The Pearl:
The pearl, a hard, round object valued as a gem, is produced as an abnormal growth within the shells of certain bi-valve mollusks: saltwater pearl oysters, saltwater and freshwater mussels, and some species of clams and abalones. All these mollusks have an inner layer of shell made of a lustrous material called nacre, or “mother of pearl”.
It is composed of the mineral Aragonite and an organic, cartilaginous substance called conchiolin. When a bit of foreign matter enters the shell--a grain of sand, a parasite, an undeveloped egg--the mollusk isolates it by gradually coating it with layers of nacre as a natural defence mechanism. The process is slow; it may take three years or more for a mature mollusk to produce a pearl large enough to be commercially valuable. The pearl is one of the few gems created by an organic process; the others are amber, coral, and jet. In ancient culture pearls have symbolized purity, uniqueness, and sublime beauty.
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