Round pearls
Round pearls are almost perfect spheres whose diameter variation rate is less than 2%. The round pearl is the most sought after and the most rare of cultured black pearls.
Semi-round pearls
Semi-round pearls are slightly imperfect spheres whose diameter variation rate is greater than 2% but less than 5%.
When a pearl is allowed two years to grow inside an oyster, the chances of even, perfectly spherical nacre accumulation are a long shot. One experienced seller of fine Tahiti pearls says true rounds rarely account for more than 10% of a Tahitian pearl farm's crop. And 5% is more the norm.
The percentage gets even smaller, he adds, when taking into account the many round pearls that are so heavily blemished they are unsellable. No wonder, then, that all other things being equal, fine-quality round black cultured pearls are the most rare and expensive of the breed.
However, more plentiful semi-rounds and button shapes can give the look of round shapes for less money, especially when these pearls are set in jewelry. In such cases, slight deviations from round and even noticeable elongation can be concealed or, at the very least, masked.
Because Tahitian pearls are most commonly used in jewelry, the low incidence of rounds is not considered a drawback. On the contrary, the wide variety of affordable fancy shapes is a big drawing card for jewellers who specialize in them.
Semi-baroque pearls
Semi-baroque pearls exhibit at least one axis of rotation and are subdivided into three shapes: drop, button and pear.
Ringed, or circled, pearls
Ringed, or circled, pearls are characterized by regular streaks, rings or grooves that are perpendicular to an axis of rotation and cover more than a third of the pearl's surface. Ringed pearls, which generally account for 25-30% of a black cultured pearl harvest, seem to fire the imaginations of many designers.
No one knows why "circle pearls" occur so often in harvests. Perhaps it is the species of oyster used to grow them. Whatever the cause of ringed pearls, they often compensate for this characteristic with pronounced color play and multiple hues.
Designers often take advantage of their low prices and high appeal by setting bands of precious metal accented with diamonds and colored stones into their grooves. These bands subdivide the pearl into contrasting spheres of color.
Baroque pearls
Baroque pearls do not have any axis of rotation. Given the transforming impact of design on the look of a pearl, it is hardly surprising that black pearl specialists usually admire drop and baroque shapes.
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