Reading Diamond Certs :: Pavilion Angle

The Pavilion Angle in the proportions drawing of a diamond below is shown on the left, indicating 40.75 degrees.

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Like the Crown Angle in the previous lesson, the pavilion angle is significant because together they determine a lot of how the light that enters the diamond will perform.

 

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If these angles are not correct, the light will not reflect and refract properly, and the light performance will decrease. Light performance is beauty.

In recent years, it has been determined that there is a range of pavilion angles that can be acceptable, even ideal, depending on the other angles and proportions of the diamond. The real factor is how everything works together, and never just about one number or measurement.

To give you an idea of how everything works together, here is a chart from the GIA website that tracks how the table %, pavilion angle, and crown angle interact to create the most beauty, as indicated by the EX (excellent) cut grade. Note these are all based on the fact that the other major factors are all kept precisely constant. Variations in any of these could result in a different cut grade.

Sample GIA Cut Grade Estimation Table(Click Image To Enlarge)

The full set of charts show that a diamond can have a pavilion angle anywhere from 40.6 degrees to 41.8 degrees, depending on table and crown, and still have enough light performance to earn the Excellent cut grade from GIA!

You can also see the full set of GIA Cut Grade Estimation Tables.

These charts are also a factor in the GIA Facetware Cut Estimator.

Cut Grade Makes It Simple

When you look at the cut grade, you know how everything works together, and numbers like the pavilion angle are less important by itself. Therefore, always give the greatest weight to the cut grade, which is the measure of overall Light Performance. Guessing from the pavilion angle alone will not be sufficient to know the beauty of the diamond.

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