The Environmental Cost of Gold

Here's an extensive article from the NY Times on the invisible costs of obtaining gold. Unbelievably, in a typical case "100 tons or more of earth have to be excavated for a single ounce of gold."

The United States, the world's second-largest consumer of gold, is also the world's largest holder of gold reserves. The government has 8,134 tons secured in vaults, about $122 billion worth. The Federal Reserve and other major central banks renewed an agreement last year to severely restrict sales from their reserves, offering, in effect, a price support to gold.

That price is not simply a matter of supply and demand, but of market psychology. Gold is bought by anxious investors when the dollar is weak and the economy uncertain. That is a big reason for gold's high price today.

For miners that price determines virtually everything - where gold is mined, how much is mined, and how tiny are the flecks worth going after.

"You can mine gold ore at a lower grade than any other metal," said Mike Wireman, a mine specialist at the Denver office of the E.P.A. "That means big open pits. But it must also be easy and cheap to be profitable, and that means cyanide."

That kind of massive operation can be seen at Yanacocha, a sprawling mine in northern Peru run by Newmont. In a region of pastures and peasants, the rolling green hills have been carved into sandy-colored mesas, looking more like the American West than the Andean highlands.

Mountains have been systematically blasted, carted off by groaning trucks the size of houses and restacked into ziggurats of chunky ore. These new man-made mountains are lined with irrigation hoses that silently trickle millions of gallons of cyanide solution over the rock for years. The cyanide dissolves the gold so it can be separated and smelted.

At sites like Yanacocha, one ounce of gold is sprinkled in 30 tons of ore. But to get at that ore, many more tons of earth have to be moved, then left as waste. At some mines in Nevada, 100 tons or more of earth have to be excavated for a single ounce of gold, said Ann Maest, a geochemist who consults on mining issues.

Mining companies say they are meeting a demand and that this kind of gold mining, called cyanide heap leaching, is as good a use of the land as any, or better.

Cyanide is not the only option. But it is considered the most cost-effective way to retrieve microscopic bits of "invisible gold." Profit margins are too thin, miners say, and the gold left in the world too scarce to mine it any other way.

"The heap is cheaper," said Shannon W. Dunlap, an environmental manager with Placer Dome. "Our ore wouldn't work without the heap."

But much of those masses of disturbed rock, exposed to the rain and air for the first time, are also the source of mining's multibillion-dollar environmental time bomb. Sulfides in that rock will react with oxygen, making sulfuric acid.

That acid pollutes and it also frees heavy metals like cadmium, lead and mercury, which are harmful to people and fish even at low concentrations. The chain reaction can go on for centuries.