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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. One
carat equals
200 milligrams. 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.
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.
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