Jewellery Guides

How To Tell If A Diamond As Real

Written by Joanna Wyganowska
December 21st, 2021 • 5 min read

So you've inherited some jewellery or found a sparkly gem second hand - but how do you know if its a real diamond, or a convincing simulant? Our gemmologists share their knowledge.

Be aware that some of these tests may compromise your stone. Be careful when carrying out tests not to drop or damage the stone - whilst diamonds can typically withstand heat, pressure and the odd small knock, not all gems are as hardy.

1. The fog test

Mist up the diamond with a breath of air as if you were fogging up a window, whilst carefully holding the gem with tweezers or between two fingers. On a real diamond, the fog should immediately dissipate as diamonds are great heat conductors, which means they will disperse heat quickly. A fake diamond with take a few seconds to clear.

The water test

This test is only possible with a loose stone, so not for everyone. Gently drop the diamond into a glass of water filled three quarters of way. A real diamond has high density, so should sink to the bottom of the glass. A fake will float near or at the surface. Be very careful with this one - real diamonds are very strong and durable so should happily withstand the test, but its always better to be safe than sorry.

The heat test

Formed over billions of years in the Earth's mantle, diamonds are made of tough stuff and can withstand a great deal of heat. With a glass of cold water on standby, heat the stone for around 40 seconds whilst holding it with tweezers or pliers (and make sure your hands are protected from the heat!). Drop the stone straight into the cold water after heating, and if real the diamond should remain unaffected. Again, heat dispersal in a real diamond happens almost instantaneously. A fake diamond will shatter due to the shock change in temperature, so don’t try this if you’re not willing to potentially sacrifice a fake diamond.

Ask an expert

The best (and probably safest) way to know if a diamond is real is to get an expert eye to look over it. A trained gemmologist will check the refractivity of light through the diamond; light should bounce off the pavilions at the base of the diamond and be refracted up through the crown, or table at the top of the diamond. This can be difficult for the untrained eye to tell, but an expert will be able to gauge the brilliance of the stone from this and may have a few tests of their own to tell if the diamond is real.

Through the use of a loupe magnifying glass or microscope, a professional will look out for the kind of blemishes and imperfections that signify a real diamond. As organic material, diamonds will contain a variety of tiny imperfections called inclusions, which are usually not visible to the naked eye. This is a good sign that reinforces the credibility of the diamond, as fake diamonds can be constructed to be flawless.

Consider buying only GIA or IGI certified diamonds

The safest way to ensure a diamond is real and know its exact specifications is to only purchase IGI or GIA certified diamonds. The Gemological Institute of America use the toughest grading standards to verify a diamonds cut, clarity, carat and colour, noted particularly for their grading of natural diamonds - whilst IGI are considered the best option for lab diamonds.

Once assessed, an IGI or GIA diamond will have a unique code of minuscule proportions inscribed onto the side. This will only be visible under a microscope, and paired with the certificate is good insurance that your diamond is real and is exactly what you have been told it is. At Queensmith, we only stock IGI and GIA certified diamonds, and will show you the unique number inscribed on the diamond through a microscope, as well as the corresponding certificate during in-store appointments.

Have your diamond GIA certified

A professional, reputable diamond lab will have the means to test the stone rigorously - most experts would recommend sending your diamond for GIA testing. Make sure you do your homework when deciding where to have your stone tested. They should have x-ray machines to detect the radiolucent molecular structure of a diamond. Diamond substitutes will have radiopaque features that will instantly distinguish the real deal from a fake.

Whilst the quick at-home tests can be an easy and experimental way to test your rock, there are various risks and limitations with donning a lab coat and playing scientist for the day. We recommend you seek professional, expert opinions from reputable diamond labs so you won’t have to second guess yourself. And remember - be careful where you buy from, choose GIA diamonds and always ask to see the GIA certifications and inscribe number.


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