Whether you are newly engaged (and have the engagement ring to prove it!) or you recently acquired some beautiful diamond jewelry, you’re probably wondering how to tell if a diamond is real. One of our resident jewelry experts has the scoop on how to distinguish a valuable rock from a less valuable look-alike.
Dazzling Diamond, or Sneaky Imposter?
The hard part’s over: in a sea of shallow clickbait meet-cutes, you’ve found the person you want to spend the rest of your life with. Congratulations! And now you even have a sparkling rock on your finger to make sure everyone you meet knows just how lucky you are.
But wait — how can you be sure that the sparkling rock is a genuine diamond? Aren’t there a lot of fakes out there on the market? How can we know for certain?
The thing to understand about imitation diamonds (called simulants in the jewelry industry) is that the term doesn’t just refer to one material. Natural stones like white sapphire, quartz crystal, or white topaz, laboratory-grown stones like moissanite or cubic zirconia, or man-made materials such as plastic or rhinestone can all be sold (sometimes transparently, sometimes less so) as alternatives to diamonds.
There’s a big industry for diamond simulants lining up to be your new forever stone — some, like fiery cubic zirconia or soft-spoken quartz crystal, are too brittle to be worn every day; others, like white sapphire, have a unique snowy beauty of their own but lack the defining, glittering scintillation of true diamonds. Moissanite has garnered a following as a budget-friendly alternative for its durability and diamond-like gemological properties, but it lacks the widespread appeal and long-standing tradition of a classic diamond ring.
While none of them match the brilliance of a natural, well-cut diamond, each of them have their own properties that can be difficult to distinguish from diamonds to the untrained observer.
Can you tell if a diamond is real or fake with the naked eye?
The short answer is not really, although there are certain giveaways that you can look out for when examining your diamond.
If you can, use an inexpensive jewelers loupe or a magnifying glass. Make sure you’re examining your diamond in a well-lit space free of clutter, and make sure your diamond is clean. Fingerprints and day-to-day build-up of dust and grime can make it much more difficult to see what you’re looking at and block some of the diamond’s distinctive features, such as dispersion and brilliance.
First, examine the surface of the diamond for scratches. If it’s been dinged up a bit from day-to-day wear and tear, it’s probably not a real diamond. While a diamond is not indestructible (it can fracture if knocked hard against something), its surface is incredibly hard and almost invulnerable to scratches.
Next, check to see if your diamond has a serial number. This is a unique identification number that gets laser engraved onto the girdle (the “belt” that runs between the upper and lower facets) of GIA-certified diamonds. You’ll be able to see it if you look very closely (the serial number also makes it easy to identify your unique stone, and makes stolen diamonds much harder to resell).
If you can find a GIA serial number, you can be sure that yours is a real diamond. However, not all laboratories use them, not all stones are sent in by jewelers for individual grading, and the serial engraving process has only been around for about thirty years. So if your stone doesn’t have a serial number, that doesn’t automatically mean it isn’t a real diamond.
Another thing you can look for is “dispersion”, which is the term used in the gemological industry to describe the colors that play across a diamond’s surface (sometimes called “fire” or “the disco ball effect”). One reason why the cut grade of a diamond is so important is that the angles of the facets work together to reflect and refract light in the most beautiful way possible. This gives us the flashes of light and color that we tend to think of as “sparkle”.
Plastic, glass, and white sapphire don’t usually display this firework effect. Cubic zirconia and moissanite refract a little bit more than diamond, displaying even more rainbow color. An experienced jeweler or gemologist can guess if a stone is an authentic diamond fairly accurately based on this observation alone, but it can be difficult for someone who hasn’t spent a lot of time looking at diamonds and diamond alternatives side by side.
Diamond Tests You Can Do at Home
This simple, oft-cited test involves breathing warm air onto the surface of the stone — as though you’re trying to fog up a window — and seeing how quickly the fog dissipates. This works because of diamond’s extraordinary thermal conductivity, or the rate at which it disperses heat. While low-quality diamond alternatives like cubic zirconia and glass will retain the heat on the surface and hold onto the condensation from your breath longer, a diamond will let go of its heat almost immediately.
This is a quick easy test to see if you have one of these less valuable diamond imitations; however, moissanite has a high thermal conductivity comparable to diamond, and white sapphire is not too far behind, so the test is not definitive.
Go back and get your jeweler’s loupe and have a look under the table, or the big flat facet on the stone’s surface. Because diamonds are naturally formed stones, they’ll often have internal variations such as included minerals or irregularities in growth. These are called “clarity characteristics.” They’re like a personal fingerprint that makes every diamond unique.
Look carefully and see if you can find the clarity characteristics of your diamond, whether that’s microscopic minerals that got caught in the diamond’s formation or minuscule hair-like fractures left behind from the cutting process. Artificial diamond simulants like rhinestone and cubic zirconia won’t have this; however, other natural stones like white sapphire and white topaz may have internal variations of their own.
This one, unfortunately, only works if you have a loose stone (not set in a piece of jewelry). Natural diamonds are very dense (one of the reasons they’re so scratch resistant) and will sink to the bottom of a glass filled with water. Simulated stones made of glass, plastic, and quartz crystal will float— if your stone floats to the top of the glass, you can be sure it isn’t a real diamond.
However, be aware that some stones like cubic zirconia and white topaz have comparable density to diamond, and white sapphire and moissanite even more so, so these stones will all sink to the bottom as well.
Using a piece of reinforced steel, like a screwdriver or a sewing needle (hardened steel is around an eight on the Moh’s Hardness Scale), try to scratch your stone in a discreet place. If it’s plastic or rhinestone it should scratch fairly easily; cubic zirconia and white topaz will scratch with a little more muscle. While diamonds are the hardest known gemstone (a ten on the Moh’s Scale), moissanite (nine and a half) and white sapphire (nine) will stand up to scratching almost as well.
Do not do this if you’re not willing to risk your stone — it would be a bittersweet victory to prove that your diamond is an imposter, only to find that it isn’t all that nice to wear anymore.
Fun fact: the only thing that can scratch a diamond is another diamond, which is why low-grade stones that don’t make the cut for jewelry get repurposed as drills and other industrial tools.
Home Diamond Testing Devices
If you’ve exhausted all of these options and you’re still not quite sure, you can get an inexpensive diamond tester to use at home. These work by transferring a small amount of heat to the diamond’s surface (remember thermal conductivity?) and measuring how quickly the heat is dispersed.
These little handheld machines are very accurate and can eliminate just about any diamond simulant, with the exception of moissanite — moissanite’s thermal conductivity is almost identical. To test for moissanite specifically you can use a similar device that measures electrical conductivity (these can get pretty expensive), or take it to a jeweler and have them test it for you.
How Do Experts Determine if a Diamond is Real?
The only way to know beyond a doubt if your stone is a real diamond is to take it to a professional to be tested. What they do is quite similar to the tests listed above that you can do at home, backed by more accurate equipment and many years of experience.
Because of the density of diamonds (remember the water test?), many jewelers will detach the stone from its setting and try weighing it alongside another diamond. Two diamonds of the same shape, size, and cut should weigh almost exactly the same. Jewelers use highly sensitive measuring scales that weigh in increments of .001g, or a thousandth of a gram. Other stones of the same size might weigh a fair bit more or less — for instance, a 1ct sapphire will be smaller than a 1ct natural diamond.
Using a high-magnification microscope, professional gemologists will do exactly the same thing you did with your jeweler’s loupe and look for defining clarity characteristics. With years of experience in the industry, they’ll know exactly what to look for and what variations they’re most likely to find in your particular stone, as well as how to compare them with inclusions and formations found in other natural white gemstones. They can also look at patterns and directions of growth to ensure it formed the way a diamond is supposed to.
A jeweler may also use diamond testing devices like the one you used at home to measure thermal and electrical conductivity. After the testing is complete, they’ll issue you with a report that tells you what it is and any identifying information, as well as any treatments they discovered during the analysis. For a real diamond, you can order a grading certificate that lists the cut, color, carat weight, clarity, notable clarity characteristics, and detailed proportions of the diamond.
No Pressure, No Diamonds
Diamonds are unmatched for their sparkling beauty and their unscratchable surface that makes them ideal for everyday wear. But what matters most, in the end, is that you wear something that makes you feel happy and loved.