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Semi Precious Stones
Types of Pearls
The following are the common
types of pearls in the market. (For information about gemstone buying tips,
jewelry care and jewelry history, you may want to browse the following website:
Gemstones which has excellent
Akoya Pearls are produced by the
Japanese Akoya oyster. Akoya pearls vary in size between 2 and 10mm in diameter,
depending on the size of the oysters in which they are formed. Akoya pearls range in
color from white, to cream, green, silver, pink, and gold. Akoya pearls are most
valued for their high lustre, and their richness of color.
Country of Origin: Japan and China
South Sea Cultured Pearls
South Sea Pearls come from
silver-lipped pearl oysters, except for the golden pearls which come from the
golden-lipped pearl oysters. South Sea cultured pearls often reach to over 10mm in diameter.
Country of Origin:
White South Sea Cultured
Pearl -Australia, Myanmar
Golden South Sea Cultured
Black South Sea Cultured Pearls
Black South Sea
Pearls come from the black-lipped pearl oysters of Pinctada Maxima in the
Tahitian and Okinawa regions. They are typically between 8 and 15mm in diameter.
Their colors range from blue to green, violet, and combinations of these colors,
as well as the most popular peacock green.
Country of Origin: Tahiti
Freshwater Cultured Pearls
These pearls are almost
exclusively cultured in the Chinese lakes and rivers, in Hyriopsis Cumingi
mollusks. They are typically oval-shaped, or in rice grain shapes.
Country of Origin: China
Quality of Pearls
The 7 most important elements to grading a pearl
Luster –Lustre is the quantity and quality of light
reflected from the surface of a pearl. This is the first and most important
factor when judging quality of pearls. To evaluate a pearl's luster, look at the
clarity of images that are reflected in the pearl’s surface. The closer to a
mirror image you see, the better the luster. Pearls with fine luster also seem
to glow warmly from within.
Size –The size of a pearl is measured by its diameter,
and ranges from 8mm to the rare 18mm. The larger the pearl, the rarer it is.
Shape – The rounder a pearl is,
the rarer and more valuable it is. This is only the most common yardstick for
the Classical category, although there are some other very valuable pearls that
are not perfectly round, such as the Baroque pearls which have a more linear
shape which is quite popular.
– The more flawless the surface of the pearl is, the higher it will be valued.
However, a flawless pearl only comes about once in about every million, as
pearls are the result of a natural process, and an oyster will usually leave
some sort of unique mark on the finished pearl.
Color –Essentially, the color of the pearl you desire
is a matter of personal taste. Color has little influence on the actual value of
a pearl. Traditionally, there is a rather consistent demand for the classic
silvery white pearls and the glowing gold shades. The rarest and most desired
are the white “rose” colored pearls.
Weight – The weight of a pearl is not always provided,
however finer jewelers will include it among their descriptions, especially in
the case of larger pearls. Pearls are usually measured in carats, grains, or
momme. Cultured pearls are generally weighed in momme, and natural pearls in
Natural/cultured – this is the difference between
pearls that are found at sea, and those grown in pearl farms
Jewellers also use the AAA-A System, and the A-D System (also
called the Tahitian System) for grading pearls.
The AAA-A System – This system uses a grading scale
from AAA to A, with AAA being the highest grade.
The A-D System (Tahitian System) – grades pearls on a
scale from A to D, with A being the highest, and anything below D being
considered unacceptable for jewelry use.
Pearls come from oysters.
Other than natural pearls, it is more common to culture them in Pearl Farms,
where they are processed under ideal conditions over about two to five years
until a pearl is formed.
Oyster eggs and sperm are first collected and fertilized to
produce new oyster larvae.
Oyster larvae spend the first few weeks of their lives in a
free float, until they reach the point in their development where they cling to
a solid surface. In nature, this would likely be a rock but in oyster farms,
“collectors” are provided as surrogate rocks. There the larvae will develop into
young oysters. This process is monitored by the pearl farmers.
The young oysters are kept in oyster
nurseries, where they spend their first couple of years growing and developing
under safe and comfortable conditions. At about two years of age, they are
considered old enough to nucleate.
Nucleation is a surgical
procedure which implants a foreign object into the oyster. The foreign object
irritates the oyster, causing it to secrete a substance called nacre, which
makes the object less irritating and smoother. The nacre eventually will grow
into a pearl over time.
Nucleation are done in two different ways, depending on if
the farm uses freshwater or saltwater oysters.
· Saltwater Oyster – The oyster is nucleated with a
mother-of-pearl based bead. The bead is coated in a tiny sample of mantle tissue
from another oyster. This coated bead is then implanted into the oyster. The
pearl grows around the bead in the same way it would occur over the grain of
shell or coral in the wild. The shape of the pearl that is produced is directly
related to the shape of the bead, allowing for a variety of outcomes.
· Freshwater Oyster – This
oyster is nucleated in the same way, except that only the sample of mantle
tissue is used without the bead. The pearl is generated around the mantle
tissue. The pearls using this process are different because the tissue will
eventually deteriorate, leaving a pearl made entirely of nacre, whereas
saltwater pearls will contain the bead for their entire existence. The oysters
are then moved to oyster beds and kept under monitoring. It will take a few
months, or a few years for them to grow into pearls, depending on the
conditions. When the pearls are ready, they are harvested by the pearl farmers,
who extract them from the oysters, wash them, dry them, and sort them into
general quality and type categories.