A pearl is a hard, rounded object produced within a living shelled mollusc. The finest quality pearls have been highly valued as gemstones and objects of beauty for many centuries.

Strictly speaking, almost any shelled mollusc is able to produce a “pearl”. However, the “pearls” produced are often undesirable because they lack the lustre and iridescence we normally associate with pearls.

Desirable pearls are composed of layers of nacre and are produced by saltwater pearl oysters and freshwater pearl mussels. These clams both have a nacre shell lining.

Freshwater mussels (Unionidae) live in lakes, rivers, ponds and other bodies of fresh water, these days with the vast majority coming from China.

Saltwater pearl oysters (Pteriidae) live in the tropical oceans and are usually cultivated in protected lagoons in

• Akoya,
• South Sea and
• Tahiti and other Pacific Islands.