Washington, October 22 : A team of geologists and archaeologists has found clues that pre-Columbian societies knew a sophisticated metallurgy technique to extract gold.

When Spanish conquistadors seized the Inka emperor Atawalpa in 1532, they demanded an enormous ransom of silver and gold.

For weeks, llama trains carried tons of gold and silver statues, cups, and other objects to the Europeans, who then ordered them melted down to ingots for transport back to Spain.

Such an enormous stash suggests that the Andean people knew sophisticated metallurgy, but there has been little evidence to support this.

Now, a team of geologists and archaeologists has found clues that these indigenous people refined gold with mercury amalgamation, an important metallurgical technique that is still in use today.

Polish engineer-archaeologist Arthur Posnansky insisted as far back as 1945 that amalgamation was used near the famed Incan site of Machu Picchu, but archaeologists have always vigorously disputed these claims, noting that much of Posnansky's work was overly credulous.

Instead, experts believed that the process was nonexistent in the Americas until colonist Bartolome de Medina developed a variant in Mexico in 1557.

But, William Brooks, a geologist based in Reston, Virginia, couldn't believe that societies, which produced large quantities of gold, lacked techniques to recover it from placer gold, the minute gold flakes in stream beds found along coastal Peru.

So, Brooks and colleagues in Peru and Colombia analyzed residual mercury levels in seven samples of pre-European-contact gold foil - three from the Sican culture, which existed between 750 C. E. and 1375 C. E. in Peru, and four from Colombia.

The team found signs of amalgamation similar to those seen in contemporary gold foil in southeastern Peru.

"We think this technique was used throughout the Andes, probably centuries before it was commonly used in Europe," Brooks said.

"They had to have some way to produce all that gold, and an obvious candidate is the metallurgical technique used everywhere else in the world," he added. (ANI)