Don’t Be Fooled: How to Check If Your Diamond Is Real or Fake

Jul 08 2025

Diamonds are one of the most precious and sought-after gemstones in the world. But with so many imitations and synthetic stones on the market, it’s easy to be fooled. Whether you’re buying an engagement ring, inheriting a family heirloom, or simply curious, knowing how to check if your diamond is real or fake is crucial. At Caratus Jewels, we want you to feel confident about your diamond. This guide explains easy and effective ways to test your stone right at home.

Key Takeaways

There are several simple ways to test a diamond at home.
None of these tests guarantees 100% accuracy — a professional evaluation is always recommended.
Knowing these techniques helps you make informed decisions when buying or inspecting jewelry.

1. The Fog Test or Breath Test

The fog test is an easy and quick test to verify your diamond's authenticity. Because diamonds are excellent heat and moisture conductor, they will not hold fog on their surface when you breathe on them for long.

Steps to do the fog test:

Clean the diamond to remove oils or dirt
Hold the stone close to your lips and breathe onto it as though you were fogging a mirror
Observe how fast the fogging clears off the surface.
If it clears instantly, there is a high likelihood that it is a real diamond. If it sits fogged for a few seconds, it could be a fake.

2. The Water Test or Floating Test

This test relies on the density of a diamond. Real diamonds are dense and sink in water, while fake stones may float or sink more slowly.

Steps to do the Water test:

Fill a transparent glass about three-quarters full with water.
Carefully drop the loose stone into the water.
Watch what happens when the stone enters the water.
A real diamond will sink straight to the bottom, while a fake one may float or remain suspended.

3. The Loupe Test

The loupe test examines the stone under magnification for imperfections, because most natural diamonds have inclusions and blemishes.

Steps to do the loupe test:

Make sure you clean the diamond well before looking at it through the loupe.
Use a jeweler’s loupe or even a magnifying glass (preferably 10X magnification), but you need good lighting.
Hold the diamond in good light and inspect its surface and inside structure.
Inspect for tiny imperfections or inclusions - if it appears to be blemish-free, it could be synthetic or even a fake.

4. The Fire Test

The fire test determines if the stone can handle extreme heat, which real diamonds can do due to their thermal stability.

Steps to do the fire test:

Use metal tweezers to hold the stone and apply heat with a lighter flame for approximately 30–40 seconds.
As soon as you remove the lighter, drop the heated stone into a bowl of cold water.
Look for cracking, shattering, or discoloration.
A real diamond will remain wholly unaffected, while a fake stone (glass or crystal) may crack or break.

5. The Scratch Test

This test uses diamond's hardness to readily scratch other materials with the diamond.

Steps to do the scratch test:

Use a plain piece of glass as your test material.
Take the diamond in hand and simply drag the pointed edge across the glass.
Check the glass for scratches.
If the diamond caused a visible scratch, it is most likely real. However, this test can potentially harm fake stones and the glass itself.

6. The Magnet Test

Because diamonds are not magnetic, this is a great test to rule out materials containing metallic components or impurities.

Steps to do the magnet test:

Get a small, strong magnet (neodymium magnets work).
Clean your stone of dust or metal particles.
Bring the magnet close to the stone.
Observe if the stone is attracted to the magnet.
If it is attracted to the magnet, then it is not a diamond.

7. The Flashlight Test

The flashlight test evaluates how the stone reflects and refracts light, showcasing its brilliance and fire.

Steps to do the flashlight test:

Dim the room lights for better visibility.
Shine a bright flashlight directly through the diamond.
Observe the way light disperses inside and outside the stone.
A real diamond produces sharp, brilliant white light and colorful flashes (fire). Fake stones may appear dull or overly rainbow-like.

How to Buy a Real Diamond?

Here are a few simple tips to validate whether a diamond is real:

Buy from a reputable jeweler: A reputable jeweler, such as Caratus Jewels, will only sell certified diamonds.
Asking for certifications: Always ask for a GIA or IGI certificate verifying the authenticity and quality of the diamond.
Understanding the 4Cs: Know the 4 Cs, which are cut, color, clarity, and carat, because they help quantify the value and look of the diamond.
Get it appraised: You can still take it for an appraisal after purchase, and have a third party verify the diamond's value.

For more tips, you can also check out our blog - How to Choose the Perfect Engagement Ring - to understand diamonds in more detail.

Final Thoughts

Checking if your diamond is real doesn’t have to be intimidating. These simple tests — like the fog test, water test, and loupe test — can give you a good idea about your stone’s authenticity. However, nothing replaces a professional evaluation.

At Caratus Jewels, we believe in transparency and trust. Whether you’re buying your first diamond or verifying an old one, we’re here to help you every step of the way.

For expert advice and certified diamonds, visit us today and make sure your sparkle is truly authentic!

Frequently Asked Questions

Q: How can I tell the difference between a diamond and Moissanite?

A: Moissanite has more rainbow sparkle and double refraction, which can often be spotted under magnification or with a tester.

Q: Can a fake diamond still sparkle?

A: Yes, fake diamonds like cubic zirconia or Moissanite can sparkle beautifully, but their brilliance and fire differ from natural diamonds.

Q: Can I use a phone flashlight for the flashlight test?

A: Yes, a smartphone flashlight is bright enough to observe the diamond’s brilliance and fire in a dark room.

Q: Can I damage my diamond by testing it at home?

A: Some tests — like the fire or scratch test — could damage a fake stone or the setting. Real diamonds are durable, but exercise caution if the stone is mounted.