Limestone is a type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). A related rock is dolomite, which contains a high percentage of the mineral dolomite, CaMg(CO3)2.

Applications:

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, as a popular decorative addition to rock gardens, and as animal food supplement (Chickens need calcium carbonate to produce eggs with strong shells).