Look for Tahitain cultured pearls for amazing hues of grey and black.
These gems are created by the beautiful, black-lipped pinctada margaritifera in French Polynesia, the Cook Islands and other nearby locations. This is the only oyster that produces predictable colors.
Each oyster is implanted with only one nucleus and left for about three years to develop. They can be implanted two, maybe three times. These oysters yield pearls measuring from 8 to 17mm in diameter with 9 to 11mm being the most common size. anywhere from 8 to 18mm in diameter with 10 to 15mm being the typical range. 30-40% of the yield is spherical.
Like the South Sea pearls, strands of large, well matched pearls command premium prices and many are used alone as focal stones. To protect the prestige associated with beautiful pearls of consistently high quality, the French Polynesian government enforces standards of nacre thickness and surface quality for exported goods.