Once an emerald leaves its country of origin and circulates around the world, the gem's provenance becomes murky. Scientists have now developed a nondestructive method for determining the source of an emerald, even down to the mine from which it was extracted. That information can affect the gem's price and make it easier for historians to reconstruct ancient trade routes.
An emerald-tracking procedure that measures the ratio of two oxygen isotopes in a microscopic sample from a gem has been available for a few years (SN: 3/11/00, p. 175: Available at Where the Gems Are). Unfortunately, that method is not foolproof, says Philippe de Donato of the École Nationale Supérie