The oysters are nucleated with a bead composed of mother-of-pearl and a small piece of mantle tissue. This bead becomes the nucleus of the pearl and is the reason akoya pearls are more often perfectly round.
Carbon definition, Chemistry. a widely distributed element that forms organic compounds in combination with hydrogen, oxygen, etc., and that occurs in a pure state as diamond and graphite, and in an impure state as charcoal.
carbon: an element that can be found in all living things. carbon dioxide: a chemical compound composed of two oxygen atoms bonded on either side of a carbon atom (CO 2); usually present as a gas. hydrocarbon: a chemical compound containing hydrogen and carbon and often occurring in fossil fuels. calcium carbonate: CaCO 3; a white, chalky substance