Luobi Cave Luobi Cave Luobi Cave () is a karst cave under the west face of Yin Ridge (印岭) located north east of Lizhigou Town (荔枝沟镇), from Sanya City, Hainan Province, People's Republic of China. The entrance to the cave is approximately high and wide. Inside the apex reaches a height of with a floor area of about Two large stalactites hang down from the roof like large pens, hence the cave's name. A number of inscriptions carved into the walls of the cave are believed to date to the Yuan Dynasty (1271–1368). One of these refers to the precise date of
Calcium carbonate Calcium carbonate shares the typical properties of other carbonates. Notably, Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate. This reaction is important in the erosion of carbonate rock, forming caverns, and leads to hard water in many regions. An unusual form of calcium carbonate is the hexahydrate, ikaite, CaCO·6HO. Ikaite is stable only below 8 °C. The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. Pure calcium carbonate (e.g. for food or pharmaceutical use), can be produced from a pure quarried source (usually marble).