Limestone is a sedimentary rock composed principally of calcium carbonate (calcite) or the double carbonate of calcium and magnesium (dolomite). It is commonly composed of tiny fossils, shell fragments and other fossilized debris. Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral with a chemical composition of CaCO3. It usually forms in clear, calm, warm, shallow marine waters.
Limestone is a source of lime (calcium oxide), which is used in steel manufacturing, mining, paper production, water treatment and purification, and plastic production. Lime also has major applications in the manufacture of glass and in agriculture.