Limestone is a sedimentary rock, during the formation of which a porous stone of various densities and shades is formed with an abundance of calcites (lime spars). The structure of the material also contains other minerals that reduce its porosity and increase its strength. Limestones are deposited mainly in saline sea basins, less often - during the evaporation of lagoons and lakes. The color of limestones is predominantly light gray, beige, yellowish. The presence of organic, ferruginous, manganese and other impurities causes a dark gray, brown, reddish and greenish color.
As a rule, the origin of limestone is associated with the vital activity of organisms that secrete calcium carbonate from salt water to form skeletons and shells. Less commonly, the material is of a chemogenic origin. The subsidence of the rock lasts for millions of years (the modern layers remained after the drying of the ancient seas). The thickness of the strata of limestone deposits is radically different: from a few centimeters to five kilometers. The lower the age of the deposits, the more loose the rocks are.