What chemical compound is the main constituent of all cave formations?

Question

Please have two sentences or more and fast.

Answer 1

Most cave structures,such as stalactites and stalagmites,are created through a process called calcification.Calcium dissolved in ground water drips into underground caverns,deposting the calcium on their way down.The water evaporates,but the calcium remains,thus building the structures of which you speak.

Answer 2

Limestone, (Calcium Carbonate) the solidified remains of organisms, soluble in weak acid such as rain water.
Over time large caverns and complex cave systems can be dissolved from the rock.