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Gemstone Infocenter
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Comprehensive Gemstone
Information
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Pearl - The Oldest Gem
A pearl is produced when the mollusk secretes layers of mother-of-pearl
(calcium carbonate in the form of aragonite) and conchiolin (a horn-like
substance) around an irritant. The irritant could be natural grit, or even small
rounded beads of mother-of-pearl placed in cultured pearls.
The layers (also called nacre) gradually build up during 3 to 7 years to form
a spherical, oblong or irregularly-shaped pearl. Light reflecting from these
overlapping layers near the surface of the pearl flash a subtle spectrum of
color, called the "orient of pearl." Depending on the type of mollusk, pearls
can be white, pinkish, brown or even black.
In 1919, the son of a Japanese noodle maker perfected and patented a method
of cultivating Pearls. This transformed the production of the pearls into an
industry.
A cultured pearl gets a helping hand from man. The irritant is a surgically
implanted mother-of-pearl bead or nuclei. The core or center of a cultured pearl
is, therefore, much larger than that of a natural pearl. As long as there are
enough layers of nacre to result in a beautiful, gem-quality Pearl, the size of
the nucleus is of little importance to beauty or durability. The culturing
process takes place over a period of from one to three years, depending on the
conditions, the species, and the desired outcome.
Saltwater Pearls are usually more expensive than freshwater pearls. One of
the most popular salt water pearls is Akoya Japanese Pearls. South Sea Pearls
also command a premium price. They are typically much larger than Akoyas. The
black pearls mostly come from Tahiti. All these pearls command a premium price
in the market.
Akoya Pearls are very popular and are named after the Japanese word for the
relatively small Pinctada Fucata oyster. Mostly grown in Japanese and Chinese
coastal waters, these oysters are nucleated with as many as five beads ranging
from 2 to 6 millimeters in diameter. Only about one out of five nucleated Akoya
produces Pearls and only a fraction of these are of gem quality.
South Sea Pearls
South Sea Pearls come from Australia, Indonesia and the Philippines. Cultured
in varieties of Pinctada Maxima, these large, warm water loving, gold and
silver-lipped oysters produce fabulous colors. They are very expensive.
Tahitian Pearls are from French Polynesia and are named after the tropical
island of Tahiti. Grown in the large black-lipped oyster Pinctada Margaritifera,
these Tahitian Pearls are usually very expensive. They are well known for their
very attractive black, gray and silver colors.
Freshwater Pearls
Freshwater Pearls are cultured by slightly different methods without a bead.
Although historically originating in Japan around Lake Biwa, Chinese freshwater
pearl production congregates on the Yangtze River in Eastern China. The US also
produces fresh water pearls in the South, especially the Tennessee River.
Freshwater Pearls are cheaper to produce as each mollusk can yield up to 30
pearls per harvest! American freshwaters are allowed to mature for much longer
than all other cultured pearls (up to 5 years, compared to 1 year for most
others) resulting in a thicker nacre which gives American pearls an unusually
high luster and orient (the iridescence from the light reflected from the inside
of the pearl).
Culturing pearls is a delicate process. Only 25 - 50% produce pearls and
generally only a small percentage of the pearls harvested are of gem quality.
The freshwater pearls comes in a range of colors - from white to tan to grey,
depending primarily on the species which is used in the production.
Enhancements are very common. Most of the pearls are bleached to remove dark
spots which show through the nacre. Other techniques such as dying or
irradiation produce pearls with exotic colors such as green, rose and lavender.
Faux
(Fake) Pearls
Faux pearls (fake or artificial pearls) can consist of a variety of materials
such as glass, ground fish scales, plastic or shell with various surface
treatments meant to simulate the pearls luster.
Fakes can be easily detected with the simple tooth test.
How to Test for Fake
A rule of thumb when testing a suspect pearl, is to rub it across the surface
of your teeth. Gently scrape the pearls along the ridges of your top teeth. If
it glides easily, it's fake. If you feel a slight gritty abrasiveness, it's most
likely cultured or natural.
There is no real way to tell if a pearl is natural or cultured. X-ray
inspection can do that. The natural pearl will not have the seed or nucleus and
the nacre or wall will be much thicker. Also, the wall will be made of webbing
for natural pearl. Natural pearls are very rare and if you find them, they will
command a premium price.
Pearls are generally named by their shape.
Baroque pearls can be any shape, stick pearls, button pearls, seed or
rice pearls, rounds and drops.
Blister pearls are created by attaching a bead or other nucleus to the
shell of the mollusk and then cutting it out after it has become nacreous.
Mabe pearls are assembled from blister pearls which are then filled
and glued to a shell base.
The term "keshi" has come to be used for just about any baroque pearl.
It really refers to a small pearl which spontaneously forms in the oyster during
the culturing process, without mantle tissue or bead.
Next: Pricing Pearls
[Pearl Page 1] [Pearl
Page 3] [Pearl Page 4]
See Also:
Products with Pearl
Therapeutic Properties of Pearl
Gemstone Infocenter Home
Gift Selections incorporating Gemstones
Guide to Caring for Gemstones
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