Glossary of Karst and Cave Terms
Sedimentary rock containing at least 50% calcium carbonate by weight. The purer limestones consist almost entirely of calcite; less pure rocks may be referred to as, for example, muddy limestone. Some limestones are porous with diffuse permeability; these rarely become truly cavernous, though some fissure flow may occur. Where groundwater flow in less porous rocks is restricted to bedding related fissures and secondary fractures it can, even when moving very slowly, corrode the almost entirely soluble rock and lead to true cave development .