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Different Diamond Certificates – what is the difference?

Compare certificates from 3 reputable US laboratories:

  • GIA = Gemological Institute of America
  • EGL.USA = European Gemological Laboratory [USA]
  • AGS = American Gem Society

GIA grading standards are stricter than 'EGL US' or AGS and the same diamond will usually receive one color grade and possibly one clarity grade higher from EGL.US or AGS than from the GIA.

Difference between EGL and GIA certificates

Information you should know:

1.] EGL.US and AGS certified diamonds should always be priced lower than GIA equivalent certificates [same weight, cut, color, and clarity]; it would be unethical to represent these 3 laboratory certificates as being equal in value.

2.] Diamond laboratories, whether GIA, EGL.US or AGS do not guarantee the desirability or value of any diamond. Correct value can only be calculated by professionals with current market knowledge and the skills to consider many factors; certificate origin is just one of these factors.

3.] All Diamond Laboratories [including the GIA] will certify any diamond submitted for grading irrespective whether the stone is beautiful or not. There can be a dramatic difference in the value and desirability of 2 diamonds with identical certificate, color and clarity grades.

4.] Provided a diamond has been valued correctly, no harm is done if the same diamond has been certified by the GIA, EGL.US or AGS. The appropriate value for the diamond remains the same.

GIA, EGL.US, AGS: Color Grades:

All three laboratories describe color in these broad categories:

• Colorless = D, E, F

• Near colorless = G, H, I, J

• Distinct color = K to Z

They disagree on where each grade should fall on the color spectrum and therefore the identical diamond submitted to the GIA, AGS or EGL.US will rarely get the same color grade.

Diamond color grades attempt to describe the amount of color present in each stone. It is commonly thought that the amount of color in any diamond is measured by how much yellow is in the stone and while this is true for diamonds with a yellow ‘core color’ there are many diamonds with a core color that could be light brown, blue, green, gray, pink etc.

The GIA typically downgrades diamonds not strictly on a ‘yellow spectrum’ by one color grade whereas the other 2 laboratories often consider the absence of yellow a positive element and upgrade the best examples of these diamonds by one color grade.


All 3 laboratories grade color with diamonds facing down, however EGL.US and AGS place value on how each stone faces up because this [they contend] is the way diamonds are ultimately seen.

GIA, EGL.US, AGS: Clarity grades:

Diamond laboratories grade clarity based on the quantity, size and position of inclusions in a diamond under 10 x magnification.

GIA clarity grades may be one clarity grade stricter than EGL.US or AGS however it would not be unusual for all 3 to be identical.


Diamonds are the most intriguing and brilliant of all gemstones. Select a company that truly cares about the brilliance, cut and proper value of every diamond they offer.

We invite you to visit an Ascot showroom where in a professional atmosphere clients enjoy a priceless education and compare diamonds from the most meticulously selected diamond inventory in the world.

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