How To Tell If A Diamond Is Real

Buying a diamond is a big decision, and usually requires a lot of time and consideration to find the perfect one for you. A big part of this journey is often dedicated to becoming familiar with a diamond’s structure and characteristics. Not only does that help you weigh what features are most important to you, but it shows you how to tell if a diamond is real. It’s safe to say this is critical information to have, so let’s review exactly how to tell if a diamond is real.

How To Tell If A Diamond Is Real At Home

With just a few household items, you can test your diamonds at home to determine their authenticity. However, any of these tests should be done with the greatest care for the diamond. And it’s important to note that while these tests can give you useful and practical information, only a diamond expert using specialized equipment can provide definitive answers about a diamond being real or fake.

Water Test

If you have a loose diamond to test, fill a regular glass about ¾ of the way full with water. Gently drop the diamond into the glass. If the diamond sinks to the bottom, it’s real. If it floats at the surface or just underneath, it’s likely a fake. This has to do with a diamond’s high density. For this test, you must use a loose diamond. Anything that is set in metal won’t be an accurate assessment since the metal will cause it to sink.

Look For Metal Markings

If the diamond is set in a ring, look at the type of setting and mount, and inspect the metal for markings that indicate the type of gold or platinum used. A real diamond is going to be set in high quality metals for its protection and durability. To find the markings, look on the inside of the ring – the part that would sit against your finger. Seeing markings like 10K, 14K and 18K are indicators of the gold used. PT and Plat refer to platinum, and numbers such as 585, 770, 900, and 950 could refer to gold or platinum.

Fog Test

To perform this test, you’ll start by holding the diamond between two fingers and then breathe on it with a puff of air. A light fog will appear on the diamond because of the heat and moisture from your breath. Diamonds conduct heat, so if the stone is real, the fog will dissipate immediately. If it takes several seconds for the fog to dissipate, the diamond is likely fake.

UV Light Test

Placing a diamond under UV light and watching the reaction can sometimes be a good indicator of whether a diamond is real or not. Most diamonds emit a blue-colored glow under UV light, but not all of them. So if your diamond does, you can feel pretty confident that it is a real diamond. However, if your diamond doesn’t, that won’t necessarily mean it’s not a diamond, and you should still get it professionally assessed.

looking at a diamond through a specialized tool

The Dot Test Using Refractivity

When diamonds sparkle, they are exhibiting their ability to bend and refract light. As light strikes the pavilions (the angled surfaces on the lower part of the diamond) it bounces and is refracted through the diamond’s table (the top, flat surface) back to the naked eye. When a diamond does this well and has a radiant sparkle, this is referred to as brilliance. Simulated diamonds do not refract light well.

To test this, place a piece of white paper on a table and draw a small dot on it with a pen. Lay the stone onto the dot with the flat surface facing down. Looking through the pointed end of the diamond, see if you can notice the dot or a reflection of the dot. In real diamonds, the light will bounce in many different directions and not a straight line, so you wouldn’t be able to see the dot through a real diamond.

Sparkle Test Using Reflectivity

The reflectivity of a diamond refers to the amount and quality of the light reflecting off of the stone. This encompasses both the brilliance (white light sparkle) and fire (colored light) that shines off of a diamond’s table. When holding the diamond in question under a normal lamp, watch how light reflects off the stone. Do you see both bright white shimmers and colorful pops of light? With a real diamond, there should be exceptional brilliance and fire when compared with the relatively dull reflectivity of fake diamonds like a Cubic Zirconia.

Synthetic Diamonds and Diamond Simulants  

There are very strict guidelines around language when it comes to diamonds that will also help you determine if something is a real diamond. Diamonds are in essence a crystallized form of pure, or nearly pure, carbon. They have unique chemical and optical properties and a specific refractive index that no other material can replicate. When they are sold, mined diamonds need only be called ‘diamonds’ while lab-grown diamonds need to be identified as such. But these are the only two substances allowed to be referred to as real diamonds.

Anything other than these real diamonds are labeled as simulated diamonds. They may be used to mimic the appearance of a diamond, but they are chemically and optically different. Some common diamond simulants are moissanite, white sapphire, cubic zirconia, and white topaz.

It’s also important to make a special note about not confusing synthetic with simulated. A synthetic gemstone has the exact same chemical and optical properties as one found in nature. Lab-grown diamonds are the synthetic version of naturally mined diamonds. Simulated gemstones can be made of anything and are not the same as the stone they are meant to imitate. Before buying, be very clear about this language and if you’re ever in doubt, ask for more details or consult a professional.

moissanite and diamond ring

Moissanite ring and diamond ring

oval lab grown diamond ring

Oval lab grown diamond ring

How to Recognize Synthetics and Simulants

With the rise in popularity of lab-grown diamonds and moissanite as substitutions for mined diamonds, it’s helpful to understand how to tell the difference between all of these stones and how they match up with a mined diamond’s features.

Lab-Grown Diamonds

While lab-grown diamonds are real diamonds, it’s relevant to be able to tell the difference between lab-grown and mined diamonds because there is a large price discrepancy between the two (lab diamonds can be approximately 30% less). They share all the same chemical and molecular properties, so because of these qualities, it’s really only possible to tell with the aid of a diamond expert. They will run a conductivity test and view the diamond under high magnification.


Moissanite is also a synthetic material as all moissanite we have is lab-grown versions of a highly rare substance found in meteorite fragments over 100 years ago. It is very difficult for the naked eye to discern differences between real diamonds and moissanite, so this is another one that would require a professional. A professional would be able to tell that due to the fact that moissanite has a higher refractive index, moissanite tend to exhibit a different kind of brilliance than a lab-grown diamond. It’s typically of a greater intensity and in fiery, rainbow-colored flashes. This effect is particularly noticeable in sunlight and in larger stones. An electricity conductivity test is the likeliest test to provide a definitive answer.

Cubic Zirconia

A Cubic Zirconia is relatively easy to spot through a few of the tests we’ve mentioned. By using the sparkle test, it is very apparent the amount of sparkle and fire a Cubic Zirconia is not giving off. Additionally, they reflect orange tinted light, weigh more than a diamond, and generally lack the imperfections that all diamonds have, like inclusions and blemishes.

White Sapphire

White sapphires don’t exhibit the same level of sparkle as a diamond, nor the contrast of light and dark areas. They are often described as appearing milky, cloudy, or more blurred in coloring, indicating that it’s lacking the distinct light and dark parts of real diamonds.

White Topaz

Several characteristics differentiate white topaz from real diamonds, the most apparent being the softness of white topaz. Diamond is the hardest substance on earth and cannot be scratched by other minerals. Topaz is significantly softer and can easily be scratched by other materials. Any scratches on the stone mean that it is white topaz and not real diamond.

While there are many tests you can perform on your own to help determine if your diamond is real or not, you will always get the most definitive answers from consulting a trained expert. They will use equipment like a jeweler’s loupe to view the stone under magnification, test for thermal or electrical conductivity, view the stone under a microscope, or even perform x-rays for conclusive answers. But if you’re starting at home, just remember to be careful with your stone, especially if there’s a high likelihood that it is a real diamond!

Moissanite vs. Diamond

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