Limestone, also known as calcium carbonate, is a compound whose chemical formula is CaCO₃. CAS 471-34-1. It is a common material on earth and can be found in rocks. The main ingredients of animal dorsal shells and snails shells. It exists in nature with calcite and aragonite two minerals. Calcite is a triangular system, hexagonal crystal, pure calcite colorless transparent, generally white, containing 56% CaO, 44% CO₂, density of 2.715 g / cm³, Mohr hardness of 3, the property of brittle. Aragonite belongs to the orthogonal strain, rhombic crystal, gray or white, density of 2.94 g/cm³, Mohr hardness of 3.5-4, dense nature. The physical properties of limestone are very important for the crystallization of calcite in China. Dense limestone exhibits a low porosity and fine grain structure with high strength. The density of limestone is about 2.65-2.80 g/cm³, dolomitic limestone is 2.70-2.90 g/cm³ and dolomite is 2.85-2.95 g/cm³. Bulk density depends on porosity.