Limestone /ˈlaɪmˌstoʊn/ – a widespread sedimentary rock; It mainly consists of the calcite mineral CaCO3 in the form of remains of calcareous shells and skeletons of various organisms or small crystalline grains. It often contains large quantities of dolomite (dolomite O.), particles of sand or clay, as well as coal or bituminous substances; accordingly, it is divided into sandy, clayey (marl), hard coal and bituminous O. Hills. Compressive strength up to 250-300 MPa. Construction (building stone, limestone, lime), metallurgy (flux), etc. (used for liming soils), chemical industry, etc