Trading Tip: Understanding a GIA Grading Report

When buying and selling diamonds, a GIA grading report can be an excellent tool to make an informed purchasing decision. Here we have outlined some of the most important parts of a GIA diamond grading report, and why they matter.  

  • Carat Weight
  • Color Grading
  • Diamond Clarity
  • Cut Grading
  • Natural or Lab Grown
  • Additional Grading Information
  • Fluorescence
  • Inscription
  • Comments
    • Clouds are not shown
    • Clarity Grade is based on clouds that are not shown.
    • Additional Twinning Wisps are not shown. 
    • Internal laser drilling not shown. 
    • Finding Laser Drill Holes on the Clarity Characteristics Diagram
    • Color Treatment
  • Country of Origin Report

Carat weight section of a GIA diamond grading report

Carat Weight

The size of a diamond is determined by its weight in carats. While size is an obvious factor in determining the value of a diamond, bigger is not necessarily better, all “4 C’s” should be considered.

GIA color Scale ranging from D-Z

Color Grading

A colorless diamond acts as a prism to form a rainbow of colors, commonly called “fire”. This scale shows the color range from colorless to a degree of a yellow tint from D-Z. Visible differences between one grade of color and the next grade are very subtle.

GIA clarity characteristics plot on a GIA diamond Grading Report

Clarity Grading

The GIA defines clarity as the absence of inclusions. GIA reports plot the clarity characteristics in a diagram of the diamond’s shape and faceting style within the report. Clarity grades range from Internally Flawless to I3. 

Three diamonds used to compare the face-up appearance effected by the cut of a diamond

Cut Grading

GIA grades the cut quality of diamonds ranging from poor to excellent by assessing the overall face-up appearance to predict the intensity of the fire, scintillation, and brightness of the stone. 

LAboratory-grown GIA diamond report

Natural or Lab Grown

As per the GIA, a lab grown diamond grading report offers the same information as the GIA natural diamond grading report, using a more general description of color and clarity. The report will include a lab grown disclosure underneath the GIA logo, next to “identification”, inscribed onto the diamond girdle and within the comments section as “man-made.”

Additional Grading Information section of a GIA diamond grading report

Additional Grading Information

This portion of the report will cover the polish, symmetry, fluorescence, inscription, and additional comments about the stone.

Fluorescence on a GIA diamond Grading Report


The fluorescence of the stone can occasionally make it appear to be hazy or milky, but will not effect the clarity of the stone. 

In diamonds with color J or darker, fluorescence can make it appear whiter. 

Diamond with inscription on the girdle


Typically, diamond inscriptions are placed on the girdle. However, if its a trademarked cut, the inscription may be placed on the table or facet. 

Comments section of a GIA diamond grading report

GIA Comments 

In the comments section of the report, you will find notes made by GIA about the stone that could not be represented well elsewhere.

GIA Grading Report Comment: Clouds are not shown, Clarity Grade is based on clouds that are not shown.

Clouds are not shown. 

Clouds within a diamond may cause milkiness or haziness. We suggest examining the stone before purchase if this comment is on the GIA report.

Clarity grade is based on clouds that are not shown.  

This comment when paired with a low-clarity grade translates to “there are so many clouds in this diamond it is not feasible to chart them on a 2D diagram.” 

A stone with this comment will be extremely milky. 

twinning wisps in diamond

Additional Twinning Wisps are not shown. 

Twinning wisps are a combination of inclusions (typically feathers, clouds, and crystals) that may show as cloudy wisps or even black/white stripes within the stone. Depending on the severity and color, these can affect the brilliance of the diamond.

Laser drill hole in diamond

Internal laser drilling not shown. 

Be on the lookout for this comment. This indicates that the stone has been clarity enhanced through the laser drilling of an inclusion.

This was a very common practice to remove inclusions, beginning in the 1960s. The FTC now requires disclosure of laser drilling to customers.

Laser Drill Hole on GIA diamond grading report inclusion plot

Finding Laser Drill Holes on the Clarity Characteristics Diagram

In this image, we have highlighted a laser drill hole as marked on a GIA diamond grading cert. As you can see, at first glance it can be easy to miss. Make sure to examine the diagram before purchasing the stone. GIA reports do not always disclose laser drill holes within the comment section, and this can be an expensive mistake.

"this diamond has been treated by one or more processes to change its color" comment on GIA report

Color Treatment

Color treatments, such as high-pressure high-temperature (HPHT) enhancements can affect the value of the stone. You must also disclose this when selling the diamond, as per the FTC. 

GIA Natural Diamond Grading Report / GIA Country of Origin Report

Country of Origin Report

This very new addition to GIA reports launched on May 24th of 2019. It is only relevant to diamond rough examined and assigned a rough ID number before being cut and polished. 

This section adds traceability to your inventory and a story to your stone!

Photos and information sourced from the GIA website and the Bluestone Trading Diamond Knowledge Center. 

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