Keokuk geodes attract rock-hunting hobbyists from all over, but just how easy is it to find one? “As a young kid, we used to go to the Mississippi over there and go fishing,” Mike Shumate recalled.

For just $10, you can be the jewel of the gem show, seated inside an amethyst geode that's 9 feet tall and 6 feet across. Oh, and since it's 6-feet-deep, they can also shut you inside the geode. This ...