These crystals are known as calcite, or cave onyx. Sometimes calcite is deposited as the drips hang from the ceiling of the cave, forming a stalactite. Other times the drops of water are still full of minerals as they drop to the cave floor and build up stalagmites. Beads of moisture sometimes deposit onyx on the cave walls in rough-looking clusters called cave coral. Water flowing slowly down the walls or across an incline in the cave form smooth looking onyx known as flowstone.
Onyx formations can take many different shapes, depending on the way the water comes into the cave.
A karst terrain is one in which solution, or dissolving of limestone, dolomite, gypsum or marble by water, plays a major role in land erosion. Karst areas are often characterized by a large number of caves, springs, sinkholes, and surface streams which disappear underground. Much like a piece of Swiss cheese coated with soil, central Kentucky contains these features and the unique environmental problems associated with them. All of these different types of water conduits contribute to the recharge of the groundwater system in the area. There are two basic ways in which waters from the surface recharge groundwater supplies in karst areas.