How to Tell if a Diamond is Real or Fake

Need to know:

This is not a guide for people buying diamonds. If that is you, all you need to do is buy a GIA or AGS diamond and check that the diamond matches the certificate that comes with it. This is a guide for people who already have diamond jewelry and want to know if it’s real. This guide will provide you with at-home tests that you can do yourself, as well as tests that an expert can do with the proper equipment.

If you aren’t a diamond expert—and most people aren’t—then you could think that a gemstone is a diamond when it is actually a cubic zirconia or a moissanite. That’s why it’s so important to know how to spot a fake.

Be careful, though. As good as these tests are, no single at-home test should be used as conclusive proof that a diamond is a fake. You should always turn to an expert for help. Only they will have the proper knowledge and equipment to prove one way or the other.

Telling if a Diamond is Fake or Not

The Water Test

You can use this simple test to see if a diamond is real.

Find a glass and fill it ¾ full of water. Carefully place the diamond in the water.

If it sinks, it’s a real diamond. If it floats, underneath the surface or on it, then you have a fake.

A diamond will sink because it is very dense.

The Fog Test

Hold the diamond or ring between your fingers and breath on it. A fog will form on the diamond. If the fog clears immediately, the diamond is real. If it takes a while to disperse, it’s probably a fake. Diamond conduct heat well, so they also disperse it quickly.

Checking the Setting and the Mount

Is your diamond in a ring? If so, check the setting and the mount. Because diamonds are expensive, real ones will only be set in high quality mounts. This is likely to be white gold, yellow gold, platinum or pave.

To find out, look inside the setting for markings. If you can see notations like 10K, 14K, or 18K, that indicates the carat gold used. PT or Plat refer to platinum. The numbers 585, 770, 900 and 950 refer to platinum as well.

If you can see a CZ anywhere, that refers to Cubic Zirconia and means it is not a real diamond.

Heat the Stone

Diamonds are one of the strongest materials on the planet. If you heat them, nothing much will happen. But a fake will shatter.

To test, source a glass of cold water. Then, using a set of pliers, heat your stone over a lighter for a minute. Then drop it immediately into the glass of water.

If it shatters, it’s a fake. If it doesn’t, it’s probably a diamond. This is because weaker materials, like glass or cubic zirconia, crack and break.

UV Test

You can also test a diamond by placing it under a UV light. A lot of diamonds will emit a bluish glow. Some don’t glow, however. If your stone does glow, it’s probably a diamond. But if it doesn’t it doesn’t mean it’s a fake. You just need to take it to an expert.

Testing a Diamonds Refractivity

When you see a diamond sparkle, it’s because of its refractivity. As light hits the bottom of the diamond, it is bounced and refracted upwards towards the top. When a diamond has good refractivity, and it sparkles, it is called brilliance. Fakes won’t refract light well, if at all.

You can use the following tests to check for refractivity.

The Newspaper Effect

Place your diamond on a newspaper in an area with lots of lettering. It should be placed flat side down. Make sure nothing is casting a shadow over the diamond and that lighting is bright.

If you can read the letters through the diamond, it is a fake. Even if the lines are a bit blurry, it’s a fake. If it is real, however, it will refract the light making it impossible to see anything clearly through it.

Obviously, the diamond has to be loose for you to use this test.

The Dot Test

You can use the dot test if you don’t have a newspaper.

Get a white piece of paper and draw a dot on it with a pen. Place the stone on the dot, flat side down. Look through the pointed end onto the paper. If you can see a dot, the diamond is fake. If you can’t, it’s real.

The science is the same as the method above. Light is refracted around a true diamond, making it impossible to see clearly through it.

Reflectivity Testing

You can also test a diamond on its reflectivity. This pertains to the amount and quality of light that is reflected off the stone. We can use the sparkle test to test this.

The Sparkle Test

You don’t need equipment for this. Just hold the diamond under a normal lamp and watch how the light is reflected. Are you seeing shimmers of light bouncing off the diamond? Are you seeing colorful reflections, too?

A true diamond is amazing at reflecting white light and also colored light. Compare a real diamond to a cubic zirconia and you will see a huge difference in the way it reflects light.

Testing a Diamond With an Expert

While the tests listed above are a good way to see yourself if your diamond is real, it is always best to speak to an expert. A professional gemologist who has a Graduate Gemologist degree will be able to tell you definitively if your diamond is real or not.

Using a Loupe

A loupe is a special magnifying glass used to inspect diamonds. A professional can use this to look for imperfections in the diamond. While a fake can be flawless, there will always be small imperfections in a diamond.

Using a Thermal Conductivity Probe

Gemologists can use a thermal conductivity probe to test the conductivity of a gemstone. As we have mentioned before, diamonds will disperse heat very quickly. Fakes won’t. It’s important to remember that moissanite stones have similar thermal properties to diamonds, so it is not an conclusive test for them.

Using Gigh Profile Weighing

A professional gemologist will have finely tuned scales that can measure small changes in weight. A real diamond will weigh less than a fake, but it will take special scales to notice the difference. You’ll need to use a known fake that’s the same size to compare it to your diamond.

Using Electrical Conductivity

Diamonds conduct electricity better than other stones, so using electrical conductivity can be another good way for a professional to determine whether a diamond is real or not. An electricity tester will make it clear whether it is real or fake.

Real Diamonds vs Moissanite

As synthetic moissanites become more common, it is important to test for genuinity. These are the tests to try.

Using a Microscope

By using a 1200x magnification on the stone, an expert will be able to see inclusions and other imperfections to tell if a diamond is real or not.

Using an X-ray

You can send a diamond to a diamond lab for testing. X-ray machines will be able to tell whether the stone has radiolucent molecular structure or radiopaque molecular structure. Diamonds are radiolucent while fakes aren’t.

Is the Scratch Test Reliable?

The scratch test used to be widely used to assess a diamonds genuinity. It involved scraping the diamond a long a mirror to see whether the mirror scratched or the diamond did. While diamonds are very strong, fakes are very strong and scratch resistant, too. That’s why this kind of test has become far less common.

Spotting other Fake Diamonds

As other gemstones grow in popularity, here’s how you can tell the real deal from the fakes.

Recognizing synthetic diamonds

You need to know how to tell the difference between real and lab-created diamonds. Lab diamonds are almost as good as the real thing. That’s why you need an expert to tell them apart. Conductivity tests and magnifying tests can tell the difference.

Recognizing cubic zirconia

This is one of the easiest fakes to spot. The sparkle test is a dead giveaway, for example. They also reflect orange tinted light, and usually don’t have imperfections.

Recognizing white sapphires

Sapphires are available in white as well as blue. White sapphires can sometimes be sold as diamonds but they don’t sparkle like the real thing. If the stone looks blurred that could also be a sign that it is a sapphire, not a diamond.

Recognizing moissanite

Synthetic moissanite is probably the hardest to spot. It’s almost impossible to tell using the naked eye. But an electricity conductivity test can tell the two apart. Be aware that thermal conductivity tests won’t work.

Recognizing white topaz

White topaz normally has a softer exterior than diamonds and it is easily scratched. If there are scratches on the surface it isn’t a diamond.

Wrapping it up

While a lot of the tests listed here that you can do at home can tell a real diamond from a fake, it is always best to visit an expert. These people are trained in spotting real diamonds from fakes and can prove conclusively which your stone is.

Of course, when you shop at a trusted retailer, like this one, you’ll know that you don’t have to worry about fake diamonds.