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Diamond Cut

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.

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.