How to Read a Diamond Grading Report

Every diamond we sell is accompanied by a GIA, AGS or IGI authentic Diamond Grading Report, commonly referred to as a Diamond Certificate. These grading reports document the characteristics and qualities of a specific diamond. Below we offer an outline of each grading report and explain the terms and evaluations listed on a typical diamond certificate.

GIA Diamond Grading Report

The Gemological Institute of America is the most highly regarded and internationally recognized gemological laboratory. GIA diamond grading reports always include the date of issue, report number and laser registry if the diamond has been laser inscribed.

  • Shape and Cutting Style
    The diamond's shape as seen from above (round, oval, heart, pear, square, etc.) and the cutting style, or facet arrangement, (brilliant, modified brilliant, emerald cut, etc.). Refer to our Diamond Learning Center for more information on Diamond Shapes and Diamond Cut.

  • Measurements
    Reports measurements of the diamond's dimensions in millimeters. For round diamonds, measurements are listed as 'smallest diameter – largest diameter x depth'.

  • Carat Weight
    Lists the weight of the diamond in carats. One carat equals 1/5 gram. Please refer to our page on Carat Weight for further information.

  • Color Grade
    Evaluates absence of color in the diamond when compared to a master colorless stone. A Color Scale is provided for reference on all reports. Visit our Learning Center for more information on Diamond Color and color grading.

  • Clarity Grade
    Evaluates the absence of inclusions and blemishes. Inclusions are internal characteristics while blemishes are external characteristics. This grade is determined by examining the diamond under 10x magnification. A Clarity Scale is provided for reference on all reports. Learn more about Diamond Clarity.

  • Cut Grade
    Evaluates quality and craftsmanship of the diamond cut. Diamonds are examined face-up. Cut grade will only appear on round brilliant diamonds from reports issued after January 1, 2006. A Cut Scale is provided for reference on all reports.             

    • Finish Grades the polish of the diamond's surface and symmetry of the facet placement.           

    • Polish Evaluates smoothness of the diamond's surface on a scale of excellent to poor.         

    • Symmetry Evaluates a diamond's outline, shape, and facet alignment on a scale of excellent to poor.       

  • Fluorescence
    Evaluates the glow of a diamond when examined under long wave ultra violet rays. Ranges from none to very strong. Low fluorescence is typically desirable, as high fluorescence is associated with lower quality and lower value stones.

  • Comments
    Lists any other relevant characteristics not mentioned elsewhere.

  • Plotting Diagram
    An approximated illustration of the shape and cutting style of the diamond as seen from above and below. Symbols representing clarity characteristics (inclusions and blemishes) are plotted according to their size, type and relative location. Symbols can be identified using the Key to Symbols.

  • Proportions Diagram
    An illustrated profile representing the diamond's actual proportions.

GIA Diamond Dossier

The GIA diamond dossier includes the same information as the Diamond Grading Report, aside from the Plotting Diagram. In addition, each diamond that is issued with a diamond dossier receives a special micro-laser inscription listed on the certificate.

AGS Diamond Quality Document

American Gem Society Laboratories is one of the most well known, highly regarded gemological laboratories in the world. They are known for developing a specialized grading system by which to evaluate the quality of a diamond's cut. AGS diamond quality documents always list the date of issue, report number and diamond carat in the upper right hand corner of their report.   

  • Shape and Style
    The diamond's shape, as seen from above, (round, oval, heart, pear, square,etc.) and the cutting style, or facet arrangement, (brilliant, modified brilliant, emerald cut, etc.). Refer to our Diamond Learning Center for more information on Diamond Shapes.

  • Measurements
    Reports measurements of diamond's dimensions in millimeters. For round diamonds, measurements are listed as 'smallest diameter – largest diameter x depth'.

  • Cut Grade
    Evaluates the quality and craftsmanship of the diamond cut. Diamonds are examined in 3-D and graded on a scale of 0-10, 0 being the highest quality cut and 10 being the lowest. A Cut Scale is provided for reference on all reports. Grade determined by the following three factors:         

    • Light Performance The light return and dispersion when viewing a diamond. It accounts for a diamond's brilliance and fire.

    • Polish Evaluates the smoothness of the diamond's surface.

    • Symmetry Evaluates the precision of a diamond's outline, shape, and facet alignment.        

  • Visit our Diamond Learning Center for more information on Diamond Cut.

  • Color Grade
    Evaluates absence of color in the diamond when compared to a master colorless stone. The stone is graded on a scale of 0-10 increasing by .5 with each grade. A Color Scale is provided for reference on all reports. The GIA equivalent grade is printed in parenthesis. Please refer to our Diamond Color page for more information.

  • Clarity Grade
    Evaluates the absence of inclusions and blemishes. Inclusions are internal characteristics while blemishes are external characteristics. This grade is determined by examining the diamond under 10x magnification. A Clarity Scale is provided for reference on all reports. The GIA equivalent grade is printed in parenthesis. Visit Zoara's Diamond Learning Center to learn more about Diamond Clarity.

  • Carat Weight
    Lists weight of the diamond in carats. One carat equals 1/5 gram.

  • Comments
    Lists any other relevant characteristics not mentioned elsewhere. Typically includes fluorescence rating (inert, faint, medium, strong or very strong).

  • Proportion Diagram
    An illustrated profile representing the diamond's actual proportions.

  • Clarity Plot
    An approximated illustration of the shape and cutting style of the diamond as seen from above and below. Symbols representing clarity characteristics (inclusions and blemishes) are plotted according to their size, type and relative location. Symbols can be identified using the Key to Symbols.

  • Computer Generated Light Performance Map
    A color-coded map of the diamond from above representing brightness, contrast, less bright light return and light leakage. Included on all AGS Diamond Quality Documents issued after February 2009.

IGI Diamond Report

The IGI is the largest international gemological institute. Using the standardized diamond grading methods, the IGI offers professional diamond grading reports for loose natural diamonds. Every diamond evaluated by the IGI is analyzed by several gemologists who use only state-of-the-art-equipment to accurately describe your diamond's characteristics. IGI Diamond Reports always print the date of issue, report number and include a special security seal.

The IGI Diamond Reports include the same information as the GIA Diamond Report but without a proportions diagram. Instead, the IGI provides specific proportion measurements and a proportion grade of Poor, Fair, Good, Very Good, or Excellent.

IGI Cut Grades
The IGI is very transparent with their Diamond Cut grades. Their grades follow the following criteria:

Ideal Excellent Very Good
Table Width 53-60 52.5-63.5 51.4-63.5
Crown Angle 33-36 32.7-36.3 31.7-36.8
Pavilion Depth 42-44 41.8-44.3 41.5-44.8
Girdle Thickness Thin to Sl. Thick Thin to Sl. Thick Thin to Sl. Thick
Total Depth 58.5-62.5 56-63 53.3-63

In addition to Diamond Reports, the IGI also issues Diamond IDs. IGI Diamond IDs are passport sized documents that list the same information detailed on a Diamond Report, without a plotted characteristics diagram. This report is also available in a 3.4in x 2.2in plastic credit card format upon request.

EGL Diamond Grading Certificates
The European Gemological Laboratory (EGL)has been international recognized for over 25 years.  Originally founded in Europe in 1974 as part of an international network of gemological laboratories, today EGL has split into two separate organizations: EGL USA, which includes EGL Canada,(labs in New York, Los Angeles, Vancouver and Toronto), and E.G.L. International (labs in Tel Aviv, London, Mumbai, Paris, Hong Kong, Seoul, Antwerp and Johannesburg). The two organizations are not affiliated.

It should be noted that the EGL, unlike the GIA, AGS and IGI, is a for-profit organization.  Their grading standards are occasionally perceived to be less strict.

EGL USA Diamond Certificate

EGL USA Diamond Grading Certificates feature the same information as the GIA Diamond Report but without a proportion diagram, or a cut grade.  Instead, polish and symmetry are given two separate grades ranging from Poor to Excellent, proportion percentages of the Depth, Table, Crown and Pavilion are listed, and Girdle thickness and Culet size are reported.

EGL USA Diamond Analysis Report

EGL USA Diamond Analysis Reports, for round stones only, include all of the information in the above Diamond Certificate as well as a final cut, proportions diagram and a UGS Consultation of Appraisal with a listed retail replacement value.

E.G.L International Diamond Certificate

E.G.L. International Diamond Certificates include the same information as the GIA Diamond Report but without a proportion diagram.

EGL International also offers a variety of other types of diamond certificates such as a Mini Certificate and a CertiCard, or credit-card sized certificate.

Before you start your shopping process, we recommend that you visit our extensive Jewelry Learning Center to learn more about engagement rings and wedding rings.

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