In 1887, as Colorado's gold production neared its peak, the Ground Hog mine near the town of Gilman yielded an unexpected treasure: a ropey branch of gold that split into a trio of curling tendrils. Standing just over 4.7 inches tall and weighing roughly half a pound, the yellow curlicues of precious metal represent the rarest form of gold ever found.

“It’s truly a unique object—there’s nothing even comparable to it,” says John Rakovan, a mineralogist at Miami University in Ohio. This rarity, however, has a scientific down side: No one wanted to damage or cut the few known samples of wire gold to do the tests necessary to figure out how they formed. For decades, the tendrils