Calcium carbonate is an inorganic compound, the chemical formula is CaCO ?, commonly known as limestone, limestone, stone powder, marble and so on. Calcium carbonate is alkaline, insoluble in water and soluble in hydrochloric acid. It is one of the most common substances on the earth. It exists in aragonite, calcite, chalk, limestone, marble, travertine and other rocks. It is also the main component of animal bones or shells. Calcium carbonate is also an important building material, which is widely used in industry.