If the budget belt is a little tighter this year, consider packing your diamond-digging trowel, bathing suit and camping gear and heading to a little-known geologic hot spot in the middle of the United States. Arkansas, “the Natural State,” boasts the world’s only public diamond mine, uniquely heated mineral springs and the Ozark Mountains of Wilson Rawls’ “Where the Red Fern Grows” lore, all within a day’s drive from much of the United States.