Limestone is a natural rock composed primarily of calcium carbonate. It often forms in ancient marine environments from the accumulation of marine organism remains, such as shells and coral reefs, over millions of years. It is characterized by its color, which is usually white, gray, or beige, and a texture that can be smooth or rough depending on its formation location. It is considered a very widespread sedimentary rock in nature and is less hard compared to some other rocks. For sale