Diamond Cut

Key Points
A diamonds cut should not be confused with it shape. Shape is round, princess etc whereas cut refers to the proportions of the diamond and the accuracy of its facets.
A diamond’s cut is one of the most important considerations when selecting a diamond.
The facets are measured and from those measurements an overall cut grade is derived. In GIA terminology these are Excellent, Very Good, Good, Fair and Poor.
The width and depth can have an effect on how light travels within the diamond, and how it exits in the form of brilliance.
Excellent or Very Good: Reflects nearly all light that enters the diamond. Termed an exquisite or brilliant diamond.
Cut Too Shallow: Light is lost out the bottom causing the diamond to lose brilliance.
Cut Too Deep: Light escapes out the sides causing the diamond to appear dark and dull.
Diamond Cut Proportion
Excellent Cut To Shallow To Deep
Diamond Cut Grades
Excellent To be an Excellent cut diamond the overall measurements must be between strict tolerances. Excellent cut diamonds represent approximately 3% of all diamonds. Excellent cut is intended to maximize brilliance and create a great deal of dispersion or 'fire'. Excellent cut diamonds are recomended.
Very Good To be an Very Good cut diamond the overall measurements must be between high tolerances. Very Good cut diamonds represent approximately 15% of all diamonds. Very Good cut is intended to have high brilliance and create a very good dispersion or 'fire'. Very Good cut diamonds are recomended.
Good To be an Good cut diamond the cutter has chosen to create the largest possible diamond from the original rough crystal. Good cut diamonds represent approximately 25% of all diamonds. Good cut offers sligthly lower sparkle and a lower price where budget is important.
Fair A diamond that is graded as Fair will reflect only a small proportion of the light that enters it. Typically these diamonds have been cut to maximize the carat weight over most other considerations. Not recommended.
Poor A diamond that is graded as Poor will reflect only a very small proportion of the light that enters it. These diamonds are generally deep and narrow or shallow and wide and tend to lose most of the light out the sides and bottom. Not recommended.

Diamond Cut Explained
A diamonds overall cut is a very important factor in a diamond’s beauty. Most gemmologists consider cut the most important diamond characteristic because a diamond with a poor cut will have dulled brilliance even if all other characteristics are of a high standard.
A diamonds cut is very important because it determines the relationship between a diamond's light performance, dimensions and finish. A well cut diamonds exhibit three different properties: brilliance, dispersion and scintillation. As light strikes a diamond’s surface, it will either reflect off the table of a polished stone or enter into the diamond.
  • Brilliance: The light that reflects is considered a diamond’s brilliance. Brilliance is the flash of white light one will see when looking at a stone.
  • Dispersion: As light travels into a stone, some of rays are divided into flashes of color, which is called dispersion. Fire is the result of dispersion, which is the separation of white light into its spectral colors.
  • Scintillation: As an observer moves a diamond back and forth, the flashes of color are called scintillation.
Diamond Anatomy
Facets The smooth, flat faces on the surface of a diamond. They allow light to both enter a diamond and reflect off its surface at different angles. A round brilliant diamond has 58 facets.
Diameter The width of diamond as measured through the widest point(the girdle).
Table The Table is the flat facet on the top of the diamond. It is the largest facet on a cut diamond.
Crown The Crown is the upper portion of the diamond, which lies between the girdle and the table.
Gridle The outer edge, or outline, of the diamond's shape. The girdle is described by its appearance at its thinnest and thickest points.
Pavilion The Pavilion is the bottom portion of a diamond, extending from the widest point (girdle) to the bottom point (culet).
Culet The Culet is the small or pointed facet at the very bottom of a polished diamond. The grading of "None" is best.
Depth The Depth is full height of a diamond measured from the culet to the table.

Also See
Diamond Education
Diamond Selection

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