Heavy metal.

• Position: International gold prices and trade - Art

Just a few years ago, African countries were begging European banks not to sell off gold bars in their vaults. The international price was so low that the extra metal on the markets was pushing high-cost producers into bankruptcy and destabilizing some countries. How times have changed. With gold around US$580 an ounce these days, even projects in unexpected places, like this gold mine in western Guatemala, means money on the table for aggressive mining companies.

Gold swung as high as $850 an ounce in the early 1980s, the last time oil spiked and the world's economies stammered to a virtual halt. But it also reliably tanks to as low as $200 an ounce as...