Tahitian pearls come in a variety of shapes, listed here in order of desirability: Round, semi-round, semi-baroque, baroque, and circle. Pearls classified as round have less than a 2% variation in diameter, and are the rarest of Tahitian Pearls, accounting for about 5% of total pearl production. Semi-round pearls have less than a 5% variation in diameter. Semi-baroque pearls have at least one axis of rotation, and can be further classified into drop, button, pear, and oval shapes. Baroque pearls have no axis of rotation.
The quality of a Tahitian Pearl is graded as an "A", "B", "C", or "D", depending on the luster and surface purity of the pearl. An "A" pearl should have superior luster and either no small blemishes or a few blemishes on less than 10% of its surface. A "B" pearl should have above-average luster and a few blemishes on less 1/3 of its surface. A "C" pearl should have average luster and blemishes over less than 2/3 of its surface. A "D" pearl should have below-average luster and blemishes over its entire surface.
Tahitian Pearl production and export are strictly regulated by the government of French Polynesia. Every pearl intended for export is x-rayed by the Tahitian Pearl Ministry to ensure that the nacre thickness meets the minimum requirements for export, 0.6mm before July 2002, 0.8mm after. In addition, the blemishes often present on the pearl surface must be fairly shallow, or the pearl will fail inspection. Pearls that do not meet the export criteria are destroyed at the inspection facility.
