U.S. REPORT Arimetco sees bright future in low-cost SX-EW

Newly listed Arimetco International (TSE) has some ambitious plans to develop low-cost copper mines in North America which make use of acid leaching followed by solvent extraction and electrowinning, also know as SX-EW technology. Arimetco, which recently began trading at $1.50 on The Toronto Stock Exchange, has three copper projects either at or nearing the production stage in southwestern U.S.

The first is its Yerington copper mine in Nevada, which is currently shipping cathode copper at a rate of 7,000 lb. per day. The two other projects — Johnson Camp and Emerald Isle — are in Arizona near Kingman and Tucson, respectively, and production is scheduled to begin at both by the fourth quarter of 1990.

Following the recent completion of a $7-million underwriting by Midland Walwyn, the company is aggressively pursuing the development of its low-cost copper mines which use the SX-EW technology.

Arimetco’s strategy is to acquire mines with established infrastructure that allow rapid production of high-quality cathode copper through conversion to the low-cost SX-EW processing technology.

That technology allows low unit costs, estimated to be 55 cents per lb. of cathode copper. They are projected to be some of the lowest costs for the copper industry.

The majority of Arimetco’s proven reserves are contained in ore that is either pre-stripped or has been mined and stockpiled.

Total recoverable pounds of copper in Arimetco’s reserves are estimated at 230 million lb. for Yerington, 90 million lb. for Johnson Camp, and 20 million lb. for Emerald Isle.

Arimetco produces 99.99% pure cathode copper right at its mine site. It does so by using a leaching process where sulphuric acid is sprayed onto metal-bearing ore, which has been dumped onto plastic-lined pads. The leaching process extracts the copper in solution form (copper sulphate), and from there the copper sulphate goes to solvent extraction (SX) and electrowinning (EW) plants.

According to Midland Walwyn Research, Arimetco has capitalized on the slowness of other larger mining companies to act in purchasing copper properties, as well as on the declining mining costs for copper oxide ores.

For the past 10 years or more, a quiet revolution has been rippling through the copper industry worldwide, says Walwyn. The revolution involves the low-cost extraction of copper from large-tonnage low- grade deposits.

In place of conventional milling, shipping concentrate to a smelter and refining, the new SX-EW process uses solvent extraction. Production costs can be as low as 30 cents per lb. of copper in the case of Phelps Dodge (NYSE), for example.

Another recently listed company that plans to acquire low-cost copper projects in the southwestern U.S. is Toronto-based Great Lakes Minerals (TSE).

Nicholas Tintor, president of Great Lakes, says there is a bright future for low-cost copper mining projects which make use of solvent extraction and electrowinning technology, or SX-EW for short.

“When I tell investors about SX-EW, a lot of them really aren’t very familiar with it,” says Tintor. “The technology is quite similar to the type of process used at open pit, heap leach gold mines.”

The heap leach technology has been successfully applied to oxide gold deposits throughout the western U.S. “The advantage with the SX-EW system is that there are no smelter charges,” says Tintor, who is negotiating to acquire an interest in some copper projects in Arizona which would be amenable to SX- EW methods.

Great Lakes’ first acquisition this year was an option to earn a 50% interest in a copper-sulphide project on the Keweenaw peninsula in northern Michigan.