The beauty of a diamond resides not
only in a favorable body color, but more importantly in its optical
properties, in particular the high refractive index and color
dispersion. Only when precisely calculated planes and angles are
used in the cut of a diamond does the stone attain its greatest
possible beauty.
The way a diamond is cut, its width,
depth, roundness, size and position of the facets determine the
brilliance of the stone. Even if the color and clarity are perfect,
if the diamond is not cut to good proportions, it will be dull
and less impressive to the eye.
The Ideal Cut Round Brilliant
Diamond
The earliest guidelines for diamond
cutting were based more on aesthetics than science, but in 1900
the round brilliant had evolved into something very close to its
current form. In 1919, Marcel Tolkowsky, a member of a Belgian
diamond cutting family, published a short paper entitled Diamond
Design. This was the first analysis of diamond cutting based
on modern science theories of light behavior.
Despite the fact that Diamond
Design was first published in England, Tolkowsky’s
design is often called the “American Ideal Cut” because
U.S. cutters were the first to produce it in significant quantities.
In the 1950’s, AGS adopted Tolkowsky’s model as its
standard for grading cut. The only modifications to the basic
design were establishing limited ranges for table
size, crown height, pavilion
depth and girdle thickness. In 1955, the updated model was
renamed the AGS Ideal Cut.
The demand for Ideal cut diamonds
has substantially increased and today numerous cutters around
the world are producing designs loosely referred to as “Ideal
Cuts.” The standards for these “ideals” vary
significantly, and as a result, the ability to recognize and evaluate
diamond cutting variations is even more important today. The popularity
of “ideal cuts” and the increased consumer demand
for verification of this quality factor, were among the primary
reasons for establishing the AGS Laboratory (AGSL). Opened in
1995, the lab has grown quickly because it is the only U.S. facility
that addresses cut grading in Diamond Quality Documents. (GIA
Gem Trade Laboratory), the primary industry source for diamond
quality documentation does not address the issue of cut grade
in its reports.
American Gem Society (AGS)
The American Gem Society (AGS) Diamond
Grading Laboratory uses a cut grade system that assigns diamonds
a cut grade as a number between 0 and 10. The AGS Cut Grade reflects
the impact of 3 key elements on a diamonds beauty and value:
proportions -- symmetry -- polish
Proportions are the sizes and angles
of the diamond’s main parts. Symmetry is the balance and
evenness of its faceting and shape. Polish refers to the diamond’s
surface quality, including the presence or absence of characteristics
such as abrasions, scratches, nicks and polish wheel lines
The AGS Ideal 0 cut grade represents
the very best in diamond cutting.
AGS 0 is only assigned to a diamond
in which correct proportions, precise symmetry and fine polish
are combined to produce an optimum display of brilliance, scintillation
and dispersion. The impression is a harmonious balance between
the physical dimensions of the diamond and the optical components
of its beauty.
As diamonds fall into grades further
from 0 (ideal), their relationship to beauty begins to diminish.
For example, a diamond with a cut grade of 1 or 2 (very fine cut)
are very close to 0 in appearance. A cut grade 5 diamond has variations
that detract significantly from overall appeal. It may appear
somewhat “washed out” or slightly dark through the
center. Cut grades 10 are the worst examples of proportioning,
symmetry and polish; so they have little visual “life.”
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