Shape: Each Tahitian pearl is classified under one of the five shape categories described below.
Sphere or less than 2% diameter variation
Imperfect sphere; 2% to 5% diameter variation
Asymmetrical in shape
Non-spherical; at least one axis of symmetry
Over one-third encircled with rings
Size: In most cases, pearl sizes are measured in millimetres. Tahitian pearls are most commonly between 8mm and 16mm in diameter.
Quality: The quality of a pearl is primarily determined by looking at its surface. The pearl is categorized into four qualities, A, B, C, or D, based on its luster and its surface flaws.
A Quality High luster, less than 10% visible flaws
B Quality Good luster, less than 30% visible flaws
C Quality Satisfactory luster, over 30% visible flaws
D Quality Poor luster, over 65% visible flaws
Colour: Tahitian pearls are generally black and grey in colour with a variety of tints, for example light grey, grey-pink, blue, green-grey, peacock green, purple, aubergine, bronze, and yellow-grey.