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. 1  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. Symbol: C; atomic weight: 12.011; atomic number: 6; specific gravity: (of diamond) 3.51 at 20Â°C; (of graphite) 2.26 at 20Â°C. carbon dioxide or other carbon compounds that are emitted into the atmosphere and cause rising temperatures: the carbon produced by burning fossil fuels. carbon copy. a sheet of carbon paper.