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P a g e
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There are essentially three types of pearls: natural, cultured and imitation. A natural pearl
(often called an Oriental pearl) forms when an irritant, such as a piece of sand, works its
way into a particular species of oyster, mussel, or clam. As a defense mechanism, the
mollusk secretes a fluid to coat the irritant. Layer upon layer of this coating is deposited
on the irritant until a lustrous pearl is formed.
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The only difference natural pearls and cultured pearls is that the irritant is a surgically
implanted bead or piece of shell called Mother of Pearl. Often, these shells are ground
oyster shells that are worth significant amounts of money in their own right as irritant-
catalysts for quality pearls. The resulting core is, therefore, much larger than in a natural
pearl. Yet, as long as there are enough layers of nacre (the secreted fluid covering the
irritant)
to result in a beautiful, gem-quality pearl, the size
of the nucleus is of no
consequence to beauty or durability.
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Pearls can come from either salt or freshwater sources. Typically, saltwater pearls tend
to be higher quality, although there are several types of
freshwater pearls that are
considered high in quality as well. Freshwater pearls tend to be very irregular in shape,
with a puffed rice appearance the most prevalent. Nevertheless,
it is each individual
pearls merits that determines value more than the source of the pearl. Saltwater pearl
oysters are usually cultivated in protected lagoons or volcanic atolls. However, most
freshwater cultured pearls sold today come from China. Cultured pearls are the response
of the shell to a tissue implant. A tiny piece of mantle tissue
from a donor shell is
transplanted into a recipient shell. This graft will form a pearl sac and the tissue will
precipitate calcium carbonate into this pocket. There
are a number of options for
producing cultured pearls: use freshwater or seawater shells, transplant the graft into the
mantle or into the gonad, add a spherical bead or do it non-beaded.
The majority of
saltwater cultured pearls are grown with beads.