There's Green in Them Thar Hills

Emerald hunting yields profits and perils in Colombia

It was just before sunrise on a recent summer morning high in the Boyaca mountains of central Colombia. Already the steep terrain was bustling with prospectors called guaqueros, or treasure hunters. They were seeking their fortunes in the Cosquez cut, a mountainside excavation rich with dazzling gems -- emeralds.

Suddenly, 25 armed men disguised as soldiers appeared and rounded up eleven miners and guaqueros. Forcing them to lie face down in the gritty black soil, the gunmen coolly shot and killed their victims one by one, then escaped into the verdant hillside. When real Colombian soldiers arrived to investigate the slaughter,...