How to know if it’s a real diamond and not cubic zirconia?

You don’t have to be Sherlock Holmes to differentiate the real from the duds. All you need is ample light, some water, warm breath, and a jeweller’s loupe is all you need

If you are curious to know, here are some tests you can easily try at home.

The Fog Test

What you need:

  • Loose diamond or ring in question

What to do:

For this test, simply hold the ring or the loose stone or between two fingers and breathe on it just like you would do to a mirror or an eyeglass. A light fog will form on the gem.

Diamonds are effective conductors of heat so it disperses heat instantly. A fake diamond will stay hazy for a short period before dispersing so if the fog disappears immediately, the stone is real.

The Water Test

What you need:

  • A glass filled with ¾ of water

What to do:

This test is one of the easiest D.I.Y. way of identifying whether a diamond is fake or not, and is only applicable to loose stones/diamonds.

Just delicately drop the stone in the glass of water. A fake diamond will just float underneath or stay on the surface of the water. And since diamond has a high density it will sink all the way down to the bottom.

The Sandpaper Test

What you need:

  • Sandpaper

What to do:

Try this only when you are prepared to lose a fake diamond jewellery.

Using a regular sandpaper scrub the gemstone. Since diamonds are known to be hard, the sandpaper wouldn’t affect it even if it’s scratched. A fake diamond, however, will have scratches when scrubbed.

diamond in black background

The Newspaper Test

What you need:

  • Newspaper

What to do:

Pick a page with a lot of letters and place the unmounted gemstone upside down on it. Real diamonds refract light. If you can read the letters and see through the gem, even if it’s blurry, then you have a fake in your hands.

This test can also be called the read-through test.

The Dot Test

What you need:

  • Paper
  • Marker

What to do:

This test is a great alternative for when you don’t have a newspaper at hand. Draw a dot on a clean sheet of white paper and place the stone above the dot. Like with the read-through test, if you can see even a little bit of the dot you drew, you have a fake.

The Temperature Test

What you need:

  • Candle or lighter
  • Tweezer/Tong/Pliers
  • A glass of cold water

What to do:

Using a tweezer, tong, or plier hold the stone directly over the candle fire for about 40 seconds, then drop it directly on the glass of cold water.

An authentic diamond will show no reaction to the abrupt change in temperature. A fake diamond will shatter.

diamonds in different sizes

The UV Light Test

What you need:

  • Strong black light

What to do:

Turn off all the lights and directly place the gem under the strong UV light. If it emits a bluish light, the gem is most likely a real diamond.

There are cases when some true diamonds do not glow even when exposed to UV light, if this happens and you are not sure, just try another one of the tests.

The Metal Check

What you need:

  • The mounted ring

What to do:

True diamonds are of great value and real jewellers know it. An authentic diamond will not be carelessly placed in a band that does not befit it. Check inside the metal for markings, real diamonds are normally set in luxurious metals like yellow, white, rose, gold, or platinum.

Need help?

If all else fails, you have tried all these tests and is still not convinced, you can always consult a trusted jeweller like Monty Adams Jewellery Concierge. Make an appointment today.




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