Whether you're buying a diamond for an engagement ring, investing in fine jewelry, or evaluating a family heirloom, knowing how to tell if a diamond is real or fake is essential. With so many diamond imitations on the market—like cubic zirconia, moissanite, and glass—being able to identify authenticity can save you from making a costly mistake.
In this guide, we’ll walk you through several simple tests and professional methods to verify whether a diamond is real or fake.
1. The Fog Test
A quick at-home method to check your diamond’s authenticity.
How it works:
- Hold the diamond close to your mouth and breathe on it.
- A real diamond will disperse heat rapidly, so the fog will disappear almost instantly.
- A fake diamond will stay fogged for a few seconds longer.
Note: This test works best in cool environments.
2. The Water Test
Another easy test to try at home.
How it works:
- Fill a glass with water.
- Drop the loose stone into the glass.
- A real diamond will sink to the bottom because it is dense.
- A fake diamond (like cubic zirconia) may float or sink slowly.
3. Check the Diamond’s Sparkle
Real diamonds reflect light uniquely.
- White light (brilliance): Real diamonds reflect a bright white light.
- Colored light (fire): You’ll also see flashes of rainbow colors.
- Fake stones often appear dull or overly colorful under light.
4. Inspect the Setting and Mount
Real diamonds are typically set in high-quality metal.
- Check for markings such as 14K, 18K, or PLAT which indicate gold or platinum.
- If the stone is set in a cheap metal or there are no markings, it might be fake.
5. Use a Loupe or Magnifying Glass
Jewelry experts use a loupe to examine diamonds up close.
What to look for:
- Inclusions or imperfections (natural diamonds usually have some).
- Sharp edges and well-defined facets.
- Fake diamonds are often too perfect and may have rounded edges.
6. Try the Heat Test (with Caution!)
This method checks how the stone reacts to heat.
How it works:
- Heat the stone with a lighter for 30 seconds, then drop it into cold water.
- A real diamond won't be affected.
- A fake diamond (like glass or quartz) may shatter.
This can damage a fake stone or setting—do not try this on valuable pieces.
7. Use a Diamond Tester
Diamond testers are affordable devices that check thermal conductivity.
- Real diamonds disperse heat quickly, which will register on the tester.
- Moissanite may also test as a diamond, so use in combination with other tests.
8. Seek a Professional Appraisal
When in doubt, visit a certified jeweler or gemologist.
- They can perform advanced tests, such as:
- UV light examination
- Refractivity tests
- X-ray examination
- They can also issue a diamond grading report for proof of authenticity.
Identifying a real diamond isn’t always easy with the naked eye, but with the right tests and tools, you can get a good idea of its authenticity. For high-value purchases or sentimental items, always consult with a professional jeweler for peace of mind.