ata field. (It acquired the remainder of the field gradually over the next 15 years). The 10,000 tons per day leaching plant was planned to produce 50,000 tons of electrolytic copper annually. Amongst the equipment purchased were steam shovels from the Panama Canal. A port and an oil-fired power plant were built at Tocopilla, 90 miles to the west and an aqueduct was constructed to bring water in from the Andes.Production started on May 18, 1915. Actual production rose from 4,345 tonnes in the first year to 50,400 tonnes in 1920 and 135,890 tonnes in 1929 before the Depression hit and demand fell.
Production for many years came from the oxidised capping of the orebody which merely required leaching and then electro winning of the copper, but by 1951 the oxidised reserves were largely exhausted and the company built a mill, flotation plant and smelter to treat the huge reserves of underlying supergene copper sulfides. These secondary sulfides arise from the leaching of the overlying ore and its re-deposition on and replacement of the deeper primary (hypogene) sulfides
