Abstract
The determination of country of origin poses a common problem in the appraisal of gemstones and is in many cases still based on the observation of inclusions and growth features of a gem, whereas chemical analysis is only done by major labs. We have used Laser Ablation Inductively Coupled Plasma Mass Spectrometry to analyze the trace element profiles of demantoid garnets from six different countries and identified a set of six elements, which are magnesium, aluminum, titanium, vanadium, chromium, and manganese, that are necessary to assign the mining regions with a good certainty. By using the logarithms of the trace element concentrations and subjecting them to chemometric modeling, we were able to separate the demantoids originating from Russia, Pakistan, Namibia, Iran, and Madagascar very well, leaving only Italy with some uncertainty. Results are presented for an “all origins” model as well as pair-wise comparison of two locations at a time, which lead to even better results.
Highlights
The correct determination of origin of gemstones has gained more and more importance recently.The desire to know where a gem comes from is scientifically driven but to a very large extent by the trade
Study higher we have focused on the determination of geographic origin of demantoids, which is concentrations very often present a problem for this technique
Representative rough demantoid samples have been collected from Tubussis (Namibia), Ufaley (Russia), Karkodin (Russia), Poldnevskoye (Russia), Bobrovka (Russia), Val Malenco (Italy), Baluchistan (Pakistan), Kerman (Iran) and Antetezambato (Madagascar)
Summary
The correct determination of origin of gemstones has gained more and more importance recently.The desire to know where a gem comes from is scientifically driven but to a very large extent by the trade. For a scientist it might be hard to understand that for example two blue sapphires, which have the same size, weight, color, clarity and cut are appraised differently only because they hail from different sources. Ethical issues associated with gemstone production are becoming increasingly important. It will be necessary in certain cases to prove that gems do not come from conflict areas as those might be banned from trade in some countries, such as jade and rubies originating from Burma which were banned in the United States from 2008 to 2016
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