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 jewelry from Blue Nile.

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