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The American Gemological Laboratories (AGL) Colored Stone Grading Report

How to Determine the Quality of a Colored Gemstone

In 1977, American Gemological Laboratories (AGL) became the first laboratory in the world to quantify colored stones in a linear, comparative manner. The organization and its President, C. R. Beesley, are internationally recognized for their expertise in colored stone research and analysis. They have enjoyed a position of leadership in gemstone documentation and have extensive experience in consumer protection programs.

The grading system which they devised is comprehensive and requires some study to realize a workable understanding of the process. However, once you grasp the basic principles, you will wonder how anyone could buy a gemstone without using this kind of vocabulary. The following "walk through" of a 3.11 Burma sapphire grading report will help you understand the various components of an AGL laboratory report.

Document NumberThe lab assigns individual, consecutive numbers for each grading report issued.

Image:

A color digital image of the stone is an important part of the grading report. This image assists in verifying the gemstone matches the grading report. Please note the image is for representational purposes and is not necessarily the actual size or color.

Identification:

In this sample, the AGL has determined the stone is a natural sapphire.

Shape and Cut

The stone is an oval cut in this sample.

Carat Weight

Colored stones are weighed with an extremely accurate scale. In the sample, the sapphire weighs 3.119 carats.

Total Quality Integration Rating

This comment integrates the total visual impact of the gem into a verbal description and may or may not have an effect on the price of the gem. In the sample it is Excellent. Look at the Color Rating (AGL). Excellent translates into 1.5. The TQIR can increase or decrease the final grade only 1/2 of a grade. Therefore, in this sample, a TQIR of 1.5 raises the 3.5 color grade to a 3. If the TQIR is lower than the color grade, it means the stone may have a problem, and the TQIR can actually lower the final grade of the stone 1/2 grade.