Tahitian black pearls come from mother-of-pearl secretions from a rare species of oyster called the pinctada margaritifera, a species cultivated in the lagoons of Polynesia. The most beautiful Tahitian pearls are used to make pendants and rings, followed by necklaces and earrings. The size of the pearls and the thickness of the mother-of-pearl are very important for the classification.
The size of the pearls and the thickness of the mother-of-pearl of the Tahitian pearl
The size of the pearls is expressed in millimetres. In general, Tahitian pearls measure between 8 and 14 millimetres. Some pearls can reach 16 millimetres and very rarely 18 millimetres. The record is 21 millimetres in diameter. Pearls of this size are called exceptional gems, regardless of their colour.
The thickness of the nacre affects the longevity and sometimes the beauty of the cultured pearl. Tahitian pearls are reputed to have a thick mother-of-pearl. This is due to the length of the gestation period with its carrier oyster. A Tahitian cultured pearl must have a nacre thickness that covers at least 80% of the surface of its nucleus according to the official classification. Pearls that have a thin layer of nacre are rejected.
Qualification of the Tahitian pearl
In general, the qualification standards are accepted by many jewellery specialists, although sometimes there are trading companies that create their own rules. They then base another interpretation of these standards. The qualification standards are always based on the official graduation of the GIA in consultation with the government of Tahiti, referring to the pearl farms in Polynesia and the export of these pearls.
It should be noted that when there is qualification of a gem quality pearl for jewellery such as rings, earrings and pendants, please note that only the best pearls from only 1% of Tahiti’s pearl production have been used.
Shapes of the Tahitian pearl
Tahitian pearl professionals classify black pearls according to five shapes: round, semiround, baroque, semi-baroque and circled.
Round pearls are spherical. There is a variation in diameter of less than 2%. The round pearl is the most sought-after and the rarest of Tahiti Cultured Pearls. This means that it is the most expensive. Semi-round pearls are slightly imperfect spheres with a variation in diameter between 2 and 5%. They can qualify as almost round pearls. Baroque pearls are irregular and have no axis of rotation. Semi-baroque pearls are subdivided into four shapes: oval, drop, pear and button. Ringed pearls have regular bands, rings or grooves perpendicular to an axis of rotation covering at least one third of the surface of the pearl.