MINING IN CHILE — Rio Algom plans expansion for Cerro

The Cerro Colorado project has been producing copper since February and, already, owner Rio Algom (TSE) is talking of expanding.

For 1994, output is anticipated to be 60 million lb. copper; for 1995, 85-90 million lb. Commercial production levels will likely be reached around mid-year.

A planned second-phase of expansion would see annual output jump to 130 million lb. by 1996 at an estimated cost of less than US$50 million. The company expects to complete a detailed feasibility study for the expansion, during the fourth quarter of this year.

“The completion of Cerro Colorado marks an important milestone,” President Colin Macaulay told shareholders at this year’s annual meeting. “Cerro will more than double our 1993 levels of copper production and significantly lower Rio’s average cost per pound.”

The project, situated in the Atacama Desert, 120 km inland from Iquique, consists of an open pit and various operational facilities. These include: crushing, screening and conveying equipment; agglomeration and leaching facilities; solvent extraction-electrowinning plants; a warehouse and maintenance shop; and accommodation and recreational facilities. Water for the 55-sq.-km project is piped from higher ground 75 km to the east. Electricity, supplied from the Chilean state grid, required the installation of a 65-km-long power line.

Rio began pre-stripping in April, 1992. Development of the pit required the removal of 43 million tonnes of overburden and low-grade ore. Some 1.5 million tonnes of low-grade ore were stockpiled to create a base for the nine leach pads, which cover 440,000 sq. metres (the equivalent of about 100 football fields).

Crushed ore piled onto the pads is sprayed with a weak acid solution which, in conjunction with the application of naturally occurring bacteria, leaches copper from the oxide and certain sulphide ores.

Rio estimates a current “minable” reserve of 79 million tonnes grading 1.39% copper.

The project’s low-cost solvent extraction-electrowinning process produces finished cathode copper.

Rio currently produces copper in Canada through its 33.6% ownership of Highland Valley Copper in British Columbia. It also mines molybdenum, uranium and coal.