What is GSI Diamond Certification?

by Willyou.net * Jun 2, 2021

GSI (Gemological Science International) is the newest gemological organization, only being established in the 21st century. A GSI diamond certification is offered in a variety of grading reports, depending on the clients needs. The grading report evaluates the diamond on its quality and structure. 

The History of GSI Diamond Certification

The Gemological Science International, GSI, has only been in existence for a few years, being founded in 2005. GSI was established in New York City, with locations worldwide. They are a for-profit organization, with the majority of their business appealing to large retail chains in the United States. A GSI diamond certification is considered “looser” in their grading reports, much like EGL. 

GSI Certification Grading Scale

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


GSI includes the diamonds carat size in its grading report. It’s important to note that a diamond’s carat is based on its weight, not it’s size. 


GSI grades the color of a diamond on the same grading scale as GIA’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. 


GSI grades clarity on how clean a diamond is from inclusions and blemishes. The diamond’s 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. 


CSI grades the cut of the diamond on the following scale, based on its proportion, angles and symmetry: 

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

GSI Quality Report 

The CSI diamond certification/grading report provides a complete assessment of the stone’s 4 C’s: color, clarity, carat and cut. The report also includes information about the cut by analyzing information about proportions, polish and symmetry. Grading reports are printed with varying formats, details and prices and include educational material to help consumers understand the information. The report also features various diagrams, illustrating the exact position, size and shape of each inclusion and blemish along with clarity characteristics and proportions.

Along with the diamond certification, GSI also provides: 

  • IDX and MDX: smaller versions of a full certificate
  • Trade Consultation Report
  • Hearts and Arrows Report
  • Light Performance PSX Report
  • Metal Engraving
  • Laser Inscription
  • Virtual Vault: a consumer security service

GSI issues grading reports for both natural and lab grown diamonds. Lab grown diamond reports use the same grading system as natural diamond grading reports.

GSI Certification Sample

GSI certificate diamond

Advantages & Disadvantages of a GSI Diamond Certification

There are both advantages and disadvantages that come with a GSI diamond certification. Advantages include: offering a grading discount to diamond vendors as well as providing fast grading services to diamond vendors. The disadvantage of a GSI diamond certification include: inconsistent, loose and weak grading.