When a diamond crystal comes from the ground, the brilliance, fire, and scintillation that constitute the unique beauty of a polished diamond are still locked within it. The way in which a diamond cutter decides to the cut the diamond ultimately determines the diamonds beauty and brilliance.

The pavilion angle is the angle of the pavilion facets in relationship to the girdle plane. Today most cutters and gemological experts agree that varying more than one degree from a pavilion angle of 40.75 degrees reduces a diamond�s optical efficiency, and thus its beauty.

The pavilion angle is a very important element of a diamonds proportions and it is greatly responsible for the amount of brilliance that a diamond will display.

In a very fine to Ideal cut diamond the diamond will exhibit a white table reflection that appears in the center of the table. This reflection should be 1/4 to 1/2 the size of the large table facet on top of the diamond

The AGS Ideal 0 Cut grade includes a narrow range of pavilion angles from 40.5 degrees to 41 degrees.

Ideal to Very Fine Cut Diamonds have pavilion angles between 39.7 Degrees and 41.7 Degrees. Diamonds within this range usually provide excellent brilliance. Diamonds that have depths outside these ranges usually cost less, but a degree of brilliance is lost. The diagram below illustrates how the white table reflection changes in size as the depth percentage changes

The white table reflection appears larger as the pavilion angle increases and smaller as pavilion angle decreases.

37.0 = Girdle seen in table
38.0 = reflection broken up
38.5 = reflection broken up
39.0 = 1/8 size of table
39.7 = 1/4 size of table
40.5 = 1/3 size of table
41.0 = 1/3 size of table
41.7 = 1/2 size of table
42.0 = 5/8 size of table
42.5 = 7/8 size if table
43.0 = Dark table facets
44.0 = Dark star facets
 

Increasing the pavilion angle causes light to leak out the pavilion and makes the center of the stone noticeable darker. In diamonds with very deep pavilions, the darkness covers the entire table and extends out into the star facets, creating what many experts call a nail head. On the other hand, decreasing the pavilion angle by just two degrees often produces a fisheye with a gray girdle reflection visible through the table.

Certified GIA diamond quality reports provide the total depth percentage but do not provide enough information on diamond cut to give you complete assurance that a diamond will have ideal or very fine cut quality.

GIA diamond quality reports do not provide crown height, crown angles, pavilion depth percentages and pavilion angles . Selecting a diamond without the assurance of these important elements of cut is not advisable.

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