Pearls are a thing of rarity and are expensive and are made by marine organisms called oysters. Other marine organisms can also make pearls but the occurrence is even rarer. Although, in the human world, pearls are sought after and a cherished piece, for oysters, it is a mechanism of self defense and a way to get rid of unwanted substances that enter its shell.
Oysters belong to the family of mollusks and those that make pearls are called feathered oysters. There are many types of pearl-creating oysters including gulf-lipped, silver or gold-lipped, Shark bay and Japanese pearl oysters. Of these the silver or gold-lipped is the largest pearl-producing oyster. Oysters live inside bivalve shells that enable them to eat when needed (by opening) and provide protection when closed. In order to protect its soft body against the shell, the oyster produces chemical called nacre, which lines the shell.
Nacre is produced from an organ called mantle, and also used by the oyster to make the pearl. A pearl is made when an irritant like sand, grit or rock enters the shell. In order to protect itself, the oysters secretes nacre to make the irritant smoother, and the end result is a pearl. It takes up to 3 years for the pearl to grow to its full size, and comes in different colors like white, pink, green, blue and even black; the black one being the rarest and most precious.
Natural pearls take years to grow and are very expensive. There are ways to culture oysters and artificially induce the production of pearls. For this, the pearl farmers, introduce irritants in the mollusks’ shell or make a slit in the mantle, to get oysters to secrete nacre. Hence pearls can be grown in a controlled environment and marketed. Understanding the process of how oysters make pearls helps justify the cost of pearls and see it in a different light.
There are pearls that can be made synthetically too. In this case, coated glass beads are used which are filled with wax. These pearls are very inexpensive compared to natural pearls, but lack the shine and lustre of natural pearls.
Natural and cultured pearls can be harvested in both salt and fresh water conditions, the latter being more uneven in shape than the former type. The majority of pearls come from regions including Japan, China, India, Indonesia, Philippines and some from Australia. The price of pearls depends on the size, shape, and shine.