American Gem Society Laboratories Diamond Quality Document

The prestigious American Gem Society Laboratories (ASGL) issue the well-regarded and universally recognized Diamond Quality Document. A Diamond Quality Document represents the findings of an ASGL member laboratory's analysis of a diamond using the ASGL grading system to rank color, cut, and clarity on a scale from zero to ten; ten being the least desirable and zero being the most desirable.
Here is a quick overview of the information presented on a Diamond Quality Document:

  • Shape and Style: Indicates the shape of the diamond (heart, pear, etc.) and the style of the diamond's cut (emerald, brilliant, etc.)
  • Measurements: Indicates the dimensions of the diamond rendered in millimeters.
  • Cut Grade: A numeric value rating the cut of the diamond; zero being the highest grade reserved for the rarest diamonds and ten being the lowest grade for poorly-cut diamonds. The Cut Grade value is obtained by analyzing the Light Performance, Proportion Factors, and Finish.
  • Light Performance: A value rating the diamond's ability to reflect and bend light when viewed from above. This value contributes tot he diamond's Cut Grade.
  • Proportion Factors: A combination of factors that include a diamond's proportions, weight ratio, and durability in accordance with the diamond's shape. These values contribute to the diamond's Cut Grade.
  • Finish: A value rating the diamond's overall polish and symmetry. This value contributes to the diamond's Cut Grade.
  • Polish: A value rating the smoothness of the diamond's surface.
  • Symmetry: A value rating the alignment and distribution of the diamond's facets.
  • Color Grade: A numeric value representing the diamond's color grade (D = zero and most desirable, Z = ten and least desirable). Half points are used to cover all color grades.
  • Clarity Grade: A numeric value representing the diamond's clarity grade (FL/IF = zero and most desirable, I3=ten and least desirable). Any remarks about the nature of the inclusions, if any, are recorded in the Comments section of the report.
  • Carat Weight: A measurement of the diamond's total carat weight, to the nearest thousandth.
  • Comments: Any information not represented in one of the above mentioned fields is recorded in the Comments section. A diamond's fluorescence properties are recorded here.
  • Proportion Diagram: A visual representation of the diamond's proportions. This diagram will include the following information:
  • Depth: The measurement of the diamond's height from culet to table.
  • Table: The largest facet within the diamond, located at the top of the stone.
  • Girdle: A measurement of the thickness of the widest part of the diamond.
  • Culet: The tiny facet, not always present, located at the very bottom of the diamond.
  • Clarity Plot: A visual representation of the size, type, and location of any inclusions within the diamond.