the identification report as follows, again with adjustments per the individual report format:

Group/Species: natural corundum
Variety: sapphire/ruby
Treatment comments: indications of heating and of surface-related color created by bulk diffusion; areas of synthetic overgrowth are present."



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