The loupe

TrueFacet's Fine Jewelry and Watch Guide

How to Spot a Fake Diamond: Easy DIY Tests

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If you’ve recently come into possession of family heirlooms or made a purchase online, you might be apprehensive about your diamond’s authenticity.

The only way to know with absolute certainty if your diamond is authentic is to have it professionally appraised. However, there are at-home tests you can conduct before paying an appraiser.

Here are our seven best tips for spotting a fake diamond.

1. Use a loupe to magnify any visible imperfections.
A loupe is a type of magnifying glass used by jewelers and watchmakers. You can purchase a loupe online, at a jeweler’s or craft store. Closely examine your stone with the loupe. Because real diamonds are naturally occurring, they often have internal imperfections. When examining your stone, look for small signs of imperfections to signal a genuine diamond. Natural diamonds may be flawless but, bear in mind that, lab-grown diamonds (diamonds that are synthetically produced in controlled environments) may look flawless under the magnifying glass as well.

inclusions chart

A chart used to examine diamonds and to determine and grade the quality of their imperfections

A related note on synthetic diamonds: while these tips can suss out a white sapphire, topaz or cubic zirconia from a diamond, it is nearly impossible to decipher a natural diamond from a lab-grown one. If you suspect that your diamond is synthetic, bring it to an expert for closer examination. While these lab-grown diamonds are still valuable, they are slightly less so than naturally-occurring diamonds.

2. Examine the stone’s edges.
While a fake will have rounded, dull edges, a real diamond’s edges are sharp and exact.

3. Consider the diamond’s mountings.
Most diamonds are set in a precious metal like gold or platinum. If the stone’s mounting appears to be plated or is only a semi-precious metal (like copper or aluminum), the diamond itself may be fake. Similarly, if the setting looks sloppy or like poor-quality craftsmanship, the diamond may not be particularly valuable.

4. Conduct the “Fog Test.”
A quick and easy test to determine if your gem is a real diamond: breathe on the stone, exhale as if you’re trying to fog a window or clean your glasses. If the surface of the stone fogs, it is not a diamond. Diamonds do not retain heat well so, even when hit with your breath’s warm air, they will not fog.

5. Try the “Transparency Test.”


Internally, diamonds sparkle grey and white; this is known as the diamond’s brilliance. Meanwhile the rainbow light reflected off a diamond is called its fire. This important distinction helps separate a real from fake diamond; look into your diamond and if you see a colorful sparkle inside the stone, it’s likely a counterfeit.

Similarly, if you have a loose diamond, place it atop a newspaper, over a line of text. A genuine diamond’s brilliance should sparkle enough to keep you from reading the underlying print through the stone. The type beneath other stones like a cubic zirconia, however, will be legible through the gem.

6. Drop the loose diamond in water.
If your stone is not set, try a water test. Simply place the stone in a glass of water. Diamonds are very dense and will sink to the bottom of the vessel. Fake diamonds, alternatively, will float at the top or fall only to the middle of the glass.

7. Test the diamond with sandpaper or heat.
A word of caution before proceeding with either of these at-home tests: If your stone in question is not an authentic diamond, these experiments will damage your stone. We strongly suggest only using these tests if you are indifferent to ruining your stone in the event it proves unauthentic.

In the first experiment, rub a piece of sandpaper against the stone. Diamonds are one of the hardest naturally-occurring minerals so, if it is scratched by sandpaper, it’s most likely not a real diamond.

The second test works only for loose stones. Heat the stone over a lighter for 30 seconds and immediately drop it into a glass of water. A real diamond will be unaffected by dramatic changes in temperature and it will simply fall to the bottom of the glass. Fake diamonds however will shatter immediately.

8. Bring in the experts.
To definitively know if your diamond is real or fake, bring it to an expert appraiser. If you do not have a go-to jeweler, look for an appraiser that is a certified gemologist and belongs to an appraisal association or organization. On average, a diamond appraisal will cost $50 or more. If you’re quoted a significantly lower rate, proceed with caution as it may be a rushed or less thorough evaluation process.

If you have further questions regarding TrueFacet’s authentication process, contact our concierge representative here.

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