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Evaluating
Gem Diamonds
In
the past the term "perfect" has been widely
used in the gem trade b indicate a flawless diamond.
The term "perfect" is a poor one and should
be completely abandoned. The Federal Trade Commission
re¬gards as "flawless" a diamond that
contains no "flaws, cracks, carbon spots, clouds,
or other blemishes or imperfections of any sort"
when examined at a magnification of by a trained eye.
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A
useful system of clarity grading has been devised by
the Gemologi¬cal Institute of America. It assesses
diamonds according to the size, location, and number
of inclusions and blemishes present. Gems con- training
no such imperfections are considered flawless (F). |
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With
increas¬ing size and number of imperfections, the classifications
are very slightly imperfect (VVSI), very slightly imperfect
(VSI), slightly imperfect (SI) and imperfect (I). Each of
these categories has two subdivisions, labeled 1 and 2 as
subscripts.
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DIAMONDS,
GEMSTONES & CRYSTALS
FACTS & FIGURES |
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inclusions may be so small that they are not readily
visible to the naked eye, and don't materially
affect the appearance of a cut gem. However, their
presence does materially affect the diamond's
value. Truly flawless diamonds are exceedingly
scarce and very expensive.
Sometimes
imperfections near the girdle of a diamond are
hidden by the setting. In addition, the true color
of a set diamond cannot be determined. For these
reasons, diamond grading can only be accomplished
with unset stones.
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The
surface finish and polish of a diamond, as well
as its proportions, affect its beauty and hence
its value. As mentioned earlier, maximum brilliance
and maximum dispersion cannot be achieved in a
single stone with one set of angles and proportions.
The ideal case would be a compromise, involving
proportions and angles that would give bril¬liance
and also substantial dispersive color. |
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diamonds are cut to these dimensions, and such gems are indeed
spectacular and beautiful. But most of the diamonds sold commercially
do not have "ideal" proportions. This is because acceptable
appearance can be achieved with less stringent requirements,
but at the same time the cutter can produce larger stones from
his rough material. |
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