Conversion Of The Cortez CCD Gold Circuit To CIL ? History

The Cortez Mining District has had a long history of mining activity dating back to 1862 as previously reported (1) (2). More recently Cortez Gold Mines (i) has operated a cyanide leach, counter current decantation (CCD) recovery gold mill from January 1969 to February 1976. This type of plant has been standard in the U.S. for treating higher grade finely disseminated gold in Carlin type ores. The mill was initially operated from 1969 to 1973 at 1520 tonnes per day on oxidized ore from the Cortez ore body. Starting in 1973, the mill was operated at 2050 tonnes per day on softer, less oxidized, high clay ore from Gold Acres which is located 13 kilometers to the west of the Cortez installation. In February of 1976 the oxidized portion of the ore body at Gold Acres was depleted and the mill ceased operation. Successful heap leaching of the lower grade portion of the ores was practiced at both Cortez and Gold Acres to supplement the milling operations. Much valuable experience was gained in the operation of these two heap leaching programs and is well described in an earlier publication (3). Releaching of the ore heaps at Gold Acres and Cortez was continued with a limited crew from 1976 to 1979.