Diamond Certification: The Complete Guide

Buying a diamond is kind of like buying a car (except a little more romantic): It's not enough to simply glance at it and call it a day. Instead, you want to try it on for size and be sure all of the corresponding paperwork is available to back up your purchase. For many couples searching for the perfect gemstone, one phrase will come up a lot: diamond certification.

Not only does diamond certification determine the quality of a gem, but it also "communicates the diamond’s qualities in a way that helps consumers understand what they are buying," explains GIA-accredited jeweler Nellie Barnett.

Read on for our complete guide on diamond certification—from how to read a diamond certificate to choosing the best type of certification—to ensure you're making the most informed, thought-out investment possible. 

Advantages of Buying a Certified Diamond

One of the top advantages of buying a certified diamond is precedent. "We’ve been doing this for decades, and have graded tens of millions of diamonds," Barnett explains. "The GIA Diamond Grading Report is the premier credential of a diamond’s authenticity and quality, especially when buying engagement rings."

This system was invented in the 1940s and '50s to create a consistent methodology for describing diamonds and their quality. "This common language and the widely accepted GIA standards, methods, and best practices to grade diamonds add a very important consumer-protection element to the way diamonds are bought and sold," she continues. "GIA reports give people confidence in their purchases because they have an independent and impartial evaluation of the diamond’s quality."

Cost of Certification

The price of a GIA grading report varies depending on the type of stone, its carat weight, and the service requested. "For D-Z diamonds, the basic grading service is about $30 for a quarter-carat diamond to about $85 for a one-carat stone, with the fee increasing based on weight and the service," Barnett says. GIA lists its full fee schedule online.

How to Read a Diamond Certificate

There are a few things to keep an eye out for on a diamond's GIA certificate:

1. The date the diamond was graded
2. The GIA report number
3. Shape and cutting style (i.e. round brilliant)
4. Measurements

After those details, the certificate will list the grading results for the carat weight, color grade, clarity grade, and cut grade. Additional grading information includes polish, symmetry, and fluorescence. The certificate also offers a profile view of the diamond with exact proportions as well as clarity characteristics. Visit GIA's website to view an example of a diamond grading report.

Types of Diamond Grading Systems

While the GIA grading system is among the most well-known and trusted, there are also a handful of other certifications to keep an eye out for, including AGS, IGI, EGL, GSI, and HRD.

American Gem Society (AGS)

Founded in 1934, the American Gem Society was created by a group of jewelers in an effort to “protect the jewelry-buying public from fraud and false advertising.” They evaluate cut, color, clarity, and carat on a 0-10 scale—the highest grade is zero and the lowest grade is 10. AGS is now joined by three thousand members including jewelers, retailers, and suppliers, and is considered a reliable source for diamond certification.

International Gemological Institute (IGI)

The International Gemological Institute has been around since 1975 and has 18 laboratory locations around the world. IGI evaluates loose diamonds as well as finished jewelry pieces and was the first gemological institute to fully grade lab-grown diamonds, starting in 2005.

European Gemological Laboratories (EGL)

Reports from European Gemological Laboratories typically include carat weight, clarity grade, color grade, cut (shape and style), finish, fluorescence, plotting, and proportions. They are also often considered looser with their grading standards. 

Gemological Science International (GSI)

Gemological Science International was founded in 2005 and grades both natural and lab-grown diamonds. Their laboratories employ advanced technology and instruments to capture a diamond’s light performance and reports include information regarding shape, weight color, clarity, fluorescence, polish, symmetry, measurements, cut grade, and plotting diagram.

Hoge Raad voor Diamant (HRD)

Hoge Raad voor Diamant issues certificates for diamonds and gemstones primarily in Europe and is located in Antwerp, Belgium—a geographical location that is synonymous with diamonds. The company uses what they refer to as a “double coding system” and provides reports for natural, lab-grown, and treated diamonds.

The Best Diamond Certification

In general, diamonds that have been graded by GIA or AGS are considered the top-tier options, especially because they are nonprofit diamond grading laboratories. We advise purchasing diamonds certified by the GIA or AGS.

What to Look for When Grading Diamonds

Consistency and strictness! You want the lab that's evaluating diamonds to treat all of the gemstones they see the exact same way. Strictness also ensures you're getting what you paid for.

Is a Diamond Certificate Necessary?

Yes! There's no way to know what you're buying without a qualified, trusted entity to evaluate your diamond. Don't buy a diamond unless it has a certificate.