Cave formations, also known as speleothems, are natural structures that develop in caves over time. They are primarily formed from the deposition of minerals, particularly calcium carbonate, which is carried by dripping water. Common types of cave formations include stalactites, which hang from the ceiling, and stalagmites, which grow upward from the floor. These formations can take thousands to millions of years to develop, depending on the mineral content and the rate of water flow. Other types of cave formations include columns, which form when stalactites and stalagmites meet, and flowstones, which create smooth, layered surfaces along cave walls.