First of all we have to make clear the difference between the natural pearl and cultured pearl. A natural pearl can be produced in several species of mollusks (freshwater molluscs are called mussels, saltwater mollusks are called oysters) without human intervention of any kind. According to the well-know explanation learned at school a piece of sand after penetrating the mollusk causes an irritation and the mollusk protecting itself secretes nacre to cover the irritant. If it were so simple, thousands of natural pearl would be found every day. Instead only sand is found. What is missing then in this story? Just a small piece of epithelial cell which is needed to form a sac around the invader. In case of cultured pearls the grafter (the key figure at the pearl culturing process) places this “invader” into the oyster. It is called nucleus, the Latin equivalent for seed.
The pearl fishing was a gamble, where millions and millions oysters were sacrificed in order to find a handful of quality pearls. With the introduction of culturing process this gamble was stopped and a unique co-operation between nature and human being began.
There are a couple of places in the world, where pearl-fishing is performed today, their total yearly outcome is less than 100 kg. Their values are different but generally they are up to the factors explained in chapter “value factors”. The best known natural pearls come from Basra at the Persian Gulf. They are rather small and are measured in carat.