Difference Between Certification Labs – GIA – AGS – EGL – IGI

When you are shopping for a piece of diamond jewelry, the grading report is an important document that helps you understand what you are buying. Among other uses, a grading report (certificate) from a reliable gemological lab also acts as a security screen against treated and synthetic diamonds.

Thanks to a series of tests and scientific analysis performed on the diamond during the grading process, it is possible for gemologists to detect the presence of artificial treatments in color or clarity. In short, a grading report not only provides you with a scientific blueprint of the diamond’s properties and characteristics, it also attests to the diamond’s authenticity.

While it is important to ONLY buy diamonds with reliable grading reports (NO MISREPRESENTATION), it is also important for you to learn how to cherry pick beautiful diamonds for their sparkle and brilliance. Make sure you read this proven step-by-step method of selecting diamonds before you go shopping!

An Abundance of Grading Labs Around the World But…

Not all laboratories are created equal. For a consumer, the most important thing is for you to understand the differences between the various gemological institutes. You see, each lab uses its own grading system and nomenclature. As a result, a report from one institute may have show different results from a report issued by another lab for the same diamond.

Let’s examine the differences between 4 of the most major gemological labs in the world – GIA, AGS, EGL, and IGI.

well known gemological labs in the world

GIA, the Gemological Institute of America, is the leading gemological laboratory in the world. It is the industry’s most trusted and most widely used service. Headquartered in Carlsbad, California, GIA has offices in many cities around the world, employing more than 1400 scientists, educators and certified diamond graders.

Besides gem grading and certification, GIA also provides educational services and carries out intensive research work to keep up with fast changing technologies in the gemological field.

GIA is a laboratory that has the highest grading standards and consistency. Click here to browse an extensive selection of GIA graded diamonds with interactive HD videos.

AGS stands for American Gemological Society and it is also a US based laboratory (with main offices in Las Vegas). The AGS laboratory is renowned for their scientific approach and research into diamond cut grading. Instead of using an alphabetical rating system, AGS uses a scale of 0-10 for rating a diamond’s characteristics, with 0 as the best and 10 as the worst.

Like GIA, AGS is also known for their ethical standards and consistency in their grading system. In the US market, the AGS lab is the second most widely used lab service after GIA. They are also globally consolidated through offices in Israel, Belgium, India, China and Hong Kong.

ags grades conversion to gia system

For first timers, the AGS methodology may seem confusing to figure out but once you get the hang of things, it’s pretty straightforward. Here’s an example to help you out: if a jeweler tells you that a diamond has an AGS cut grade of 0, clarity grade of 3 and color grade of 2.5, the equivalent on the GIA scale is a diamond with Excellent cut, VS1 clarity and I color.

AGS is a trusted gemmological lab with reliable grading standards. Click here to browse through handpicked collections of AGS ideal cut diamonds.

EGL is an abbreviation for European Gemological Laboratory. It is a European founded grading agency and has a big global presence – with offices in London, Paris, Tel Aviv, Tokyo, Johannesburg, among others. EGL is known for pioneering diamond grading techniques for stones weighing less than a carat. They are also notoriously known for the introduction of the ‘SI3’ clarity rating for diamonds and have a large market share in Europe.


And finally, IGI is the International Gemological Institute that is based in Antwerp, Belgium. After GIA, they are actually the 2nd most well-known lab in the world. A significant amount of polished diamonds in the market are actually graded by IGI and they are very popular in Asian countries.

sorting loose diamonds

While EGL and IGI are more widely known outside the US, particularly in Europe and Asia, they both operate offices in key cities like New York. As a result, it won’t be uncommon to see retailers carrying diamonds with reports from these labs. Now, I’m going to go on record saying that these are labs I DO NOT RECOMMEND.

It’s ironic in the sense that gemological laboratories were created with the goal to protect consumers by providing reliable information. Yet, I am warning you against them. Find out why on the next page…

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  1. mark-
    May 21, 2015 at 1:46 am

    Clearly to me there is very little. A must read for all the diamond trade and consumers, GIA is not as clean as the trade report. http://www.nationaljeweler.com/diamonds/grading/GIA-recalls-hundreds-of-diamonds-8457.shtml

  2. Paul Gian-
    May 21, 2015 at 3:02 am

    Lapses do occur from time to time no matter how reliable any grading lab is. This story only cements the reason why you shouldn’t buy diamonds that aren’t graded by GIA/AGS labs. Unlike many other labs who do not routinely invest (or have the capital) in research or new equipment (and allowing treated diamonds to bypass the grading process), GIA is actively at the forefront of identifying such treatments and taking measures to prevent such recurrences.

  3. S-
    December 3, 2015 at 1:21 am

    Hi Paul,

    Understand from the retailer that IGI offers the “ideal cutting” in their report while GIA only offer “3ex”. And they really proof to me that the IGI diamond tends to be more brilliance than the GIA diamond although the GIA one has better colour and clarity.

    Which made me confuse on what to choose for. Can you advise?

  4. Paul Gian-
    December 6, 2015 at 2:40 am

    There are many factors at play here. For example, diamonds may not be cleaned properly etc…

    Also, GIA triple excellent is very broad and there’s garbage there in terms of cut quality.


    CUT determines the diamond’s sparkle; not color and not so much on clarity. What GIA offers is an accurate grading standard of color and clarity. Stick with GIA and use this step by step process to cherry pick the best stone.


  5. D J Smith-
    December 9, 2015 at 3:45 pm

    Anybody heard of UGL – USA please, an independent laboratory for the Certification of diamonds and coloured stones

  6. Paul Gian-
    December 10, 2015 at 12:18 am

    Nope. Never heard of them and even if I did, I won’t trust their grading report to be on par to similar standards like GIA or AGS.

  7. Nat-
    January 7, 2016 at 6:35 pm

    What about AIG?

  8. Paul Gian-
    January 8, 2016 at 8:11 am

    You can safely assume all other labs not mentioned here WILL NOT have grading standards on par with GIA or AGS.

  9. Bahman-
    January 20, 2016 at 7:21 pm

    Anybody heard of DIA (diamond institute of America)

  10. Paul Gian-
    January 21, 2016 at 2:09 am

    Never heard of them. Take what they grade and the documents they provide with a pinch of salt.

  11. Lucy-
    January 22, 2016 at 6:45 am

    Very informative article! Now I can be able to identify different certificates needed for diamonds to identify its worth. Thank you so much!

  12. Nicole-
    February 14, 2016 at 2:32 pm

    I am picking out a diamond for the first time for my engagement ring. With much research I think this diamond, well it appears to be good quality and a great choice. Going to set it on an 18k solitaire, six prong. Prongs are white gold. Just wondering if you think this diamond is a good purchase. Ty!

  13. Nicole-
    February 14, 2016 at 2:33 pm

    Here’s the website, thought it posted sorry.

    https://beyond4cs.com/go/ja/ SKU-586963

  14. Paul Gian-
    February 14, 2016 at 2:40 pm

    This is not a well cut diamond. I would recommend this stone instead: https://www.jamesallen.com/loose-diamonds/round-cut/1.06-carat-k-color-vvs1-clarity-excellent-cut-sku-19429

  15. Nicole-
    February 14, 2016 at 5:52 pm

    Unfortunately that’s out of my price range, can’t go beyond $4,000 for a diamond right now.

  16. Nicole-
    February 14, 2016 at 6:24 pm

    Thanks for your help! I really appreciate it. I am concerned because I am going for a yellow band the diamond will look yellow with a K cut.

  17. Paul Gian-
    February 15, 2016 at 2:23 am

    With a yellow band, even if you bought a D colored diamond, the stone will still look yellowish. If you don’t want to see any color in the diamond, I would advice you to consider white gold or platinum instead.

  18. Nicole-
    February 15, 2016 at 5:08 pm

    Thanks for all your help and advice! Really appreciate it. I found a k, vvs1 in my price range. I am going to go for it, based on research and your advice, I think it will be well worth it. Thanks again!

  19. Clifford-
    February 20, 2016 at 4:19 pm

    Has anyone heard of the International Institute of Diamond grading and Research – part of the De Beers group.

    on the face of it their reports look pretty detailed.

  20. Paul Gian-
    February 22, 2016 at 1:51 pm

    It’s a relatively new grading service who expanded their reach across Asia and Europe. Personally, I don’t have any prior experience with them and can’t tell you much that you don’t already know.

  21. Jo-
    April 17, 2016 at 1:11 pm

    Hi I got an engagement ring (from IGI) per below spec;
    Cut – ideal cut
    Carat – 0.53g
    Grade – f
    Clarity -v s1
    Cost S$5337
    Is it a good buy

  22. Paul Gian-
    April 18, 2016 at 3:40 am

    I will never spent a single cent on a diamond that isn’t graded by GIA or AGS and that’s coming from someone with a professional background in the trade. As I had mentioned in the article above, my stand is pretty obvious,

  23. Robert Tyrrell-
    June 21, 2016 at 6:03 pm

    Yet oddly enough ALL gemological certifications have some sort of small print-downloadable disclaimer. To the effect that they will not be held legally responsible for any inconsistencies. Even the GIA was fooled by Boron treatments.

    A certification is not a guarantee of anything. Shhh we can’t tell the public..

  24. Paul Gian-
    June 22, 2016 at 1:42 am

    Anyway, it’s not odd. A certificate is a guarantee of something.

    GIA has always been upfront that the grading report is NOT a “certificate”. The issues lies at the bottom of the sales channel where people assume or get misled by sales tactics.

  25. Mehari Mustafa-
    June 23, 2016 at 7:42 am

    What is the best diamond certification if I am buying a 0.3 carat ring? I tried asking for a ring with certification but they only have appraisal documents or are uncertified.

  26. Paul Gian-
    June 23, 2016 at 8:45 am

    The statement about the “best diamond certification” is technically incorrect. Gemological labs do not certify anything but offer an opinion on a diamond’s quality. GIA is the best and most consistent among all the labs. You get what you pay for and if you think “cheaper” diamonds with unreliable lab reports are deals, they will only end up as costly mistakes.

  27. Peter Williams-
    July 11, 2016 at 12:08 am

    Dear Friends – Warning about BEVERLY DIAMONDS of California:
    I am filing a formal complaint against Beverly Diamonds, also known as Luxurious Jewelry, of 550 S. Hill St., Suite 542, Los Angeles, California.
    I purchased a wedding ring set consisting of an engagement ring and a wedding ring from Beverly Diamonds (BD) on 12/26/2015 for $3,475.31. BD advertised that the center diamond was graded as a .70 Carat, (F) Color, VS2 Clarity Enhanced diamond.
    I took the rings to three different jewelers to get quoits for resizing the rings and to have the jewelers evaluate the quality of the rings. All three jewelers said the rings were of poor quality with four of the small side-mounted diamonds set incorrectly. The four smaller, side diamonds had the sharp edges of the diamonds exposed and posed an injury risk to the wearer. The jewelers also noted the larger center diamond was of extremely poor quality and certainly not a VS2 Clarity Enhanced grade. It was suggested that I take the rings to a professional consultant for evaluation. I had a Gemological Institute of America (GIA) professional grade the “Clarity Enhanced” center diamond. The GIA consultant graded the center diamond as a .68 Carat, (G) Color, I2 Clarity Enhanced, Class 2 Cut diamond. The GIA consultant also noted that the exposed side diamonds posed a risk to the wearer and the exposed diamonds were unprotected from damage. The GIA professional agreed that the rings were of general poor quality and that to call an I2 Clarity Enhanced diamond a VS2 Clarity Enhanced diamond was fraud.
    I have contacted BD many times asking to return the rings for a full refund. Beverly Diamonds has not complied with my request. I filed a complaint with the Better Business Bureau (BBB). BD has 33-other complaints filed with the BBB for similar fraudulent business practices. Other consumer protection web-sites have dozens of complaints posted about Beverly Diamonds.
    I am available to provide any additional information and/or documentation.
    Thank you,
    Peter Zane Williams

  28. Alex-
    January 13, 2017 at 12:34 am

    Hi Paul. Great blog. I was wondering if you have heard of any difference in grading levels between GIA labs in US v. India. A jeweler suggested to me that GIA India tends to be less strict on the color grade than GIA US. Upon inquiry, online retailers seem to not know which GIA lab rates the stones they sell. Thanks!

  29. Paul Gian-
    January 13, 2017 at 2:42 am

    Well, that’s just rubbish. Unless your jeweler sends his own stones to a particular labs and reveals all the paper work involved in that, he probably has no idea where the diamonds in his inventory is graded from.

    Secondly, GIA India and GIA US labs have similar standards. In short, your jeweler is just trying to make a case against changing technology and retail habits. It’s just a narrow business mindset they have and I can tell you these kind of jewelers won’t last long in the industry.

  30. David-
    February 20, 2017 at 5:35 pm

    Your responses are so timely! Your website has great information. How do you match a GIA report to an actual diamond? What’s stopping a sales person or jeweler from showing me a diamond with a GIA report that matches a different diamond? What protection do I have against that.

    Also-I will probably buy online, but what’s the negotiating power for a consumer at a physical store, what percentage can I expect to negotiate?

  31. Paul Gian-
    February 21, 2017 at 6:39 am

    Read this: https://beyond4cs.com/care-and-maintenance/how-to-avoid-diamond-switching/

    As far as I know, prices are non-negotiable online. They are already low to begin with. You may get a one-time discount $25 at White Flash if you sign up for their newsletter: https://www.whiteflash.com

  32. Nis Daniel-
    May 6, 2017 at 4:15 am

    Have you heard oF GGL certification, website is here http://www.globalgemlab.com
    Thank you in advance

  33. Paul Gian-
    May 6, 2017 at 7:54 am

    Nope. Don’t rely on grading reports by them when making a purchase or you’ll end up overpaying for inferior quality.

  34. Lap H-
    May 11, 2017 at 5:45 pm

    Hi Paul,
    I was just about to ask a question about India GIA vs NewYork GIA, but I see that you’ve already answered the sames question, from Alex.

    I wanted to let you know that I have taken your advice and only accept GIA diamonds.
    I also wanted to let you to know that I appreciate your free knowledge and responses to questions and I have recommended friends to read up before they consider an engagement.


  35. Victor Pau-
    May 26, 2017 at 3:15 pm

    Hi Paul,

    I was wondering if you had heard of a grading outfit called WGI, and whether you had a view on the accurateness of their assessments and if they are reputable?


  36. Paul Gian-
    May 27, 2017 at 2:57 am

    I will say again for the benefit of readers who can’t seem to read or understand English. I’m going to restate it and make it real simple.

    Unless the lab is GIA or AGS, 99.99% of ALL other labs are not reliable and ones that you can trust for accurate grading.

    You would be a fool to think otherwise.

  37. April-
    June 10, 2017 at 9:10 am

    A local jeweler showed me an IGI diamond with better proportions than an GIA diamond, in fact within the ideal specifications. If IGI certification is more lax, why is it more expensive than the GIA diamond? GIA: 1.2ct, D, VS2, triple Ex, 61%table width, 41.4deg pavilion angle, strong blue fluorescence.
    IGI: 1.2ct, I, VS1, Ideal cut, 56% table width, 34.8deg pavilion angle, no fluorescence.


  38. Paul Gian-
    June 10, 2017 at 12:36 pm

    You aren’t comparing apples to apples. You are basically comparing a rotten apple against a rotten orange. The strong blue fluorescence and the terrible cut proportions will cause lower prices. Both stones aren’t good options.

  39. C.Marie-
    June 15, 2017 at 6:11 am

    Ive been a Master Diamond Grader for the last 10+yrs. Ive worked as a grader at both GIA & AGS Labs. Honestly, I have more trust in AGS.

  40. Jan Wade-
    July 6, 2017 at 8:49 pm

    Does anybody know anything about IDGL (Independent Diamond & G.R. Laboratory)?

  41. Steve M-
    August 24, 2017 at 3:30 pm

    Hi Paul, we recently bought an “I Am Canadian” diamond ring in St John ND, that was marked as clarity IMP1 and color K. We can’t any charts or references to IMP1, so I’m supposing we were ripped off. Just found your website. Can you offer any info on IMP1? Many thanks

  42. Paul Gian-
    August 25, 2017 at 8:30 am

    IMP1 is not a gemological term that GIA uses. From the looks of things, I can tell you that you had likely been ripped off and bought a diamond that’s “overgraded”.

  43. Scarlett S.-
    November 18, 2017 at 4:12 am

    Hi Paul,

    My ring is being auctioned online. I have access to a supposedly downloadable grading report. My question is how do I verify if the Report is legit? I see an item number and a Certificate Number. However, there is no Report Number to verify.

  44. Paul Gian-
    November 19, 2017 at 4:28 am

    If you know a little basic gemology, it is possible for you to verify the report in person by verifying the inclusion plot against the diamond. Otherwise, as a layman consumer, you don’t. You just have to take the word of the seller (better make sure they are reliable). And as a word of caution, nothing good comes out of auctions (unless you are talking about big names like Sotheby’s and buying the one of a kind rare diamond) as they usually offload low quality stuff to unsuspecting consumers. There’s too much junk at overpriced costs such that you would be far better off shopping for a brand new ring at an online jeweler.

  45. Adrian S.-
    November 28, 2017 at 7:18 pm

    Anybody heard of ‘ DGI New York ‘?
    Guess it is not comparable to GIA or AGS so better not to buy?

  46. Paul Gian-
    November 29, 2017 at 8:05 am

    Never heard of this company or gemological institution. There are literally hundreds of dubious grading labs in New York and NONE would be on par as GIA or AGS.

  47. Perez-
    March 14, 2018 at 6:35 am

    Poor European countries we are … especially france huh ? Why ?? French pples are the best in jewellery this country is asked by Americans ,Japanese ,Chinese Arabic saoudite etc…. why lab Europeans is ever attack by you ? First remember who invented the shape : marquise ok ? Also much country say American GIA is the best nooooo !!! Is a liar !!! American copy french jewellery first and have study french and European Gemmes so please leave us in peace and copy us like ever thanks.

  48. Paul Gian-
    March 14, 2018 at 6:39 am

    This article is in no way attacking Europeans or Europe countries. There are plenty of mediocre labs in the States and many parts of Asia as well. The fact is, these 2 laboratories which just happen to be US based companies are the best in the industry.

  49. Bhavik-
    March 24, 2018 at 6:44 am

    hi Sir,
    i very confused in GIA Best Measurement (like wise 6.35*6.35-6.40)
    so give me best measurement was best suitable with weight…

    your knowledge is very use full to resale of diamond..

    thanks boss

  50. Paul Gian-
    March 24, 2018 at 2:37 pm

    You can refer to the dimensions and charts here: https://beyond4cs.com/carat/size-chart/

  51. Dudhela-
    April 15, 2018 at 5:51 am

    Hi Paul, i have bought a diamond from a shop in Jaipur (India) saying that this diamond is origin of the Golconda mines. Can we get the origin of the diamond by getting tested in GIA/IGI/AGS laboratory?

  52. Paul Gian-
    April 15, 2018 at 6:27 am

    GIA doesn’t grade diamonds or provide info based on the stone’s origin. Also, I can tell you outright that you probably made a big mistake buying the diamond without a report in the first place. It’s silly and to think that you are now trying to pay good money after bad.

  53. Luk-
    May 7, 2018 at 8:43 pm

    Is Gemological Institute of Europe (GIE) cert reputable? Thanks

  54. Paul Gian-
    May 8, 2018 at 1:39 am

    No. I have stated clearly over and over again. If the report doesn’t come from GIA or AGS, it is NOT reliable. Period. It really is as simple as that.

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