How To Tell if a Diamond Is Real (Guide by Expert Jewellers)
There’s nothing quite like the brilliance of a diamond—it sparkles, it mesmerizes, it turns heads. But what if that dazzling stone isn’t the real thing? With loose diamonds, mounted diamonds, and high-end jewelry flooding the market, it’s easier than ever to second-guess whether that engagement ring or heirloom piece is authentic. And here’s the kicker—diamond fraud is a billion-dollar industry, tricking even seasoned buyers into purchasing misrepresented stones.
In today’s booming diamond market—valued at approximately $97.57 billion in 2024 and projected to reach $138.66 billion by 2032—fakes are everywhere. From sophisticated lab-grown lookalikes to counterfeit certifications, the risks of buying a misrepresented diamond ring are higher than ever. Reports from the industry reveal a rise in cases where lab-grown diamonds were submitted as natural, and fake inscriptions were used to pass off lesser-quality stones. Even reputable jewelry stores can unknowingly carry stones that aren't what they seem.
The good news? You don’t need a gemologist’s loupe to tell if a diamond is real. While professional grading is always the safest bet, there are plenty of at-home tests to help you determine if your diamond ring—or any stone you’re eyeing—is the real deal. Let’s break them down so you can shop smart and sparkle with confidence.
Color Test
The color test helps tell if a diamond is real by examining how it reflects white light (brilliance) and colored light (fire). Real diamonds have a balanced sparkle, while fake diamonds like moissanite or cubic zirconia often appear unnaturally vibrant.
How to Perform:
Place the diamond (loose, in a ring, or mounted) under direct light (sunlight or LED).
Tilt the stone at different angles and observe the reflections.
Results:
Excessive rainbow flashes = Likely a fake diamond (moissanite or cubic zirconia).
Balanced white and subtle rainbow light = Likely a real diamond (natural or lab-grown).
Why It Works:
Real diamonds have a high refractive index, primarily reflecting white light with controlled fire. Diamond simulants scatter too much light, creating an exaggerated "disco-ball" effect.
Dot and Text Tests
The dot and text tests help tell if a diamond is real by analyzing how it bends and distorts light. Real diamonds have a unique crystal structure that prevents clear visibility through them, unlike fake diamonds such as moissanite, glass, or cubic zirconia.
How to Perform the Dot Test:
Draw a small dot on a white paper placed on a flat surface.
Position the loose diamond, diamond ring, or mounted diamond over the dot.
Look straight through the stone and observe.
Results:
If you can’t see the dot, your diamond is likely real. Natural diamonds and lab-grown diamonds bend white light in different directions, preventing clear visibility.
If the dot is visible, the stone may be glass, moissanite, or another fake diamond. These materials allow light to reflect in a more direct way.
Why It Works:
Real diamonds have a high refractive index, causing light to bend and scatter rather than pass straight through. Fake diamonds lack this effect, making objects beneath them more visible.
Book Test
If you want to tell if a diamond is real, grab a book and a little light. The book test checks a diamond’s light refraction, helping you spot a real diamond versus a fake diamond like glass, moissanite, or cubic zirconia.
How to Perform:
Open a book and lay it on a flat surface.
Place your loose diamond, diamond ring, or mounted diamond over the text.
Look through the stone and observe the text.
Results:
If the text is readable, it’s likely a fake. Moissanite, white sapphire, and other synthetic gemstones allow light to pass through more directly.
If the text appears distorted or unreadable, your diamond is likely real. Natural diamonds and lab-grown diamonds scatter white light, making the text disappear.
Why It Works:
Real diamonds have a high refractive index, bending light in different directions and preventing clear visibility. Fake diamonds like cubic zirconia or glass allow text to remain visible due to their lower refraction.
Light Tests
A quick way to tell if a diamond is real is by observing how it interacts with light. Real diamonds reflect white light (brilliance) and subtle rainbow flashes (fire), while fake diamonds often appear overly colorful or dull.
Lamp Light Test
Real diamonds sparkle mostly with white light and subtle rainbow flashes.
If the stone produces excessive rainbow reflections, it may be moissanite or a simulant.
Flashlight Test
Real diamonds reflect bright white light with minimal color.
If the stone creates intense rainbow patterns, it’s likely fake.
Sunlight Test
Real diamonds sparkle brilliantly from all angles.
If the stone looks dull, it may be cubic zirconia or glass.
UV Light and Black Light Tests
Many real diamonds glow blue under UV light, though some don’t fluoresce.
A bright green or yellow glow suggests a synthetic or fake diamond.
Why This Works
Real diamonds bend and disperse light in a balanced way, while fakes like moissanite or cubic zirconia either overdo it or lack proper sparkle.
Lighter Test
The lighter test helps tell if a diamond is real by exposing it to extreme temperatures. Real diamonds have high thermal conductivity, allowing them to withstand sudden heat changes, while fake diamonds like glass, quartz, or cubic zirconia may crack under heat stress.
How to Perform:
Hold the diamond (loose, in a ring, or mounted) with tweezers.
Heat it with an open flame for 30 to 45 seconds.
Drop it into cold water and observe.
Results:
If unaffected, the diamond is likely real. Natural and lab-grown diamonds endure rapid temperature shifts.
If it cracks or shatters, it’s likely fake. Glass, quartz, and cubic zirconia cannot handle thermal shock.
Why It Works
Real diamonds have high resistance to heat and do not expand under extreme temperatures. Fake stones lack this durability, making them prone to cracking.
For best accuracy, combine with the fog test, scratch tests, or a diamond tester.
Markings Test
The markings test is an easy way to tell if a diamond is real by checking the metal setting. Real diamonds are typically set in high-quality metals, while fake diamonds like cubic zirconia are often placed in cheaper settings.
How to Perform:
Examine the inside of the ring band or the setting under good lighting.
Look for stamps or engraved markings indicating metal type.
Results:
"18K," "PT," or "Platinum" = Likely a real diamond. Precious metals are used for natural diamonds and lab-grown diamonds.
"CZ" = Likely cubic zirconia. This stamp indicates a diamond simulant.
Why It Works
Most diamonds, especially in engagement rings and fine jewelry store pieces, are set in gold (14K/18K) or platinum. Fake diamonds are usually placed in silver-plated or low-cost alloy settings.
Mirror Test
The mirror test helps tell if a diamond is real by analyzing how it reflects white light. Real diamonds have exceptional brilliance, meaning they sparkle intensely without creating a strong mirrored image. Fake diamonds, like white topaz or cubic zirconia, may appear overly reflective or too dull.
How to Perform:
Hold the diamond ring, loose diamond, or mounted diamond in front of a mirror.
Observe how the stone interacts with the light reflecting in the mirror.
Results:
Bright white light reflection without a clear mirrored image = Likely a real diamond. Natural and lab-grown diamonds scatter light, preventing strong reflections.
Too dull or an exaggerated mirrored reflection = Likely a fake diamond. Cubic zirconia, glass, and white topaz reflect light differently.
Why It Works
Real diamonds have a high refractive index, which disperses light in multiple directions, preventing clear reflections. Fake diamonds may either over-reflect or fail to sparkle properly.
Scratch Tests
Since diamonds rank 10 on the Mohs scale, they can scratch almost any material. These tests help tell if a diamond is real by checking its durability, but some diamond simulants like moissanite are also hard, so additional tests are recommended.
Sandpaper Test
Use 240-grit or higher sandpaper.
Gently rub it against the diamond.
Results:
No scratches = Likely a real diamond.
Scratches appear = Likely a fake diamond (cubic zirconia or glass).
Mohs Scale Test
Find a lower Mohs-rated material like glass (5.5) or quartz (7).
Scratch the material with the diamond.
Results:
Leaves a scratch = Likely a real diamond.
No scratch = Likely fake.
Mirror Scratch Test
Scratch a mirror or glass with the diamond.
Results:
If it scratches, it may be real, but moissanite can also pass this test.
White Topaz Test
Scratch white topaz (a softer material) with the diamond.
Results:
If it scratches white topaz, it's likely a real diamond.
If not, it's probably a simulant.
Why These Tests Work
Diamonds are the hardest natural material, resisting scratches better than glass, cubic zirconia, or white topaz. However, moissanite is also highly scratch-resistant, so combining these tests with the fog test, light tests, or a diamond tester is recommended.
Sparkle Test
The sparkle test helps tell if a diamond is real by analyzing its sparkle. Real diamonds balance brilliance (white light reflection) and fire (subtle rainbow flashes), while fake diamonds like moissanite or cubic zirconia often appear too dull or overly vibrant.
How to Perform:
Hold the diamond ring, loose diamond, or mounted diamond under a bright light source (lamp, LED, or sunlight).
Rotate the stone and observe how it reflects light.
Results:
Bright but balanced sparkle = Likely a real diamond. Natural and lab-grown diamonds reflect white light dominantly with subtle fire.
Dull shine = Likely a fake. Glass, white topaz, and some synthetic gemstones lack intense brilliance.
Exaggerated rainbow effect = Possibly moissanite or cubic zirconia. Moissanite disperses too much light, creating a "disco-ball" effect.
Why It Works
Real diamonds have a high refractive index, allowing them to reflect white light effectively while keeping fire subtle. Fake diamonds either lack sparkle or overdo it, making this test a simple way to differentiate between a real diamond and a fake one.
Testing Device: Diamond Tester
A diamond tester is one of the most reliable ways to tell if a diamond is real at home. It measures thermal conductivity, helping distinguish a real diamond from a fake diamond like cubic zirconia, moissanite, or glass.
How to Use a Diamond Tester:
Turn on the tester and let it warm up.
Place the tester’s tip against the stone’s surface.
Observe the reading or sound alert.
Results:
High thermal conductivity = Likely a real diamond. Natural and lab-grown diamonds disperse heat quickly.
Low thermal conductivity = Likely a fake. Cubic zirconia, glass, and some synthetic gemstones retain heat.
Moissanite reading = Use a moissanite-specific tester, as moissanite also has high thermal conductivity.
Why It Works
Diamonds dissipate heat instantly, unlike most diamond simulants. A diamond tester provides fast, accurate results, making it one of the best at-home tests.
For extra confirmation, combine this test with the fog test, scratch tests, or a professional evaluation.
Water Test
Water-based at-home tests help tell if a diamond is real by analyzing moisture interaction and density. Real diamonds have high density and repel water, while fake diamonds behave differently when exposed to water.
Fog Test
Hold the diamond between your fingers.
Breathe onto the stone to create condensation.
Results:
Fog dissipates quickly = Likely a real diamond. Natural and lab-grown diamonds disperse heat instantly.
Fog lingers for a few seconds = Likely a fake diamond. Cubic zirconia, glass, and other simulants hold moisture longer.
Droplets Test
Place a small water droplet on the diamond’s surface.
Observe the droplet’s shape.
Results:
Droplet stays round = Likely a real diamond. True diamonds repel water due to their surface properties.
Droplet spreads out = Likely fake. Glass and synthetic gemstones absorb moisture differently.
Sink Test
Fill a glass with cold water.
Gently drop the diamond into the glass.
Results:
Diamond Sinks immediately = Likely a real diamond. Diamonds have a higher density than water.
Floats or sinks slowly = Likely fake. Cubic zirconia, moissanite, and glass have lower densities.
Why These Tests Work
Real diamonds have high thermal conductivity, hydrophobic properties, and density, making them react differently to water than fake diamonds.
Ultimate Test: Get a Professional Evaluation
No single at-home test is 100% conclusive.
For absolute certainty, have your stone examined by a diamond expert.
Look for a diamond certificate from GIA, IGI, or another reputable gemological institute.
Final Thoughts
From the color test to water tests, these DIY methods can help you figure out if your stone is a true diamond or a clever fake. But not all diamonds are created equal, and even experts sometimes need professional tools to confirm authenticity. Distinguishing between real and fake diamonds — whether mined diamonds or lab-grown diamonds — requires careful testing and expertise.
For expert evaluations and stunning natural diamonds, lab-grown diamonds, and fine jewelry, visit us at Arte Oro — where craftsmanship meets authenticity.
Because when it comes to diamonds, only the real thing will do.