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AGSL Diamond Quality Document

A Diamond quality document, issued by the American Gem Society Laboratories (AGSL), is one of the most respected grading reports and usually used for high-quality investment grade stones.

The AGSL uses a diamond grading system that ranks cut, color, and clarity on a numbers scale, zero is the most valuable and rare and 10 being the lowest or least desirable quality.

Diamond Characteristics Documented by the AGSL

• Shape and Style: Describes the overall shape cutting patterns.
• Measurements: Details the length, width, and depth in millimeters.
• Cut Grade: A grade proportions thus determining the cutter's ability to produce brilliance, zero is the rarest and most desirable and ten indicating the lowest quality. The three most important criteria are proportions, polish and symmetry.
• Light Performance: The diamond's ability to produce light, scintillation, and brilliance. Usually affect by the diamond's cut grade.
• Proportion Factors: Factors which are determined by the diamond's shape, proportions, depth, table size, and length to width ratios.
• Finish: The overall measure of a diamond's polish and symmetry. Finish is one of the three factors used to determine cut.
• Polish: The rating that determines if the surface of the diamond is smooth and free of abrasions made during the cutting process.
• Symmetry: Measurements that determine how balanced and equal-in-size the diamond's facets are.
• Color Grade: A grade of clarity, 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 desireable and ten (I3) signifying the least desirable. Look in the comments section for remarks about the finish.
• Carat Weight: The unit of measurement used to determine a diamonds weight, in terms of carats.
• Comments: Any additional information like whether or not the diamond was laser inscribed or if it has fluorescence.
• Proportion Diagram: A map of the diamond's actual proportions.
• Clarity Plot: The fingerprint of a diamond showing exactly how many inclusions, location of inclusions, and size of inclusions.

Reading a Proportion Diagram

Proportion diagrams will typically include the following information:

• Depth: The height of a gemstone or diamond in terms of millimeters from the top of the diamond to the very point at the bottom.
• Table: The large flat surface on top of a diamond.
• Girdle: Range of gridle thickness.
• Culet: Appearance, or lack thereof, of the culet facet.