Demantoids can be heat treated

Laboratory Approaches Towards Disclosure

In the beginning the labs would not make the heat-or-no-heat call because it was undetectable. As their databases grew and internal characteristics began revealing more clues, new assumptions were made. Below are some of the current approaches the major laboratories are taking.


  • Gemological Institute of America (GIA) – Will not identify whether a demantoid garnet has been heat treated; will not determine origin on demantoid garnets
  • American Gem Trade Association (AGTA) disclosure – Enhancements: Indications of heating. Gemstones of this type may be heated to improve their appearance. This treatment is not detectable using current technologies; such heating is generally stable under normal wearing conditions. AGTA is not giving country of origin
  • American Gemological Laboratories (AGL) disclosure – AGL will make the heating call, and give country of origin
    • “It is in the opinion of the Laboratory, based on the weight of evidence, that the origin of this material would be classified as Russian. It is the opinion of the Laboratory that this material has been subjected to a low to moderate heat enhancement process to produce a permanent and stable color.”
  • Gübelin Gemmological Laboratories – Will denote the country of origin but not whether the material has been subjected to heat
  • SSEF Swiss Gemmological Institute – Will state country of origin and whether there are indications of heat treatment

The labs that do report country of origin are not able to pinpoint specific mines at this time.

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