Best Diamond Certificates

Diamond Certificate
Photo: Björn Wylezich / Adobe Stock
If you’ve started looking for a diamond but are now confused by the various certifications and what all the acronyms mean, you aren’t alone. In this guide, we’re going to explain the difference between GIA and AGS, EGL and IGI, and what you should be looking for when spending your hard-earned money!

How to Read a Diamond Grading Report

Before we launch into the major labs and organizations who provide certifications, we first want to talk about grading reports. For every diamond, it will come with a grading report and this document will explain the shape, measurements, weight, color, clarity, cut, carat weight, polish, symmetry, and more. With a date at the top, you know when the diamond was graded and the overall standard of the gem.

If you want to read a diamond grading report, the first thing we suggest you do is read our guides on the four Cs. In a series of articles, we covered clarity, cut, carat, and color so that readers have a better idea of what labs look for when grading a diamond and what you should look for when choosing a gem.

Once you’ve read these, come back and review some example grading reports. Now, it should make sense since you’ll understand the scales for the different components of a diamond. The GIA also provides a fantastic guide to reading diamond grading reports, so check this out too.

GIA (Gemological Institute of America)

In the diamond industry, the GIA is the most respected and well-known name for grading. When it comes to assessing diamonds, labs need to have a few qualities; this includes consistency, accuracy, and a positive reputation. For many years, the GIA has topped the list for all three, and we don’t see this changing any time soon.

With no financial stake in diamond transactions, they’re completely impartial and have just one goal; to judge diamonds fairly and accurately. Compared to others, the GIA has garnered a reputation for rating two of the most subjective categories rigorously; clarity and color. If you see a GIA diamond grading report, you can be sure of its reliability, credibility, and accuracy.

AGS (American Gemological Society)

While the GIA has reputation and accuracy, the AGS has history. Even before the cut grade from GIA, the AGS would offer diamond cut grades from their labs and it offers a scale from 0 to 9. For a long time, they were the only organization operating in the market and vendors wouldn’t dare label a diamond ‘ideal’ if the word didn’t come from the AGS itself.

What are the differences with GIA? Well, some say the AGS is more refined and even ‘fancier’. However, they have the same fantastic reputation, and many see the GIA and AGS as the two leading labs in this arena.

EGL (European Gemological Laboratory)

From the top two services, we move down a tier to the EGL and a laboratory that has encountered many problems in the past. We’ve seen people get excited over what they think is a superb deal only to learn that it was just a selling trick or a poor piece of judgement. Both the EGL in Europe and the EGL USA are looser with their grading standards and this means they can never have the same consistency and accuracy as the GIA or the AGS. On average, EGL certified stones are more expensive than GIA certified stones (even when identical).

IGI (International Gemological Institute)

Similarly, it’s no secret that the IGI also has more relaxed grading standards with diamonds compared to the first two organizations. They did have a section of the market for a while, but this quickly disappeared after inconsistencies with grades. Unfortunately, the IGI is a for-profit business which instantly calls into question the credibility of grades.


Grading diamonds is a process that will always be subjective, but it’s fair to say that the GIA and the AGS are the two most reputable, consistent, and accurate services. Even today, in a world of affiliation and companies working together, the two remain independent from jewelers and this means they have no motivation to do anything other than be honest and reliable. As well as grade, they want to educate, and this is just as important.

With these two organizations, you can rely on the grading report and choose a diamond you know will last the test of time (while looking and performing excellently!).