AGSL Diamond Quality Document | Blue Nile
Find Your Perfect Diamond  | Explore Our Diamonds >

AGSL Quality Document

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

AGSL Diamond Quality Document

The AGSL uses a diamond grading system that ranks cut, color, 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.

Color Grade: A grade of color, zero (D) being the most rare and desirable and ten (Z) being the least desirable. Assigned half points to accommodate all the grades of color.

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.