How to Tell if a Diamond is Real or a Fake

Are you wondering how to tell if a diamond is real or fake? In the past, many people would try a “scratch test” to determine whether a loose diamond was real or fake. Authentic diamonds are known for their hardness, so you would scrape a mirror with the stone. The idea was to see if a scratch appeared on the mirror or on the gemstone.

The problem is that common fake diamonds or lab-created diamonds like moissanite or cubic zirconia are also extremely scratch-resistant. Therefore, the scratch test that was used for so long is no longer valid. If you want to know how to tell if a diamond is real or a fake, you could have a gemologist or a professional jeweler examine your stone with a loupe. Or, you could test it yourself using the following methods:

Simple Tests to Verify the Authenticity of a Natural Diamond (including home tests)

The Water Test For Your Engagement Ring

This test must be done on a loose stone only. Pour water into an average sized glass of water so that it’s ¾ full. Drop your stone gently into the glass. If this is an authentic diamond, it will sink. But, if it floats around in the water or comes up to the surface, your stone is a fake. A real diamond is extremely dense, that’s why it sinks.

The Fog or Breath Test

For this test, you should hold the ring or loose stone between your thumb and forefinger. Inhale and then exhale on the stone with a quick puff of air. This will cause a foggy film to appear from your warm breath.

If the fog immediately dissipates, you have a real diamond. If you’re waiting several seconds, you probably have a fake. Diamonds are good heat conductors so they quickly disperse heat.

The Heat Test

If you don’t mind-shattering the stone, you can heat it up and see if it breaks apart. Diamonds are comprised of extremely strong material and are unaffected by high heat.

Start this test by filling a glass with cold water. Wear fireproof gloves or use plyers to hold the loose stone. Take a cigarette lighter and heat the stone up for 40 seconds before dropping it into the water. If it breaks up into pieces, it’s not a real diamond. An authentic diamond will not be affected.

The Ultra Violet (UV) Light Test

This test is not considered definitive. Take a UV light and place your stone directly under it to see if there is any reaction. Most real diamonds will give off a bluish colored glow, but this won’t occur with every diamond. Therefore, the results won’t tell you with certainty whether a diamond is fake or not.

Testing the Refractivity or Reflectivity of a Stone

The Newspaper Letter Test

Fake diamonds, like the well-known cubic zirconia, do not refract light to the extent that a real diamond will. In fact, they hardly sparkle at all.

To determine the stone’s refractivity, lay out a newspaper with a lot of lettering flat on a table in an area that is brightly lit. Place the stone flat side down on the newspaper. Make sure there is nothing casting a shadow over the diamond.

Here’s how to tell if a diamond is fake with this test: If you can see the letters well enough to read them through the diamond it’s a fake, even if they are slightly blurry.

With an authentic diamond, the facets would be refracting the light in all directions. This would prevent you from clearly making out the letters through the diamond.

The Dot Test – How to tell if a diamond is real or fake

You can also try the dot test. Use a clean piece of white paper placed on a flat table. Using a pen, make a tiny dot. Place your diamond flat side down directly on top of the dot. The pointed end will now face up. Stand over the diamond and peer directly down to the paper.

If inside the stone, you can see a round reflection it’s a fake diamond. If you see no dot or any reflection at all inside the stone, you’ve got a real diamond.

Test the Reflectivity with the Sparkle Test

The reflectivity of a diamond is a combination of its brilliance or sparkle and the amount of fire or colored light shines from its table. Hold your diamond under a lamp. Is bright white light shimmering off the diamond? Are there some colorful fiery reflections of light coming from the stone as well?

Here’s how to tell if a diamond is real with this test: An authentic diamond is known for reflecting white light exceedingly well, which is what makes it sparkle. Real diamonds are also great at reflecting colored light, which is its fire. A fake diamond will not reflect much light, if any.

Use a Loupe to Inspect Your Diamond

A loupe is a tiny magnifying glass that jewelers routinely use to examine diamonds and other gemstones. The loupe allows the jeweler to look for inclusions and flaws within the stone.

Here’s how to tell if a diamond is fake using a loupe: A fake diamond will often look perfect. If the jeweler sees no imperfections at all, it’s a fake. A real diamond is going to have some small inclusions and/or blemishes, due to nature.

Use “The Diamond Tester”

The technical name for this device is “thermal conductivity meter or probe.” Jewelers usually have these on hand so they can measure the gemstone’s thermal conductivity. Since diamonds effectively conduct heat, they quickly disperse it after they’ve been warmed up.

Here’s how to tell if a diamond is fake using a thermal conductivity meter: If the stone disperses heat slowly, it’s a fake. But, this test is not conclusive because synthetic moissanites disperse heat at the same or similar rates as authentic diamonds.

It doesn’t take any special skill to use a diamond tester, so you can buy one to use yourself if you wish. Amazon has some nice examples, as you can see in the photo above.

Weigh the Diamond

You can take your stone to a gemologist or local jeweler to be weighed. They will use a finely tuned specialized scale to measure the carat weight. Authentic diamonds the same size and shape of a cubic zirconia will weigh less.

Here’s how to tell if a diamond is real by using its carat weight: The jeweler will use a fake diamond of the same size and shape as your diamond and compare its carat weight with yours. If your diamond weighs less, it’s real.

Use Electricity

A gemologist or jeweler can determine whether a diamond is fake by performing an electricity conductivity test. Diamonds are excellent electricity conductors compared to other stones. When a jeweler measures the diamond’s conductivity he/she will know immediately whether the stone is real or not. Real diamonds show conductivity. Fake diamonds like cubic zirconia or synthetic moissanite have no conductivity.

Use a Power Microscope

Using a power microscope with a 1200x magnifier, a jeweler or gemologist can examine stones very carefully. With this degree of magnification, inclusions and tiny blemishes can easily be spotted. Laboratory created fake diamonds have no flaws.

How to Tell if a Diamond is Real or Fake

With synthetic diamonds becoming so common, you need to spot the difference between a fake diamond and a real one. Labs have done a great job creating synthetic diamonds because they use molecular and chemical components that are very much like those of authentic diamonds.

Because diamonds have very intricate internal features, you may need an expert to examine the stone. They will look at it under a powerful magnifier and do a conductivity test. For insurance as well as resale purposes it is important to know whether you have a synthetic or real diamond.

How to Determine if You Have a Cubic Zirconia

Testing a cubic zirconia for authenticity is relatively easy. The sparkle test works because you can see how much sparkle and fire the stone displays or not. Also, cubic zirconias reflect a hint of orange light. They also won’t have any inclusions and they’ll weigh more. Authentic diamonds do have inclusions.

How to Spot a White Sapphire

Sapphires are usually blue, but they do come in other colors as well, including white. White sapphires are clear, which makes them look somewhat like diamonds. However, they do not sparkle or have the contrasting light and dark features of real diamonds. If the stone looks a little blurry rather than having distinct areas of light and dark, you probably have a white sapphire.

How to Tell If Your Stone is a Moissanite

Synthetic moissanite is the one fake diamond that is most difficult to spot. Seeing the difference between this fake diamond and the real thing is almost impossible unless you are a diamond expert. By performing an electrical conductivity test a jeweler or gemologist can easily tell if the stone is a moissanite or an authentic diamond. A thermal conductivity test won’t work because the moissanite and diamond are very similar in this regard.

The Bottomline

Now you know more about real vs fake diamonds. If you are looking to get a 100% certified diamond with an original diamond certificate from GIA I would recommend you check out reputable online vendors such as James Allen. I do not recommend purchasing diamonds online from lesser-known vendors as they often cheat on their certificates.