Learn More:
Gemstone Glossary
Ask Alvaro Coronado for Custom Gemstones
GEMSTONE GLOSSARY
Gemstones
“Natural gemstones are found in nature.
Laboratory-created stones, as the name implies, are made in a laboratory. These
stones, which also are referred to as laboratory-grown, [name of
manufacturer]-created, or synthetic, have essentially the same chemical,
physical and visual properties as natural gemstones. Laboratory- created stones
do not have the rarity of naturally colored stones and they are less expensive
than naturally mined stones. By contrast, imitation stones look like natural
stones in appearance only, and may be glass, plastic, or less costly stones.
Laboratory-created and imitation stones should be clearly identified as such.
Gemstones may be measured by weight,
size, or both. The basic unit for weighing gemstones is the carat, which is
equal to one-fifth (1/5th) of a gram. Carats are divided into 100 units, called
points. For example, a half-carat gemstone would weigh .50 carats or 50 points.
When gemstones are measured by dimensions, the size is expressed in millimeters
(for example, 7x5 millimeters).
Gemstone treatments or enhancements refer to the way some
gems are treated to improve their appearance or durability, or even change
their color. Many gemstones are treated in some way. The effects of some
treatments may lessen or change over time and some treated stones may require
special care. Some enhancements also affect the value of a stone, when measured
against a comparable untreated stone.
Diamonds
A diamond's value is based on four criteria: color, cut,
clarity, and carat. The clarity and color of a diamond usually are graded.
However, scales are not uniform: a clarity grade of "slightly
included" may represent a different grade on one grading system versus
another, depending on the terms used in the scale. Make sure you know how a
particular scale and grade represent the color or clarity of the diamond you're
considering. A diamond can be described as "flawless" only if it has
no visible surface or internal imperfections when viewed under 10-power
magnification by a skilled diamond grader.
As with other gems, diamond weight usually is stated in
carats. Diamond weight may be described in decimal or fractional parts of a
carat. If the weight is given in decimal parts of a carat, the figure should be
accurate to the last decimal place. For example, ".30 carat" could
represent a diamond that weighs between .295 - .304 carat. Some retailers
describe diamond weight in fractions and use the fraction to represent a range
of weights. For example, a diamond described as 1/2 carat could weigh between
.47 - .54 carat. If diamond weight is stated as fractional parts of a carat,
the retailer should disclose two things: that the weight is not exact, and the
reasonable range of weight for each fraction or the weight tolerance being
used.
Some diamonds may be treated to improve their appearance in
similar ways as other gemstones. Since these treatments improve the clarity of
the diamond, some jewelers refer to them as clarity enhancement. One type of
treatment - fracture filling - conceals cracks in diamonds by filling them with
a foreign substance. This filling may not be permanent and jewelers should tell
you if the diamond you're considering has been fracture-filled…
Another treatment - lasering -
involves the use of a laser beam to improve the appearance of diamonds that
have black inclusions or spots. A laser beam is aimed at the inclusion. Acid is
then forced through a tiny tunnel made by the laser beam to remove the
inclusion. Lasering is permanent and a laser-drilled
stone does not require special care.
While a laser-drilled diamond may appear as beautiful as a
comparable untreated stone, it may not be as valuable. That's because an
untreated stone of the same quality is rarer and therefore more valuable.
Jewelers should tell you whether the diamond you're considering has been
laser-drilled.
Some common treatments that you may be told about and their
effects include: Heating can lighten, darken or change the color of some gems,
or improve a gemstone's clarity. Irradiation can add more color to colored
diamonds, certain other gemstones and pearls. Impregnating some gems with
colorless oils, wax or resins makes a variety of imperfections less visible and
can improve the gemstones' clarity and appearance. Fracture filling hides
cracks or fractures in gems by injecting colorless plastic or glass into the
cracks and improves the gemstones' appearance and durability. Diffusion treatment adds color to the surface
of colorless gems; the center of the stone remains colorless. Dyeing adds color and improves color uniformity in some gemstones
and pearls. Bleaching lightens and whitens some gems, including jade and
pearls.
Imitation diamonds, such as cubic zirconia,
resemble diamonds in appearance but are much less costly. Certain
laboratory-created gemstones, such as lab-created moissanite,
also resemble diamonds and may not be adequately detected by the instruments
originally used to identify cubic zirconia. Ask your
jeweler if he has the current testing equipment to distinguish between diamonds
and other lab-created stones.
Pearls
Natural or real pearls are made by oysters and other
mollusks. Cultured pearls also are grown by mollusks, but with human
intervention; that is, an irritant introduced into the shells causes a pearl to
grow. Imitation pearls are man-made with glass, plastic, or organic materials.
Because natural pearls are very rare, most pearls used in
jewelry are either cultured or imitation pearls. Cultured pearls, because they
are made by oysters or mollusks, usually are more expensive than imitation
pearls. A cultured pearl's value is largely based on its size, usually stated
in millimeters, and the quality of its nacre coating, which gives it luster.
Jewelers should tell you if the pearls are cultured or imitation.
Some black, bronze, gold, purple, blue and orange pearls,
whether natural or cultured, occur that way in nature; some, however, are dyed
through various processes. Jewelers should tell you whether the colored pearls
are naturally colored, dyed or irradiated…”
Information provided by Federal Trade Commission’s Website
entitled Protecting the Consumer. www.ftc.gov
