What is the difference between natural pearls and cultured pearls?

Natural pearls have grown inside a mollusk, be it fresh or sea water, as a result of an irritant entering into the shell and the creature lays down protective layers of Nacre and so creates a pearl. The nucleus of a natural pearl is usually a grain of sand. Natural pearls are extremely rare, usually misshapen and very, very costly.

Since the late 1800s it has been possible to grow pearls in oyster farms after Japanese entrepreneur Mikimoto Kokichi created the world’s first cultured pearl. Over a relatively short period of time this has revolutionised the jewellery industry and made pearls much more accessible. Yet high quality, spherical pearls with luster and desirability are still extremely valuable. Cultured pearls have a nucleus inserted into the shell of either Mother of Pearl or soft tissue, the mantle, which the mollusk then covers with "Nacre" so producing a pearl. Today, high quality cultured pearls, of different types from different species of mollusk, are widely available and Heidi Kjeldsen specialises in them.