Physical Properties of Calcite
Calcite contains calcium carbonate, which has a molecular formula of CaCO3 with a molecular weight of 100.09. These stones are soft and can be scratched with a knife. The rocks are soluble in dilute hydrochloric acid.
Calcite in Caves
Rain water reacts with decaying leaves, becoming slightly acidic and forming carbonic acid. It percolates through the aquifer, dissolving rocks. It drips into caves and dries, leaving behind calcium carbonate deposits that eventually form stalagmites and stalactites.
Calcite Deposits
Old seabeds offer another source of calcite. The bodies of crustaceans are rich in calcium. As crustaceans die, they get deposited on the ocean floor. Acidic seawater, time and pressure turn the bodies into limestone deposits.