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FABLES about the origins of some of the world鈥檚 most prized gemstones are
being put to the test by geochemists in France and Colombia. By analysing oxygen
levels in famous emeralds they have proved that some of the gems did indeed come
from forgotten mines in Asia.

Half of all emeralds hail from mines discovered 400 years ago in Colombia by
the Spanish. The only established sources of emeralds before then were in Egypt
and Austria. But the origins of so-called 鈥渙ld mine鈥� emeralds sold by Indian
traders in the 16th century have been a mystery.

Experts suspected that the gems came from old mines in Asia, but there has
never been any proof. 鈥淚t鈥檚 a fable of the mining road, that the cut emeralds of
India came from old mines that were forgotten,鈥� says Gaston Giuliani of the
French government鈥檚 Centre for Petrography and Geochemistry in Nancy.

The researchers used the ratio of two oxygen isotopes to work out the origin
of a gem from a collection owned by the Nizam of Hyderabad in the 18th century.
The proportions of oxygen-18 varies relative to oxygen-16 from 0.06 to 0.25 per
cent. Because the ratio remains fixed for a particular place, you can pinpoint
where a gem came from.

Surprisingly, the analysis proved the fables are true. The isotope content
matched that of emeralds from the Panjshir Valley in Afghanistan. The Soviet
Union first mapped these mines in 1976. But the analysis proved they must have
been discovered hundreds of years earlier and then abandoned.

More proof of the fabled Asian mines came from an emerald embedded in a
Gallo-Roman earring found in France. 鈥淥ur biggest surprise was when we found
that it probably came from Pakistan,鈥� says Giuliani. 鈥淭ill then, everyone
assumed it came from Egypt or Austria.鈥� The isotope ratio matches that of gems
from the Swat and Penshawar valleys in Pakistan. 鈥淭hese deposits are along the
banks of the rivers, which are part of the ancient Silk Route connecting Egypt
and Afghanistan,鈥� he says.

Other emeralds examined included one from the Holy Crown of France, worn
between 1226 and 1270 by King Louis IX, which turned out to be from Austria.
Next, the researchers hope to apply their technique to rubies and sapphires.