How To Tell If A Diamond Is Real

Gem Identification

How To Tell If A Diamond Is Real

You love that sparkler adorning your finger. But something in the back of your mind makes you wonder whether it’s genuine. Or perhaps you’re planning to buy a piece of diamond jewelry. Whether for yourself or someone else, you want a bona fide gem. Keep reading to learn how to tell if a diamond is real.

Forgetting about love and romance for a moment, consider some of the more practical aspects of diamonds. They are best known as the hardest substance on Earth. Diamonds also have numerous other properties that make them valuable for a variety of industrial uses. Only a very small percentage of diamonds are of gemstone quality and suitable for use in jewelry.


For countless reasons, diamonds are the preferred gem for most people. Their desirability and expense mean that fake diamonds abound. The fakes may be other gemstones that look enough like diamonds to trick some people. But fakes are often synthetic imitations. Synthetics are described as lab-grown or similar terms. There’s nothing inherently wrong with buying a fake if you know that you are not getting a real diamond.  

Diamond Substitutes

The most common gemstones that resemble a diamond are colorless zircon, white sapphire, and white topaz. Zircons are natural gemstones with their own appeal in jewelry. They exhibit a range of colors. Colorless zircons may be called Matura Diamonds. Although they can flash “fire” like a genuine diamond, they are softer.

White sapphires and white topaz are colorless gems that are popular diamond substitutes. While sapphires are only slightly less hard than diamonds, they don’t have comparable brilliance or fire. A white topaz is also less sparkly than a diamond and softer. It is also significantly less expensive. 

You may also find low-price diamonds. They are real, but they may be poor-quality specimens that have been treated or enhanced. Those “improvements” can be challenging to detect other than by a professional. While the improvement can create a lovely diamond, it can be unstable. It may need extra care to remain intact. Diamond sellers are required to disclose any treatments and enhancements. 

Synthetic Diamonds

Synthetic diamonds are created by humans in labs. They are not natural gems mined from the Earth, even though they may be composed of the same mineral as authentic diamonds. Most have the same properties as natural diamonds. But they are made by humans, not nature, and are not eons old.

Cubic Zirconia

Cubic zirconia (CZ) is a popular synthetic diamond. CZ is entirely different from zircon. Although CZ can imitate a diamond’s beauty, it is soft, and its loveliness quickly fades. CZ’s big draw is the very low price, as it is mass-produced and made into many types of jewelry. 


Moissanite diamonds are a synthetic that’s more difficult to distinguish than others are. Natural moissanite is a very rare mineral that isn’t used in jewelry. A moissanite diamond, however, is created in a lab from silicon carbide. Like most synthetics, moissanite is less expensive than genuine diamonds. They are nearly as hard as real diamonds and can be more brilliant. They can also have more “fire” than natural diamonds. But the color is of lesser quality, although it’s continually being improved. 


Genuine diamonds are formed from carbon deep within the earth. Very often, small amounts of trace minerals or other materials become part of the diamond. These are called inclusions. Inclusions and other minor imperfections are typically unnoticeable to the naked eye. 

The presence of inclusions and imperfections was traditionally how to tell if a diamond is real. The synthetics were flawless. That’s no longer true in many instances. The manufacturers learned to incorporate small flaws in their products. A reputable diamond seller will disclose a synthetic. Otherwise, professional testing with precision equipment is typically the only reliable way to distinguish between real and well-made fake diamonds. 

How Can You Tell If A Diamond Is Real?

Along with hardness, the properties that make a diamond what it is include density, thermal and electrical conductivity, luster, refractivity, dispersion, and weight, among others. As esoteric as these may seem, they are the basis of how to tell if a diamond is real.

If you’re not a jeweler or gemologist with lots of sophisticated testing equipment, how can you tell if a diamond is authentic? There are several at-home ways to do preliminary testing. Most are not definitive, but they’ll give you a clue as to whether you should invest in professional testing. And they can be fun to experiment with.

Can You Scratch It?

The scratch test has lost its status as a reliable test. Because diamonds are so hard, they will scratch other objects, such as glass. But nothing can mark them because nothing else is hard enough. Many of the contemporary synthetics are hard enough to make a scratch in other gemstones. Most will resist being scratched by anything other than a genuine diamond. 

Does It Float?

Without getting too much into physics, density is a measure of how close the atoms in a substance are to each other. The carbon items in a diamond are tightly packed together. Diamonds, therefore, do not float. If you have a loose diamond, gently drop it in a glass of water. If it immediately sinks, it’s probably a diamond. If it doesn’t sink, it’s not a diamond. Keep in mind that this isn’t proof because some manufacturers of fakes know how to make their synthetics equal to diamonds in density.

What Happens When You Breathe On It?

In basic terms, thermal conductivity rates how quickly heat passes through a substance. Diamonds have one of the highest possible ratings. That means they lose heat rapidly. The fog test takes advantage of that. It’s also a test that you can do even if your diamond is in a setting or mounted. Hold your gem in front of your mouth and breathe on it. Fog will appear on it. If the fog disappears within a couple of seconds, the gem may be a real diamond. If it lingers for a few seconds, you probably have a fake in your hand. A natural diamond instantly dissipates the heat of your breath.

Can You Set It On Fire?

Diamonds are formed from immense heat and pressure below the surface of the earth. When they are mined and turned into gemstones, they retain their ability to withstand heat. That ability, along with their high thermal conductivity, makes the heat test a way to tell if your diamond is real. Prepare a glass of cold water. Use tweezers, pliers, or a similar tool to hold your loose diamond over a lighter for about 30 to 40 seconds. Then, drop the hot gem in the glass of cold water. If it sinks to the bottom of the glass intact, it’s mostly likely a diamond. If it breaks or shatters, it definitely wasn’t a diamond. The fakes won’t survive the expansion and contraction of sudden temperature changes.  Obviously, with this test, make sure you don’t mind if the test gem is destroyed.

Does It Sparkle?

Luster is the reflection of light from a surface, in this case a diamond facet. Diamonds have an adamantine luster, which is the most reflective type. In gemologist terms, luster is the diamond’s sparkle. This test relies on your vision and is most reliably used by individuals who are familiar with the sparkle of a real diamond. If you aren’t, you will need a genuine diamond with which to compare your diamond. If your gem is a fake diamond, you will notice an immediate difference.  

Do You See A Dot?

Light travels in waves. The waves appear to “bend” when they pass through different substances or when viewed from different angles. This is called refraction. Diamonds are highly refractive, so a ray of light does not pass through them intact. It bounces around inside the diamond. 

Testing your diamond involves drawing a small dot on a piece of plain paper. Place the paper on a flat surface, and then lay your diamond on it with the pointed side up. Look through the diamond at the dot. If you see it reflected inside the diamond, you’re looking through a fake. If you can’t see the dot, then you probably have a genuine diamond. That’s because real diamonds keep the light from passing through them. This is also known as the newspaper test. If the words on the newspaper appear inside the diamond, it’s a fake.

Does It Emit Fire?

Refraction also causes the dispersion of light. Although light looks clear to the human eye, it consists of many colors. Dispersion occurs when the light beam is “broken” into its component colors. Due to refraction, each color bounces around separately inside the diamond. Each flashes as it exits. This is the fire that diamonds are known for. Skilled faceting can increase the fire. 

Gems other than diamonds can show fire. If you are familiar with diamonds, you may be able to discern real from fake by looking. If not, try to compare your gem with a genuine diamond. Like many tests, looking at the fire may not be conclusive, as many fakes, such as moissanite diamonds, can reflect as much fire as a real diamond. And other factors, such as ambient light, can affect how much fire a diamond exhibits.

Do You See A Rainbow?

Hold your gemstone with the pointed end up. Shine a flashlight through it. Due to the way a real diamond refracts light, you will see a rainbow of color on the surface of it. If you see white light on the surface, it isn’t a diamond. If the rainbow of light is on the inside of the gemstone, it’s synthetic. An internal rainbow is especially indicative of moissanite. 

Does It Turn Blue?

Some, but not all, diamonds will fluoresce blue under an ultraviolet or black light. Moissanite will turn other colors. Because fakes can be modified to turn blue, this is one of the less reliable tests. Some people check their diamond by holding it up in bright sunlight to see if it turns blue.

What Is It Set In?

Diamonds sold as jewelry are usually in a setting or mount of some kind. You don’t expect a real diamond to be set in cheap metal. Nor are fakes typically mounted in 24-karat gold. Look for fineness marks on the setting. That gives you a reliable clue as to how real your diamond is. If there are no marks, you know the setting isn’t anything special, and more than likely, the diamond is a fake. 

Are You Sure?

These and similar tests are helpful but not always the last word. They are all subject to error. You risk mistaking a genuine diamond for a fake or thinking a fake is real. 

Make sure also that you truly want to know if your diamond is genuine. How will you feel if you discover that a diamond from a loved one or a treasured family heirloom is fake? Think about it before testing, especially if you chose a test like heat that will destroy a non-diamond gemstone. 

Tools For Testing

If you plan to buy more than an occasional diamond or invest in diamonds, you may want to purchase tools designed for reliable testing. Those can include a jeweler’s loupe to look for inclusions. A diamond tester measures the thermal conductivity. You may need a special scale that weighs carats. Another useful tool tests the electrical conductivity of diamonds, which differs from most fakes. If results are inconclusive, you may need to send your gem to a gemologist or lab for evaluation.

As with all gemstones, purchasing your diamonds from a reputable seller is the best way to ensure you are getting what you are paying for, whether natural, man-made, or a substitute. The experts at Philophrosyne welcome your questions about all types of diamonds. They will gladly provide any information that will help you make a good choice. 

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