Differences Between GIA, AGS, EGL, IGI Certification Labs

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A diamond report, sometimes referred to as a certificate, is an extremely important document that details the precise qualities and attributes of a diamond. The best diamond certificates are provided by an unbiased party, who’s goal is simply to express the exact quality of the diamond.

If you’ve read my summary of the GIA vs AGS labs, you will already know that these are the top tier labs and represent the gold standard of diamond grading; but why? And how do the other labs match up? This guide will cover everything you need to know.

Why Do I Need a Diamond Certificate?

Let’s begin with the basics. A diamond report from a good lab is of great value to buyers. The first advantage of a lab report is that it certifies that a diamond is real. We aren’t just talking about sorting your cubic zirconia from your diamonds either; synthetic diamonds are sophisticated and pose a real issue to the natural diamond market. The leading labs have invested millions into detecting synthetic diamonds, and this offers great peace of mind to the buyer.

A certificate expresses the exact qualities of the diamond so you know exactly what you are buying. This makes comparison, and decisions surrounding budget and spend much easier. If you’re comparing two diamonds, both with GIA reports, you can see exactly which qualities are pushing the price up – for example, if one diamond has a higher color grade than the other.

Ranking Diamond Certificates

Having just any diamond certificate is not enough. Sadly, they are not all equal and this can add an additional layer of confusion for buyers. The four most popular grading labs are GIA, AGS, EGL and IGI. Each have their own approach to grading and with differing results. Let’s look at the highlights.

The GIA

The Gemmological Institute of America is the diamond industry’s most trusted and known grading lab. Started in the 1930’s it is a non-profit, unbiased organization that is committed to further diamond research and education. The GIA’s discoveries have been ground-breaking, and there are renowned the world over for their consistent and reliable grades. Their grading nomenclature is the most widely recognised, grading colour from D-Z, clarity from FL-I3 and cut quality from Excellent – Poor. 

The AGS

The American Gem Society (also known as AGSL) was also founded in the 1930’s and is often considered to have built upon the foundations of the GIA. An AGS certificate offers the same reliable consistency as the GIA but have taken the approach to grading a step further, specifically in the crucial area of cut quality. The AGS take a more stringent approach to cut quality, giving grades from 0-10.

While AGS offer a more detailed assessment of cut quality, a top designation from either lab doesn’t automatically equal the perfect diamond. Whiteflash are a great example of taking a lab’s specifications and bettering them. Their A CUT ABOVE® super-ideal cut diamonds use an AGS triple 0 rating as a minimum requirement. Their stringent diamond specifications are clearly outlined and these world class diamonds demonstrate what’s possible when you pay attention to the cut.


The EGL

The European Gemological Laboratory has proved problematic for buyers. They have a large presence across the world but are notorious for overstating grades and controversially introducing the SI3 clarity grade (such grade does not exist in the eyes of the GIA). Moves such as this make the EGL appealing to large chain jewellers – a higher grade means a higher priced diamond and an SI3 sounds more appealing than an I1. However, labs like this do not benefit buyers and the EGL has been subject to multiple lawsuits as a result of their lax gradings.

The IGI

The image below was presented by the CEO and founder of the Rapaport, Martin Rapaport, at a trade members convention is Las Vegas. It is a great visual representation of the labs and their reliability, showing the lower tier labs trading lower than the GIA and AGS. The significance of getting a true value of a diamond is undermined by second tier labs - this was acknowledged and acted upon in the decision to exclude EGL affiliated labs from trading on the Rapnet Trading Network due to their poor grading practices and over inflated grades.

The International Gemological Institute are based in my home of Antwerp, Belgium. However, this lab does nothing to uphold Antwerp’s rich history and impressive standing in the diamond industry. The IGI falls foul to the same issues as the EGL – I have personally seen IGI graded diamonds that sit as far as 4 grades away from their true quality. This can result in overspending thousands of dollars.

Diamond Grading Myths Debunked

A GIA certified diamond is more expensive.

False. All diamond labs charge a small fee for grading and reputable vendors are happy to pay this to ensure accurate grades. A GIA diamond may appear more expensive compared with a diamond holding a lower tier certificate due to inflated grades.

In-house diamond certificate saves you money.

False. In-house diamond certificates carry absolutely no weight and are offered by vendors who are looking to make a sale. Buying in a low-quality diamond and giving it some impressive grades is perhaps one of the worst selling tactics around. Avoid in-house certification at all costs.

You’re paying for a piece of paper.

False. You’re paying for peace of mind, transparency and consistency.


I only recommend diamonds carrying a GIA or AGS lab report. A lesser certificate will result in a worse looking diamond a serious price hike. Reject misrepresentation and go for education, legitimate certification and customer transparency. James Allen carries a good selection of GIA and AGS diamonds with 360 video to assist your search. However, in this area my top choice is Whiteflash, whose detailed specifications go beyond diamond certification for an in-depth understanding of diamond quality and performance and whose diamond imaging and performance reports exceed 360 video.. For fancy shapes with a GIA report, Blue Nile’s inventory is unrivalled. Three great options to suit all budgets and needs; never settle for a subpar certification again.