Which type of cultured pearl is primarily cultivated using a bead nucleus?

The type of cultured pearl primarily cultivated using a bead nucleus is associated with the South Sea pearls. South Sea pearls are unique among cultured pearls because they are usually produced by inserting a round bead made from mollusk shell or another suitable material into the oyster. This bead serves as a nucleus around which the oyster secretes nacre, ultimately forming the lustrous pearl.

This cultivation method for South Sea pearls allows for the creation of larger and more lustrous pearls, as these oysters tend to have a longer formation time and produce a thicker layer of nacre, contributing to their overall quality and size. Other types of cultured pearls, such as freshwater and Akoya pearls, typically do not use a bead nucleus; instead, they can be cultivated using a small piece of mantle tissue from another oyster.