AGSL Quality Document

A Diamond Quality Document, issued by the American Gem Society Laboratories (AGSL), is universally accepted and respected by the jewellery industry as a document of authenticated quality.

AGSL Diamond Quality Document

The AGSL uses a diamond grading system that ranks cut, colour, and clarity on a zero to ten scale, with zero signifying the rarest and most desirable and ten indicating the least desirable.

Diamond Characteristics Documented By The AGSL

Shape and Style:: Describes the diamond shape and cutting style.
Measurements:: Lists the diamond's dimensions in millimeters
Cut Grade:: A grade of cut, zero being the rarest and most desirable and ten indicating the least desirable. There are three components that determine a cut grade: Light Performance, Proportion Factors, and Finish.
Light Performance:: The overall appearance of a diamond when it is viewed from above. Light Performance is one of the three factors used to determine cut.
Proportion Factors:: Factors which determine a diamond's shape, including the proportions, weight ratio and durability. Proportion Factors are one of the three factors used to determine cut.
Finish:: The overall measure of a diamond's polish and symmetry. Finish is one of the three factors used to determine cut.
Polish:: Rating the overall smoothness of the diamond's surface.
Symmetry:: Measuring the shape, alignment and placement of the diamond's facets in relation to one another as well as the evenness of the outline
Colour Grade:: A grade of colour, zero (D) being the most rare and desirable and ten (Z) being the least desirable. Assigned half points to accommodate all the grades of colour.
Clarity Grade:: A grade of clarity, zero (FL/IF) being the most rare and desirable and ten (I3) signifying the least desirable. Look in the comments section for remarks about the finish.
Carat Weight:: Diamond weight is measured to the third decimal place.
Comments:: A description of additional diamond characteristics not already mentioned in the report, as well as fluorescence, which is rated on a scale and categorized using the words inert, faint, medium, strong, very strong.
Proportion Diagram:: A map of the diamond's actual proportions.
Clarity Plot :: A map of the approximate size, type, and position of inclusions as viewed under a microscope.

Reading a Proportion Diagram

Proportion diagrams will typically include the following information:

Depth:: The height of a gemstone measured from the culet to the table.
Table:: Located at the top of the diamond, the table is the largest facet of a diamond.
Girdle:: Range of girdle thickness.
Culet:: Appearance, or lack thereof, of the culet facet.

For More Information...

Learn about our appraisals and other grading reports that accompany diamonds and fine jewellery from Blue Nile.