Pearl

Pearl is formed in shellfish – especially oysters and mussels – as a natural defense against an irritant, such as a piece of grit. Layers of aragonite, known as nacre, are secreted around the irritant, and gradually build up to form the solid pearl. Light-reflecting from these overlapping layers produces a characteristic iridescent luster, also known as the ‘orient of pearl.’

In cultured pearls, an irritant is introduced to initiate the formation of a pearl. Similarly, in a ‘nucleated’ cultured pearl, a small bead is used as the nucleus, upon which the layers of nacre are secreted. Pearls vary in color from white, white with a hint of color (often pink), to brown or black, depending on the type of mollusk and the water.

A pearl’s color is a mixture of the body of color and luster. It is sensitive to acids, dryness, and humidity, and so is less durable than many other gems.

A pear forms as a sphere when an irritant is not attached to the shell. Natural freshwater pearls may occur in different shapes. Cultured pearls have the same pearly luster as natural specimens.

For hundreds of years, Mumbai (India), has been an important center for the buying and selling of pearls. To present them for selling, pears are sorted by size, then strung into bunches on silk thread. Different sizes are included so that a complete necklace can be made from a ‘bunch.’

In Japan, it is common to use seawater cultures pearls in jewelry. The country leads the world in the production of cultured pearls, although they have been used by the Chinese for hundreds of years.

Pearls were once thought to be the tears of the gods.

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Occurrence

Natural Pearl has been harvested from the Persian Gulf, the Red Sea, and the Gulf of Manaar (Indian Ocean) for thousands of years. The coasts of Australia and Polynesia produce mainly cultured pearls. Both seawater and freshwater pearls are cultivated in China and Japan. Freshwater pearls occur in the rivers of Germany, Austria, France, Ireland, Scotland, and Mississippi (the USA).