More miners are processing former waste rock as new deposits become harder to find
KIMBERLEY, South Africa—Every day De Beers sends trucks of waste rock through this celebrated mining town, part of its effort to squeeze the remaining diamonds out of the deposit that started the company in 1888.
De Beers, a unit of Anglo American PLC, is still the world’s biggest diamond miner, with operations in Namibia, Botswana, Canada and South Africa. The company stopped mining in Kimberley nine years ago, but as new deposits of the scarce mineral grows even harder to find, exploiting waste pits now represents a lucrative niche—and one that more miners are trying to tap.
Mining companies say processing tailings, as former waste rock is known, is increasingly becoming an economic imperative.
As miners have already plumbed some of the world’s richest deposits, grades of most metals and minerals have declined. That means processing already-mined tailings can be a more attractive proposition than traditional mining.
“Over the past century, the average copper grade has fallen to 1% from 4%, and production has gone up 16-fold,” says Ruban Yogarajah, a spokesman for BHP Billiton, the world’s biggest mining company. “So every year, it gets harder and harder.”
Companies don’t always disclose how much revenue they derive from tailings, and quantities mined vary greatly depending on price. But Mr. Yogarajah, echoing others, says it “will increasingly be an important part of our business.”
There are currently around 75 major tailings mining projects globally, according to research done by Magnus Ericsson, a professor of mineral economics at the Luleå University of Technology in Sweden. Projects include iron ore in Minnesota, copper in the Democratic Republic of the Congo—and, pretty much everywhere, gold.
Gold is present in slivers that couldn’t be collected 50 years ago, but can now be retrieved thanks to leaching technology, making it a byproduct in many copper mines.
In Canada, Goldcorp Inc., the world’s largest gold miner by market capitalization, has taken its quest to reclaim lost gold to downtown Timmins, Ontario, the historic heart of the country’s mining industry.
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