The cut of the diamond determines its shape. There are many different shapes for diamonds. What gives diamonds
its brilliance is its facets. Each flat surface you see on a diamond is called a facet. These allow
light to enter the diamond where it refracts into a rainbow of colors reflecting against other facets until the
light comes out another facet. A diamond cut ideally will reflect the light towards your eyes as shown in the example.
As the image shows, an ideal cut diamond is more effective at reflecting the light back at the viewer. The
less-than-ideal cuts lose the light either through the side of the bottom.
Diamond Proportions
Uncut diamonds are studied and measured in many ways to find its ideal
proportions to maximize its light refraction properties. Each facet must be cut at the correct angle relative
to each other. The top and bottom halves must have the proper depth relative to each other. The table
must be the correct size in proportion to the diamond. And finally, the crown and pavilion must be perfectly
aligned.
These measurements and
percentages are different for
each diamond, and are all taken
into account in the evaluation
of a diamond's cut. In fact,
each diamond shape (heart,
round, oval, emerald, etc.) has
its own set
of guidelines for what makes a
Premium or Good cut. An 'ideal
cut' is a specific set of
guidelines that delineate the
proportions that give a diamond
the highest amount of fire and
brilliance.
Although the proportions of an ideal
cut vary depending on the source you
talk to (from jeweler to jeweler,
country to country), there are
certain ranges that are generally
accepted as capable of evoking the
most desirable fire and brilliance
from a stone. These ranges must
cause the light entering the diamond
to be reflected and dispersed
through the table (top), not through
the sides or bottom But most of all,
an ideal cut diamond must be cut to
bring out the stone's brilliance and
fire, not retain the most weight
from the rough cut stone.
DiamondOction.com
measures each diamond we sell by hand on a digital calipers. Our digital caliper has a ±0.02mm margin of
error.
The following table describes our cut grades for a round brilliant diamond.
The table percentage is the table width relative to the width of the entire stone. This relationship is
important in determining the maximum fire and brilliance of the stone. A table percentage that is too big
or too small can effect how well the diamond disperses the light. The depth percentage shows the
relationship of the length of the stone from the table to the culet expressed as a percentage. This
depth-to-width relationship is responsible for the diamond proportion resulting in the proper refraction of
light and maximum fire and brilliance.
It's
important to note that some independent
grading laboratories do not grade a
diamond's cut, while others do. The
Gemological Institute of America (GIA),
for example, will only give an
evaluation of the quality of a diamond's
cut for round brilliant diamonds. For
all other diamonds, only the shape and
measurements of the stone are part of
the report. It does, however, give the
proportions of the diamond (depth and
table percentages), girdle thickness,
and culet size (if any) as well as a
general rating of the stone's finish,
including its polish and symmetry.
