Rawhiti Cave become increasingly finer deeper down into the cave. A short walking track leads halfway down into the cavernous opening to a viewing platform. The diverse twilight-zone flora near the entrance of Rawhiti Cave makes this cave nationally significant. Over long periods of time, plant growth on the cave formations causes them to grow towards the sunlight as more calcium carbonate is deposited regularly on top of the plant growth. This phenomenon, called phytokarst, is most evident on the larger stalactites near the cave entrance, which are strongly curved outwards due to the heavy moss and fern growth on their sunlit
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