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DIAMOND GRADING
Princess Cut Grading
The most extensive research into how light acts in a princess cut has been conducted by tht American Gem Society (AGS).
Unlike past less-accurate cut grading systems, the AGS system detects the actual light performance produced by each
individual diamond. The grade is then categorized on a 0-10 scale, with "0" being the best. Most untrained eyes will
see little brilliance difference in the top four grades.
The Big Problem
The most common problem with princess cuts is that almost all are cut too deep. Deep diamonds are not as brilliant as
they could be. Worse, a deep diamond looks small. For instance, you may buy a ¾ carat diamond, and in fact, it will
weigh ¾ carat. However, if it's cut deep (as most are) it will only have the face up size (dimensions) of a ½ carat.
Cutters leave extra weight on diamonds to make more money. It's like buying cheap hamburger which is loaded with
worthless fat. You may think it's a great price per pound, when in actuality you are just buying unwanted bulk.
Below is an invaluable chart showing proper average length and width millimeter measurements for princess diamonds that
are not cut deep.
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Carat
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Length and Width
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.40
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4.1 mm x 4.1 mm
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.50
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4.5 mm x 4.5 mm
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.60
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4.7 mm x 4.7 mm
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.75
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5.0 mm x 5.0 mm
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.85
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5.2 mm x 5.2 mm
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.90
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5.4 mm x 5.4 mm
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1.00
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5.6 mm x 5.6 mm
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1.25
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6.0 mm x 5.6 mm
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1.50
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6.4 mm x 6.4 mm
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2.00
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7.0 mm x 7.0 mm
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Does Proper Size Guarantee Brilliance?
Finding a princess with the proper size for its weight reveals it is not a deep cut. However, proper size is just the
first step. Even though a princess measures correctly, several other things could be wrong with the cut, any of which
could kill the brilliance. Measurements are only one of eleven crucial factors needed to grade a princess cut diamond.
The Princess Cut Grade
Just like the other diamond grading categories of color (yellowness), carat (weight), and clarity (inclusions), the
crucial area of cut also has a defined, measurable grade. Both the size and beauty are evaluated in a comprehensive,
0-10 scale which measures the actual brilliance of each diamond tested.
If no cut grade is offered while comparing different sellers, then the cut is most likely poor. A savvy buyer will not
buy at places incapable or unwilling to offer a verifiable princess cut grade based on the AGS 0-10 scale. This system
is accessible to any jeweler, and is the only system recognized for assessing princess cuts.
(GIA has no princess
system).
A Note on Squareness
Squareness by itself does not create brilliance, just a pleasing symmetry. Rectangular princess diamonds can still be
beautiful, even though they cost slightly less. Most princess diamonds are not perfectly square. The AGS cut grade
system takes squareness into account. Noticeably rectangular princess cuts are downgraded, but princess cuts that are
close to square get no deductions.
Rule: In order to purchase a great princess diamond you can be proud of for years to come, do not
allow any seller to leave out the cut grade. You wouldn't allow them to leave out carat weight, or clarity, so insist
on cut grade as well. Remember, cut is absolutely crucial to the look of the diamond and makes up as much as 40%
of the cost.
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Diamond Grading