In part one of this series we discussed how the Table and Depth Percentage effect the cut of a diamond.
In part of two, we’ll take a look at the last two important factors of cut, the crown and pavilion angles, to give you a better idea of what you should be looking for when you purchase a diamond.
The relationship between the crown angle and the pavilion angle has the greatest effect on the appearance of any diamond. A slightly steep pavilion angle can be complemented by a shallower crown angle, and vice versa.
Crown Angle
The crown angle is the degree of the angle formed between the table and the girdle. This angle determines the bezel facet positions and, subsequently, the amount of fire or dispersion seen in the diamond. According to most diamond certificate adjudicators, the crown angle in the well-cut diamond should come between 33 to 35 degrees.
Pavilion Depth and Angle
Pavilion depth may be judged by looking through the table by viewing the diamond from the crown. It is widely thought that the best cut is indicated when the table reflection is approximately 1/3 of the table size, indicating a pavilion angle close to 40.75 degrees.
According to the American Gemological Society (AGS) Lab, the Pavilion depth of the stone should ideally be 42.5% to 43.5%. Pavilion Depth is a portion of the overall diamond Depth and represents the height of a diamond Pavilion or the distance from the Girdle to the bottom of Pavilion, called Culet.
In diamonds with extremely deep Pavilions, the whole surface of the Table appears to be darker creating what experts within the industry call a “Nailhead”. However, gems with more shallow Pavilions often produce a “Fisheye” effect due to Girdle’s reflection in the diamond’s Table. The image below shows an example of both of these effects:
Pavilion angle is another important dimension of the stone, which determines its brilliance and fire. However, many gemological certificates do not provide information on the diamond’s Pavilion angle. Learn to rely primarily on the information on the stone’s overall quality of the Polish and Symmetry as well its Table size and Depth. Once these proportions are determinable one can calculate the Pavilion angle and test the level of brilliance projected from the angles reflections.
