Every pearl is unique and natural. Only a small fraction of pearls are perfectly round. While the perfect rounds are the most valued, pearls of other shapes are still considered quite beautiful and valuable, provided that the luster is good and there are minimal flaws. Keishi and mabes are also used in jewelry. They are often used to accent cultured pearls.
Some pearl farmers graft special nuclei to the actual shell of the oyster.
At harvest time, mabes are cut out of the mother of pearl and polished. Mabes come in a variety of shapes including round, teardrop and even heart-shaped, depending on the shape of nucleus that is used. It is very difficult to distinguish between Natural pearl and cultured pearl. But when it is a plastic pearl, it is not so hard. Normally plastic pearls are lighter or less in weight compare to cultured or Natural pearl of same size.