is a white solid substance which is abundantly found in cliffs and (almost) all over the world. Its main minerals are aragonite, marble and travertine, which dissolved in water incompletely, however it is completely dissolved if water contains co2, and it produces calcium carbonate (which dissolves in very small amounts in water but dissolves completely in water containing soluble CO2 to form calcium carbonate). When calcium carbonate dissolved in running water, causes hardness in them. Consequently, soap doesn’t foam in this water, however, the hardness caused by carbonate is temporary and it is balanced with boiling water. (Dissolution of calcium carbonate in running water causes hardness in them, which is associated with the fact that soap does not foam in such water, but the resulting hardness of calcium carbonate and bicarbonate is temporary and can be relieved by boiling water.
Stalactite and stalagmites in(inside) caves are (also) caused by the reaction of limestone with water containing co2. This substance turns into lime by heating and losing co2. It has crystalline structure of calcite and aragonite with molecular weight of 100/1 gr, density 2/7 gr/cm3, and boiling point of 899’c.