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Are all diamond grading labs created equal? Take a deep dive into diamond grading, including who’s doing it well and which labs you should avoid.

By Stephanie Dore

Diamond grading is one part art, one part science, and the reality is—not every lab is created equal. But they all claim to do the same thing. So how exactly does this grading system work? Lord knows it’s not a simple pass, fail system. And why does it matter? 

Well, first thing’s first, a diamond’s grade, well, grades (plural) is a major part of how it’s priced. So it matters a lot. But how impartial is the process? What if a diamond is graded incorrectly? Are lab created diamonds graded the same way as natural diamonds? To answer all your burning questions, and hopefully take some of the chaos out of the conversation, we’re taking a deep dive into how diamonds are graded, who’s setting the bar, and who’s dropping it. 

When Does a Diamond Get Graded?

Diamonds are graded after they’re cut and polished and all prettied up. And they’re graded loose, which means not in a ring (or any other) setting. They’re also graded blind so that the lab doesn’t know who it belongs to—and can’t play favorites. They’re certainly not graded blindfolded. That would make this a very different story. 

Once the lab has the diamond, they’re responsible for verifying the type of diamond (lab created vs. natural) and evaluating the diamond’s quality characteristics. You know, the whole 4 Cs thing. But it’s not just one person. In fact, two or three diamond graders will review each stone, and a grading report (or certificate, depends on who you ask), isn’t issued until they all agree.

How are Diamonds Graded?

Step 1: Carat

After a diamond arrives at a lab, it is weighed using an electronic micro-balance. But this isn’t just about how much it weighs. A diamond is also 3D-scanned to determine how it carries that weight—it’s measurements, proportions, and angles. After all, sometimes it will be hiding weight in its belly, or it might be shallow and spread out. 

Step 2: Authenticity

Next, the diamond is analyzed for authenticity, to determine first, well, if it’s a diamond at all. Assuming it is, then the lab is going to determine if the diamond is mined, lab-grown, or color-treated. They have all kinds of crazy cool gadgets to help them do so! As lab-grown diamonds have risen in popularity, this process has become essential.

Step 3: Clarity

Another cool way to evaluate a diamond’s origin is through its clarity characteristics. Much like a fingerprint, they can help identify a diamond, they’re that unique! Diamond clarity is graded by multiple graders using 10x magnification. They evaluate the diamond’s polish, symmetry, and clarity, and in some cases create an entire plot map of inclusion types and locations. They are also looking for evidence of artificial treatments which impact the value of the diamond. Curiosity piqued? Read our guide to diamond clarity and discover which inclusions you should probably avoid.

Diagram depicting Frank Darling's diamond clarity chart

Step 4: Color

Party over here! Again, multiple diamond graders evaluate the color of the diamond, this time with some help from their friends. See, they have a set of “master stones” ranging from D (colorless) to Z (yellow), and the graders will go stone by stone until they find a color match. The grader also reviews the diamond under UV light to assess its fluorescence. This is the blue glow that some diamonds emit under UV light. Untz. Untz. Untz. 

Frank Darling diamond color grade chart

Step 5: Cut

Last but certainly not least (in fact, it’s kind of the most important), a cut grade is assigned. But only for rounds! It’s a cruel, cruel world for all those fancy shapes, I tell you. The cut grade takes into account the diamond’s proportions, brightness, fire, scintillation, polish, symmetry, and more. That’s a lot! But all that stuff is determining just how brightly a diamond is going to sparkle, which, frankly, is what it’s all about. 

These grades, taken together, inform the price you pay, the cost of your insurance, and ultimately the diamond’s resale value. While the standards for diamond grading are rigorous and mature, in many ways, it’s as much an art as it is a science. If you’ve ever squinted, looking at a G color round brilliant next to an H color round brilliant, and wondered whether they are the same color, you’re not alone. Diamond graders go through rigorous training, yet grades can still vary from person to person and lab to lab. 

Diamond depicting diamond cut for round diamonds.

So, Who’s the Best Grading Lab?

If you’ve tried to buy a diamond, you’ve most likely come across an article that starts: The only reputable diamond lab is the GIA. As a rule of thumb for natural diamonds, this is OK. While there’s a lack of data to validate the claim, there’s more than enough GIA certified mined diamonds on the market, so unless you have something particular in mind, there’s not a good reason to look elsewhere.

Does the GIA Grade Lab Diamonds?

Not really.

Unfortunately, while other diamond grading labs have embraced lab-created diamonds, the GIA, well, not so much. Despite the rise in popularity of lab diamonds, the GIA’s position has remained relatively unchanged. They still grade lab created diamonds with much more leniency than mined diamonds, not issuing specific color or clarity grades. Instead, they use a grade range. For instance, instead of assigning a D color grade, they assign a D-F grade defined as “colorless.” This lack of specificity affects the price and value of GIA-graded lab diamonds.

Under mounting pressure and a recent change in legislation from the Federal Trade Commission (FTC), the GIA announced recently that they would no longer refer to lab-grown diamonds as “synthetic” on their reports but as “Laboratory-Grown Diamonds.” Well. That’s something, right?

While the intent is to avoid consumer confusion, the reality is that consumers purchase lab-grown diamonds similarly to mined diamonds, with distinct preferences for cut, color, and clarity, and the report is misleading and insufficient, particularly when a “D” color grade diamond can sell for hundreds if not thousands more then it’s “E” counterpart.

So Who Grades Lab Created Diamonds?

IGI and GCAL have both stepped in to fill the gap. Both labs provide full grading reports for lab-grown diamonds. All Frank Darling lab diamonds come with an IGI or GCAL certificate of authenticity based on an internationally recognized trading system, and they use similar state-of-the-art equipment and grading processes to guarantee authenticity.

In addition to the standard grading report, GCAL analyzes each diamond using its proprietary Direct Assessment Light Performance analysis. This method analyzes each diamond’s light performance and generates a much more in-depth report. GCAL even goes so far as to offer a cash back guarantee which protects the consumer in the event of an error.

Are All Lab Diamonds Graded?

Absolutely not. One only has to do a quick online search to find a long list of non-graded lab diamonds, or lab diamonds with misleading language, or even worse—falsified grading reports. Synthetic diamonds being mislabeled and sold as “lab diamonds” or even “natural diamonds” is a growing and worrisome trend in the industry. Purchasing a non-graded lab diamond is risky. It’s most likely CZ or moissanite masquerading as a lab-grown diamond. Good to know? If the price looks too good to be true, it probably is.

Ready to Find Your Own Diamond?

Check out our diamond search where you can view 360-degree images of more than 10,000 diamonds (including lab created and mined) and don’t forget to zoom out (because size can be deceiving), or book a virtual or offline appointment at our New York salon to view certified lab-grown and natural diamonds in person. 

Not finding what you’re looking for? Email us with what you’re looking for at We’ll curate a list of 5-7 exclusive stones that are just right for you.

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