Diamond Cuts - AGS Grading

In the US the generally accepted standard for grading the quality of a diamond cut is the American Gem Society (AGS) rating. Since 1996 AGS diamond grading reports have been produced by AGS Laboratories via a Diamond Quality Document (DQD).

The AGS grades stones on a number of criteria including the "Four Cs" of Carats, Colour, Clarity and Cut. Of particular interest here is the AGS Cut Grade.

The Cut Grade has traditionally been used for round brilliant diamonds, however in 1994 AGS labs published their report on the cut grading of fancy diamonds. They are currently cut grading Square Princess stones and plan to grade others in the future.

What Is The AGS Cut Grade?

The AGS Lab Report assesses three elements that go towards the quality of a diamond cut - Light Performance, Proportions Factors, and Finish. From these key elements a single number from 0 to 10 is assigned - 0 is best, 10 is least good. Grade zero diamonds are essentially perfect in terms of cut.

The AGS Grade can be thought of as a "fault" system. For each element of the grading process a number is assigned which represents the deviation from the ideal. These values are then totalled up to give the final grade.

The AGS Laboratories website describes their gradings as follows:

Grade	Description
0	AGS Ideal
1	AGS Excellent
2	AGS Very Good
3 - 4	AGS Good
5 - 7	AGS Fair
8 - 10	AGS Poor

As you would expect the better grade diamonds usually cost more to buy than lower grades. This premium represents the extra time and effort taken by the cutter - and possibly his or her level of skill.

External Links:
AGS Laboratories