This is done by sorting them through sieves. Some pearls reach 16mm and very exceptionally 18mm. To date, the record diameter is 21mm. For some jewellery makers, shape is purely a design element, be it the sensuous curves of the drop or the flowing free-form lines of many baroque shapes. For such artists, all shapes that inspire them share aesthetic equality.
Most designers agree it is difficult to favor one kind of shape over another.
The round pearl is the most sought after and the most rare of Tahiti cultured pearls. When a pearl is allowed two years to grow inside an oyster, the chances of even, perfectly spherical nacre accumulation are a long shot. 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 Tahitian cultured pearls are the rarest and most 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 jewellery.