It is widely distributed in nature and is the main ingredient in limestone, marble, and coral. In caves, ground waters deposit calcium carbonate over time to form stalactites and stalagmites.
Calcium carbonate is an ingredient of some toothpastes and toothpowders.
It is also used in some medicines to reduce acidity in the stomach. Calcium carbonate dissolves only slightly in pure water but forms calcium bicarbonate if carbon dioxide is present. Robert J. Ouellette, Ph.D., Professor of Chemistry, Ohio State University. How to cite this article.