gemologists consider cut to be the most important characteristic of a
diamond. Cut determines the fire and brilliance of a
diamond. In order to maximize this fire and
brilliance, the diamond cutter must place each
of the stones facets and angles, which act as
light-dispersing mirrors, in exact geometric
relation to one another. The "cut" of a diampond refers to the
proportions of the diamond and its ability to refract light. A poor cut
will result in a diamond that has very little brilliance or sparkle.
Every diamond has a cut grade which is determined by its proportions: the
height compared to the depth and the size of the table compared to the
width. An Ideal Cut is only for round diamonds and produces the most
amount of sparkle. A Very Good Cut refelcts nearly all light and some
consider a better value than the ideal cut. A Good Cut reflects back a
large percentage of the light while a Fair Cut maximizes carat weight not
sparkle. Finally, a Poor Cut results in a diamond that is somewhat dull.
Diamonds that are poorly cut are usually shallow or too deep and
cause light to escape out the sides, rather than reflect back.
On a classic round, brilliant-cut diamond, for
instance, fifty-seven or fifty-eight facets must be
The proportions of a diamond determines its ability to refract light, so
these measurements are also used to determine a cut grade. A diamond that
is cut too shallow or deep will lose light out the sides and bottom and will appear dull, with
A well-cut round diamond is completely symmetrical and, like a funnel, refracts nearly all the
light that enters upward and out to your eye. Without this "funnel" effect,
light can escape out the sides and bottom of a fancy diamond. So for the beauty of a fancy diamond
shape, there is some tradeoff in the amount of diamond sparkle. Because of this, the grade of
a diamond's cut is determined by the diamond's proportions: the height compared to the depth,
and the size of the table compared to the width.
The polish grade, which describes the smoothness of the diamond's finish,
and the symmetry grade, which refers to alignment of the facets, are called out
separately on a diamond certificate, even though their qualities are determined in the
diamond cutting process. Poor polish will dull a diamond's sparkle. If a diamond has
poor symmetry, it will not refract and reflect all the light that enters.
Some Common Diamond Shapes