Archaeologists have discovered a 12,000-year-old iron oxide mine in Chile that marks the oldest evidence of organized mining ever found in the Americas, according to a report in the June issue of Current Anthropology.

A team of researchers led by Diego Salazar of the Universidad de Chile found the 40-meter trench near the coastal town of Taltal in northern Chile. It was dug by the Huentelauquen people -- the first settlers in the region -- who used iron oxide as pigment for painted stone and bone instruments, and probably also for clothing and body paint, the researchers say.

The remarkable duration and extent of the operation illustrate the surprising cultural complexity of these ancient people. "It shows that [mining] was a labor-intensive activity demanding specific technical skills and some level of social cooperation transmitted through generations," Salazar and his team write.

An estimated 700 cubic meters and 2,000 tons of rock were extracted from the mine. Carbon dates for charcoal and shells found in the mine suggest it was used continuously from around 12,000 years ago to 10,500 years ago, and then used again around 4,300 years ago. The researchers also found more than 500 hammerstones dating back to the earliest use of the mine.

"The regular exploitation of [the site] for more than a millennium … indicates that knowledge about the location of the mine, the properties of its iron oxides, and the techniques required to exploit and process these minerals were transmitted over generations within the Huentelauquen Cultural Complex, thereby consolidating the first mining tradition yet known in America," the researchers write. The find extends "by several millennia the mining sites yet recorded in the Americas."

Before this find, a North American copper mine dated to between 4,500 and 2,600 years ago was the oldest known in the Americas.