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A Complete Guide to Diamond Certification

Why independent lab certification is so important when buying a diamond

By Mike Fried,

A diamond’s certification offers a detailed breakdown of its characteristics, including its 4Cs: carat weight, color, clarity, and cut quality. Notably, the Gemological Institute of America (GIA) is a leading authority in this field. A diamond’s final grading significantly impacts its price. Always ensure that the diamond you’re considering comes with a reputable lab certification, as this guarantees you’re paying a fair price for its actual quality.

In this article we cover everyting you need to know about diamond certification and why the certificate itself may be more important than the 4 C’s they are grading.

Here’s what we’ll cover in this article:

What is a diamond certificate?
What should I look for in a diamond certificate?
What is the best diamond certification?
Are GIA certified certificates better?
FAQs about diamond certification

What Is Diamond Certification?

Diamond certificates, or grading reports, are issued by accredited gemological laboratories, such as the Gemological Institute of America (GIA). The diamond certificates contain information and grades for each of a diamonds characteristics based on the 4Cs – carat weight, color, clarity, and cut quality. The final grading has a major influence on the diamond’s price.

Along with each diamond you’re considering, you should receive and review its lab certification. This lab report or certificate will be issued by a grading entity and describes various elements of the diamond, such as color, clarity, length and width. Trained professionals evaluate, scrutinize and measure the diamonds using professional tools, such as a loupe or microscope.

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.

Each entity grades and describes diamonds differently—and sometimes the difference is significant. Several lab entities exist and it’s important to know which ones are trustworthy and reliable, and which ones are not.

Because diamond certificates are not created equal, the price and value of diamonds are not comparable across varying certifications. Ensure that you purchase a diamond with a certificate from a highly reputable grading entity—and that you review the diamond closely before purchase.

If you have a diamond in mind and would like an expert’s review about its certification, contact us.

What to Look for in a Diamond Ring Certification

Consistency comes first

When it comes to comparing lab grading entities, it’s more important to watch for consistency than the strictness of grading.

For example, the GIA will not grade a diamond the same way the IGI rates a diamond. The reliability of the color and clarity grades—and in some instances the cut grades—is only as good as the certifying lab’s reputation. But if one lab consistently gives a single clarity grade higher than another lab, that lab is by no means less “authentic.”

GIA, the world leader in certification puts it this way: “The GIA Diamond Grading Report is similar to house deeds or vehicle registrations in that it offers information on your purchase, and this information can be used to determine the value of the purchase.”

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To highlight the importance of this issue, take the diamond color grading as an example. We recommend sticking with an H color or better when putting a diamond in a setting like this one from James Allen. You may think you have found a steal with an H color diamond with an IGI certificate. But once you have it home, you realize the diamond has a yellow tint. This is because the diamond is really an I color—by GIA certification—and the IGI just offers a weak certificate.

Rather than simply comparing grades between certifications, look for consistency within the entity’s grading decisions.

Think You’re A Diamond Pro?

Both of these diamonds have an “SI2” clarity grade.
One of them is certified by EGL,
the other by GIA.
Can you tell which is which?

Diamond grading is subjective

All diamond grading is subjective—and contrary to popular belief—there is not a central organization that mathematically defines what a “G” color is or what an “SI1” clarity looks like.

If one lab consistently calls one color grade “G” while another lab will consistently calls that same color “H”, it’s perfectly acceptable and reasonable—as long as they do so consistently.

It’s important to note that even when an entity is consistent in its grading, it doesn’t necessarily mean the entity is reliable and trustworthy. Buying a diamond with a weak certificate at a high price point is not prudent—even if the entity consistently grades diamonds this way—because you are not getting the value for the price you’re paying.

Considering the price over the certification

Regardless of the certificate you receive, the price of the diamond should be heavily evaluated. The price should reflect the actual quality, beauty and Cut of the diamond—both on the certificate and to the naked eye.

If you’re unsure if a diamond is priced well or too high, be sure to have a diamond expert review it before purchasing. For questions about diamond prices and certifications, contact us.

Different certification labs give different results

Every lab has its quirks. Some are looser in grading diamond clarity, while others are looser in rating color. Some labs will always upgrade specific color ranges, while others favor particular arrangements of inclusions.

Smart diamond companies use this knowledge—gained from sending thousands of diamonds to different labs each month—to maximize their results. Knowing which labs are trustworthy and consistent will help you avoid purchasing a diamond worth much less than what the certificate is stating to be true.

What Are The Best Diamond Certifications?

The best diamond certifications are the GIA and AGS because they’re the most consistent lab grading entities. That means you can trust their grading in all aspects like color, clarity and diamond cut. These labs also grade more rigorously than other labs. When a diamond comes with a GIA or AGS certificate, you can trust what the report is saying. That’s why we only recommend buying diamonds with GIA and AGS certificates.

The top two diamond certifications are:

  1. GIA (Gemological Institute of America)
  2. AGS (American Gem Society)
diamond certification pyramid

1. GIA Certification

The GIA (Gemological Institute of America) is the most well-respected and renowned diamond grading entity. They are incredibly consistent and provide the greatest peace of mind when purchasing any diamond.

GIA has no financial stake in the sale of the diamond and evaluates diamonds on a variety of qualities and elements, including:

  • Diamond’s evaluation date
  • Measurements (in millimeters)
  • Cutting style and diamond shape
  • Carat weight
  • Table %
  • Depth %
  • Culet size
  • Symmetry
  • Proportion diagram
  • Polish grade
  • Girdle thickness
  • Cut grade (Excellent, Very Good, Good, Poor)
  • Color grade (ranging from D to J)
  • Clarity grade (IF, VVS1, VVS2, VS1, VS2, SI1, SI2)
  • Diamond plot showing all blemishes and inclusions
  • Fluorescence grade
  • Laser inscription (if applicable)
  • Security features
  • General comments

GIA has a reputation for rating rated Color and Clarity, the most subjective scales, more rigorously. Because of GIA’s high reputation, proven consistency and history, we recommend only buying diamonds with a GIA or AGS certificate. Now, GIA even certifies lab-grown diamonds.

We recommend these diamond sellers who provide GIA certificates with their diamonds:

  • Brian Gavin Diamonds: 20+ years of experience, dedicated to offering the best cut diamonds. They offer a collection called “Brian Gavin Signature” Hearts & Arrows, showcasing super ideal cuts
  • James Allen: 18+ years of experience, focused on customer satisfaction and excellent pricing. They have the most high tech diamond imagery in the industry, making it easy to accurately search and review diamonds.
  • Blue Nile: 17+ years of experience, offering the largest inventory of diamonds. Blue Nile provides excellent diamond quality and an array of well-crafted settings.

If you need help choosing a GIA diamond seller, contact us.

We have also recently developed Ringo, a patented artificial intelligence model, that can examine videos of diamonds and determine if they are eye-clean. Ringo will also filter for other parameters like making sure the diamond is well-cut, doesn’t have fluorescence issues and will match the style setting you choose.

Ringo Approved Eye Clean Diamonds

What is Ringo?

2. AGS Certification

The AGS (American Gem Society) prides itself on being the original lab to provide diamond cut grades. Long before the GIA introduced their cut grade a few years ago, the AGS has been offering its unique cut grade scale from 0 to 9 (with 0 being termed “ideal”).

Back in those days, the AGS had the monopoly on the “ideal cut” market (with top vendors such as Brian Gavin Diamonds). A diamond couldn’t be called “ideal” unless it has an AGS certificate claiming so. Now that the GIA has entered the cut grade game, though, their share in this market has dropped significantly.

The AGS generally tries to bill itself as being a bit more fancy and refined than the GIA. In reality, there’s hardly anything at all to distinguish the two laboratories. AGS is still the go-to choice for many retailers selling perfectly cut round diamonds.

The one issue to look out for is “upgrade shopping”. No lab is 100% accurate as color and clarity are not objective grades (like weight and dimensions are). If there is a diamond that is somewhere in between grades, a manufacturer or retailer may send the diamond to multiple laboratories looking for the better grade. For example, say a diamond is a weak I color or strong J color, and they received a J color from GIA. The wholesaler/retailer may try sending it to AGS for the I color (they can then sell it for much more money). Its far more likely that the grades will be the same, but its possible they will get the upgrade (which more than makes up for the cost of sending it to AGS for certification).

It is very common for companies to use AGS for branded super ideal diamonds (like True Hearts, or Hearts on Fire). But AGS is not as commonly used for non-round diamonds. So if a retailer has 50 cushion cut diamonds, 49 of which are GIA certified and one AGS diamond, that diamond is likely to have received an upgrade.

This is not a knock on AGS, merely an observation of how some wholesalers and retailers may try to take advantage of the end consumer. All in all, AGS is a very reliable laboratory. We only recommend diamonds certified by GIA or AGS and we only work with vendors (such as James Allen, Brian Gavin Diamonds, and Blue Nile) that emphasize these two labs.

If you have more questions about the reliability of an AGS certified diamond, contact us.

3. IGI Certification

The IGI (International Gemological Institute) began as the blue collar workhorse of the diamond business.

They were the most popular gem lab for major jewelry chains in the United States and Canada, like Kay, Zales and others.

IGI is like a factory: they work fast, and their prices are much better than those of GIA—which appeals to diamonds sellers but not necessarily the end consumer.

While IGI bills itself as a top-of-the-line laboratory, this is unfortunately not the case. From extensive experience in the diamond industry, we have continually seen that their grading is lax and less consistent than the standard bearers in the industry, like GIA.

Even the largest jewelry insurance underwriter writes:

“The most reliable diamond certificates (also called diamond reports) come from the Gemological Institute of America (GIA) and the American Gem Society (AGS). These are the most respected labs, known for their accuracy and professionalism. These reports are not appraisals and do not carry valuations. Certificates from any other sources are often questionable and should not be relied upon by insurers.”

Likewise, Dateline raised serious questions about IGI’s integrity in 2005 as it pertains to their appraisal values.

Pro Tip: We recommend only buying a GIA or AGS certified diamond. In addition, purchase diamonds from reputable vendors that sell diamonds certified by these labs—such as Blue Nile and Brian Gavin Diamonds.

We also recommend purchasing diamonds from James Allen. They do sell IGI certified diamonds, but we steer customers away from purchasing those particular stones.

Buying a diamond with an independent certificate should give you peace of mind, knowing your diamond is equivalent to the quality and value that is claimed. With our years of expertise, we do not believe IGI certificates provide this assurance.

To further learn how IGI grades, we sent four diamonds to various lab entities including the IGI, EGL, GSI, and HRD for a Clarity and Color grading. Because these two categories are the most subjective, we knew they would tell us a lot about how IGI grades diamonds.

IGI DiamondColorClarity

4. EGL Certification

The EGL (European Gemological Laboratory)—vastly and inconsistently—inflates their quality claims. When considering an EGL certified diamond, you may think you’re getting a better deal. In reality, the price is highly inflated for an inferior product.

We unfortunately have seen many customers purchase an EGL certified diamond thinking they found a great deal, only to realize they fell for a selling trick. We wish they had hit the contact us button sooner, so we could assist them in making a well-informed purchase.

As an example of one of these selling tricks, we found an EGL certified 1.00 Carat H VS1 ideal cut online for $4,450. At first, it seems like an incredible deal. In reality, though, when EGL claims it’s an H VS1, 50% of the time it’s actually a J SI1—and 50% of the time it’s a J SI2 or K SI1: not an H VS1.

Searching for a GIA certified diamond two or three Color grades lower or one or two Clarity grades lower will ensure you purchase a higher quality diamond for a cheaper price.

The bottom line is: don’t buy an EGL certified diamond. No matter how “cheap” it seems to you compared to GIA certified diamonds, it’s all a game.

Any EGL certified stone in the market is, by definition, more expensive than its identical self as certified by the GIA.

Our founder, Ira Weissman, digs more deeply into this issue in the video below:

As evidence, we sent in the same four diamonds to EGL to receive Color and Clarity gradings — the most subjective scales.

It’s evident that the EGL graded the diamonds higher than the other labs. An EGL graded diamond with a Clarity of VS2, for example, it is not comparable to a VS2 given by the GIA. For this reason, the price and value of a EGL diamond is incomparable and inequivalent to a diamond certified by GIA.

In addition, the two EGL labs that graded these diamonds offered different results. The inconsistency among the labs makes it difficult to trust the grading and verify the actual quality and value of an EGL diamond.

EGL DiamondEGL ColorEGL Israel ClarityColorClarity

5. HRD Certification

HRD (Hoge Raad voor Diamant) is a diamond grading organization based in Europe. Not generally regarded as a legitimate alternative in the United States, HRD still claims to be the authority for diamond grading in the world.

Over the years, we have experienced incredible inconsistency with HRD grading. They usually average about two Color and/or Clarity grades above the GIA’s grading. HRD graded diamonds are usually priced much higher than equivalent diamonds graded by the GIA. This allows for significant profits to be made by diamond companies.

To offer a comparison between HRD grading and other labs, we sent four stones to various lab entities. In the chart below, you can see HRD graded the same four diamonds better than the GIA in the categories of Color and Clarity: two highly subjective grades.

The clear difference between the grading demonstrates that it’s not prudent to compare apples to apples among lab entities. Simply put, an F Color grading given by HRD will not mean the same as a GIA F Color diamond. The price you’ll pay for an HRD diamond will not compare to the value and quality of a GIA graded diamond—even if it’s a grade or two higher

HRD DiamondColorClarity

If you are considering an HRD certified diamond, we suggest reconsidering. We recommend only purchasing diamonds that come with a GIA or AGS certificate.

In case you live abroad, James Allen offers free overseas shipping and great conditions for overseas buyers.

6. GSI Certification

The GSI (Gemological Science International) is a new grading entity that’s only been around for a few years. Unfortunately they didn’t come to the industry with fresh ideas or innovative technology. They built their business by appealing to the big retail chains in the United States like Jared The Galleria of Jewelry, Kay and Zales.

Scoring those major companies means millions of dollars in business. The Capital Forum claims that GSI took Sterling’s (parent company of Kay, Jared and Zales) business away from IGI by opening up a laboratory down the street from their headquarters to make it easier to cooperate and undercut their pricing significantly.

We have found that GSI grading is not only looser than the gold standards (GIA and AGSL labs), but weaker than than the next level down (IGI and HRD) as well. GSI also doesn’t maintain consistent gradings, to try, for example, adjusting the grades down 1 or 2 qualities and calculating the value.

For these reasons, we do not recommend buying a diamond that has a GSI certificate. We strongly encourage only buying diamonds that have a GIA or AGS certificate. By doing so, you actually know what you’re getting 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.

To demonstrate how GSI grades diamonds compared to other labs, we sent four stones to GSI, IGI, HRD, EGL and GIA. For the Color and Clarity grades—the two most subjective categories—we received distinctly different results.

GSI graded some of the diamonds higher than the GIA and some lower, making it hard to determine the consistency of a GSI grading. When looking for a diamond, it’s critical to chose a diamond certified by a reliable, consistent entity, like the GIA, so you know that what you are buying matches the actual value of the stone.

GSI DiamondColorClarity

FAQs About Diamond Certification

How important is diamond certification?

Diamond certification is essential for any diamond because it verifies and describes what it is you’re buying. Without a certificate from a reliable lab, there’s no way to know if the diamond you’re buying is what the seller claims. A diamond certificate includes details like the cut quality, color grade, carat weight and other characteristics. Having proof for what you’re buying is paramount, especially with such a large purchase like a diamond.

Does my diamond really need a certificate?

Yes, your diamond needs a certificate because, without one, there’s no way to know what it is you’re actually purchasing. A certificate offers proof of aspects like its carat weight, cut quality, color grade, clarity and more. Without a certificate, you won’t even know with certainty if the diamond is real or synthetic.

What is the difference between a certified and non-certified diamond?

A certified diamond has been evaluated by a third-party lab and comes with a certificate, whereas a non-certified diamond does not. Certified diamonds can be better trusted because they’ve been verified by a professional gemologist. With a non-certified diamond, it’s hard to know if aspects like the diamond’s color and cut quality are what the seller claims them to be. That’s why we only recommend certified diamonds from the reputable labs of the GIA and AGS.

What is the difference between a diamond certificate and a diamond grading report?

Nothing! Sometimes you will see a grading lab refer to its reports as a certificate and other labs will refer to it as a grading report. Both provide information about a diamond that has been inspected visually by the gemologist.

Bottom Line Recommendation

If you’re buying online, use James Allen’s highly recommended cutting edge diamond viewing tool or Blue Nile’s 360° Videos and stick with the GIA or AGS certification—the most consistent lab available. We have witnessed numerous gross mistakes by each major gemological lab, and want to ensure you make a safe and smart purchase.

Keep in mind that you are buying a diamond, not a piece of paper. If you feel at all hesitant about the paperwork—or anything else for that matter—don’t hesitate to contact our experts and run it by us.


We only recommend diamonds certified by GIA or AGS because we know their grading is consistent, reliable and trustworthy. We only work with vendors (such as James Allen or Brian Gavin Diamonds) that emphasize these two labs.

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.

Here are more specific certificate topics to browse:

James Allen James Allen is the leader in online diamond sales. Their imaging technology is the same as inspecting a diamond with a jeweler's loupe. They have the largest exclusive loose diamond inventory online and fantastic prices. They also have the nicest collection of lab-created diamonds online.
What we love about them:
  • No questions asked returns within 30 days of shipment. James Allen will send you a paid shipping label to return the ring.
  • Lifetime Warranty
  • Free International Shipping
  • Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
  • Provide insurance appraisals
  • One free resizing within 60 days of purchase
  • Free ring inscriptions
  • Best-in-class high quality imagery of all diamonds in stock
  • 24/7 Customer Service
  • Best-in-class packaging
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Blue Nile Blue Nile is the largest and most well-known internet jewelry seller. They have a very large exclusive online inventory. Their high-quality images are catching up to James Allens' and their prices are amazing. 
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)
  • Best in class fulfillment
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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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