claims and estimated the reserves at 690 million tonnes of 2.58% grade copper. The Guggenheims also had discovered a process for treating the low grade ores developed by Elias Anton Cappelen Smith and were immediately interested. They organised the Chile Exploration Company (Chilex) in January 1912 and eventually bought out Burrage for US$25 million (or $ million today) in Chile's stock market. E. A. Cappelen Smith, consulting metallurgist for M. Guggenheim's Sons, worked out the first process for the treatment of Chuquicamata copper oxide ore around 1913 and led a team of engineers operating a pilot plant in Perth Amboy, New Jersey for a year. Chile then went ahead with the development and construction of a mine on the eastern section of the Chuquicamata field, gradually expanding it to include the rest of the field over the next 15 years. A leaching plant was planned with a capacity to produce 50,000 tons of electrolytic copper annually. Among the equipment purchased were steam shovels from the Panama Canal. A port and an oil-fired power plant were built at Tocopilla, to the West and an aqueduct was constructed to bring water in from the Andes. Production started on May 18, 1915. Production rose from 4,345 tonnes in the first year to 50,400 tonnes in 1920. The Guggenheims sold the mine to Anaconda Copper in 1923, and production increased to 135,890 tonnes by 1929 before the Great Depression hit and demand fell. For many years, production came from the oxidized capping of the orebody, which only required leaching and then electrowinning the copper, but by 1951 the oxidized reserves were primarily exhausted. The company then built a mill, flotation plant and smelter to treat the enormous reserves of underlying supergene copper sulfides. These secondary sulfides arise from the leaching of the overlying ore and its re-deposition and replacement of the deeper primary (hypogene) sulfides. In 1957 the Exotica deposit (South Mine) was discovered beneath tailings, and turned out to be the largest known deposit of exotic copper. This led Anaconda to build an oxide plant, concentrator, smelter, refinery, and town next to the mine, as well as a power plant in Tocopilla. In 1971, the mine was nationalized and operations were then assumed by CODELCO. For many years it was the mine with the largest annual production in the world but was recently overtaken by Minera Escondida. Nevertheless, it remained by far the