Knowing the background of the material gives a base to know the trade routes and relations between ancient people. A common example of this is through the assessment of the origins of the rubies of a Parthean statue, discovered in Mesopotamia, whose previous analysis that took place at the Louvre had already proved the authenticity.
The Parthean Empire lasted around five centuries from 250 before JC to 250 after JC. It was situated within the boundaries of the Roman Empire, where Iran is now located. To determine the history of these rubies of the Goddess Ishtar, the Louvre laboratory has measured using the PIXE method the composition of around 500 rubies from different mines. Every ruby was characterised by different traces of natural elements.
The composition of rubies of the statue has been compared to the rubies of all the mines from where the precious stone may have been extracted. Traces of natural elements of the rubies on the statue indicated that they came from Burma, which was an important testimony to a trade route of precious gems between Mesopotamia and the Far East
More recently, this method has been applied to the study of the origin of emeralds belonging to Visigoth votive crowns. The Visigoths dominated Spain, from the fall of the Roman Empire to the Arab conquest. The crowns belong to the royal treasure of Gurrazar (VIII century) near Toledo, part of which is conserved in the National Museum of the middle ages in Paris.
The impurities detected at the level of traces by the PIXE and PIGE methods could be compared, using a police image, to genetic fingerprints. They have led to the conclusion that these emeralds had most probably been extracted from the Habachtal mines, in Tyrol. It is an interesting result because, the exploitation of these mines was only attested much later on, towards the XV century.
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