I was reading this interesting dispatch from Indonesia about a gold rush on the island of Buru when I realized that I have no idea why mercury is used in gold mining. So, I looked it up and got my answer:

A gold miner stands waist-deep in a polluted pond, dumps a capful of mercury into a bucket of ore and mixes it in with his bare hands.

The darting liquid metal wraps itself around the gold to form a silver pellet the size of a marble.

The use of mercury in gold mining is illegal in Indonesia because it is toxic to both human health and the environment. But the price of gold has tripled since 2001, and mercury is the easiest way to extract it.

“Of course I’m worried,” said miner Handoko, 23, a grim man in a baseball hat who goes by one name. “But this is the job.”
Tens of thousands of remote mining sites have sprung up mostly in Asia, Latin America and Africa, using as much as 1,000 tons of mercury each year. The mercury ravages the nervous system of miners and their families. It also travels thousands of miles in the atmosphere, settling in oceans and river beds in Europe and North America and moving up the food chain into fish.

Going back to the dispatch, it turns out that it isn’t just the use of mercury that is illegal, but the mining itself.

The mining operations are illegal and unregulated, though locals say the Indonesian military has been taking a cut of the profits in exchange for turning a blind eye (standard practice in my decade in Indonesia between 1993-2003).

And some more on the environmental impact:

Small-scale gold mining is the second-worst source of mercury pollution in the world, after the burning of fossil fuels. And Indonesia ranks behind only China in the use of mercury in gold mining.

Mercury’s impact is evident in mining regions like Central Kalimantan, on the island of Borneo. Acres of tropical forest are now virtual desert. Villagers say fish populations have dropped by 70 percent. The Galangan gold mining site stretches several miles, stripped of trees and dotted with mercury-laced ponds.

“This area is finished,” said Fauzi Achmad, a gold shop owner, as he drove past the moonscape-like dunes and abandoned mine sites.

Despite the hazards, buying mercury at gold mining sites is as easy as purchasing toothpaste.

Now I’m depressed.