The pearl is the result of the natural body's reaction to the introduction of a shell of a foreign body within it: the shell, to defend against the intruder, secretes a substance white, iridescent nacre, which accumulated and compacted around to it in multiple layers (nacre), goes on to form the pearl.
In the market there are two types of pearls: the NATURAL PEARLS and CULTURED PEARLS. Natural pearls are so rare in nature that most of those marketed are grown; to obtain a cultured pearl a small foreign body is purposely inserted into the shell. There are different types of pearls, the most notable are the Akoya pearls, Freshwater pearls, South Sea pearls, Tahitian pearls.
Akoya pearls are produced by the Pinctada Fucata Martensii, better known as Akoya Oyster, named after the mollusk concerned, grown mainly in Japan and China. Renowned for their excellent luster, Akoya pearls are considered the most classic pearls. They are usually white or ivory / cream, with hints of pink, silver or ivory / cream.
The Freshwater pearls are generally less bright pearls than Akoya sea water ones, and are not round in shape. They have a wide variety of shapes and natural colors, and tend not to be as expensive as saltwater pearls.
The South Sea pearls or Australian pearls are the largest pearls in the world. The size of the diameter of an Australian pearl is ranging from 9 to 20 mm. The areas where it is possible to grow such big pearls are limited, and this fact explains why these pearls are extremely rare. The South Sea pearls are produced by the Pinctada Maxima Oyster and are grown between the Indian Ocean and the Pacific Ocean, primarily in Australia but also in the Philippines and Indonesia.
The Tahitian black pearls are among the most beautiful pearls in the world. These pearls are produced by the Pinctada Margaritifera Oyster in black lips, in Tahiti and in the archipelago of French Polynesia, and they are the only cultured pearls that are naturally dark. In fact, the color of these pearls is never really black, as there are no black pearls in nature: Tahitian pearls have colors ranging from gray to silver, or colors that have green tones with fantastic reflections of peacock green, bronze, silver and pink.