June 11, 2012
Jewel Cave, carved into South Dakota’s Black Hills, is the second longest cave in the world, with just over 151 miles of mapped passageways.
Inside the visitor’s center, there’s a small exhibit of some of the rock formations found in the cave as well as historical photos from the cave’s past.
Frank and Albert Michaud, two local prospectors, discovered the cave in 1900, when they felt cold air blowing out of a small hole in a canyon. As recently as 1959, less than two miles of passageway had been discovered. That year, however, Herb and Jan Conn, local rock climbers, began exploring, and within two years had mapped 15 miles.
Much of Jewel Cave is covered with spar crystals. Typically they are a dull brown color, but rarely they are clear crystalline structures.
Jewel Cave was formed by the gradual dissolution of limestone by stagnant, acid-rich water. The water enlarged a network of cracks that had formed during the uplift of the Black Hills approximately 60 million years ago.