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 Alternatively, calcium carbonate is prepared from calcium oxide. Water is added to give calcium hydroxide then carbon dioxide is passed through this solution to precipitate the desired calcium carbonate, referred to in the industry as precipitated calcium carbonate (PCC): The thermodynamically stable form of CaCO under normal conditions is hexagonal β-CaCO, (the mineral calcite). Other forms can be prepared, the denser,(2.83 g/cc) orthorhombic λ-CaCO ( the mineral aragonite) and μ-CaCO, occurring as the mineral vaterite. The aragonite form can be prepared by precipitation at temperatures above 85 °C, the vaterite form can be prepared by precipitation at 60 °C. Calcite