A pearl is a biological product produced naturally by certain oysters as a defense mechanism. They are formed when a foreign body such as a sand particle enters the body of the oyster. The oyster in order to get rid of the foreign body coats it with a material called nacre which is basically the chemical calcium carbonate.
Over a period of time these layers make the pearl grow in size until they are taken out. Pearls are cultured by inserting an artificial irritant into the oyster. The oysters are then carefully tended in special beds. Cultured pearls usually take three to six years to grow to a good size.
