Every diamond is unique. However, all diamonds share certain structural features. Diamond anatomy determines its proportions, brilliance, dispersion and scintillation. Having a basic understanding of how each part contributes to the diamond will help you find your perfect stone.
Before starting with diamond anatomy, let’s be clear that no single proportion measurement is an indicator of what that diamond’s cut grade will be. While every individual facet matters, a diamond’s cut is graded based on the result of its all proportions.
Table Size: The table is the top horizontal facet of the diamond. The average table size is expressed as a percentage of the diamond’s average girdle diameter.
Total Depth: Total depth/height is measured from the surface of the table to the culet. This measurement is expressed as a percentage of the average girdle diameter.
Pavilion Depth: The pavilion is the lower portion of a diamond from the bottom edge of the girdle to the culet. It is expressed as a percentage of the average girdle diameter.
Pavilion Angle: It is the average of the angles formed by the diamond’s pavilion main facets and its girdle plain. This dimension highly affects a diamond’s brilliance.
Crown Height: The crown is the upper portion of a diamond, from the top edge of the girdle to the table. Crown height is expressed as a percentage of the average girdle diameter. This dimension affects both dispersion and brightness of a diamond.
Crown Angle: Crown angle is the angle formed where the bezel facets meet the girdle plane. It has a large effect on the face-up appearance of a round brilliant cut diamond.
Girdle: The girdle is the middle portion of a diamond, narrow section separating the crown from the pavilion. It functions as a diamond’s setting edge. Girdle thickness is described as a range from its thinnest to the thickest parts.
A thick girdle is not desirable as it unnecessarily adds weight to the stone where it matters the least. For example, a diamond of 2 carats with thick girdle will appear smaller than a diamond of the same weight and thin girdle.
From the other side, an extremely thin girdle is more fragile and exposed to chipping. Therefore, a girdle that is “medium” or “slightly thick” is preferable.
Culet: Culet is a small facet at the bottom of a diamond. It prevents chipping and abrasion to the point. Size of the culet can affect face-up appearance of the diamond. The size is expressed as none, very small, small, medium, slightly large, large, very large and extremely large. When there is no culet, it may be indicated as a pointed culet.
Preferably the culet should not be visible with a naked eye. None, very small or small culet falls in the “Excellent” range.
Cover image credit: L’Excellence Diamond