Shape

Pearls grow as the oyster dictates, and keishi pearls show this best: they form when the graft tissue keeps secreting nacre after the bead nucleus is rejected, so they are solid nacre with no core. Tahitian cultured pearls, grown in Pinctada margaritifera, sort into the standard trade shapes: round, semi-round, oval and button, drop, circled, and the baroque and semi-baroque pieces. Round has always commanded the highest prices, but more designers now build around drops, circles and baroques precisely because each one is irregular in its own way.

Colour

"Black pearl" is shorthand, not a description. In their natural state Tahitian pearls run through grey, charcoal, green, blue, aubergine and the prized peacock, plus warmer cherry and pistachio tones. These colors are the oyster's own; our Tahitian pearls are never dyed. The deep peacock and aubergine overtones are unique to Pinctada margaritifera and are exactly what you do not get from a white or golden South Sea or an Akoya. Choosing among them is mostly personal taste.

Size

Size is measured across the diameter in millimetres, and it is the single biggest driver of price because larger pearls are exponentially rarer. Most Tahitian cultured pearls fall between 8 and 14mm. Anything from 15mm up is genuinely scarce, and the rare pieces past 18mm are treasures that command a steep premium.

Surface Quality

Surface is judged by eye, in good light, because Tahitian pearls are an organic product and almost none are flawless. French Polynesia's official scale runs Top Gem (no visible defects), then A (tiny, barely visible marks), B (light imperfections over a small area), C (marks across up to two-thirds of the surface) and D (heavier marks). This is a producer and trade scale, not a GIA standard, and you will sometimes see the same pearls described with the AAA-to-A retail shorthand instead.

Radiance

Radiance is luster plus orient, and it is what separates a good pearl from a forgettable one. Luster is the sharpness of the reflection on the surface: high luster gives an almost mirror-like return with crisp edges, while weak luster looks chalky and soft. Orient is the iridescence that floats over the color, produced as light splits through the stacked aragonite platelets of the nacre. Strong orient throws a faint rainbow across the pearl, the same effect you see on a soap bubble, and it depends on the nacre being thick and well ordered.

Pearl Valuation

As a rule, the larger the diameter and the rounder the shape, the higher the price, but the rule has exceptions. A big pearl with poor luster and a marked surface can be worth less than a smaller one that is clean and bright. For Tahitians specifically, color and radiance carry the most weight with experienced buyers, which is why two pearls of the same size can sit at very different prices.