How to Tell if a Diamond Is Real or Fake

5 Tests to Spot a Fake Diamond

how to test a diamond illustration

The Spruce / Melissa Ling

Sometimes a deal on a diamond may be too good to be true. Or, you may have what appears to be a piece of diamond jewelry that you'd like more information about. If you want to know if you have a real diamond, you can do five tests on the stone at home. These can help distinguish between diamonds and artificial diamonds and which one you may have.

The Most Common Fake Diamonds

Cubic zirconia (CZ) and moissanite are considered artificial diamonds. For instance, moissanite is a diamond simulant that is nearly indistinguishable from natural diamonds without gemological testing by experts who can recognize fakes. In addition, there are other gemstones and minerals that resemble diamonds in their appearance and can often be passed as fakes, including:

  • White sapphire
  • White topaz
  • Colorless garnet
  • Spinel
  • Rutile

How to Tell if a Diamond is Real: 5 Tests

Out of the five tests, the last three tests work better if you have a loose stone. If the stone fails all five tests, your diamond is likely fake. However, if the stone passes at least one test, there is a chance you have a real diamond. Take the suspect diamond to your local jeweler or gemologist for an official jewelry appraisal. It can be difficult to know if a diamond is natural without a gemologist's help. They have powerful tools and intricate tests to determine the value and validity of your stone.

Breath Test

Position the stone close to your mouth and breathe onto the flat surface of the diamond. Imagine you are breathing into a mirror to make it foggy. Diamonds immediately dispense heat, so instead of remaining cloudy, the diamond would become instantly transparent. Try this same test on cubic zirconia. The surface of the CZ will continue to be foggy. This test will help you determine if you have a CZ instead of a diamond, but the test will not tell the difference between moissanite and diamond. 

Loupe Test

If you have a jewelry loupe at home as well as a basic understanding of diamonds, this test will help you quickly pick out lower grade diamonds. Most diamonds have some inclusions or flaws. If you inspect your stone under magnification in good light, you might notice a small piece of carbon or a white spot that looks like a feather. Cubic zirconia and other synthetic diamonds like moissanite do not have these types of inclusions and are internally flawless.

The presence of inclusions will help you determine if your diamond is real. However, if you don't see any flaws, do not use this test as the deciding factor. Diamond-specific inclusions will indicate a real diamond, but there may be instances where you are inspecting an internally flawless diamond that is without any inclusions.

Scratch Test

For the scratch test, take the stone and try to scratch a piece of glass with it. This should be done with caution because it is possible to damage or chip a diamond. Because diamonds are ranked hardest on the Mohs scale, a real diamond should scratch glass. If your stone does not leave a scratch on the glass, it is most likely a fake. If it does leave a scratch, proceed with some additional tests because some synthetic diamonds will also scratch glass.

Newspaper Test

The newspaper test works well when you have a slightly larger stone. If you place cubic zirconia over a piece of a finely printed newspaper, you should be able to read the print underneath the stone. Diamond, however, refracts the light in such a way that you cannot read the print below it. If you don't have a piece of newspaper lying around, take a piece of paper and draw a small dot on it. You will not be able to see the dot through a real diamond.

Water Test

Drop a diamond into a glass of water. This will only work if your diamond is loose. Due to the differing densities, a real diamond will sink to the bottom of the glass where most diamond simulants will float.