In October of 1987, the U.S. Bureau of Mines (Bureau) initiated a study on the applicability of cyanide technology to the Alaska mineral industry. The study included the collection and analysis of cyanide literature and leaching costs, as well as the generation of several generic feasibility studies. Although other methods of cyanide use in the mining industry such as in situ and vat leaching have been examined, heap leaching is the main focus of the study.
This report discusses heap leaching methodology and evaluates the capital and operating costs of a “typical” Nevada heap leach operation of variable tonnage as it would exist in Interior Alaska. Cost data was generated by the Bureau’s Cost Estimation System (CES), Western Mine Engineering’s Mining Cost Service (MCS), and published case histories. The objective of these analyses is to compare the hypothetical costs of heap leach mining in Alaska to those of Nevada.
Heap leaching is a metal recovery method which typically uses a sodium cyanide solution to dissolve and remove precious metals from low-grade ore that is stacked into piles. In the last decade, the number of mines using this technology has mushroomed with the majority of this increase occurring in the Western United States.