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Cut is the primary determinacy of a diamond's brilliance. Cut consists of
proportions, symmetry, and polish. The precision of how facets are applied,
angles derived, uniformity of shape, and final polish all affect the beauty of
a diamond. Cut is considered the most important diamond characteristic because
it has the most dramatic effect on appearance and can affect the value of a
diamond by up to 60%! A poorly cut diamond will have a dulled brilliance.
Proportions-
It has been shown through numerous studies that specific angles and
relationships of depth compared to width of the diamond determine how well
light will reflect back to the eye. A diamond that is cut too shallow will
appear washed out and lifeless because incorrect angles allow light to leak out
of the pavilion instead of reflecting back out the top.. One that is cut too
deep will appear dark as light is reflected poorly and will also appear small
for its weight due to the excess depth.
Symmetry-
This refers to the alignment of a diamond's facets. Poor alignment can cause
light to be misdirected and create distortions in the pattern of brilliance and
sparkle. Such distortion is confusing to the eye and very undesirable.
Polish-
Because diamonds possess a great hardness they have a very high luster when
polished. The degree of skill when polishing can greatly affect the overall
brilliance and sparkle of a diamond. Poor or marginal polish can make a diamond
look dull or oily. Very good or excellent polish really makes a diamond "pop"!
Cut quality is based on how well a diamond is able to reflect light. The chart
below can be used to explain the differences that cut quality can have on light
reflection.
| Cut Quality |
Ranking |
Proportions |
Polish |
Symmetry |
Light Reflection |
Comments |
| AGS 000 |
Top 1% |
Excellent |
Excellent |
Excellent |
98-100% |
Highest grade- exquisite Most costly |
| Ideal |
Top 3% |
Excellent |
Vg - Ex |
Vg - Ex |
95-97% |
Rare & beautiful Premium price |
| Very Good |
Top 15% |
Very Good |
Very Good |
Very Good |
90-93% |
Visually beautiful at a more affordable price |
| Good |
Top 25% |
Good |
Gd - Vg |
Gd - Vg |
85-88% |
A pretty diamond at a much lower price |
| Fair |
Top 35% |
Fair |
Fair - Gd |
Fair - Gd |
80-83% |
Lacks brilliance and "pop" |
| Poor |
Bottom 2/3 |
Poor
(very lumpy) |
Poor - Fr |
Poor - Fr |
20-70% |
Avoid not good value |
AGS triple zero: A diamond certified by the AGS laboratory receiving the grade
of excellent for cut category (proportions, symmetry, and polish). Such a
diamond reflects nearly all light that enters it and represents the top 1% of
diamond quality based on cut.
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