Dear Dr. Hassan,
Its true that if the origin is mentioned for a gem then the experienced buyers can guess the quality of the stone better. However, I think few sellers have documentary proof to establish the country of origin of the gems. Hence, some of them (incl. me) tend to avoid making such non-documented remark in the listing. I have many gems in my collection for which I can guarantee the origin (from the quality of the gem) but do not have any documentary proof for those.
Sometimes the stones change the chemical composition if the origin is mentioned. Say by mentioning just Cat's Eye it means from Chrysoberyl group but if we mention Sulemani Cat's eye then its from the Quartz family. Similarly Orissa Panna (it looks like excellent quality Emerald to untrained eyes) is normally Green Fluorite and not Beryl. In such cases the seller must describe the gems well and must mention about the group to avoid any controversy.
Lastly, I wish to say that apart from the expensive stones, most of the other stones in auction have good sources in our own Indian sub-continent.
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Best Regards
🙂
Swarup Dutta
Kolkata
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Best Regards
😄
Swarup
Kolkata