Is Your Diamond Real or Fake? – Your complete guide to determining authentic diamonds

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If you are an ordinary consumer shopping for a diamond, the information presented below is not for you. If you have a jewel collection and there’s that itch that won’t disappear until you know that every piece of your prized collections is real, then this guide is for you. If you have been following our advice, the diamond you purchase will come with authentic GIA or AGS certificates attached to them. All you need to do is to ensure that the diamond matches the certificate.

Every person who has been a student in our diamond education or relying on our experts to help him or her in their quest has found it easy to spot a fake or real diamond.

And if you have valuable stones and ancestral jewelry that you wish to verify, this guide will give you proven DIY diamond tests that you can accomplish at your home along with high-level tests that diamond experts and jewelers use specially designed tools.

Is a gemstone a diamond? You might come to the quick conclusion that it is, especially if you are unaware of a diamond’s innate structure and components. But just like cubic or moissanite, the diamond is a completely distinct stone. With that being said, it is crucial that you know how to detect a fake diamond from a bogus one.

This guide is a straightforward and convenient way to spot a fake diamond. While the home-tests provided will help you in your quest for authenticity, keep in mind that every test is not 100% conclusive. It is always best to rely on an expert to evaluate your diamond and its quality.


Water Test

It’s the same straightforward but effective test that helped Archimedes uncover a fraud in the manufacture of a golden crown back in the 4th century B.C.

Get hold of a regular-sized drinking glass and pour water until it reaches 3/4 level. Gently lower the loose stone inside the glass.

If it descends to the bottom, you have yourself an authentic diamond on your hands. If it hovers beneath or at the surface level of the water, tough luck because it’s definitely fake.

Different stones possess different densities. Genuine diamonds have high density and an ordinary water test will reveal whether that stone in your possession is real or not simply if it floats or sinks.

Fog Test

With a fog test, all you need to do is hold the stone or jewel with your fingers and exhale warm air to it. You will immediately notice a thin fog enveloping the stone due to your breath’s warmth and moisture.

If it’s genuine diamond, the fog will disappear instantly. If it takes a while to vanish, chances are it’s unauthentic. Diamonds are remarkable heat conductors and can diffuse heat swiftly.

Inspect Setting & Mount

When the diamond has already been crafted to a ring, inspect the kind of setting and mount that’s been used.

Since diamonds are normally expensive, an authentic one will always be crafted in premium jewelry. Normally, diamonds will be crafted with valuable materials such as white gold, platinum, yellow gold, pave or side-stone setting and halo setting rings.

To determine whether the setting is really what it says it is, examine the ring’s center for any engravings. If its gold, then there should be 10K, 14K, and 18K that illustrates the quality of gold utilized for the setting. PT and Plat engravings, meanwhile, pertain to platinum. If there are numbers like 585, 770, 900, and 950, they reveal platinum or gold as well.

If there is a “C.Z.” mark, the gemstone is a cubic zirconia, and you’ve been fooled to think that it was a diamond.

Heat the Stone and Observe What Happens

Because of strong covalent bonds between its atoms, diamonds have the highest hardness and thermal conductivity of any bulk material. This simply means that they are highly resistant to heating and temperature shocks.

To determine whether your stone is indeed a genuine diamond, find a drinking glass and pour cold water inside until its full. Using a set of plyers or crucible tongs, hold the diamond and heat it using a lighter for roughly 40 seconds, then unload it into the cold water.

If it breaks, then it’s not an authentic diamond. If nothing happens, then it’s real.

The test will reveal the distinct material of the stone. Flimsy materials like glass or cubic zirconium crumble under rapid temperature changes. Try putting a drinking glass in a hot oven and then fill it with water immediately; it should crack or break in an instant.

Since diamonds are the hardest natural substance on Earth, such a heat test won’t have any effect on them.

UV Light Test

Another good way of testing a Diamond’s authenticity is by putting it under UV light. The majority of diamonds will produce a blue colored glimmer but there are those that don’t. There are genuine diamonds that do not emit any glow under UV light.

Because the test is inconclusive, it is ideal to let a diamond expert or jeweler use their advanced equipment to evaluate the stone.


Ever wonder why diamonds sparkle beautifully? This is because of the stone’s unique ability to bend and refract light. Every time light touches the pavilions (the angled surfaces on the lower half of the diamond), the rays are reflected and refracted up through the stone’s table (the top, flat surface) towards the human eye. The result is a distinct radiant sparkle that is called brilliance.

Because other stones like Cubic Zirconia do not carry the same refracting quality, they won’t shine as bright as diamonds.

To determine whether or not your stone has the same unique light bending capability, here are some of the tests that you can do.

Newspaper/‘Read-Through’ Effect

Carefully lay the stone on top of a newspaper page with plenty of printed letters. Make sure there is significant lighting, and no obstructions are casting a shadow on the stone.

If you can read the letters – even if they are little obscured – the stone is not a diamond. Genuine diamonds will bounce the light away, which means it would be impossible for you to see through the letters.

You can test the optimum effectivitness of such test when it comes to loose diamonds. If the diamond is already crafted on a ring, a fog test or a thorough evaluation from a diamond expert is the ideal route.

The Dot Test

If you can’t find a newspaper at home, a dot test should do just as well.

Put a clean white paper on a table or any flat surface and make a small dot using a pen. Rest the stone on top of the dot and through the pointed end of the diamond; focus your gaze on the paper. If there is a circular reflection or a figure that resembles the dot, the stone is not a diamond. If you can’t see through the stone, then it is a genuine diamond.


Aside from testing stones refractive qualities, you can also look into its innate reflectivity. If refractivity applies to the directions that light is dispersed from the stone, reflectivity pertains to the extent and quality of light that is reflected.

The reflective quality of the stone covers both its brilliance (white shine) and fire (colored light) that radiates from a diamond’s table.

To determine reflective quality, the sparkle test is a great home reflectivity test.

Sparkle Test

The only thing you need to conduct a sparkle test is your eye. Hold the stone in scrutiny under a normal lamp and look for lights reflecting off it. Do you notice sparkling white lights bouncing or colorful rays reflecting?

Genuine diamonds reflect white light exceptionally well, giving them that distinct sparkle that you won’t find with other stones like Cubic Zirconia. They also reflect colored light, or fire, in a uniquely beautiful and captivating fashion.


In the end, the best route in verifying a diamond’s authenticity rests in the hands of a professional diamond expert. A professional gemologist who holds a Graduate Gemologist (GG) degree has all the knowledge and expertise needed to determine whether a diamond is genuine or fake.

Relying on a diamond professional guarantees that much needed peace of mind knowing that the expert has a number of proven techniques and equipment used in confirming a diamond’s authenticity.

Inspecting a Diamond with a Loupe

Professional diamond experts use an instrument called a loupe, which is a kind of magnifying glass intended purely for inspecting diamonds, gemstones, and jewelry. Because diamonds are formed deep within the earth, under extreme heat and pressure; virtually all diamond stones carry “birthmarks”; small imperfections inside the stone called inclusions or on its surface called blemishes. Through the loupe, an expert can spot these marks to determine a diamond’s authenticity.

The Thermal Conductivity Probe (aka “The Diamond Tester”)

Aside from the loupe, gemologists also use a special tool called thermal conductivity probe, which identifies a gemstone’s natural thermal conductivity. Since diamonds are excellent in conducting heat, it can quickly cool down after heated. If takes a while for the stone to cool, then it’s not a diamond. However, it’s important to note that certain synthetic stones such as moissanite share the same heat dispersement capability as diamonds making Thermal Conductivity probe inconclusive with such stones.

High Profile Weighing Test

Jewelers and gemologists are typically adept at recognizing minor weight variations in gemstones. Genuine diamonds are lighter than fake stones such as Cubic Zirconia although it would be impossible to detect such minute details if you are not a professional and do not possess special scales used for weighing Carats.

Electricity Conductivity Test

Jewelers and gemologists also spot fake diamonds through what is known as an electrical conductivity test. Diamonds are superior electric conductors making them easy to recognize from synthetic copies like moissanite and cubic zirconia through an electricity conductivity tester.


As synthetic moissanite continues to flood the precious stones market, relying on specialized tools from jewelers that will help flush out the fake ones from the real has become even more crucial. With these tools at your disposal, you will know instantly whether a stone is a genuine diamond or not.

Microscope Examination

Through a microscope’s powerful magnification, a jeweler or gemologist can detect minute details that are virtually invisible to the naked eye. At 1200X magnification, small inclusions and variations are clear as day helping the diamond experts determine authenticity.

X-ray Examination

If you want an even thorough examination of your diamond, you can use X-ray technology to reveal its molecular structure. This means sending your stone to a diamond lab for X-ray testing. The X-ray machine will penetrate deep into the diamond and reveal whether it has a radiolucent molecular structure or a radiopaque molecular structure. Diamonds are radiolucent while fakes like cubic zirconium and crystals have more radiopaque features.

Can you still rely on a simple scratch test?

In the past, the scratch test was a popular means of determining the rigidity of a gemstone. It normally involved scraping the loose stone on a mirror’s surface and since diamonds are the strongest natural substance known to man, they would easily slice through the mirror without incurring any cuts or scratches.

While diamonds are naturally strong, fakes and synthetic copies like cubic zirconia and moissanite maintain deceptive durability and scratch resistance features. With that being said, the scratch test is no longer a reliable means to determine a diamond’s authenticity. More precise and conclusive tests like thermal conductivity tests or having your stone inspected by a professional through a loupe would serve you best.


As gemstones continue to enjoy growing popularity among consumers, differentiating the fake ones from a real diamond through the naked eye is all the more crucial. Here are some steps that you can do to accomplish it.

Recognizing Synthetic Diamonds

Synthetic diamonds are increasingly common in the market today, which is why it’s important that you know how to tell if it’s a diamond created synthetically in a lab or naturally underneath the earth’s surface for billions of years.

Lab-grown diamonds are extremely hard to spot because they possess similar chemical and molecular elements to their natural counterparts. With that being said, it would be best to have your diamond examined by an expert. They can perform conductivity tests and thorough scrutiny through high magnification.

Recognizing Cubic Zirconia

Fortunately, spotting a cubic Zirconia is not that complex compared to a synthetic diamond. A simple sparkle test will tell you immediately that it doesn’t have that special brilliance and shine that comes with a real diamond.

Cubic Zirconia also reflects orange tinted light making them easy to spot with the naked eye. They are also heavier than diamond and do not carry imperfections or inclusions that are unique to real diamonds.

Recognizing White Sapphire

Sapphires normally come in blue and an extensive array of colors including clear white. White sapphires are often misleading but can be easy to spot because they do not have that signature sparkle and dark and light contrasts that real diamonds have.

Recognizing Moissanite

When it comes to the undisputed fake king in the world of diamonds, the title rests with synthetic moissanite. Differentiating a genuine diamond from a synthetic moissanite is an impossible task for the naked eye alone and will require the expertise of a diamond professional.

Thermal conductivity test also won’t work since both moissanite and diamond possess similar conductivity. An electric conductivity, however, will reveal if the stone is moissanite or a true diamond.

Recognizing White Topaz

At first glance, a white topaz can easily resemble a diamond but there a number of distinct traits that make it different from a true diamond.

A simple scratch test will immediately tell you that it does not possess the same superior strength that comes with diamonds. White topaz also normally exhibits scratches and damages in its surface, which can easily be spotted through magnification. Diamonds are flawless because of their rigid composition.


A good number of the tests mentioned in this guide, like the fog test and the thermal conductivity test, will help you verify your diamond’s authenticity.

However, considering the variety of synthetic gemstones and the intricacies in spotting them, we recommend the professional guidance of a diamond expert or jeweler to evaluate the precious stones that you have in your home. These experts know exactly how to spot a fake diamond.

If you’re relying on our diamond education or diamond experts to buy a diamond, you will find it easy to get the real one. Any diamond you purchase will always have a legitimate GIA or AGS certificate attached to it and all you need to do is ensure the diamond matches the certificate.

If any questions and queries come to mind, feel free to check out our questions page where we answer common inquiries with the best of our knowledge and abilities.

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Kevin Lee is a former tech advisor who cut his teeth in Silicon Valley. He now spends his time sharing his passion for investing in diamonds and jewelry. You can reach Kevin for any comments by using this form.