The Complete Guide to Diamond Certification

In addition to considering a diamond’s cut and color, there’s something else that you need to take into account before purchasing such a jewel: its certification. Before it makes its way into a setting, a stone should be properly evaluated by the experts. “A diamond will go to a gemological laboratory, where trained gemologists examine it to assess its qualities based on the 4Cs: cut, color, clarity, and carat,” says jewelry designer Ashley Zhang. “Once those qualities are determined, the lab will issue a detailed report.”

The document produced by this process is known as a diamond certification or a diamond grading report; it’s an incredibly important step in the life of a diamond. “The certification verifies a diamond’s authenticity,” Zhang says. “It determines a diamond’s true value, which allows for accurate pricing and can be important for resale and insurance purposes. A certification significantly adds value to a diamond.”

Here, the experts explain everything you need to know about the diamond certification process, including why it matters, who is authorized to do it, and where to store the resulting documentation such an evaluation produces.

Why Is Diamond Certification Important?

“As a gemologist and jeweler, I can’t stress enough how important it is to have a diamond report; it is a must-have,” says Malyia McNaughton, the founder of Made by Malyia. “Diamond reports are essential because they provide an unbiased, expert assessment of a diamond’s quality. They detail the stone’s characteristics like cut, color, clarity, and carat weight, so buyers know exactly what they’re purchasing.” 

Without a certification, there’s no way to tell—at least from the buyer’s perspective—that the diamond is authentic. “A diamond report is crucial for consumer confidence because it ensures transparency and fairness in pricing,” McNaughton says. “A diamond with a report typically holds its value better because there is documented proof of its quality. Reports from a reputable lab, such as The Gemological Institute of America (GIA), can add value to the stone because they are trusted for accuracy and consistency.” As a buyer, you’ll want to see the diamond report before making such a large purchase. Additionally, if you choose to sell your diamond, you’ll want to have such an evaluation available.

How to Understand Diamond Certification

A diamond certification is proof that your sparkler—whether natural or lab-grown—is authentic and that its qualities are indeed what the seller says they are. It’s like a birth certificate for a person. “A diamond certification is a document that verifies and states the qualities of a diamond,” Zhang says. “It states the 4Cs by using a standardized grading system. The 4Cs determine a diamond’s price, so it’s important for shoppers to understand or know what qualities they want in order to choose a diamond within their budget.” She suggests doing your research well in advance to know what you’re looking for or working with a trusted jeweler to identify your preferred stone.

Jewelers will also be able to explain the details included in the report; each gemological lab uses its own grading system, and some even include diagrams of the stone to mark the location of inclusions, facets, and more, making them difficult for the average consumer to understand.

Just like with a birth certificate, this report is something you should plan to hold onto. “You will receive a physical copy of your report detailing the diamond’s characteristics, and it’s crucial to keep this in a safe for insurance, resale, and verification purposes,” McNaughton says. “Some labs, like the GIA, also offer digital versions of their reports, which are easy to access online. Both are valuable, but I always suggest holding onto the physical copy as well.” If you do happen to lose this evaluation, know that it will require some extra legwork on your end. “In order to have another one printed, the diamond will need to be re-sent to a lab for grading,” Zhang says. “And if the diamond is already set in a ring, it will need to be taken out.”

Types of Diamond Certification 

“When a diamond is given a report, it means it’s been carefully evaluated by an independent gemological laboratory like the GIA, which is the most trusted name in diamond grading,” McNaughton says. “Shoppers should be aware of which laboratory has issued the report to ensure they are receiving a report from a recognized and respected laboratory.” Here, we break down the most notable laboratories.

GIA (Gemological Institute of America)

Most jewelers agree that the GIA is the most trusted lab in the industry. “It is widely recognized as the gold standard because of its strict grading system and consistency,” McNaughton says. “GIA offers several grading reports. The GIA Diamond Grading Report is used to determine the natural diamond’s shape, the 4Cs, as well as proportions, finish, and treatments. It includes a plotted diagram that maps your diamond and identifies its unique characteristics. The Diamond Origin Report identifies a natural diamond’s country of origin through a series of tests and examinations in the lab.” For natural diamonds that weigh less than 2 carats (and more than 0.15 carats), she adds that the GIA also offers the Diamond Dossier, a compact version of the Diamond Grading Report. 

IGI (International Gemological Institute) 

“Though GIA is the most widely known and universally trusted, there are other labs that also provide diamond reports that are equally as legitimate,” Zhang says. That includes the International Gemological Institute (IGI). Established in 1975, this organization is relatively young compared to the GIA, which was founded in 1931, and is known for a slightly looser grading standard. Its certification includes a detailed report outlining the 4Cs of a diamond, as well as grading its fluorescence, polish, and symmetry. If you’re covering the cost of a report yourself, rather than through a jeweler (say, on an heirloom diamond), getting an evaluation from IGI may be cheaper than obtaining one from GIA. 

AGS (American Gem Society) 

Founded in 1934, the American Gem Society (AGS) grades diamonds on a scale of zero to 10, with zero representing the highest quality diamond. AGS is known for its cut grading system, as it issues a different type of report for each diamond cut.

EGL (European Gemological Laboratories) 

At an European Gemological Laboratory (EGL), four gemologists evaluate each diamond for certification. Depending on the characteristics of the jewel, it may receive a specialized evaluation, such as a Colored Diamond Report or Lab-Grown Diamond Report. While this laboratory is legitimate, some jewelers consider it less trustworthy than other institutions, as it sometimes overstates the diamond’s value by two or more grades.