How to Tell if Your Diamond Is Real or Fake With 10 At-Home Tests

Buying a diamond is an emotional and important purchase, so of course, you'll want to know whether or not a diamond is real before you sign on the dotted line. But how can you tell if a diamond is real? Whether you're in the market to purchase a diamond ring or you want to inspect your own jewels, it's understandable that you'd want to know the authenticity of your engagement ring.

According to The Knot's 2023 Jewelry & Engagement Study, clear diamonds remain the most popular engagement ring style. Of 5,000 couples who got engaged in 2023, 85% went with a clear diamond center stone—now that's a lot of diamonds. And if that's you, you want your stone to stand the test of time. So if you're questioning whether or not a diamond is real, we highly recommend you seek out the advice of a reputable jeweler. However, if you're in a pinch, we have ten simple tests you can use at home to tell if a diamond is real or fake.

In this article:

• Real vs. Fake Diamond: What You Need to Know
• Mounted vs. Loose Diamonds: What's the Difference When Testing
• How to Know if a Diamond Is Real Using 10 At-Home Tests

Real vs. Fake Diamond: What You Need to Know

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Diamonds have several "fake" counterparts that can easily be mistaken for real diamonds—natural gemstones with a strong resemblance to diamonds are white sapphire, white topaz and colorless zircon. There are also gems created in a lab, like YAG (yttrium aluminum garnet), GGG (gadolinium gallium garnet), CZ (synthetic cubic zirconia) and synthetic moissanite that look like real diamonds to the average person.

For many couples, moissanite engagement rings are a sustainable and cost-effective option. According to our study data, moissanite center stones increased in popularity by 10% over the past 5 years. Of course, if you want the real deal, all of these look-alikes probably leave you wondering how to tell if a diamond is real.

Experts advise that you do your homework on the types of diamonds. "The biggest misconception is there's just one type of 'fake.' There are several diamond substitutes and stimulants on the market. Some of these substitutions have value in their own right—others are completely worthless," says Shannon Delany, director of communications for James Allen. A real diamond has some qualities that can't be faked.

Pro tip: It's also important to know if the diamond is certified within one of the three top grades – GIA, AGS, and IGI. When in doubt, you can use tools like Diamond Display Technology provided by James Allen that reviews and evaluates inclusions.

Mounted vs. Loose Diamonds: What's the Difference When Testing

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Before we dive into the home tutorials, it's important to know the difference between mounted and loose diamonds. How to tell if a diamond is real will vary, depending on whether the diamond is loose or set in a mounting.

It's easiest to test a loose stone or one that hasn't been mounted in a setting, for both authenticity and determining if there are any flaws. Often, a mounted diamond's setting can hide potential flaws, cracks or chips. Mountings also usually reflect light into the diamond, which makes it difficult for anyone but a reputable jeweler to assess the stone's clarity, color or carat. If you're purchasing a mounted diamond, you may want to ask the jeweler to remove the stone so you can have it thoroughly inspected while it's loose.

"Occasionally, we do encounter stones that are not real diamonds. What we see more often than not are actually real diamonds of poor quality or enhancement," says Judd Rottenberg, principal at Long Jewelers, a graduate gemologist at GIA and certificated gemologist at AGS. "For example, laser drilling and fracture fill are two ways to alter a stone to [make it] look better than it actually is."

Rottenberg says another big misconception is that real and fake diamonds look the same. "At first, a diamond and a cubic zirconia may look similar, but in a short period of time, a cubic zirconia stone will lose its brilliance and look damaged," Rottenberg says. "It's not as hard as a diamond and won't wear as well." So, if you're wondering how to know if a diamond is real, know that while the test of time will tell you, there are other ways to test your stone, too.

How to Know if a Diamond Is Real Using 10 At-Home Tests

Now it's time to test your diamond. We've got tests you can try on a loose or mounted diamond, however, you'll find it's likely easier to distinguish between real and fake if you have a loose diamond.

1. How to Tell if a Diamond Is Real With the Fog Test

To tell if your diamond is real, place the stone in front of your mouth and, like a mirror, fog it up with your breath. If the stone stays fogged for a few seconds, then it's probably a fake. A real diamond won't fog up easily since the condensation doesn't stick to the surface.

2. How to Tell if a Diamond Is Real With a Magnifying Glass

To determine if your diamond is real, hold a magnifying glass up and look at the diamond through the glass. Look for imperfections within the stone. If you're unable to find any, then the diamond is most likely fake. The majority of real diamonds have imperfections referred to as inclusions. There are flawless diamonds out there, but they're either lab-created diamonds or pretty pricey given the unusually high quality.

3. How to Tell if a Diamond Is Real With a Black Light Test

You'll need a black light (a.k.a. UV light) for this one, obviously. Once you have it, turn off the lights and hold the diamond in front of the black light. Most diamonds will reveal blue florescence under a black light; therefore, you'll see a medium to strong color of blue, which means the diamond is real. If you don't see the blue color and instead see a slight green, yellow or gray fluorescence then this usually indicates the gem is not a real diamond. But remember: This is not a conclusive test and not all real diamonds will reveal a blue fluorescence.

4. How to Tell if a Diamond Is Real With a Loupe

A loupe is a small magnification device that's used by jewelers to see small details up close. The difference between a loupe and a magnifying glass is simply that a loupe doesn't have an attached handle and its lens frame is slightly more conical. Most jewelers use loupes when inspecting diamonds for class and clarity. If you don't have one (weird!), Amazon has a large selection of loupes to choose from for a reasonable price.

Once you have one, look through the loupe, look for inclusions. Mined diamonds usually have tiny, natural imperfections which indicate the diamond is real. Next, check to see if there are small flecks of minerals or slight color changes. If there are signs of slight color changes and flecks, then the diamond is more than likely real. (Keep in mind that some natural diamonds are flawless. If there are no flaws or imperfections, this doesn't necessarily mean that you're dealing with a fake stone, but it does mean you're dealing with a rare perfect diamond). While most real diamonds often have imperfections, don't rely on this method as your final determination. Lab-grown diamonds normally don't have any imperfections since these gems are produced in controlled environments.

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5. How to Tell if a Diamond Is Real With a Sparkle Test

Here's a test you can perform without a loupe. Hold the gemstone under a lamp to see how it refracts white light. What makes real diamonds so beautiful is the way they sparkle and shimmer. In comparison, a fake diamond will look dull.

6. How to Tell if a Diamond Ring Is Real Based on its Setting

This is by no means a conclusive test on its own, but we suggest it as a way of quickly determining if you have a fake ring on your hands. Real diamonds are usually set in precious metal such as yellow gold, white gold or platinum. The type of gold (e.g. 10K, 14K, and 18K) or platinum (PT or Plat) is stamped into the inside of the band. If the setting doesn't have any precious metal markings, then the stone is likely fake.

7. How to Tell if a Loose Diamond Is Real With Water

This water test is easy if you have a loose diamond: Get a glass and fill it with water (it doesn't matter what type of water you use). Drop the diamond into the glass of water. Due to the high density of diamonds, when dropped into the water a real diamond will sink. If the diamond floats to the top or middle of the glass, it's fake. It's simple physics.

8. How to Tell if a Loose Diamond Is Real With a Heat Test

To conduct the heat test, use a pair of pliers to hold the loose diamond while you heat it up with a lighter. After 45 seconds, drop it into a glass of cold water. A real diamond has a high resistance to heat and is one of the strongest materials on earth and so it will remain unaffected by the extreme change in temperature. Whereas, a fake diamond made of glass or zirconium, will shatter.

9. How to Tell if a Loose Diamond Is Real With the Dot Test

A real diamond will refract light—this is what gives it sparkle and brilliance. To test your stone's reactivity, take a piece of paper and draw a small dot on it. Place the diamond over the dot and see if you can see the dot through the stone. If the diamond is real, then you won't be able to see it as the image is refracted. You can also conduct a similar test using a newspaper. Place the diamond flat-side down and if you can see the black type through the stone then it's probably fake. On the other hand, a real diamond will refract the image and so you will not see anything through the stone if it's the real thing.

10. How to Tell if a Diamond Is Real Using a Diamond Tester

If you have the time or inclination to order equipment online, you can perform a test using a thermal conductivity probe (a.k.a. diamond tester). This device will test your stone's conductivity to determine whether it's a real diamond. However, moissanite is a material that will provide the same result so you'll need to perform a second electrical conductivity test to distinguish a real diamond from moissanite.

So how can you tell if a diamond is real? Try a few of these at-home tests and see how your stone responds. They're not all foolproof, but they'll give you a good idea about whether you should be suspicious of your diamond or not. Most importantly, if you doubt that what you have is a real diamond, particularly if it did not pass one or more of the at-home tests, it never hurts to take it to a reputable jewelry store for a professional evaluation. They can give you more information about your stone and the peace of mind that your diamond will last a lifetime. (Plus, it doesn't hurt that they're actually experts in how to tell if a diamond is real.)