Flowstone

Flowstones were composed of sheetlike deposits of calcite formed where water flowed down the walls or along the floors of a cave. They were typically found in "solution, or limestone caves, where they were the most common cave formation. However, they could have formed in any type of cave where water entered that had picked up dissolved minerals.

The subterranean Coway tribes, on the planet Mimban, made spears and other implements from flowstone.