From a news story entitled "Visitor discovers nearly three carat diamond at Arkansas state park, I learned about the existence of Arkansas’s Crater of Diamonds State Park:
Arkansas The Natural State is blessed with an abundance of geological wonders. Crater of Diamonds State Park, the only diamond-producing site in the world open to the public, stands out as a unique geological “gem” for you to explore and enjoy.
Here you can experience a one-of-a-kind adventure hunting for real diamonds. You’ll search over a 37 1/2-acre plowed field, the eroded surface of an ancient volcanic crater that 100 million years ago brought to the surface the diamonds and some of the semi-precious stones lucky visitors find here today.
How cool.
