It doesn't take a gemologist to figure out where the world's famous emeralds--like those found in the Holy Crown of France and in the treasures of Hyderabad, India--have ended up. But where did they come from? In the journal Science, French researchers report that, by analyzing the stones' ratio of normal oxygen (O16) to heavy oxygen (O18), they can trace the green jewels' provenance. The technique has yielded surprising results. It turns out that Austria and Egypt, thought to be the only emerald sources in antiquity, were not alone. Trade routes for the gems, meanwhile, were far more extensive than originally thought, reaching from the New World not only into Europe, but India too.