By RANDOLPH E. SCHMID Associated Press Writer
WASHINGTON (AP) - New tests on some of the world's best-known emeralds show that ancient miners took the stones from deposits supposedly discovered only in this century and that some gems thought to be from ancient Middle East mines actually originated in South America.
A team of French researchers studied the types of oxygen found in the green gems, using the ratio of one type to another to determine where the stones originated.
Legends surrounding some of the stones claimed they originated in ``old mines'' in the Middle East. But that had been questioned because the emerald mines in those areas were only officially discovered in this century.
The tests proved at least some of the legends true, indicating that the stones were traded along the ancient Silk Route connecting China and Europe through the Middle East, according to the paper in Friday's issue of the journal Science.
But other old mine emeralds turned out to have been brought back from South America by Spanish explorers.
The tests were conducted by a team of researchers led by Gaston Giuliani of the Center for Research in Petrography and Geochemistry at Nancy, France.
The group analyzed an ancient Roman emerald earring from the French Natural History Museum; four from the treasury of Nizam at Hyderabad, India, cut in the 18th century but thought to date back to old mines worked in the time of Alexander the Great; an emerald from the Holy Crown of France; two large emeralds in the French Natural History Museum used in 1806 to describe the mineral content of these gems; and one rough cut emerald from the Mel Fisher Maritime Heritage Society in Key West, Fla.
The Florida emerald was from mines in Colombia, which became the major source of emeralds once discovered by the Spanish, with South American stones becoming widely traded worldwide, the researchers noted.
Indeed, the group found that three of the four old mine stones tested from Hyderabad, India, had oxygen ratios that indicated they came originally from Colombia.
The fourth originated in Afghanistan, they said. The Afghan mines were first mapped by the Soviets in 1976, but the presence of this stone in a collection formed in the 18th century shows they were being exploited much earlier.
Before the opening of the South American mines the only widely known sources of emeralds had been in Austria and Egypt.
The emerald from the crown of France and the two gems used to describe emeralds in the early 19th century originated in Austria, the researchers concluded.
But the one from an ancient Roman earring did not. Its oxygen ratio is the same as that of stones from the Swat-Mingora district of Pakistan, indicating the mines there, discovered in the 20th century, actually had been worked in antiquity. Thursday January 27 2:08 PM ET
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Using the latest techniques and equipment, geologists said on Thursday they had ''fingerprinted'' some of the world's oldest and most famous emeralds, and come up with surprising results.
Legend had long held that emeralds used to decorate the crown of an Indian potentate and a Roman earring came from ancient mines in Austria or Egypt, but they in fact came from mines in Pakistan and Colombia that people had believed were only recently discovered, the researchers said.
They also found that emeralds from Colombia, held by experts to be the finest in the world, were traded worldwide almost as soon as they were discovered by Spanish conquistadors in the 16th century.
Gaston Giuliani, a geologist at the Centre de Recherches Petrographiques et Geochimiques-CNRS in Vandoeuvre-les-Nancy, France, and colleagues used oxygen isotopes to ``fingerprint'' the emeralds. Isotopes are slight variations of the elements.
Giuliani said he and colleagues had been studying the development of emeralds in Brazil and Colombia, and discovered that they could pinpoint their origin by looking at these variations in oxygen, a major constituent of emeralds.
``It was easy to distinguish emeralds from Brazil from emeralds from Colombia,'' Giuliani said in a telephone interview. ``The second step is to say, 'Now we have to see what happens with other deposits in the world.'''
They looked at a gold and emerald earring dating back to when Roman occupied France. ``We also analyzed four emeralds from the treasury of the Nizam of Hyderabad (India) cut in the 18th century A.D.,'' they wrote in their report, published in Friday's issue of the journal Science.
``They are classically called 'old mine' emeralds and their historical record could go back to Alexander the Great, around 300 B.C.,'' they added.
``We also studied the emerald from the Holy Crown of France, which was set on the central jewel lily of the crown of France by Louis IX, king of France between 1226 and 1270.''
They also looked at some geological specimens of emerald, as well as one salvaged from the wreck of the Atocha, a Spanish galleon that sank off Florida in 1622.
The researchers used ion microprobe oxygen isotopic analysis, in which the emerald is bombarded with an electron ion beam. This dislodges oxygen ions from the crystal lattice of the gem, which can be collected and analyzed.
It causes only microscopic damage to the emeralds, and after a few demonstrations, Giuliani said he was able to persuade museum curators to let him try it on the priceless emeralds.
They found the emerald in the ancient Roman earring matched emeralds from the Swat-Mingora district of Pakistan. One of the Indian stones from Hyderabad originated in Afghanistan.
Mines there were only opened in the 20th century, or at least that is what people thought.
``The deposits in these areas fall along the old Silk Route and it may be that they were mined or collected there as traders passed though, and brought to Rome and France and elsewhere,'' Giuliani said.
The royal French emerald was traced to Austria, but the other Indian emeralds came from Colombia and were not, as had been believed, ancient stones carried from Asia.
As would be expected, the Atocha emerald also came from Colombia, which suggests the Spaniards were very quick to recognize and exploit the green gems.
``Colombian emerald deposits are unique in the world, producing stones with richer color, clarity, and bigger crystals than most emerald deposits,'' Giuliani said in a statement.
``We imagine that these were the qualities that the Spanish, and the rest of the world, were interested in.''