Table giving some specifics for methods of heat and diffusion treatment:

Details not required for Students of EPS2 (concepts are required)


Heat only1300 C possible asterism
1600 C removes silk and asterism
Heat and reducing atmosphere1600 C develops blue color
Heat and oxidizing atmosphere1600 C diminishes blue color
Extended heating1800 C diminishes banding and strain
Diffusion and heat1800 C(+TiO2) asterism
1800 C (+TiO2,Fe oxides) blue color
Heat near melting point+Cr2O3 red and other colors

Gem dealers who do a lot of business in Thailand have not been able to learn the methods. Onegem dealer offered what he knows for sure: that the method is fairly primitive, that the details of treatment vary from miner to miner, and that the material is treated as rough rather than after cutting.