Calcium carbonate (CaCO₃) is an inorganic compound commonly known as greystone, limestone, powdered stone, marble, etc. Calcium carbonate is neutral, insoluble in water, soluble in hydrochloric acid. It is one of the common substances on earth, which exists in aragonite, calcite, chalk, limestone, marble, travertine and other rocks, and is also the main component of animal bones or shells. Calcium carbonate is also an important building material and is widely used in industry.