Crater of Diamonds State Park

At the Crater of Diamonds State Park in southwest Arkansas, visitors are free to dig and sift for diamonds blasted to the surface eons ago via a rare volcanic pipe formation. In 2007 alone, the park says more than 1,024 diamonds were discovered, from sand-grain-size specks on up to something mountable on a ring. The park’s “finders keepers” policy lets diggers pocket all the diamonds, semiprecious stones, rocks, or minerals they can unearth in a day.