Calcium Carbonate

Abstract

Calcium carbonate, CaCO3, occurs naturally as the principal constituent of limestone, marble, and chalk. Powdered calcium carbonate is produced by two methods on the industrial scale. It is quarried and ground from naturally occurring deposits and in some cases beneficiated. It is also made by precipitation from dissolved calcium hydroxide and carbon dioxide. The natural ground calcium carbonate and the precipitated material compete industrially based primarily on particle size and the characteristics imparted to a product. Calcium carbonate is one of the most versatile mineral fillers and is consumed in a wide range of products, including paper, paint, plastics, rubber, textiles, caulks, sealants, and printing inks. High purity grades of both natural and precipitated calcium carbonate meet the requirements of the Food Chemicals Codex and the United States Pharmacopeia and are used in dentifrices, cosmetics, foods, and pharmaceuticals. Calcium carbonate occurs naturally in three crystal structures: calcite, aragonite, and, although rarely, vaterite. The commercial grades of calcium carbonate from natural sources are either calcite, aragonite, or sedimentary chalk. In most precipitated grades aragonite is the predominant crystal structure. Calcium carbonate is listed as a food additive and not considered a toxic material. The exposure to dust is regulated, and both natural ground and precipitated calcium carbonates can contain low levels of impurities that are regulated.