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September 09, 2003

Pre-Columbian mining

A geologist and mineral commodities specialist with the U.S. Geological Survey demonstrates the advantages of bringing specialized technical and scientific skills to bear on archaeological contexts with this Geotimes article. A couple neat photos, too.

Although recent mining activity over the past few years has overprinted evidence of pre-Columbian mining, several features we observed at a small copper mine near Santa Rita B indicate the many-thousand year history of mining in the area. Adits (tunnels) in the mine have undulating walls, originally opened by firesetting — an ancient mining technique in which miners set a fire adjacent to the face and then threw cold water on the hot surface to make the rock shatter and facilitate excavation of the ore with bone or stone tools. Also, the floor of the adit slopes downward approximately 30 degrees, representing a style of excavation, not used today, known as “medio barreto.” The adits are only 3 to 4 meters in length because pre-Columbian miners rarely penetrated beyond the distance where the sun would easily illuminate the adit.

Posted by Ghost of a flea at September 9, 2003 05:13 AM