What is IGI Diamond Certification?

by Willyou.net * Jun 2, 2021

IGI (International Gemological Institute) is the largest independent gemological laboratory in the world. Established in 1975, it has locations in all major diamond trade cities. An IGI diamond certification (grading report) evaluates the diamond on its quality and structure as well as the 4 C’s: cut, clarity, color and carat according to international standards. 

The History of IGI Diamond Certification

The International Gemological Institute, ISI, was established in 1975 in Antwerp, Belgium. After GIA, they are the 2nd most well known lab in the world, grading a significant amount of diamonds and are widely known outside the United States, especially popular in the Asian region.  

IGI Certification Grading Scale

IGI’s diamond grading system is categorized by 4 C’s: carat, color, clarity, and cut:  


The carat scale for IGI diamond certification depends on the size and weight ratio. IGI does not include larger gems if the weight does not match the size in their IGI certification, due to the fact that it isn’t considered “perfect”. 


IGI grades the color of a diamond on the same grading scale as IGI’s grading scale – a letter color scale from D – Z. The less color a diamond has the higher the value it has. A diamond graded with the letter D represents a colorless diamond and continues up the scale to a diamond with the letter Z representing a light yellow or brownish tint. 


IGI grades clarity on how clean a diamond is from inclusions and blemishes. The diamond’s size, number, location and nature of internal characteristics are aspects that are inspected during the clarity assessment. Clarity is based on the 0-10 scale, with a score of 0 being completely flawless up to a score of 10 which includes flaws. 


IGI grades the cut of the diamond on the standard cut-based scale, based on its proportion, angles and symmetry: 

  • Ideal
  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor

IGI Diamond Grading Chart

IGI diamond certification reports are provided for diamonds of any size and can be customized for a variety of customers throughout the diamond industry. The grading report provides a complete assessment of the stone’s 4 C’s: color, clarity, carat and cut. The report also includes a plotted diagram of the characteristics and proportions of each diamond as well as information about the cut by analyzing proportions, polish and symmetry. 

IGI also issues and IGI Diamond ID which is a passport-sized document containing the same information as the grading report, just without the plotted diagram. It is comes in a credit card size. 

IGI certificate diamond


Advantages & Disadvantages of an IGI Diamond Certification

There are both advantages and disadvantages that come with an IGI diamond certification. Advantages include: lower costs of certification and processed quickly. The disadvantage of an IGI diamond certification includes inconsistency, as reports are pumped out at a faster pace than other grading labs, loose and unpredictable results.