The shape of black Tahitian pearls varies significantly, which is why the best Tahitian pearl necklaces are extremely costly. It is very expensive to get enough pearls that are nearly equal in size to create a necklace, and even more so if you are using Tahitian black pearls that are nearly perfect spheres. The pearls used to make a black Tahitian pearl necklace are usually round or semi-round, though Tahitian pearls can also be found in other shapes, namely semi-baroque, baroque, and ringed/circled.
Round – pearls that are considered round are nearly perfectly spherical, and when measured, only have a variation in diameter of 2%. Basically, they look perfect to the human eye. These are extremely rare, and therefore extremely expensive. To give you an idea of their rarity, only about 5% of a farmer´s crop of pearls are round pearls. However, keep in mind that of these 5%, there can be many that are flawed, and therefore not used. If you expect to buy a black pearl necklace with round pearls, be prepared to spend a lot of money.
Semi-Round – a Tahitian pearl necklace made with semi-round black pearls makes a great alternative to one with round pearls. It is far cheaper, and the pearls still appear to be nearly perfect spheres. The variation in diameter of semi-round pearls is between 2%-5%. This difference is slight, so must be measured.
Semi-Baroque – semi baroque pearls are not spherical, but are an equal shape on each side, meaning they have an axis of rotation. On each side of that axis, the shape is identical. These symmetrical pearls are broken down into four different shapes: drop (like a teardrop), button, pear, and oval. These stones are often used to make Tahitian pearl necklaces, either by themselves or combined with round or semi round pearls.
Baroque – baroque Tahitian pearls are asymmetrical pearls, and can be found in any random shape. It is difficult to find large numbers of them are identical, and for this reason, it is rare to find them used to make a necklace. They are more commonly used by artisans the make jewelry or pieces of art.
Ringed/Circled – ringed or circled pearls are an interesting display of nature. They make up around 30% of a Tahitian pearl harvest, but it is unknown why this is so common. A ringed Tahitian pearl has one of more rings or grooves that are perpendicular to the axis of rotation. They look like rings going around the pearl. These pearls often have more color hues than the other shapes of Tahitian pearls, and therefore can be very special.