A natural calcium-carbon-oxygen combination, that occurs in limestone, chalk, marble, dolomite, eggshells, pearls, coral, stalactites, stalagmites, and the shells of many marine animals. Calcite is often the adhesive in composite rocks. The most abundant dissolved solid in dry land groundwater is calcium carbonate. When deposited, this mineral forms the hard, calcareous cement known as caliche. Caliche is a crust of calcium carbonate often present in semiarid or arid areas, either on top of or within the soil.