The Accredited Gem Appraisers (AGA) was the first national gem laboratory to offer a cut grade for round and fancy shaped diamonds. David S. Atlas is the President and head appraiser of this 100-year-old+ family firm. He oversees the varied business functions of D. Atlas & Co., Inc. and of this subsidiary, the AGA laboratory. He also heads the Accredited Gemologists Association, Accredited Gem Laboratory, which has operated at this same Philadelphia location for many years.
The AGA established a cut brilliance grading system in 1986 that classifies a diamond’s proportional cut into four categories (1 through 4), each with an A and B value. The resulting eight cut categories are as follows:
- AGA 1A and 1B – Ideal / Premium Cut
- AGA 2A and 2B – International Fine Cut
- AGA 3A and 3B – Domestic Average Cut
- AGA 4A and 4B – Below Average Cut
Accredited Gem Appraisers combined similar shapes together into four basic groups for determining cut grade.
- Round Brilliants
- Princess Cuts
- Emerald and Radiant Cuts
- Pear, Heart, Oval, Marquise Cuts
Because there are so many possibilities with fancy shaped diamonds, only the round brilliant shape was assigned parameters prior to 2002 for the 1A and 1B cut grades. In March of 2002, AGA introduced Ideal Cut (1A) and Premium Cut (1B) parameters for the major fancy shaped diamonds.
The AGA cut grades provide guidelines that optimize the brilliancy, fire and scintillation while avoiding stones that are small for the carat weight or have a durability concern. The top AGA cut grades target the best combinations of beauty and value in round and fancy shape diamonds.
The following chart shows the cut parameters for the top six AGA cut grades as they apply to round brilliant diamonds.
|Lab||Accredited Gem Appraisers (AGA)|
|Table width %||53.0 - 58.0||52.0 - 60.0||51.5 - 63.0||51.0 - 64.0||50.5 - 67.0||50.0 - 70.0|
|Crown Height %||14.3 - 16.3||13.5 - 16.8||11.6 - 17.9||11.1 - 18.1||9.6 - 19.3||8.5 - 50.5|
|Crown Angle||34.3 - 34.8||34.2 - 35.0||32.1 - 35.8||31.6 - 36.4||30.1 - 37.9||29.6 - 39.4|
|Pavilion Depth %||42.8 - 43.2||42.7 - 43.5||42.4 - 44.0||41.9 - 44.9||41.4 - 45.5||40.9 - 46.0|
|Pavilion Angle||Not Addressed||Not Addressed||Not Addressed||Not Addressed||Not Addressed||Not Addressed|
|Girdle Thickness||Thin to Med or Med to Sl. Thick||Very Thin to Med or Med to Sl. Thick||Very Thin to Sl. Thick||Very Thin to Thick||Very Thin to Very Thick||Very Thin to Very Thick|
|Total Depth%||58.7 - 62.3||58.3 - 62.9||57.9 - 63.5||57.5 - 63.8||57.0 - 64.1||56.5 - 65.0|
|Culet size %||Pointed to Med||Pointed to Sl. Large||Pointed to Sl. Large||Pointed to Large||Pointed to Large||Pointed to Large|