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AGSL - American Gem Society Laboratories:
The American Gem Society Laboratories, ASGL, was established to provide consumers with an unbiased, credible analysis of a diamond. The AGSL maintains the most stringent criteria in the industry based on the American Gem Society's Diamond Standards.

Since 1996 the AGSL has been issuing 'Diamond Quality Documents' evaluating three of the 4C's --cut, color and clarity-- on its own stringent 0-10 scale. The scales begin at 0 (zero), the highest grade, and go down to 10, the lowest. The three factors are expressed separately along with the fourth factor, the carat weight of the stone, for the final AGS Grade. The three factors are expressed separately along with the fourth factor, the carat weight of the stone, for the final AGS Grade.

Currently the AGSL is one of the few laboratories that documents a diamonds cut quality (Ideal, Premium, Good, Fair and Poor).

The AGSL's Diamond Quality Documents lists the following:

 Cut Grade: The AGSL Laboratories was the first diamond grading entity to provide consumers with a credible analysis of diamond cut, including the diamond's symmetry, proportions and polish. A grade of cut, 0 being most rare and desirable and 10 being least desirable. Only round diamonds are graded.

Proportions for an ASGL Ideal Cut diamond:


At DoW we would recommend that, that if you are looking for an ‘ideal cut’ round brilliant diamond, to look at diamonds with an AGSL diamond report.

Measurement: Documents millimeter measurements and proportions of diamond.

Color Grade: A grade of color, 0 being most rare and desirable and 10 being least desirable. Half points are assigned to accommodate all the grades of color.

Clarity Grade: A grade of clarity, 0 being most rare and desirable and 10 being least desirable. Look in the Comments section for remarks about the finish.

Carat Weight: Diamond weight is measured to the third decimal place.

Comments: Extra details for any of the above four "C"s are listed here, as well as fluorescence, which is scaled by the words inert, faint, medium, strong, very strong.

Plot: Every diamond is 'plotted' for or clarity from the top (crown) and bottom (pavilion) views, with the table size (large top facet) printed on each grading document in its actual percentage dimension.