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 from Blue Nile.

GIA Diamond Grading Report
GIA Diamond Dossier®
AGSL Diamond Quality Document
GCAL Diamond Certificate of Authenticity
Blue Nile Appraisal