You've found an old ring at the bottom of a drawer, you've just been given a piece of jewelry, or you've inherited a family ring and the question is burning on your lips: "Is it a real diamond?"
The doubt is legitimate. Is this sparkling stone the jackpot or simply zirconium? Modern imitations have become terrifyingly convincing to the naked eye.
Fortunately, there are simple methods to declutter at home before consulting an expert.
⚡ In Brief: How to recognize a real diamond?
Four quick tests to identify a stone:
Frame Test A genuine diamond is set in gold (hallmarked 750/Eagle's Head) or platinum (950). If the metal tarnishes or has no hallmark, be wary.
Fog Test Blow on it. The condensation disappears. instantly on a diamond. It remains for 3-4 seconds on glass or zirconium.
Reading Test Place the stone on a newspaper. If you can read the letters through it or see a black dot, it's a fake.
Reflections Test A diamond has predominantly grey and white reflections (brilliance). If it shines "rainbow" like a disco ball, it's an imitation.
Clue #1: Look at the Mount (The Logic Test)
Before even looking at the stone, examine the metal who wears it. It's the quickest and often the most revealing test.
Economic Logic
A real diamond is expensive. Nobody sets a real diamond in low-grade metal.
Golden rule: A real diamond is almost always set in gold . (yellow, white, pink) or of platinum .
How to check? Look for the hallmark.
Use a magnifying glass or your phone's zoom to examine the inside of the ring.
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✅ Good Signs: "750", "18K", "Eagle Head" (18 carat Gold) or "PT950", "Dog Head" (Platinum).
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⚠️ Mixed signs: "925" (Silver). Sometimes used for very small diamonds, but often for zirconium.
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❌ Bad Signs: "CZ" (Cubic Zirconia) or no hallmark on a color-changing metal.
Are you unsure about a symbol or unusual shape engraved on the ring? For accurate identification, consult our Complete guide to recognizing 18k gold hallmarks > .
Test #2: The Fog Test (Grandma's Trick)
This test is based on a unique physical property of diamond: its Exceptional thermal conductivity . It dissipates heat immediately.
The Tutorial
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Clean the stone with a cloth.
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Bring the ring close to your mouth and blow on it to create condensation (like on a mirror).
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Observe.
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💎 True Diamond: The mist disappears instantly (before you've even finished blowing). The stone remains clear.
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❌ Imitation (Glass/Zirconium): The condensation remains visible 2 to 4 seconds , the time it takes to evaporate.
Note: Moissanite (high-end imitation) reacts like diamond in this test.
Test #3: Observing Reflections (Grey vs. Rainbow)
Let's correct a common misconception: no, a diamond does not have to shine with all the colors of the rainbow.
The Visual Test
Place the ring under a white light and tilt it.
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💎 True Diamond: You mainly see splinters white and grey intense (the brightness) with a few touches of color (the lights).
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❌ Fake Diamond: You see an explosion of colors (orange, blue, green, red) like a prism or a disco ball. This is a sign of zirconium oxide or moissanite with excessive dispersion.
Test #4: The Reading Test (Refraction)
Diamond deflects (refracts) light so strongly that it acts like an internal mirror. Light does not pass through it in a straight line.
How to do it?
This test works best if the stone is removed, but you can try it on a ring.
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Place the ring, stone down, on a newspaper or book.
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Try to read the letters or see the black lines through the stone.
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💎 True Diamond: You don't see Nothing . It's blurry or illegible.
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❌ Fake Diamond: You can make out the black letters or lines through the stone.
Test #5: The Examination Under the Microscope (Inclusions)
This is the most reliable test to differentiate between natural and synthetic materials. You will need a 10x magnifying glass (€15 online).
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💎 Genuine Diamond (Natural): It's not perfect! You'll often see tiny black spots, white dots, or little "feathers" inside. These are nature's fingerprints.
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❌ Fake Diamond (Synthetic): He is Too perfect . Zirconium is manufactured in a laboratory without any flaws. A completely clean stone (magnifying glass clean) is either a fake or an extremely expensive museum-quality diamond.
Summary: The Decision Table
No single test is infallible, but combined they provide a reliable answer.
| Test | Result | Hint |
| Mount | Punch 750 or PT950 | ✅ Very Positive |
| Fog | Disappears instantly | ✅ Positive |
| Reflections | Predominantly white/grey | ✅ Positive |
| Reading | Impossible to see through | ✅ Positive |
| Inclusions | Visible under 10x magnification | ✅ Very Positive |
⚠️ Warning: The Scratch Test is to be BANNED.
Never try to scratch a window with your ring. Diamonds are hard but brittle: you risk breaking your stone or damaging the setting for an unreliable result.
Conclusion: Expertise is the only guarantee
These tests give you excellent clues. If your ring passed the setting test, the fogging test, and the grey reflections test: congratulations, it's very likely a diamond!
However, some imitations such as the Moissanite or the Synthetic Diamonds (Lab-Grown) can mislead these tests. For absolute certainty (especially for a sale or insurance), only a gemologist with a thermal tester can issue you a certificate.
If authenticity is confirmed, the value of your jewelry will also depend on the setting and the market. To understand how to estimate this value, read our article on the Price of a ring and its evaluation criteria > .
At the house of The Southern Girl , no guesswork. Our diamond-set jewelry is always:
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In 18-Carat Gold (750) certified.
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Sourced from ethical and natural sources.
Are you looking for the eternal beauty of a real diamond?
💎 Discover our rings with certified diamonds in 18-karat gold >
Quick FAQ
What is zirconium?
It's an artificial stone (Zirconium Oxide). It's very shiny but scratches easily over time and is very inexpensive.
What is the difference between a diamond and moissanite?
Moissanite is another stone that imitates diamond very well. It passes the fog test! The difference is visible in the reflections (more rainbow-like) and with a professional tester.
Can a diamond break?
Yes! It's scratch-resistant (hardness), but it can crack if it receives a violent impact at a certain angle (toughness). Take care of it.