Dramatic stone masks, iconic finds in the ancient Mexican city of Teotihuacan, were supposed to be made from a jadelike stone. Many researchers also thought the large faces were made on the site of the pre-Columbian metropolis. Instead, they seem to have been made in workshops a great distance to the south of the city. And they are made of softer stone like serpentinite and polished with quartz. Quartz does not appear around Teotihuacan, bolstering the notion that the masks were made far away. “Almost everything that has been written about the making of the Teotihuacan masks is untrue,” says Jane Walsh, an anthropologist at the Smithsonian National Museum of Natural History in Washington, D.C.

New details about the manufacture of these old and valuable masks are coming to light, thanks to modern technology: a special analytical scanning electron microscope that can identify the atoms and minerals that make up the stone, and show miniscule marks left by the artisans who carved them. Timothy Rose, a geologist at the Smithsonian, presented the results of microscope studies last week at the annual meeting of the American Vacuum Society, a group of material scientists, in Baltimore. “We examined about 150 of these masks with good provenance, from several museum collections,” says Rose, who works with Walsh.

Within that group he found about three fakes, uncovered because the microscope showed the telltale marks of modern tools. “We were pleased the number was so small,” he adds. “But it is important to have this technology to tell what is real, because many masks, in both museum and private collections, don’t come with good documentation about their origins.”

There is plenty of other evidence that Teotihuacan had far-flung connections, notes Geoffrey Braswell, an anthropologist at the University of California, San Diego, who studies Mesoamerica. Other imports have been found in the city, he said in an email. Walsh and Rose, however, note that the mask-makers have not been traced.

via Electron Beam Points to Origins of Teotihuacan Stone Faces – Scientific American.