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GSI Certification: What You Should Know Before Purchasing a Diamond

By Mike Fried,

“Make sure you buy a certified diamond with a GIA certificate, or an AGS certificate, those are nonprofit testing labs that tell you what you’re buying so there’s no bait and switch going on.” Mark Vadon, Founder of Blue Nile, in a CNN interview.

Bottom Line Recommendation:

We do not recommend buying a diamond with a GSI certificate. We’ve found that GSI grading is not only looser than the gold standards (GIA lab), but weaker than the next level down (IGI and HRD) as well. Unfortunately, GSI does not even carry the consistency to purchase a lower graded diamond and adjust the value accordingly. You should only buy diamonds with a GIA certificate from a reputable vendor like Blue Nile or James Allen. You will actually know what you’re getting from a value perspective and you can compare apples to apples. Retailers don’t use inaccurate certificates like GSI in order to give the consumer a better deal; they do it to make more money off of those consumers.

History of GSI

Gemological Science International (GSI) is a recently established for-profit organization. This commercial laboratory has been around for a few years, not decades like other lab organizations. It’s the only major gemological lab to be founded in the 21st century. Unfortunately, they didn’t come to the industry with fresh ideas or innovative technology. They built their business by appealing to big retail chains in the United States, like Jared The Galleria of Jewelry, Kay and Zales. GSI primarily grades diamonds for large chain stores, and their service is usually speedy.

With locations all over the world, GSI provides gemstone identification as well as grading and appraisal services in the fine jewelry industry. Overall, like EGL and IGI certifications, GSI is consistently looser in their grading than GIA.

To help you with the diamond buying process we lean on our expertise and experience. The author of this article, our CEO, Mike Fried has over 20 years of experience in the diamond industry. Mike started from the bottom, sorting and evaluating hundreds of thousands of diamonds to learn every facet (pun intended) of diamond quality and value. Mike followed that up by spending years buying and selling diamonds on the wholesale market as well as selling tens of millions of dollars worth of diamonds to diamond retailers.
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GSI Diamond Grading Report

A GSI report shows the evaluation of a gemstone based on its structure and quality. The scales and measurements are intended to provide a reference point when purchasing.

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Grading Results and Scales

The 4 C’s of diamonds (Cut, Color, Clarity and Carat) represent their four main components. Each C is graded on a scale to help determine the quality and value of a diamond.

IDX report recreation


Diamond cut refers to the quality of a diamond’s proportions, angles and symmetrical facets.

GSI designates Cut grade on the following scale:

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

Diamond color

A diamond is evaluated for how white or colorless it is. The GSI grades diamonds from D to Z: D being the best diamond color and Z containing noticeable brown or yellow tinting. It is difficult for the naked eye to distinguish two diamonds of adjacent color grades, especially ones graded by the GSI. It is best to seek a more reliable certificate, like one from the GIA, and ensure that the diamond looks colorless to the naked eye.

Diamond clarity

Clarity grade determines how clean a diamond is from inclusions and blemishes. We recommend purchasing a diamond that is eye clean, so inclusions do not interfere with natural light reflection.


Carat is measured in standard fashion across all grading entities, as it is based on weight. A 2 Carat Diamond equals 400 milligrams or 0.4 grams—weighing approximately the same as a quarter of a raisin. A GSI report will disclose the Carat of a diamond, though Cut quality remains the most important of the 4 C’s.


A diamond’s proportions can help determine the quality of the Cut, although it is difficult for someone without diamond expertise to make a judgment based on the measurements provided in a GSI report.

Graph of diamond proportions

Additional Grading Information

Other details, like symmetry and polish, will also appear on a GSI certification. While these aspects contribute to the beauty of a diamond, the more important factors are the 4 C’s.

How GSI Certification Impacts Cost

Because GSI primarily works with large chain jewelers like Zales and Jared The Galleria of Jewelry, it is difficult to assess how truly objective they are in grading diamonds. While a diamond graded by the GSI will be less expensive than a diamond who achieves the same grades on a GIA scale, the GSI diamond will be worth much less. The inconsistency and looseness in grading make a GSI certified diamond a risky purchase at best.

Advantages of GSI Certification

  • Provides an indication that you should look for another diamond (one certified by the GIA)
  • Offers a grading discount to diamond vendors
  • Provides fast grading services to diamond vendors

Disadvantages of GSI Certification

  • Very loose grading
  • Lacks quality and consistency in grading
  • Does not allow you to compare two diamonds due to weak grading
  • Unique Reports and Additional Services

The GSI provides full reports for their diamonds along with:

  • 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)

Overall, we do not recommend buying a diamond that has a GSI certificate. We strongly encourage only buying diamonds that have a GIA certificate. By pursuing a more reliable certificate, you actually know what you are purchasing and you can compare diamonds fairly. Retailers don’t use inaccurate certificates like GSI in order to give the consumer a better deal; they do it to make more money off of those consumers.

If you have questions about lab certifications or want assistance in ensuring you purchase only a high-quality diamond, please don’t hesitate to contact us.

If you’re looking for more information about diamond certificates, cheack out our guide on diamond certification.

Here are more specific certificate topics to browse:

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What we love about them:
  • No questions asked returns within 30 days of shipment. Blue Nile will send you a paid shipping label to return the ring.
  • Lifetime Warranty
  • Free Shipping
  • Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
  • Provide insurance appraisal
  • One free resizing within the first year of purchase
  • High quality images of about half of their diamonds
  • 24/7 Customer Service
  • 100% credit towards future upgrades (must be at least double in value)
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About the author

Mike Fried Mike Fried Mike Fried has over 25 years experience in the diamond industry working with Leo Schachter Diamonds, Moshe Namdar Diamonds, and joining The Diamond Pro in 2007. He is recognized as an industry expert and has been quoted in publications such as Us, People, Page Six, The Next Web and more.

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