Cave rainwater and groundwater charged with HCO (carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as "karst", characterized by sinkholes and underground drainage. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws and columns. These secondary mineral deposits in caves are called "speleothems". The portions of a solutional cave that are below the water table or the local level of the groundwater will be flooded. Lechuguilla Cave in New Mexico and nearby Carlsbad Cavern are now believed to be examples of another
Calcium carbonate caves. Two hydrated phases of calcium carbonate, monohydrocalcite, CaCO·HO and ikaite, CaCO·6HO, may precipitate from water at ambient conditions and persist as metastable phases. In contrast to the open equilibrium scenario above, many swimming pools are managed by addition of sodium bicarbonate (NaHCO) to about 2 mM as a buffer, then control of pH through use of HCl, NaHSO, NaCO, NaOH or chlorine formulations that are acidic or basic. In this situation, dissolved inorganic carbon (total inorganic carbon) is far from equilibrium with atmospheric CO. Progress towards equilibrium through outgassing of CO is slowed by (i) the slow reaction HCO