KGHM is looking past its new grinding line at the Sierra Gorda copper mine in Chile. The Polish group has signed a cooperation deal with BHP, the world’s largest mining company, that could finally bring millions of tonnes of oxide ore — treated as waste for years — into production.
The fourth grinding line at Sierra Gorda, work on which began last week, is only one part of the changes planned at the site. Once the investment is completed, the mine will be able to turn out roughly 150,000 tonnes of copper a year; it already produces more than 100,000 tonnes. KGHM holds 55 percent of the operation, with Australia’s South32 owning the remainder.
– There is a willingness to further develop the mine – said Piotr Krzyżewski, KGHM’s vice-president for finance.
From a viewpoint overlooking the pit — about 700 metres deep and 2.5 kilometres wide — piles of rock are visible on the left. They contain copper, yet they sit idle.
A deposit of two kinds of ore
Sierra Gorda works a copper-molybdenum deposit that holds both sulphide and oxide copper ores. The sulphides pose no difficulty: KGHM has processed similar material in Lower Silesia for years, and the method is efficient, well known and already applied at the Chilean mine.
The oxide rocks, counted in millions of tonnes, are a different matter. They cannot be treated in a smelter; recovering the metal requires leaching with the SX-EW method (solvent extraction-electrowinning), which yields copper cathode through chemical processes. In practice, a new processing plant would have to be built. KGHM tested the technology and found it workable, but after those trials more than a decade ago almost nothing was done. Developing the oxides through a Sierra Gorda Oxides programme would markedly improve the economics of the whole operation — what now looks like waste could become a source of valuable metal.
Ten kilometres away, a matching interest
Roughly 10 kilometres north-east of Sierra Gorda lies Spence, a mine belonging to BHP. It was launched in 2007, seven years before Sierra Gorda, and from the start it concentrated on oxide ores, producing about 200,000 tonnes of copper annually. A later expansion costing 2.46 billion dollars allowed it to process sulphides too, and last year’s output reached 254,000 tonnes. The Australians could extract more metal, but they do not have the land needed for it.
This is where the two sides converge. If KGHM chose not to build its own plant for oxide ore, it could simply send the material to Spence, while BHP would gain access to KGHM’s land resources. KGHM would not answer questions about such a scenario, pointing to the negotiations over the terms of cooperation that are under way. Sharing installations between companies is not unusual in metals mining, as producers try to squeeze the most out of production that is costly and slow by nature.
Adding cathodes from oxide ore would raise Sierra Gorda’s potential considerably. Oxide ore alone could deliver as much as 30,000 tonnes of extra copper a year. In 2014 the mine’s management talked about output of 200,000 tonnes annually, a target that now appears within closer reach.
Chilean politicians are following the plans with interest. Marcelo Bustos, general director of Sierra Gorda, said during the inauguration of the new grinding line that the company is currently the eighth-largest copper producer in Chile, responsible for 3.1 percent of national output.
– Projects such as Sierra Gorda will help overcome the current transformation and the expansion cycle that is to begin in 2027 – said Daniel Mas, Chile’s minister of economy and mining.
The country’s metals mining sector is living through a difficult period, with production falling. That is why the authorities in Santiago are likely to be rooting for a deal between KGHM and BHP.
Źródło: WNP.PL, Fot. Dariusz Malinowski / PTWP
