World's Deepest Mines Highlight Risks of New Gold Rush

Nicholas Wadhams in Nairobi, Kenya
for National Geographic News
November 6, 2007
As gold prices reach near-record highs, South Africa's mining companies are keeping up by drilling to record depths.

The Gold Fields Ltd company intends to set a new record by drilling down 2.5 miles (4 kilometers) at its Driefontein mine, about 37 miles (60 kilometers) southwest of Johannesburg. An estimated 8.5 million ounces (240 million grams) of gold is thought to lie at such depths. (See a map of South Africa.)

Meanwhile, mining firm AngloGold Ashanti, which currently has the world's deepest mine, plans to extend its TauTona, or "Great Lion," mine, west of Johannesburg, to more than 2.4 miles (3.9 kilometers) deep. (See photos of South African mining.)

South Africa is known for having the deepest mines in the world. In comparison, the deepest mine in the United States—the now-defunct Homestake Mine of South Dakota—went down about 8,000 feet (2,438 meters).

Allure of the Ultra-Deep

The ambitious new mining projects are "ultra-deep" mines with shafts that are deeper than 2.2 miles (3.5 kilometers) in the ground, where temperatures rise well over a hundred degrees Fahrenheit (55 degrees Celsius) and rock shatters like glass.

Rocketing gold prices have made ultra-deep mining more attractive in South Africa, the world's largest gold producer.

Recently, gold hit a 28-year high: 770 U.S. dollars per ounce. That means deposits that were once too impure or too deep to mine are now worth prospecting.

"That's all part of the risk ... the investors and the decision-makers have to factor that in," said Ray Durrheim, a seismologist at South Africa's Council for Industrial and Scientific Research who does occasional consulting work for the mining industry.

"New shallow deposits [of gold], aren't easily being discovered around the world," he said. "The resources are at greater depths."

But the gold is dwindling: Analyses of current resources in South Africa suggest that shallow gold reserves have already been tapped.

Ultra-deep miners often have no other choice but to go deeper or look beyond South Africa—and they're doing both.

Companies are also prospecting for new ore veins in Colombia, the Democratic Republic of the Congo, and Australia. (See photos from gold mines around the world.)

Though South Africa is by far the largest producer of gold, its output has fallen by an average of 4 percent each year for 30 years. In 1970, a thousand tons were mined. In 2004, only 342 tons were extracted.

Risky Business

While mining companies are forced to dig deeper for gold, questions persist about the safety and technological challenges of ultra-deep mining.

For example, some scientists believe that deep mining may set off tremors in the Earth.

Transporting miners and rocks up and down such a long shaft also isn't easy: There is currently no rope or cable that could support its own weight at such lengths. And because temperatures are so high at the ultra-deep level, mine operators must come up with new ways to keep their miners cool.

And mine companies' quest for greater profit raises the fear that they are willing to risk the lives of their miners.

Several accidents in recent weeks have drawn attention to safety standards of the mining industry.

Earlier this month, a power failure at Harmony Gold's Elandsrand gold mine trapped 3,200 miners underground for more than 24 hours.

Mining took 199 lives in 2006, and so far in 2007, 150 people have died.

Mining has also become intertwined with race issues, as the majority of miners are black.

South Africa's National Union of Mineworkers is planning a one-day industry-wide strike in the coming weeks to protest mine conditions.

President Thabo Mbeki has ordered an audit of all the country's mines to figure out what's going wrong.

Some propose ultra-deep mining could be done mechanically, with robots or by automation.

But unions oppose that idea because it could cost some South Africans their jobs.

"We would not generally oppose the idea of ultra-deep mining if our people were safe, but we are opposing it on the basis that ... we have already seen a significant rise of fatalities," said National Union of Mineworkers spokesperson Lesiba Sheshoka.

Many of these fatalities are occurring in mines that are not ultra-deep, he added.

"[This] is sufficient evidence of negligence on the part of mine owners," he said.

Despite regular accidents, many companies, such as Gold Fields Ltd and AngloGold Ashanti, insist that safety is their main concern.

Some mining companies have set a goal of zero mining deaths by 2013—but even they acknowledge it's no guarantee.

"We have to concede that our safety performance in the last year and a half or so has been quite a lot less than satisfactory," said AngloGold Ashanti spokesperson Alan Fine.

Deaths at AngloGold mines jumped to 37 in 2006 from 25 in 2005, the Reuters news agency reported. During the first half of 2007, 18 AngloGold mineworkers have died, according to the agency.

Most recently, a miner's death on November 2 forced AngloGold to temporarily shut down its TauTona mine.

"We've got to fix our safety performance generally, but obviously ... ultra-deep level mining is risky," Fine said.

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