IN THE MID-1800s , America was smitten with gold fever. The mineral, used to make jewelry and other goods, was discovered in California in 1848, and thousands of people raced across the country in the hope of striking it rich. To encourage Americans to settle the western frontier, the government urged prospectors to head west in search of gold, which was extremely valuable—discovering it was like finding buried money. By paying just five dollars per acre for land, they bought the right to keep whatever gold they found.

Minerals of the earth

The gold that created such furor in America during the nineteenth century is also found in many other areas of the world, including Brazil, New Guinea, and Australia. But gold is just one of many valuable minerals that exist beneath the surface of the earth. Worldwide, there...