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Diamond Cut Education

Cut is one of the most important factors to consider

A diamond’s cut grade is really about how well the facets interact with light, whether its round, heart-shaped, marquise, or pear. Diamonds are renowned for their ability to transmit light and sparkle so intensely.

Precise artistry and workmanship are required to fashion a stone so that its proportions, symmetry, and polish deliver the magnificent return of light only possible in a diamond. The cut is measured using the GIA’s international grading system in which cut grades range from Excellent to Poor. A diamond’s cut is crucial to the stone’s final beauty and value. Of all the diamond 4Cs, it is the most complex and technically difficult to analyze.

Excellent

The diamond, which has an even pattern of bright and dark areas, scores in the top category for all grade-setting determinants.

Very Good

This diamond’s grade is determined by brightness, scintillation, and polish. Although no individual proportions would necessarily cause its brightness or scintillation to perform poorly, the combination of this particular set of proportions leads to increased darkness in the pavilion mains.

Good

This diamond’s grade is limited by its scintillation. In this case, the somewhat shallow pavilion angle produces dark pavilion mains.

Fair

This diamond’s grade is limited by its scintillation. The combination of a shallow crown angle and a somewhat shallow pavilion angle leads to a face-up appearance with a lack of contrast and general darkness.

Poor

This diamond’s grade is limited by its weight ratio. Although most of the proportions for this diamond are fairly standard, the extremely thick girdle greatly increases the total depth. Therefore, this diamond’s diameter is much smaller than its carat weight would indicate.

To determine the cut grade of the standard round brilliant diamond – the shape that dominates the majority of diamond jewelry – GIA calculates the proportions of those facets that influence the diamond’s face-up appearance. These proportions allow GIA to evaluate how successfully a diamond interacts with light to create the three desirable visual effects such as

Brilliance: Internal and external white light reflected from a diamond
Fire: Internal and external white light reflected from a diamond
Scintillation: The amount os sparkle a diamond produces, and the pattern of light and dark areas caused by reflections within the diamond

GIA’s diamond cut grade also takes into account the design and craftsmanship of the diamond, including its weight relative to its diameter, its girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.

Note: Only round brilliant cut diamonds in the D to Z color range get a cut grade from GIA while all the other shapes do not have a cut grade.

Derco only sells and recommends excellent cut to good cut grades because they will maximise the sparkle and shine.