Cominco leases Mesaba copper-nickel deposit (June 25, 2001)

Vancouver — Cominco (CLT-T) intends to apply its new hydrometallurgical technology to the Mesaba copper-nickel deposit in northern Minnesota. The company acquired the rights to the large, undeveloped property from Longyear Mesaba and the Minnesota government.

The technology, developed by Cominco Engineering Services Ltd. (CESL) involves the extraction of copper, nickel and other metals from concentrates and ores based on patented applications of pressure leaching, solvent extraction and electrowinning. It does not produce significant gas emissions or any toxic waste.

“This is just a testing program,” says David Godlewski, a spokesman for Cominco’s American division. “We’re in the process of testing the new CESL technology to see whether it can be commercialized in a way that makes sense for the Mesaba orebody.”

The deposit, which is accessible by open-pit methods, contains a resource of about 700 million tonnes grading 0.46% copper and 0.12% nickel. A further 300 million tonnes of higher-grade resources can be mined from underground. In addition to copper and nickel, the deposit contains cobalt and precious metals, including platinum group elements.

The 2,344-acre site was extensively explored by a host of companies in the 1970s and 1980s, including Kennecott, a division of Rio Tinto (RTP-N). However, development was suspended as a result of low metal prices and the complexity of the mineralized material.

The metallurgical problems centre around one of the main minerals, cubanite, which is a copper-nickel sulphide. The copper concentrates that were produced contained too much nickel for smelters to handle, whereas the nickel concentrates contained too much copper.

“The product was just not marketable as a bulk concentrate,” says Godlewski. “If you excluded nickel and just floated the chalcopyrite, the grade of the resulting copper concentrate was not marketable either.”

Cominco is processing a 5,000-tonne bulk sample of the Mesaba material in order to produce concentrate for testing in the CESL pilot plant, in Vancouver, B.C.

“We have a pretty good handle on the copper end of things,” says Godlewski. “The question mark comes with the nickel-cobalt circuits.”

The major says that if it can produce metals economically using the CESL process, it will consider building a large prototype test plant in Minnesota.

John Key, general manager of Cominco’s Red Dog mine in Alaska, has been re-assigned to manage the Mesaba project. His replacement at Red Dog is Robert Jacko.