How Do I Know a Diamond is Real?

Pro Tips for Checking for a Genuine Gem

Whether you’re designing a ring from scratch or are dusting off a storied stunner that’s been in your family for a century, when it comes to engagement rings, you might find yourself wondering how to know if the rock you’re planning on proposing with is real. (You’re an expert on your partner, after all—not diamonds!) But, not to fear—from at-home tests to telltale signs, today, we’re breaking down our top tips for knowing if a diamond is real and spotting stone imposters.

Tests To Try At-Home

If you’re curious about a diamond that you’ve already purchased or that’s been passed down from family, try the following experiments to test the stone’s authenticity.

  • The Water Test (for loose stones): Real diamonds are dense and will sink in water, whereas fake ones will float. Fill a glass about ¾ of the way up with water and drop in a loose diamond. If it sinks to the bottom, it’s real—if it floats near the surface, it is unfortunately not.
  • The Reading Test (for loose stones): Real diamonds refract light; fake ones do not. Take a loose diamond and place it—flat side down—on a piece of paper with small type on it (like a newspaper or greeting card). If you can still read the words or see the letters through the stone, the diamond is likely fake. A real diamond refracts light in all different directions, making the letters impossible to read when the stone is placed over them.
  • The UV Test (for loose or set stones): Most real diamonds will emit a blue color when placed under UV or black light, so placing your stone under a UV light source can be a simple way to check its authenticity. (Note, however, that not all authentic diamonds glow blue under UV light—so, if your diamond “fails” this test, it doesn’t necessarily indicate it’s a fake. Try taking your stone to a professional jeweler for further authentication if you’re worried.)
  • The Heat Test (for loose stones): Real diamonds can withstand drastic temperature changes, while fake ones cannot and will shatter. Expose a loose diamond to a direct heat source (like a lighter) for 30-45 seconds (make sure you’re wearing heat-resistant gloves and holding the stone with tweezers or pliers so you don’t burn yourself). After you’ve heated the stone sufficiently, drop it immediately into a glass of ice water. A fake diamond will likely shatter at this point, whereas a real one will be able to withstand the drastic change in temperature. (If you choose to perform this test, just keep in mind you’ll have to clean your diamond of any residue that may have formed as a result of it being exposed to the heat.)
  • The Fog Test (for loose or set stones): One of the oldest tricks in the book? Check to see if you’re able to “fog it up”. Simply place a stone near your mouth and breathe as you would trying to fog up a pair of glasses or a mirror. A real diamond conducts heat well and will immediately dissipate the fog, whereas a fake diamond will stay fogged up.

Common Diamond Lookalikes

Unsure if whether or not you have a natural diamond on your hands? Below are three stones that can often be mistaken for one:

  • White Gemstones: Topaz, sapphire, and moissanite can all often pass as diamonds to the untrained eye. Some tips to help you out? While Sapphires can look clear to the naked eye, they don’t have distinct light and dark areas that are distinctive to diamonds; topaz is a softer stone than a diamond and is easily scratched by other hard materials, so simply looking at it under a magnifying glass should help you tell; and moissanite is the best at faking it and is nearly impossible to tell apart from a diamond with the naked eye, so you should definitely take it to a diamond expert for appraisal and review.
  • Synthetic or Man-Made Diamonds: Lab-made diamonds are on the rise (and for good reason!), but if you’re trying to get a definitive answer on whether a diamond is natural or man-made, this is a case that’s best left to professionals. To spot a man-made diamond, you’ll need to have a diamond expert review the stone.
  • Cubic Zirconia: Another synthetic stone, cubic zirconia (CZ) is perhaps the most famous diamond-lookalike in the book. The giveaway here is that a cubic zirconia will reflect orange-tinted light in addition to the fact that it weighs more than a natural diamond.

PRO TIP: An engagement ring is a serious investment—and, while at-home tests are a great way to get an idea of your stone’s authenticity, they may not always tell the full story. If you’re seriously worried about your stone, take it to a professional diamond expert for further evaluation. Groups like the Gemological Institute of America and the American Gem Society Laboratories offer evaluation and certification services.

Psst..don’t forget: there’s more to proposing than the stone! Learn how to plan the perfect proposal here.