File:Broken travertine stalactites (Crystal Onyx Cave, near Cave City, Kentucky, USA) 4 (23624554460).jpg

Travertine stalactites in a Tertiary-Quaternary cave in Kentucky, USA.

Crystal Onyx Cave is a relatively small, speleothem-rich cave on the eastern flank of Prewitts Knob, southwest of the town of Cave City, Kentucky, USA. The walls of the cave are limestones and dolostones of the Ste. Genevieve Limestone (upper Middle Mississippian).

Crystal Onyx Cave was discovered in 1960 as a sinkhole. The name of the cave refers to the whitish-colored travertine (composed of calcite). Fifty-three Indian bones dating to about 680 B.C. were found wrapped up at the bottom of the main shaft of this cave.

The structures shown above are stalactites, one of numerous types of speleothem that occur in caves. "Speleothem" is the technical term for "cave formations", and refers to all secondary mineral deposits in caves. The most common speleothem-forming mineral is calcite (CaCO3 - calcium carbonate), the same mineral in limestone, which is the host rock for almost all caves on Earth. Speleothem composed of calcium carbonate is given the compositional rock name travertine. Some travertine forms at the surface, at hot springs or cold springs. Cave travertine forms in many specific ways, and genetic rock names have been established for the many known varieties (e.g., dripstone, flowstone, helictites, coralloids, shelfstone, rimstone, etc.).

The stalactites shown above are a variety of travertine speleothem called dripstone, which forms by calcium carbonate precipitation from dripping water. Stalactites are vertically-oriented dripstones attached to cave ceilings or upper slanted walls. Rapid dripping produces relatively small stalactites. Slow dripping produces relatively large specimens.

These specimens have been broken, either by reckless, nature-hating visitors or previous cave owners, or by criminals during the infamous "Cave Wars" of the early 1900s.

The interiors of these broken stalactites show light-colored, relatively impurity-free travertine. The outer portions are yellowish-brown to orangish-brown, caused by iron oxide staining.

The photos in this album were taken in boreal summer 2008. The cave closed in 2008 or 2009 when a cell phone company (Bluegrass) bought the entire hill of Prewitts Knob to prevent competition from other cell phone companies. The hill now has cell phone towers.