Hierve el Agua mountainside. The water has a temperature of . As the water runs down the rock face, it forms large stalactites similar to those found in caves. The flow of water from the spring varies significantly between the dry and rainy seasons. 95% of the surface rock formations are of calcium carbonate; however, lower layers of both rock and water currents are little known as they are sealed by the above layers. The calcium carbonate gives the formations a white or near white appearance, but other minerals that can be present in the water, such as silver, barium and iron can
Calcium oxide are important commodity chemicals. Calcium oxide is usually made by the thermal decomposition of materials, such as limestone or seashells, that contain calcium carbonate (CaCO; mineral calcite) in a lime kiln. This is accomplished by heating the material to above , a process called calcination or "lime-burning", to liberate a molecule of carbon dioxide (CO), leaving quicklime. The quicklime is not stable and, when cooled, will spontaneously react with CO from the air until, after enough time, it will be completely converted back to calcium carbonate unless slaked with water to set as lime plaster or lime mortar. Annual worldwide