A Complete Guide to Diamond Certification

A Complete Guide to Diamond Certification


Leon Mege is an honest jeweler. We offer only GIA certified diamonds and here is why:

Unlike anything else we sell (something you actually need), selling a diamond requires a massive amount of BS. Among professionals it is known as “Romancing a stone.” After all, when you need to sell a breakfast cereal, you can simply say, “Look, you need to eat something, why not our brand? How bad could it be?”

Even the famed florist’s technique is not useful for selling jewelry: “Look how pretty it is! It will make her happy and render her speechless” does not work with loose diamonds.

No matter how much praise a salesperson showers on a particular diamond it always boils down to two properties based on which a consumer can judge a stone’s “value” - it’s color and clarity.

There is no government mandated standard for grading diamonds. In the past there were competing systems, but they slowly gave way to a universally accepted diamond grading system pioneered by GIA. While the system is the same (letters from D to Z for color and abbreviations for clarity i.e. VVS or SI) the grading standards vary from lab to lab.

Most people do not realize that an E-color diamond could be easily assigned a G-color grade by a different lab. Given the huge price difference, it opens up the stone’s value to be ripe for misrepresentation without any legal repercussions.

In the world of diamond labs there are only two options: GIA and everything else. To compare GIA to any of it’s “competitors” is as laughable as to compare an iPhone to a rotary phone, they are simply not in the same category.

GIA is a giant of the gem world. Over 90% of diamonds are graded by its labs which are spread all over the world.

GIA certificate as explained and curated by Leon Mege
Diamonds graded by GIA sell on average for 14-21 percent more than the average price for any given diamond (source: IDEX online). This is because GIA is the gold standard of the diamond grading and provides the only certification that is taken at it’s face value by members of the diamond trade.

Buying a diamond in the USA without a GIA certificate is a serious mistake.
You can quickly learn the importance of a GIA certificate in the event that you want to sell your stone. Any other certificates will be laughed at.

Currently, GIA offers four types of reports:

  • Full Diamond Grading Report for loose, D-to-Z color diamonds weighing 0.15 carats or more.
  • Diamond Dossier® for loose, D-to-Z color diamonds weighing 0.15 -1.99 carats.
  • Diamond eReport Online for loose D-to-Z color diamonds weighing 0.15 -2.99 carats.
  • Diamond Focus™ Report online for select loose diamonds under 0.40 carats.

There are many compelling reasons to choose ONLY a stone certified by GIA:
It’s universal acceptance
Easy to use, simple to understand system
Diamond prices are based on GIA standard exclusively
Ability to view and download a certificate online
A great majority of reputable retailers sell only GIA-graded diamonds
Trying to sell a stone without a GIA certificate will result in substantial money loss

GIA is not just a gem lab, it’s a research center, as well as educational institution. GIA’s diploma program offers the most respected gemological degree in the world. For the sake of a full disclosure, Leon Mege graduated from the Gemological Institute of America in 1991 with a Graduate Gemologist degree, and he is a member of the GIA Alumni Association.


EGGIA-EGL_IGI-HRD-comparison chartL’s certificate is not worth the value of the paper it’s written on. The lab has lost all of its credibility and the stones graded by EGL are banned from trading networks.
In 2008, an experiment was conducted by sending the same diamond to different labs and comparing the results.
EGL graded the one carat stone G/VS1 as opposed to the K/SI1 grade by both GIA and IGI, a difference of more than 50% in value.


AGSThe American Gem Society was founded in 1934 as a trade group of jewelers, appraisers, and dealers. However, it was not until 1996 that they started their lab to grade diamonds, a fact that they tend to omit, instead using the year 1934 in all official publications.

Despite the fact that AGS bills itself as a well-respected lab, that is unfortunately not the case. AGS’s lax grading standards are so low that they are neither reliable nor consistent. An average stone graded as a G by AGS is likely to get an H-I color grade by GIA.

The resulting over-grading is actively exploited by some vendors in order to increase their profit margin. Helped by a network of online shills and fake bloggers who are getting kick-backs for aggressively promoting virtues of AGS stones, they attempt to divert internet traffic to fake “independent” websites and blogs that they have set up.

An AGS grading report itself is deceitful - it shows the GIA grading scale, falsely implying that the color and clarity are on par with the GIA grade, while it is certainly not.

Deceitful color grading scale used by AGS

The infamous ASET cone - a gizmo that a majority of professionals have never heard of, let alone use, is a marketing ploy designed to impress the unsuspecting consumer by its ”scientific look,” while offering zero substance.


HRD strictly adheres to GIA grading standards, and in most cases an HRD grade is considered to be a GIA equivalent.

This well respected and very reliable lab is run by the Antwerp World Diamond Center and is located in Antwerp. They also follow grading rules set by the International Diamond Council.

HRD grading reports have an exclusive security feature - a microscopic print visible only in UV light, protecting it from counterfeits.

The rest of the gem labs in this list are better described as appraisal services with better equipment. The value of their certificates is zero, just like of those in-house certificates issued by jewelry stores themselves.
We will list just few, since they open and go out of business too often for the list to be relevant in the near future.


Founded in 2001 in New York City. Since the share of their certificates in the marketplace is negligible there is no reliable data on their ability to grade stones according to universally accepted standards.


The International Gemological Institute was established in 1975 in Antwerp. It has a relatively small impact on the diamond industry, in the USA in particular, and it’s certification is not considered overly reliable.


No, it’s not Ceylon Gem Laboratory, it’s certainly not Colorado Genetics Laboratory, and it’s not Chanthaburi Gemological Laboratory, for the sake of humanity!!

It’s not even a Certified Gemological Laboratory of Europe with branches in Israel, Miami and Bulgaria (which is conveniently located in Europe) whose website looks suspiciously like a clone of the GIA site.

What is it? It’s the Central Gem Laboratory Co., Ltd. located in Japan. The lab is hardly known outside of Japan. They do offer an online certificate check.


Gemological Science International - an innovative lab with offices in India, Africa, and the US. Unfortinately, the only innovation is their VirtualVault™ or, in simple terms, a one-time fee of $35 for the right to access a picture of your own certificate online.


Gem Studies Laboratory, established in 1985 in Sydney, Australia.

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