What You Should Know About Diamond Certification

Most people can’t tell the difference between 2 diamonds that are thousands of dollars different; this is why we need diamond certificates. Laboratories that are qualified and specialize in diamonds perform diamond certification. There are dozens of labs to choose from, but not too many of them are credible enough to be on our list of recommendations.  From the dozens of labs available, we think that just 6 are worth your attention, good and bad. However, PhD’s top 2 picks for diamond certification labs are GIA and 


Reading a Diamond Certificate

A diamond certificate covers the ever-popular 4 C’s that are used to measure the Color, Cut, Clarity, and Carat of a diamond. No matter the certificate, they will cover these four areas; some in more depth than others. The color will be graded on a scale of D-Z, cut will vary in vocabulary between the labs but range from poor to excellent, clarity will be a scale of FL to I3, and carat is always measured using the scale of .20 grams for every 1-carat.

The importance of the details within each of the 4 C’s becomes increasingly important as the price increases. So, the importance of a credible laboratory to certify the diamond is increasingly necessary as you raise your budget, don’t you think?

Let’s take a look at the most notable labs from the best to the worst. We have decades of experience and training in the diamond industry, so we have some strong opinions.


Gemological Institute of America (GIA)

The Gemological Institute of America, founded in 1931, is known as the crème de la crème of all gemological laboratories. This non-profit lab actually created and mainstreamed the 4 C’s grading scale that is used today by all other labs in one form or another.

GIA is the lab known and respected worldwide as the foremost authority on diamonds. With 3 locations in the USA and offices in all the major diamond hubs throughout the world, they are well connected.

Below you can see a GIA certificate. Notice that the 4 C’s are in a single area. Further, they give a full plot of the diamond to demonstrate where each inclusion lies for easier identification 

One thing that we aren’t thrilled about with GIA, their cut grading is not at the level of their competitors. First, they only provide a cut grade for round diamonds. Second, they don’t use demonstrate how they found the cut grade as so many other labs do. Unfortunately, GIA has always been behind the times when it comes to cut grading. Almost perfect.


American Gem Society (AGS)

A close second place is given to the American Gem Society which was founded just years after GIA in 1934. The entire purpose of this lab is to act as an advocate for the consumer. They are all about transparency and honesty with the public. Bravo, AGS! Their certifications are given the same respect as GIA within the USA; yet, they aren’t as internationally accredited as GIA.


One feature that we love is their Light Performance Cut Grading. They judge the brightness, fire, leakage, contrast, weight ratio, durability, tilt, girdle, and culet in relation to the light performance of every diamond that they grade. That’s 9 different considerations!

Take a look at a sample certification from AGS below and notice that Light Performance, Polish, and Symmetry are all listed to establish a final cut grade. If all 3 are considered Ideal, the diamond is known as a triple-zero, meaning that it has a perfect cut.


Hoge Raad voor Diamant (HRD)

Hoge Raad voor Diamant or much easier, HRD is a grading laboratory founded in 1976 in Antwerp, Belgium. They are third on our list because they follow the strict grading guidelines that are assigned by the International Diamond Council and have a number of impressive relationships with diamond industry insiders. 

This lab is based in the country where more than 80% of all diamonds travel. They may not have the convenience for Americans of USA based labs, but they have still made a name for themselves within the USA.

As for their grading, they are usually on par with GIA and AGS, but when push comes to shove, they are easier on diamonds. In our experience, when GIA would call a diamond SI2, HRD might call the same diamond SI1. Take a look below at their certification. They give all of the necessary information without confusion. We like them.


The Gem Certification and Assurance Lab (GCAL)

The Gem Certification and Assurance Lab boast the fact that they offer a grading guarantee with all of their certificates. They actually have the least information about themselves and their history available online. So, although we think their grading is trustworthy, they fall behind our favorites on the list. Their clarity grading might be a little easier than we prefer.

Take a look at their certificate below. The Light Performance analysis is comparable to AGS and we love it! They have a lot of information on their certificates and offer a full report of the diamond.

The International Gemological Institute (IGI)

The International Gemological Institute is headquartered in Antwerp like HRD and was established in 1975, just a year before them.  They have labs all across the world, so the grading will be slightly different depending on which lab you choose. Each lab seems to be run autonomously, so we can only speak for the general view of them.

Below you can see that their certificates are very straightforward and cover all the essentials. Their grading seems to be much easier than the more credible laboratories, so they can’t be compared to other diamond certs so easily.

Final note on IGI, they offer appraisal certificates for finished jewelry as well and assign retail pricing that is inflated. Further, the appraisals often have typos and need corrections. Not a very professional lab in our opinion.

The European Grading Laboratory (EGL)

The European Grading Laboratory has gone through a huge shake up within the past decade. Their USA office was founded in 1975 and has been making huge strides to clean up their act. EGL has been known throughout the diamond industry as the Easy Grading Lab due to their generous grades of diamonds that will make them look like the best choice in terms of price when compared a certified diamond from GIA or AGS.

This lab is our least favorite and the last on our list because they have taken the well-established 4 C’s and made a mockery of them. For decades, they were well known and used by diamond industry insiders. Yet, their reputation has caught up with them.

Take a look at on of their certificates below.  They use the standard 4 C’s in a way that looks similar to other labs. Please beware of these certificates! We maintain that some paperwork is better than no paperwork, but you can’t price a diamond graded by EGL based on what’s on the certificate.

PhD Conclusion

Our final recommendation comes in the form of a 4 star chart comparing the color, cut, clarity, carat, price of certificate, value of certificate, and credibility of each of the diamond grading laboratories.

What you are looking for in a diamond certificate might be different than the next guy; that’s why there are so many different choices. Take a look at the chart and you’ll see that each lab gets 4-stars for the carat grading; it’s the only C that’s 100% objective. Each other area varies based on the lab, so look at the areas that are the top of your list for consideration

PhD Diamond's Lab Ratings

Color Grading★★★★★★★★★★★★★★★★★★
Cut Grading★★★★★★★★★★★★★★★★★
Clarity Grading★★★★★★★★★★★★★★★★★
Carat Grading★★★★★★★★★★★★★★★★★★★★★★★★
Price of Certification★★★★★★★★★★★★★★★★★★★★
Value of Certification★★★★★★★★★★★★★★★
Lab Credibility★★★★★★★★★★★★★★★

Whatever you end up buying and whichever certificate you end up having; make sure that you love the diamond. Ultimately, a diamond is only worth the amount of happiness that it ends up bringing you.