Limestone is a sedimentary rock made of calcium carbonate (CaCO3), usually in the form of calcite or aragonite. It may contain considerable amounts of magnesium carbonate (dolomite) as well. However, minor constituents of clay, iron carbonate, feldspar, pyrite, and quartz is also commonly present.

Limestone has numerous uses: as a building material, an essential component of concrete (Portland cement), as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, and as a popular decorative .