Tahitian pearls are known for their dark colors and exotic features. Often referred to as black South Sea pearls, Tahitian pearls are harvested in more than 80 different natural colors and overtones. When grading Tahitian pearls, however, the Ministry of Perlicultre in French Polynesia has defined export standards of grading only reflective of two considerations: shape and luster/surface.
Nacre thickness, while a grading factor in evaluating other saltwater pearl types, is no longer considered with Tahitian pearls as export is limited to pearls with adequate nacre coverage.
There are five shapes of cultured Tahitian pearls. All pearls exported from French Polynesia fall into one of the following categories:
Round: Perfectly round shape or nearly round with no more than a 2 percent variation in diameter.
Semi-round: Very near-round shape that has a diameter variance greater than 2 percent, but less than 5 percent.
Semi-baroque: Noticeably off-round shape that includes pear, oval, button and drop.
Baroque: Irregular, asymmetrical shape. Baroque pearls, by definition, lack an axis of symmetry.
Circles: More than a third of the surface exhibits distinctly visible circles thought to be produced by a ’spinning’ of the nucleus during pearl formation. If circles are present but do not cover at least third of the pearl surface, the lines are graded as inclusions in the luster/surface category.
The second consideration taken into account when grading Tahitian pearls is the surface and luster consideration. Surface takes into account the smoothness and perfection of the pearl skin while luster judges the quality and quantity of light reflecting from the pearl surface.
The Ministry of Perliculture in French Polynesia uses a five-tier system of grading which includes top-gem, grade A, grade B, grade C, and grade D. Anything falling below grade D is refused for export and is destroyed. This system corresponds to the US grading system which includes gem, grade AAA, grade AA+, grade AA, and grade A.
Top Gem: Perfect, inclusion-free surface. Luster is excellent.
Grade A: Perfect or slight blemishing that does not exceed 10% of the pearl surface. Luster is at least good.
Grade B: Surface blemishing that does not exceed 30% of the pearl surface. Luster is medium.
Grade C: Surface blemishing that does not exceed 60% of the pearl surface. Luster is medium to low.
Grade D: Surface blemishing exceeds 60% of the pearl surface. Luster is low.
Understanding Tahitian pearl grading enables consumers to make educated choices when shopping for Tahitian pearls. After learning to evaluate the core grading principles one can then determine what other value factors are most appealing to their personal style and taste. These value factors include body color, overtone and size. While certain colors and larger pearls are considered more valuable, the most valuable pearls to you should be those that fit your style and personality the best.
Ann McCarville is a pearl expert with years of pearl buying, selling and grading experience. She is the founder and president of PearlStruck.com, an online purveryor of fine cultured pearls. http://www.pearlstruck.com