CUT:PROPORTIONS
To bring out each individual rough diamond crystal's maximum potential beauty,
a cutter decides the best shape, facet placement, and three-dimensional outline,
or proportions, for the stone. A highly skilled cutter can then bring out a
pleasing shape, carefully polishing up the facets and creating an attractive
fancy-shaped diamond. The finished stone is then visually inspected to confirm
that is has the proper balance and sufficient attractive brilliance.
In the market there are people who, lacking an understanding of the true nature
of diamond quality, try to determine quality based solely on the symbols and
numerical values of a grading report. Using symbols and numbers as a reference
is part of a professional jeweler's job, but one must understand that the beauty
of diamonds and other gemstones cannot be expressed as symbols and numbers.
There is also a subjective element to beauty, and relying on objective numbers
and symbols to judge beauty is unsounded. One must fully understand this when
attempting to analyze the objective elements of proportions. |
On the
other hand, experience teaches us
certain objective values, such as
how deep a stone should be in relation
to its diameter or width in order
to maximize beauty. This depth ratio
is called the "total depth percentage,"
or simply "total depth." Marquise,
ovals, pear shapes, and heart shapes
appear beautiful when total depth
is in the range of 50 to 70 percent.
The marquise cut shown in the center
of the photograph below has a total
depth percentage 0f 58.8 percent,
which falls well within the generally
preferred range. The diamond on the
right is extremely long, and its
depth is 44.5 percent of the shortest
width. This cut is too shallow, allowing
light entering the diamond to leak
out of the back of the stone. The
diamond on the left has a total depth
of 74.0 percent, lowering its brilliance
and making the stone look whitish.
Excessively deep stones not only
lack beauty, but also have problems
fitting into jewelry settings.
Regardless of the quality of proportions,
a crystal with inferior transparency
will never achieve beautiful brilliance.
Additionally, it is important for
the girdle thickness and the balance
between the crown and pavilion to
be within certain ranges.
Especially in pear shapes or marquises
weighing several carats, stones with
high transparency may be quite attractive
even if the total depth is around
50 percent, which may well be due
to the sheer size of the stone. This
example reemphasizes how conclusions
about beauty cannot be made based
on numbers alone. |
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Weight:0.26 ct
Size(mm):L5.9 W3.0 x D2.22
Total Depth Percentage:74.0% |
Weight:0.24 ct
Size(mm):L6.5 W3.3 x D1.94
Total Depth Percentage:58.8% |
Weight:0.25 ct
Size(mm):L10.3 W3.1 x D1.38
Total Depth Percentage:44.5% |
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JUDGING QUALITY
Stone of beauty grade S in the quality
scale have high transparency and strong
brilliance, and they show colors such as
orange, blue, and violet in an attractive
balance of rainbow-colored dispersion.
These stones also have a pleasing overall
appearance and sparkle brilliantly when
moved. Among S-grade gems, those tones
preferred by more people are gem quality.
The gray area in the lower chart represents
jewelry quality. To enjoy the highest level
of beauty, tone levels of1,2, or 2 with
a beauty grade of S are recommended.
There is infinite variety in the quality
of smaller stones that are used in jewelry,
but when making jewelry, a trust-worthy
stone will establish a limit to the range
of yellowish colors it will accept, and
lower limits for imperfections and finish.
Even if they are colorless, stones showing
very poor brilliance like the one shown
in 0-D cannot be recommended for jewelry
use. Stones made from inferior rough material,
or with shabby proportions, will fall in
this range (D). |
