Cultured pearls can be divided in two main categories, Freshwater and Seawater pearls. The Seawater pearls can also be subdivided into three categories, Akoya, Tahitian and South Sea pearls.
Freshwater pearls: All pearls producing countries combined can only produce about 10% of the volume produced in China. In addition to the quantity the Chinese pearl farmers have also greatly increased their focus in quality in the recent years. The shape of the freshwater implanted tissue strongly influences the shape of the resulting pearl. Only about 2% of the harvested pearls are round or near round. The sizes of the freshwater pearls range from 2mm to 12mm.
Akoya pearls: Japan and China are the main producers of Akoya cultured pearls however Japan is still considered producing the best quality as is still boasting a tradition of over 100 years. Akoya Pearls, larger than 8mm, are very rare. All of the PearlsOnly strands bear the JPEA inspection tag. The Japan Pearl Exporters Association is an internationally respected pearl-quality-assurance organization and has initiated a strict inspection system and provides a quality assurance inspection tag per strand inspected
Tahitian pearls: Tahitian pearls are actually cultured in the islands of French Polynesia but not in Tahiti. Their cultivation is tricky as they cannot survive out of seawater for more than 4 hours at best, and contact with freshwater (like rain) kills them. They are the only naturally black pearls. Tahitian pearls can reach sizes up to 16mm. A 18mm pearl is very rare.
South sea pearls: They are farmed in the warm waters of the South Sea (Australia, Indonesia, the Philippines, Myanmar (Burma) and Thailand. South Sea pearls can reach sizes up to 20mm, and their natural color is typically white with silver overtones or golden.