Understanding Diamond Certification

The paperwork accompanying your diamond is an important piece of information but will never tell the full story of the stone’s value. Diamond certification is an in-depth process where independent labs evaluate diamonds based on specific properties and characteristics. Every lab is different and each will have varying standards, so knowing how to evaluate the labs is crucial.
For lab-grown diamonds, the certification process has more variables that limit lab options. Since all gem labs are not created equal, we’ve put together our complete guide to diamond certification. We want to help you feel the most secure with your diamond purchase. So we’ve outlined the essential information to know about diamond certificates and the labs that provide them, with special details about non-traditional diamonds like lab-grown and rustic.

What Is Diamond Certification And Why Is It Important?

A diamond certification is a document accompanying diamonds issued from an objective third party lab describing the unique characteristics of a specific diamond. In order for the lab to issue their findings, they test and assess the quality of diamonds based on grading standards.

As a benchmark, any diamond valued at $500-$1000 is worth getting a certificate for, and if over $1000, it’s imperative to have a certificate before buying. The certification proves that the diamond has been tested and verifies the stone as natural or lab grown (more on that later). They prove the diamond quality and provide a basis for comparison on diamond value and pricing.

At this point it’s important to make the distinction between an authentic diamond certification from a leading lab and an appraisal or jeweler’s letter. At a lab, trained professionals use tools and specialized machines to measure, scrutinize, and test a diamond. These tools and pieces of equipment simply aren’t used for an appraisal process and don’t exist in jewelers’ showrooms due to the high cost of the most advanced equipment. 

What To Consider About Diamond Certifications

Since diamond certificates are not created equal, it’s important to know how different certificates will affect a diamond. The various labs will have their own accepted standard for grading and describing diamonds. Sometimes the difference can be significant and a clear sign about which lab entities are trustworthy and which ones are not.

There are a few rules to consider when it comes to a solid understanding about labs and their diamond certifications.

1. Consistency is more important than strict grading.

All labs have differing standards for interpreting the grades of a diamond. Consistency in color and clarity grades are often considered a true marker of a lab’s reputation. While it may be important to see why an entity is applying a certain grade, it’s more important that the entity’s decisions are consistent across that grading category.

For example, a group of diamonds receiving H color grades from GIA should appear very similar in color to each other. This consistency illustrates the reliability of the grading entity.

2. All diamond grading is subjective.

It usually comes as a surprise to people that there are no internationally set standards for defining the character graded qualities of a diamond. There’s never been a leading organization to provide final clarity about definitions. And the two most subjective categories for diamond grading are color and clarity.

So this tells us two things: first, that labs may determine different grades for the same diamonds but this is fine as long as it’s done consistently; and two, a weak certificate from an unreliable entity accompanying a high-price diamond is a cause for concern about the real value of the diamond.

3. Differing certification labs gives different results.

We’ve already covered how different labs will have their own set of standards for grading. Some may be looser in the color classifications while others will have strict guidelines. The differences in these standards can be used for the benefit of diamond companies.

If a diamond company deals in diamonds that are typically of a lesser quality in color, for example, they can send them to a lab known for looser color gradings. The certifications that come back will show a diamond with great value when it’s actually worth far less.

4. Diamond certification is an unregulated industry.

There are no laws governing gem labs. That means any company can present itself as a reputable lab. There are only generally accepted norms for who is qualified to write certifications, how diamonds need to be tested, and what qualities and elements of a diamond are reported on the certificate.

An immediate red flag that should call into question any diamond certificate is if it puts a value on your diamond. Credible labs only evaluate and grade a diamond from scientific standards. They do not attempt to indicate how the diamond should be valued in the marketplace.

5. Diamond companies often partake in “upgrade shopping”.

Since color and clarity are very subjective grades, a diamond may often appear between grades. If a dealer or retailer has a diamond falling in one of these ranges, they may send it to multiple labs looking for the best grade.

It will more than make up for the cost of sending a diamond to multiple labs for certification if one comes back with a better color or clarity grade. So your best defense is always to analyze the diamond in detail, and in comparison to other diamonds.

Don’t assume all SI1 clarity rated stones will have the same appearance, or that all Excellent cut diamonds will have the same brilliance, or that all G color diamonds will have the same colorlessness. You’ll want to view each diamond through the loupe and assess the levels of eye-perfect clarity, fire, and brightness.

How To Compare Diamond Certification Labs And Who Is Best?

The best labs, and the ones we’ll discuss first, are the GIA and AGS. They have proven to be the most consistent and trustworthy in their standards and practices.

GIA - Gemological Institute of America

The GIA stated mission is to ensure the public trust in gems and jewelry by upholding the highest standards. Established in 1931, they are an independent, non-profit organization dedicated to research and education in the field of gemology.

They are the most well-respected lab in the industry and their diamond certifications are considered the gold standard. In delivering their assessment of a diamond, they observe a wide variety of qualities and elements, and all their locations across the globe are known to have very consistent grading standards. Historically, 99.99% of all the natural diamonds that we've ever acquired were certified by the GIA, and on rare occasions we have purchased AGS graded diamonds.  

Our only criticism of the GIA is that they do not currently (as of 2024) offer physically printed certificates of lab grown diamonds (only digital copies are available). While the GIA is the most sought after lab for natural diamonds, they only certify a small fraction of the lab grown diamonds on the market (about 9% as of 2024).

AGS - American Gem Society

The AGS is a non-profit, trade association with members across the professional fine jewelry industry. Founded in 1934, they operate under a high code of ethics with an emphasis on consumer protection and education.

The GIA and AGS have each developed a unique way of grading the diamond cut. The GIA uses a scale of Excellent, Very Good, Good, and Poor while AGS uses a numbered scale from 0 to 9, a 0 being considered “ideal”. The AGS was the first to institute a cut grade system, but once the GIA introduced theirs, the market share for AGS fell significantly.

Additionally, their color and clarity grading scales use a system of numbers and decimals compared to GIA’s more commonly understood D-Z color and FL-I3 clarity ranges. To some consumers this may be confusing. But the AGS uses strict guidelines and continues to be well-respected in the industry.

IGI - International Gemological Institute

The IGI is a diamond, colored stone, and lab-grown diamond certification organization. Established in 1975 with headquarters in Antwerp, the IGI is comprised of a collection of labs around the world. While they operate under the IGI umbrella, the consistency in grading varies between the global labs.

While the IGI is not as reputable as the GIA, and their standards are indeed less consistent and more lax on the color grading, they are the dominant choice for lab-grown diamond certifications. To compensate for these lower standards, we recommend buying the best quality lab diamonds (D or E color, VS1 or VVS clarity) available. And since the best quality lab diamonds are only slightly more expensive than the next grade down, we believe they are well worth the extra cost.  

As of 2024, about 87% of all lab grown diamonds are certified by the IGI.  


EGL - European Gemological Laboratories

Founded in Belgium in 1974, the EGL is actually a collection of independently owned franchises around the world. When comparing their certifications with other respected labs, diamonds are typically upgraded one to two grades above the true quality.  

The EGL’s reports are widely considered to be unfairly upgraded, and consistency in standards across all locations is very low.

HRD - Hoge Raad voor Diamant

The HRD is a diamond grading organization based in Europe presenting itself as a European counterpart to the GIA. Claiming status as the leader in the the global diamond trade and at the forefront of research and education, the HRD is actually incredibly inconsistent and typically shows upgrades in their grading.

Diamond certification is an essential component for any diamond as a way to reliably prove the value of what you’re purchasing. Color and clarity gradings are critical information for investment grade diamonds because they allow consumers to ascertain the true value (or at least a trading range) of a diamond, thereby allowing them to purchase with confidence.  

But with gemstones that have no quantifiable comparable (such as rustic diamonds or opals), then the traditional gradings are not applicable. Rustic diamonds of a salt and pepper variety, or something like our Audrix which features a rustic diamond, do not go through the same certification process as investment grade diamonds. Rustic diamonds are more like gemstones and more subject to personal opinions than standard diamonds.

There is no way to compare rustic diamonds or opals from one stone to the next based solely on color and clarity. Gemstones and rustic diamonds are more like art; their general appearance and specific shade of color must speak to you, and finding the perfect one requires a different set of standards.

Among tens of thousands of rustic diamonds that we see each year, there may be only 50 to 100 with the right amount of color, translucency, clean surface, and pretty shape that we like enough to consider acquiring; all factors that have nothing to do with color or clarity grades.

So for these stones (especially those over $1,000), we might send them to a local lab to verify the authenticity of the stone (i.e. that a sapphire is indeed a sapphire) and to record basic facts of the stone, such as the weight and the size measurements. However, we are not concerned about getting an accurate read on the color and clarity because neither are metrics used to value a gemstone or rustic diamond.

When shopping for a diamond, you’re buying the stone and not a piece of paper. But the papers accompanying the diamond ensure you’re spending your money wisely and getting the value you’re expecting. And if you’re ever unsure about what you’re seeing on the certification, ask questions and seek other expert opinions. We’re always here to help you make the best decision for your diamond purchase!

Have questions? We're happy to help.