The GIA Colored Diamond Grading Report - a User's Guide (Part 3)

In a previous article - GIA Certification of Colored Diamonds – background was provided of the Gemological Institute of America and the GIA Colored Diamond Grading Report. This article is the 3rd section of the GIA Colored Diamond Grading Report, User's Guide and should be an integral part of buying a colored diamond as it affords buyers the security and peace of mind that they are buying a stone that has been objectively appraised by one the most reputable authorities in the diamond industry.


Reference Diagrams


Following the Additional Grading Information is the Reference Diagrams. The reference diagrams include the Plotting Diagrams and the Proportion Diagram. The Key to Symbols is located below the plotting diagrams. The plotting diagrams, the two diagrams on the left of the page, render an approximate shape and cutting style of the diamond. Symbols indicate the type, position, and approximate size of a clarity characteristic.


Colored Diamond Grading Report-3

The Key to Symbols lists the characteristics and symbols shown on the plotting diagrams, if present.

The proportion diagram, located to the right of the plotting diagrams is a representation of the diamond’s actual proportions and displays the following characteristics:


  • Table - the table is the diamond’s largest facet and is the large flat top of the diamond. The percentage figure for the table represents the ratio of the table to the diamond’s diameter. The method of calculation of this table differs if the diamond is round or fancy shaped. In the sample above, the table percentage is 64%.


  • Girdle – the girdle is the outside band that runs around the entire outer edge of a diamond. It is the widest part of the diamond and separates the table from the pavilion. The girdle is graded according to eight levels from “Extremely thin” to “Extremely thick.” If a girdle’s thickness fluctuates, then two levels may be listed representing the minimum and maximum thickness/thinness. The girdle thickness is not a great determinant on the value of a stone, however, as a general rule, a thinner girdle is preferred; especially for round diamonds. In the sample above, the girdle is Medium-Thick.
  • Pavilion – the pavilion is the lower portion of the diamond below the girdle. The height of the pavilion greatly contributes to the diamond's overall brilliance. It should not be too long or too shallow in proportion to the rest of the diamond. If it is, light is not “held” in the stone resulting in a duller looking diamond. It is measured by dividing the length below the girdle by the total height of the diamond.
  • Culet – the culet is the very small facet on the pointed end of the diamond. The culet is graded according to eight levels from “None” to “Very Large”. If the culet is large or very large, it may be visible with the naked eye from the table, generally resulting in a decrease in value of the diamond. In the sample above, the culet is None. This is almost always the assessment.


Colored Diamond Grading Report


Scale References

To assist people in reading the report, two scales are displayed – the GIA Clarity Scale and the GIA Colored Diamond Scale.

  • GIA Clarity Scale – this scale displays the GIA Clarity grades and their relative positions in the GIA Diamond Grading System. The diamond grading scale is divided into six categories and eleven grades as displayed in the table below.
 Flawless  FL – Flawless A stone that is completely flawless. This is an extremely rare find.
 Internally Flawless  IF – Internally Flawless A stone that has no internal flaws at all but does have surface flaws. Also, an extremely rare find.
 VVS1/VVS2  VVS1/VVS2 – Very Very Slight Inclusion A stone with very small internal inclusions. These inclusions can only be determined with a X30 magnification.
 VS1_VS2  VS1/VS2 – Very Slight Inclusion A stone with very small internal inclusions. These inclusions can be determined with a X10 magnification.
 SI1/SI2  SI1/SI2 – Slight Inclusion A stone that has slight inclusions that can be determined with a X10 magnification.
 L1/L2/L3 Clarity Grades  I1/I2/I3 (P1/P2/P3) - Inclusion or Pique A stone that has inclusions most often visible with the naked eye. Inclusions of this level drastically bring down the diamonds value.


Read more about diamond clarity...


  •  GIA Colored Diamond Scale - this scale (pictured below) displays the general interrelation of GIA fancy-grade terms, used to describe the combined effect of tone and saturation, in color space. The following terms can be used in the color grade: Faint, Light, Very Light, Fancy, Fancy Light, Fancy Intense, Fancy Vivid, Fancy Dark, and Fancy Deep.

GIA diagram

Read more about diamond color...



Bar Code, Disclaimer and Security Features:
Displayed horizontally on the right-hand side of the report is a bar code. This is used for internal purposes to track the diamond and its progress through the GIA Laboratory during report preparation. This number differs from the GIA Report Number. 

Beneath the bar code is the GIA disclaimer followed by the GIA hologram - one of the numerous security features of the report that ensure the report is authentic and safe from forgery. Other security features include a security screen, micro-print lines, and chemical sensitivity.



The GIA Colored Diamond Grading Report should be used by all potential buyers of a fancy color diamond as intended – an authoritative, objective, appraisal of the diamond under consideration. However, what should be apparent after reading this series of articles, is that there are so many subjective measures to consider when buying a fancy color diamond, that your perfect stone is out there waiting to be found.


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