How to Tell a Real Diamond From a Fake: A Guide

Dacy Knight

Diamonds may be forever, but cubic zirconia certainly isn't. If you're purchasing the former, it's advised you seek out a jeweler with a GIA or AGS certificate, but if you've inherited some family heirlooms, received a gift, or have just scored a vintage find, it isn't always so straightforward. The question is how to tell a real diamond from a fake. Short of turning to a professional jeweler for their expert assessment, there are some at-home tricks you can do yourself to determine whether or not you have a real diamond in your possession. The only props you need are what you already have on hand—and a couple of the tests require nothing more than your own two eyes. Follow these five simple tricks that separate the real deal from the sparkly stand-ins. Head below to study up on five ways you can tell a real diamond from a fake.

Setting Test

If the diamond is already in a setting, such as a ring, you can typically determine the authenticity of the diamond by the quality of the metal. A real diamond will most likely be set in gold or platinum, so look for an engraving that says 10K, 14K, 18K, 585, 750, 900, 950, PT, or Plat. A C.Z. engraving is an instant giveaway that it's fake, as it stands for cubic zirconia.

Water Test

Genuine diamonds have a high density. You can test for this density if it's a loose diamond by filling a glass of water three-quarters of the way full, and then dropping the diamond into the glass. If the stone sinks, it's likely real. If it floats at the top or just beneath the surface, it's fake.

Fog Test

The fog test is one of the simplest and quickest tests to differentiate a real diamond from a fake. Just hold the diamond between two fingers, and breathe on it, fogging up the surface of the diamond in question. If the fog from your breath dissipates right way, it's a sign that the diamond is real. If it takes several seconds to clear, it is likely fake.

Read-Through Test

If it is a loose diamond, you can use a newspaper or a paper and pen to determine whether or not it is real. Place the gemstone onto a piece of paper with the flat side down. If you're able to read the letters through the diamond, it is fake. With a real diamond, you won't be able to see clearly through it because of how it refracts the light. You can also draw a dot onto a piece of black paper, and place the stone on top of it. Again, if you are unable to see the dot's reflection in the stone from above, then the diamond is real.

Sparkle Test

One of the most straightforward tests you can conduct relies entirely on your eye. Hold the diamond under a normal lamp, and observe how the light reflects off of it. A real diamond will sparkle exceptionally, giving off colorful and white light reflections. If you're still unsure, it can help to compare the diamond in question against a fake diamond like cubic zirconia, which will be drastically less vibrant.

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