On a glittering trail

Researchers unravel the origins of some of the most precious emeralds known to humankind

 
Last Updated: Saturday 04 July 2015

a group of French researchers claim to have discovered a method to trace the genesis of emeralds and the route they travelled prior to being set in the crowns of oriental emperors and European kings.

The emerald analysis method has been developed by Gaston Giuliani, a researcher with the Centre for Petrographical and Geochemical Research in Vandoeuvre-ls-Nancy, and his colleagues elsewhere. To determine the origin of any emerald, the researchers analyse inherent traces of water from which the precious stone had crystallised eons ago.

The method involves vaporising a small sample from the surface of the stone in order to be able to measure the ratio of oxygen isotopes. Isotopes are atoms of the same element that differ in the number of neutrons.

The oxygen present in the stone is derived from the hot waters out of which the emeralds crystallise and ach of the mines in the world is known to have water with different isotope ratios. Following this method of analysis can also reveal the country and the individual mine from where the emerald came.

Before the emergence of the New World, the only known source of emeralds was Queen Cleopatra's mine in Egypt and a small mine discovered in the Austrian Alps by the Romans. Later, another source of emeralds was found in Mexico and Peru.

But a recent analysis by the French researchers of an emerald set in a Roman earring found in France showed that the precious stone may have come from a mine in the ancient kingdom of Gandhara - now Pakistan. The emerald may have reached Europe via the Silk Road, say Giuliani and his fellow researchers.

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