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.”