Certified Diamonds - What You Need to Know
A diamond certificate, also known as a diamond report, is issued by an accredited independent gemological laboratory. The certificate includes the diamond’s carat weight and measurements, cut, color and clarity. The certificate can also include information about the diamond’s polish, symmetry and fluorescence and a graphical depiction of the diamond, showing the locations of the diamond’s inclusions.
A diamond certificate is graded based upon the lab’s own subjective grading standards. Some labs tend to stricter when grading Cut, Color and Clarity, while others are more consistent in their standards. Hence, if two different labs were both grading the exact same diamond, they could give two different diamond grades.
Below is a brief description of the top gemological laboratories and their grading standards.
GIA- Gemological Institute of America
The GIA is the original creator of the 4C’s grading system. GIA is the industry’s most trusted and most widely used service. GIA is well known for having the strictest grading standards of all the leading labs and is the most consistent. The GIA certificate is considered the benchmark to which all other labs are compared.
IGI- International Gemological Institute
The IGI are actually the 2nd most well-known lab in the world after GIA. Although,very well respected, their grading parameters are less restrictive when it comes to color and clarity compared to GIA.
AGS - American Gem Society
The AGS laboratory is renowned for their scientific approach and research into diamond cut grading. AGS uses a scale of 0-10 for rating a diamond’s characteristics, with 0 as the best and 10 as the worst. The AGS’s grading standards are nearly comparable to GIA’s grading standards and have an excellent reputation for consistency. In the US market, the AGS lab is the second most widely used lab service after GIA.
EGL- European Gemological Laboratory (USA)
The EGL is a European grading agency and has a large global presence. EGL is known for pioneering diamond grading techniques for stones weighing less than a carat. They are also notoriously known for the introduction of the ‘SI3’ clarity rating for diamonds.The EGL has looser diamond grading standards compared to GIA, although not as loose as EGLI.
EGLI- European Gemological Laboratory International
The EGLI typically has looser diamond grading standards compared to GIA. EGLI consistently grades diamonds 2-2.5 total grades higher than GIA. For example, a difference in color of one grade higher plus a difference in clarity of one grade higher equals a two-grade higher difference.