Speleothem

Speleothem is a term given to those cave features that form after a cave itself has formed. They are secondary mineral deposits that are left after the evaporation of mineral-rich water. These mineral deposits usually contain calcium carbonate (CaCO3) or limestone, and sometimes contain gypsum or silica. Stalactites, stalagmites, soda straws, cave coral, boxwork, and cave pearls are all examples of speleothems.