Flowstones are composed of sheetlike deposits of calcite formed where water flows down the walls or along the floors of a cave. They are typically found in "solution caves", in limestone, where they are the most common speleothem. However, they may form in any type of cave where water enters that has picked up dissolved minerals. Flowstones are formed via the degassing of vadose percolation waters.

Formation

Flowing films of water that move along floors or down positive-sloping walls build up layers of calcium carbonate (calcite), aragonite, gypsum, or other cave minerals. These minerals are dissolved in the water and are deposited when the water loses its dissolved carbon dioxide through the mechanism of agitation, meaning it can no longer hold the minerals in solution. The flowstone forms when thin layers of these deposits build on each other, sometimes developing more rounded shapes as the deposit gets thicker.

There are two common forms of flowstones, tufa and travertine. Tufa is usually formed via the precipitation of calcium carbonate, and is spongy or porous in nature. Travertine is a calcium carbonate deposit often formed in creeks or rivers; its nature is laminated, and it includes such structures as stalagmites and stalactites.