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A pearl is a hard, rounded object produced by certain animals, primarily mollusks
Pearl is valued as a gemstone and is cultivated or harvested for jewelry. The pearl is
also the birthstone of June.
Pearls are formed inside the shell of certain bivalve mollusks. As a response to an
irritating object inside its shell, the mollusk will deposit layers of calcium carbonate
in the form of the minerals aragonite or calcite (both crystalline forms of calcium
carbonate) held together by an organic horn-like compound called conchiolin. This
combination of calcium carbonate and conchiolin is called nacre, or as most know it,
mother-of-pearl.
The unique luster of pearls depends upon the reflection and refraction of light from
the translucent layers and is finer in proportion as the layers become thinner and
more numerous. The iridescence that some pearls display is caused by the
overlapping of successive layers, which breaks up light falling on the surface. Pearls
are usually white, sometimes with a creamy or pinkish tinge, but may be tinted
with yellow, green, blue, brown, purple, or black. Black pearls, frequently referred to
as Black Tahitian Pearls are highly valued because of their rarity; the culturing
process for them dictates a smaller volume output and can never be mass produced.
This is due to bad health and/or non-survival of the process, rejection of the nucleus
(the small object such as a tiny fish, grain of sand or crab that slips naturally inside
an oyster's shell or inserted by a human), and their sensitivity to changing climatic
and ocean conditions.
Pearls fit into two categories: freshwater and saltwater. Astheir name implies,
freshwater pearls are formed in freshwater mussels that live in lakes, rivers, ponds
and other bodies of fresh water. Most freshwater cultured pearls sold today come
from China. By contrast, saltwater pearls grow in oysters that live in the ocean,
usually in protected lagoons. Akoya, South Sea and Tahitian are the three main
types of saltwater pearls.
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