Pearls are the most popular of the organic gems. Pearls are created from organic mater by the oyster, mussel, clam, abalone or conch (mollusk). Pearls can form either naturally or be cultivated by mans intervention. Natural pearls are very rare, probably only one oyster in ten thousand farmed would produce a pearl naturally.
Pearls are formed when a piece of shell, sand or other organic matter invades the mollusk. The mollusk will emit a black coating known as conchiolin. Then the mollusk will emit a white nacre, which surrounds the intruder and eliminates the source of irritation.
The introduced irritant for cultured pearls is slightly different, but the process of pearl creation is the same for both a cultured and natural pearl.
Pearls can be cultivated from either salt water or fresh water mollusks. The Akoya oyster produces most of the pearls cultivated by man (80%). The Akoya pearl generally takes three years to grow. The most desired shape amongst pearls is the near round, as it is difficult to get perfectly round pearls.
Other types of pearls include the Mabe pearl, south sea pearl and the conch pearl. The south sea pearls are popular due to being larger pearls. They can be up to 15mm in diameter compared to up to 10mm in diameter of their cold water cousins. South Sea pearls come in a variety of colors including cream, pink, green, blue and black.
The black pearls can be found to have underlying colors of blue, green, violet or a mixture. These mixed colored pearls can sometimes be referred to as the peacock pearl. The black pearl market is dominated by Tahiti.
The fresh water pearl market is dominated by China, although Japan and the United States both produce fresh water pearls. Generally the fresh water pearls are produced by mussels. The freshwater pearls come in a variety of colors including pink, orange, violet, grey and blue.