While nearly any shelled mollusk can produce some sort of pearl, the great majority of these pearls are not valued as gemstones.

Nacreous pearls - perhaps the best-known and most commercially significant pearl that is produced by two groups of bivalves or clams. This pearl is made from layers of nacre by the same process as is used in the secretion of the mother of pearls which lines the shells.

Natural pearls - this is a pearl that forms with a total lack of human intervention. This type of pearl is very rare. In order to find one wild pearl, hundreds of pearl oysters or pearl mussels must be gathered in open. This of course results in a death but centuries, this was the only way to obtain a pearl. This is also one of the main reasons that pearls fetched such an extraordinary price.

Cultured pearls - formed on a pearl farm, with human intervention cultured pearls comprise the vast majority of pearls on the market today. They are the most common pearl, as well as the most cost effective.

Freshwater pearls - although they may look similar to the saltwater pearls, natural freshwater pearls form in a variety of species of freshwater mussels. These muscles may be found in lakes, ponds, rivers and other bodies of fresh water. Most freshwater cultured pearls today come from China.

Saltwater pearls -grown in several species of marine pearl oysters in the family Pteriidae. Today, saltwater pearls may still be found but the yields extremely small. Today, Pearls cultured in mollusks are considered saltwater pearls. Ajkoya pearls, Tahitian pearls, and South Sea pearls are the most common types of saltwater pearls.