Limestone is an important industrial raw material in metallurgy, building materials, chemical industry, light industry, construction, agriculture and other special industrial sectors. Especially in North China and the southern part of Northeast China, thick and pure limestone is generally deposited, which is a valuable raw material for cement and metallurgy industry. With the development of steel and cement industry, the importance of limestone will be further enhanced.
The main component of limestone is calcium carbonate, which can be dissolved in water containing carbon dioxide. Generally, one liter of water containing carbon dioxide can dissolve about 50 mg of calcium carbonate.
Limestone is the rock formed by the compaction and cementation of calcium carbonate deposited in the lake and sea after losing water. The mineral composition of limestone is mainly calcite (accounting for more than 50%) and some impurities such as clay and silt. The formation of the vast majority of limestone is related to biological processes. The limestone formed by the accumulation of biological remains includes coral limestone, shell limestone, algal limestone, etc., which are collectively called biological limestone. Limestone formed by chemical precipitation of calcium carbonate (CaCO3) in aqueous solution is called chemical limestone. Such as ordinary limestone, siliceous limestone, etc.