How To Tell If A Diamond Is Real Or Fake

Photo: fizkes / shuterstock
woman looking at a diamond ring

There are few things more beautiful in this world than a brilliant diamond. But diamonds are extremely valuable and expensive, and sometimes people try to pass off a fake as the real thing.

There are a couple of stones that often replace diamonds for alternative bridal items, including white sapphire, cubic zirconia, and moissanite (and even glass).

But if you have a sparkly diamond and you aren't sure if it's real or fake, there are several tests you can do to figure out if your precious gemstone is the real deal.

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How To Tell If A Diamond Is Real Or Fake

1. Look at the sparkle.

Diamonds will sparkle even when dirt, oil, and lotion get on them. White sapphires are a great example because if they're dirty they won't sparkle.

According to Tracy Matthews, creative director of Flourish Thrive Academy, “If you notice the sparkle factor or brilliance of the 'diamond' dimming if your diamonds are dirty, that might indicate that the stone is not real.”

You can also perform a sparkle test. Put your stone under a lamp light and inspect its sparkle. Diamonds reflect white light extremely well so the sparkle should be exceptional under the lamp light.

2. Blow on it.

If you blow your breath on a diamond, it will fog up, but only for a second or two. This is known as the fog test.

“If you blow your breath on a stone that's not a diamond and the 'fog' lingers, you might have a fake stone,” Matthews warns.

3. Do a heat test.

Leave your stone in a fire for about 30 seconds. If the stone shatters, it's fake.

“Intense heat and fire might shatter glass or fake stone. If you put fire on a diamond for 30 seconds and it remains intact, it's likely a real diamond,” Matthews adds.

4. Use diamond dust.

Try cutting a piece of glass with the point of your diamond. If the glass cuts, the diamond is real.

“Diamond dust is used to cut and clean gemstones and glass and many other materials. If you have a loose diamond and a sheet of glass, you can cut glass with the diamond point,” Matthews suggests.

5. Do the water test.

Does it float? Grab a glass of water and throw that diamond in.

“Diamonds will sink to the bottom of a full glass of water,” Matthews reveals. And fake gemstones will float as well.

6. Do a UV test.

Grab a UV light and place your diamond under it. If the stone glows a blue color, it's real.

“Diamonds emit a blue-colored glow when placed under a UV light,” says Matthews. But fake diamonds or other stones will not.

7. Use a microscope.

"We look for different kinds of inclusions/flaws within the crystal structure and where they are located. If the stone was cubic zirconia or moissanite, it would most likely have no inclusions. Natural diamonds with no inclusion are very rare, so this would be an indicator it was not a real diamond," says Kaeleigh Testwuide, diamond expert and owner of The Diamond Reserve.

Matthews agrees, adding, “A real diamond will typically have small inclusions that are detectable under a loupe or microscope.”

A fake diamond might be "perfect" and have no flaws under a loop. So, yes, if it's too good to be true, it probably is.

Testwuide also advises taking note of the diamond's faceting: "Examining the diamond's faceting under magnification, if the faceting of the stone is strange it would be a sign it was not real."

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8. Take it for x-rays.

“If you really want to go ‘ninja,’ you can have the diamond x-rayed and you'll know if it's a fake!” suggests Matthews.

Not sure why you want to do this? Well, diamonds have a radiolucent molecular structure. That means they won't show up in an x-ray.

9. Do the newspaper/'read-through' test.

This test puts the diamond's refractivity on trial. Place the flat part of your diamond on a page of a newspaper that has tons of lettering. If you're able to read the letters (even if it's a bit blurry), the diamond is fake.

A diamond's refractivity is off the charts. It will bend the light every which way except straight, which is why you wouldn't be able to see clearly through the diamond if it were real. This test is best done with loose diamonds.

10. Do the dot test.

If you don't have a newspaper, this is a good alternative. Grab a white piece of paper and draw a tiny dot on it using a pen.

Place the stone with the flat side facing down on top of the dot. If you can see a reflection of the dot in the diamond looking down through the point, the diamond is fake.

11. Do the sandpaper test.

The diamond is one of the hardest materials on the planet and cannot be scratched or destroyed easily.

To test if a diamond is real or not, scratch the stone with sandpaper. If the stone is unaffected, the diamond is real. But if it gets scratched up, it's fake.

12. Check the polish.

"Moissanite or cubic zirconia will have a plastic-type feel to it," says Testwuide. So feel your stone between your fingers and if it feels like plastic it's probably fake.

13. Use high profile weighing.

"Another really great indicator is if the diamond's measurement-to-weight ratio is off; for instance, it has a measurement of 1 carat, but when put on the scale weighs in as 2 carats," Testwuide explains.

14. Use a thermal probe.

This tool is used to determine the thermal conductivity of a diamond. Diamonds will disperse heat rapidly once they have been warmed, so if the stone disperses heat slowly, it's not real.

15. Take it to a professional.

If all else fails and you want a 100% guarantee your diamond is real, it's best to see a professional who knows what they're doing.

"When trying to determine if a diamond is real, I always recommend visiting with a diamond expert, especially because lab-grown diamonds are now in the marketplace and special equipment is needed to determine if a diamond is a natural or lab-grown diamond," concludes Testwuide.

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Aly Walansky is a NY-based lifestyle writer who focuses on health, wellness, and relationships. Her work appears in dozens of digital and print publications regularly.