Solutional cave and most abundant solutional caves are located in limestone. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws, calcite rafts and columns. These secondary mineral deposits in caves are called "speleothems". Limestone dissolves under the action of 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. Solutional caves in this landform—topography are often called karst caves. Lechuguilla Cave in New Mexico and nearby Carlsbad Cavern are now believed
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