There are a number of competing groups providing diamond certification, however when it comes to rating the cut of a stone there’s one clear winner: the American Gemstone Society Grading (AGS) report.

What Is The AGS Cut Rating?

As with other diamond certification systems an AGS report will describe a stone’s weight, colour and clarity. What makes the AGS report special is its analysis of the stone’s cut.

The AGS grades a gemstone cut on a “faults” basis. Thus a rating of zero is the best, going up to 10 for worst. The grades are categorised as follows:

• 0: AGS Ideal
• 1: AGS Excellent
• 2: AGS Very Good
• 3 – 4: AGS Good
• 5 – 7: AGS Fair
• 8 – 10: AGS Poor

Rating a cut like this is only possible when there exists an ideal version to compare against. For this reason the AGS cut rating is currently limited to round brilliant and square princess cut diamonds.