Four Labs Agree on ‘Padparadscha’ Terminology

The American Gem Trade Association's Gemological Testing Center, the Gemological Institute of America's Gem Trade Laboratory, the Gübelin Gem Lab, and the SSEF Swiss Gemmological Institute all have agreed that the padparadscha-like orange-on-pink corundum recently encountered in the market is to be called "treated sapphire." Previously, both the AGTA lab and GIA's GTL had called the material "surface diffusion-treated sapphire." From now on, reports for these treated sapphires will read: "Species: Natural Corundum "Variety: Treated (Orange) Sapphire "Comments/Treatments: Indications of heating. "The orange coloration of this stone is confined to a surface-related layer." But in a combined statement, the labs noted that "none of the agreeing laboratories knows of a likely mechanism that could produce these visual effects or apparent differences in trace-element concentrations

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