Whether you own a diamond that’s sitting pretty on your left ring finger, nestled in a tennis bracelet or pronged on a pair of earrings, you want to know it’s good quality. But it’s hard to be sure. And sometimes that’s because what sets it apart can’t even be seen with the naked eye — and customers can easily be tricked.
Just recently, Costco was caught selling counterfeit Tiffany diamond engagement rings, using the jeweler’s name without permission. A federal judge ruled that Costco was infringing on Tiffany & Co’s trademarks, writing that “no rational finder of fact could conclude that Costco acted in good faith in adopting the Tiffany mark.”
Marketing ploys aside, it is incredibly difficult to know what you’re getting when buying a diamond ring, especially as the naked eye can’t tell the difference between what makes one ring more expensive than another.
Russel Shor, a senior industry analyst for the Gemological Institute of America (GIA), says that the institute’s 4 Cs—color, clarity, cut and carat—should be judged in a lab by experts. Any diamond you buy should come with a report from that lab that shows exactly how it ranks in each category.
Heirloom diamonds you may not be sure about can be sent to the GIA, which will get the same report from its labs, though you’ll have to remove them from their setting first.
“A human eye generally can’t tell the difference” between color grades and “if you get a 1.02 carat and a .95 carat, the price difference is going to be 30 percent higher for the 1.02, but you won’t see the difference,” Shor says.
So when there’s a trade-off between size and clarity, here’s what to look–and more importantly, ask—for.
Carat weight is pretty straightforward. Diamonds are weighed in metric carats, with two carats weighing about the same as a small paper clip, according to the GIA. Ask your jeweler for a Diamond Grading Report and you’ll see exactly how much it weighs.
When a gem is under five carats, a human eye likely won’t be able to detect flaws without a microscope, but if you’re going big (Kim Kardashian West’s ring from Kanye is 15-carats), then you’ll probably notice some of the clarity issues.
The GIA says nearly all diamonds contain unique internal characteristics called “inclusions” and external characteristics called “blemishes,” or what most would call flaws. These are so tiny, only a trained gemologist can see them.
“If it’s flawless, it means using 10-power magnification, you cannot see anything in the stone other than the diamond,” Shor says. The clarity scale includes 11 specific grades running from FL, meaning Flawless, to I1, I2 and 13, meaning Included. On the grading report, you can see where yours falls, even if you won’t be able to tell yourself.
The cut of your diamond can be graded on a scale ranging from excellent to poor. “The cut is really the indicator of whether you have a beautiful diamond or not, because that’s what makes the sparkle,” Shor says. “Diamonds that are poorly cut will be lifeless.”
So, if you go for something with more flaws but an excellent quality cut, it will still look perfect to you, even if not to a gemologist under the magnification of a microscope.
Color is where things can get a little confusing. A majority of the diamonds sold today go through a gem lab, and the GIA lab has a “very, very, very tightly controlled environment.” The lightbulbs are identical so every grade can be on the exact same scale. “The color differences are so fine, there’s no room for any variation.”
The GIA color scale runs from D to Z, with D being colorless and Z being light.
“When they talk about color, they’re really talking about the lack of color,” Shor says. The lack of color is more desirable—and the grade is found by comparing every diamond to a master diamond at the extreme top end of the grade. Of course, the fancier colored diamonds—like the recent popularity in yellow diamonds—is an entirely different ball game. Those grades relate to color intensity.
All this information is available in a diamond report, created by a third-party with zero interest in what company is selling the diamond or how much it sells for.
Read more: How To Buy an Ethical Diamond