How do Oysters make Pearls

A pearl is a small hard object, roundish in shape, formed within the marine organisms known as the oysters. Pearl oysters belong to a totally different family known as the Pteriidae or feathered oysters. Both cultured pearls as well as natural pearls can be obtained from these variety of oysters. Natural pearls are created in the wild, without any human intervention whereas cultured pearls are created in a pearl farm under specific conditions. Though both types of pearls are considered to be of equally good quality, natural pearls are more expensive than their cultured counterparts, as they are rare in nature.

How are Pearls Produced by Oysters?
It is very important to know the anatomy of an oyster, and its body mechanisms to understand how oysters make pearls. The shell of the oyster is made of two parts, which are connected by an elastic ligament. The ligament facilitates opening of the shell so that the oyster can feed. As the oysters start to grow, its shell also starts increasing in size. This growing of the oyster shell is facilitated by an organ known as the mantle. The mantle uses the minerals in the oysters food to form this shell.

The inner part of the shell is lined by nacre, a material created by the mantle. Sometimes when the shell is open, a foreign substance manages to slip inside the shell and resides between the shell and the mantle. As a natural reaction to this, the oyster covers this foreign substance as a part of its self-defense mechanism. The same nacre that is used to form the shell is used to cover this substance by forming several layers over it. This eventually leads to formation of a small object which is referred to as a pearl.

Manual Assistance
Cultured pearls are formed with a little bit of manual assistance. The pearl farmer opens the shell of the oyster, cuts a small slit in the mantle and inserts a small irritant, such as a grain of sand, inside it. The oyster treats it as foreign objects and covers it with layers of nacre to form a pearl. Oysters can produce pearls in freshwater as well as saltwater. To form cultured pearls in freshwater, only cutting a slit in the mantle is required, eventually nacre is secreted because of this irritation, and a pearl is formed.

Some Facts and Myths about PearlsContrary to the popular belief that pearls are perfectly round shiny objects, not all pearls, are so well-formed. Some pearls are formed in an uneven shape, owing to the shape of the irritant embedded between the mantle and the shell. These pearls are known as the baroque pearls. Pearls come in various colors, and are found all over the world. But black pearls, which are very rare in nature, are only found in South Pacific. Though all varieties of oysters produce pearls, those produced by some varieties are unattractive and lack commercial value and hence, are not used to make pearl jewelry.

Natural pearls are rare in nature, as not all oysters necessarily produce pearls, and the formation of a single pearl takes many years. On an average any oyster takes 3 to 6 years to produce a perfect pearl. Though pearl diving has become an important commercial activity today, hundreds of oysters are killed just to obtain a single pearl.