GSI Diamond Certification: What You Need to Know

by * Jun 2, 2021

Key Takeaways

  • The GSI is not backed by a long history of bringing clarity to the diamond industry. Instead, they are backed by a relatively brief history offering fast turnaround for large jewelry store chains around the US.
  • These chains have different requirements to shoppers. They need their diamonds to be graded as fast as possible, and as highly as possible, in order to make a strong profit.
  • Shoppers need their diamonds to be studied and graded as accurately as possible, in order to ensure that they are making the most informed decision possible and, most importantly, not being overcharged on this expensive purchase.

There’s no objectively ‘right’ way to grade a diamond. Yes, most of the diamond world has long-since embraced the GIA’s pivotal Four Cs – including us – but, even so, there are plenty of other bodies and organizations offering their own methods for certifying diamonds.

What is a GSI certificate?

The GSI (or the Gemological Science International) is the newest gemological organization, having only been established in the 21st century. AS a result, it’s not as widely recognized as some of the more established institutes, such as the Gemological Institute of America, although, even as a first-time shopper, you’ll likely see the name crop up from time to time.

A GSI diamond certification is offered in a variety of grading reports, depending on the client’s needs. The grading report evaluates the diamond on its quality and structure, and its own list of advantages and disadvantages to buyers.

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 – primarily as a result of their rapid turn-around and cost-effectiveness for these vendors.

A GSI diamond certification is considered “looser” in their grading reports, much like EGL, which leads to inconsistent results and, in effect, less reliable prices.

The GSI Certification Grading Scale

Much like many of the most prominent grading methods, the GSI’s diamond grading approach 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 its size, with one carat equaling 0.2 grams.


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 its value will be. 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.


Much like the GIA, 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 

While the GSI diamond certification/grading report follows a similar structure to the GIA’s own reports, in that it provides a complete assessment of the stone’s 4 C’s, it 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

Are GSI Diamonds Real?

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.

GIA vs GSI Diamond Grading

The main reason why a diamond report is seen as an essential document for any diamond buyer (whether first-time, or old-hat) to look for is because it offers a neutral appraisal of the diamond’s value.

The trouble with the GSI is the fact that it has made its name offering a fast turnaround for some of the largest jewelry chain stores in the country. There is a reason why they favor this system: not only is it cost-effective and fast, but it’s also known for being pretty loose.

What does this mean? It means that a diamond graded by the GIA is likely to be subjected to much stricter standards than it would be by the GSI, and that unwary shoppers could end up paying more for a lower quality diamond as a result.

The GIA is a non-profit organization, offering a much more cautious and consistent approach to grading diamonds. As a result, the information found within one of their reports will be composed in a way that does not favor the seller, but which imparts a more neutral appraisal of the diamond’s strengths and weaknesses as an investment.

So, in spite of the fact that there is considerable crossover between the grades used by the GIA and the GSI, there is a world of difference between the two organizations’ approaches to diamond quality – and how they report on that quality.

GSI Certification Sample

GSI certificate sample
GSI certificate sample

Is GSI diamond certification good?


A GSI diamond report offers a grading discount to diamond vendors, as well as providing fast grading services. This can make it a lot easier for sellers to get larger numbers of diamonds checked and certified, at a much lower cost.

For buyers, these reports can also offer a little more in terms of education, ensuring that less experienced shoppers and investors can understand the report, and why each section matters.


Unlike some of the more established gemological organizations (and their widely-used methodologies for grading) the GSI’s reports can lead to inconsistent, loose, and weak grading. The time- and cost-effectiveness of a GSI report generally falls in favor of the vendor, rather than the buyer, and is outweighed by the lack of reliability.

Buyers would be better advised to opt for a GIA graded diamond instead, and to avoid paying over the odds for a diamond that has been graded in favor of the company selling it, rather than the individual buying it.

You can browse our full range of GIA certified diamonds here.