How To Tell The Difference Between Diamond And Cubic Zirconia

By Debra Kelly on Saturday, January 18, 2014
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“There are only diamonds in the whole world, diamonds and perhaps the shabby gift of disillusion.” —F. Scott Fitzgerald, The Diamond as Big as the Ritz

In A Nutshell

While one is obviously naturally formed and the other is a man-made impostor, telling the difference between the two can be difficult if you don’t know what you’re looking for. The most conclusive way to tell the difference is with an electronic device that reads the stone’s electrical and thermal conductivity, but you can also look at the surface of the stone for any tell-tale scratches (diamonds shouldn’t have any), the color of the stone’s refraction (the light of a diamond will refract gray), and for flaws that will suggest a naturally made stone. Other tests include breathing on the stone, putting it under a black light, and trying to scratch glass with it.

The Whole Bushel

To the naked eye, a diamond and a cubic zirconia can look exactly the same—that’s the idea, after all. But while it’s long been said that a diamond is a girl’s best friend, that’s absolutely never been said about a cubic zirconia. So how can you tell that you’re getting what you pay for?

With recent advances in the manufacture of faux diamonds, this is made a little more difficult. Some of the tests still stand, but as various stones share qualities with diamonds, it’s important to look at more than one aspect of the stone. In fact, some high-quality cubic zirconia can also pass some of these tests (such as the scratch tests) but generally cannot pass all of them.

Diamonds are the hardest naturally-occurring surface; as such, they shouldn’t be able to be scratched easily. That’s the first step. Take a look at the surface of the stone in question: closely. There shouldn’t be any surface scratches on it if it’s a real diamond. Then, try to scratch glass with it. This isn’t a foolproof test, as there are also some fake diamonds that can scratch glass, but it’ll give you a good idea on whether or not you need to keep going.

One of the most time-honored tests used by gemologists is still one of the most effective. Place the stone on a newspaper. Because a real diamond refracts light—a lot—it’s impossible to read letters through it. Many cubic zirconia you’ll be able to make out letters through.

Another easy test is to breathe on the stone. Diamonds don’t retain heat, so they’ll become almost instantly clear again. Cubic zirconia tends to retain heat longer than a diamond and will stay cloudy.

If you have access to a black light, take a look at the diamond beneath it. Real diamonds should turn blue. However, the brighter the blue, the less pure the diamond. Those of extremely high quality will, ironically, fail this test. A cubic zirconia won’t reflect a blue fluorescence.

Also, if you have access to a stone that you’ve already confirmed the properties of, it’s easy to compare weights between cubic zirconia and real diamonds. A cubic zirconia is about 50 percent heavier than a real diamond.

Make sure the stone is clean before conducting any of the tests. If there’s a film or dirt present on the surface of the stone, it can interfere with results.

It’s also important to note that there are two distinctly different types of diamonds. There are those that are formed naturally, beneath the earth, created from carbon dioxide that was subjected to an amazing amount of pressure. There are also diamonds that were made in a laboratory; these diamonds are, in all purposes, diamond. They’re not fakes in the sense that they’re not going to have all the same qualities as a stone made in nature. But if your heart’s set on a diamond that was made in nature, it’s worth asking some more questions about where exactly your stone came from.

Show Me The Proof

LiveScience: How to Test a Diamond
Abazias Diamonds: Tests to Tell Genuine Diamond from Cubic Zirconia
Gemesis: Lab-Created Diamond FAQ

  • jihadbob

    First these nuts(lol) have been good and then boring diamonds….

  • Hillyard

    As long as your wife/girl friend can’t tell the difference you’re ok.

    • Lisa 39

      You know every woman who read this went straight for her diamond’s ;)

  • SensiblePerson

    Either way diamonds are still beautiful, just look at this wonderful 3,000,000 euro diamond encrusted watch created by the Swiss watchmaking company of Hublot. Not only that but also this watch is also the most expensive watch in the world!

    • Lisa 39

      That’s beautiful but to big and glitzy for me

    • aliendreams

      Not very pretty, IMO. Maybe a color photo would help.

      • SensiblePerson

        It is in color

    • Exiled Phoenix

      I’d sport it!

    • http://www.seguebythesea.com/ segue

      It’s okay, but not my style. I don’t wear watches anyway, so it could be the most amazing watch in the world I wouldn’t wear it. Even as a piece of jewelry it doesn’t really speak to me.

  • Costanza

    even glass can scratch glass; a diamond can scratch a cubic zirconia but it can’t be scratched by it.

  • delta-hb18

    DO NOT under any circumstances attempt to scratch glass with a diamond. Yes, it is true, in general that a diamond will scratch glass, but you can still damage the diamond in the process. What’s the point of verifying the diamond is real if all you also scratch or chip it?

    Just skip the CZ if you can, a great alternative are Moissanite diamonds, an affordable diamond “knock off” that comes from a naturally occurring mineral. Just be aware that to the trained eye, they are easily spotted as fake from across the room (they are “too perfect”) but to the average person, they are totally passable. They are a great alternative to diamonds for anyone who wants the look and quality of genuine diamonds at a lesser cost and without the the potential ethical issues. Moissanite gems are diamonds in every sense, a similar chemical make-up and pressure-induced process, with a hardness rating just below that of a diamond (Moissanite is 9.5 vs diamonds at 10 on the Mohs hardness scale). On a standard heat-conducting diamond tester, they will test as diamonds. The difference is, Moissanite will conduct electricity, and natural diamonds will not, and there are special diamond testers to test for this.

    I am not trying to sell anyone on anything, I don’t work for a jewelry company nor for a retailer of Moissanite, but I used to, and I enjoy educating those who may be interested in knowing what’s out there. Hope this helps someone :)

  • Errkism

    Not sure why materialistic things mean so much to people. Obviously materialism fuels capitalism and there are some things that have a purpose, but jewelry? Really? What is the value in having a shiny object placed around oneself? To show off you can afford something? To feed your egotistic view of yourself? Do explain, anybody.

    • disqus_fikVYdMc0U

      I do it to piss off the poor.

    • akvneia

      Rings have been around for a very long time. They represent the love and commitment you have for another person by openly displaying it for everyone to see. Its an open statement that you have no interest in anyone but the one that shares your commitment. The diamond-mostly a gimmick. But a pretty good one at that. Why not choose the clearest and strongest stone we know of to represent the strength of a relationship?

      • Errkism

        Just because something has been around for a long time doesn’t make it right. If it was really that strong of a feeling then you wouldn’t need to prove your love through an object. The feeling itself would be enough. And if the diamond was of such importance why would only the women wear one?

        • eyes like the sky

          Awww the lonesome human being is upset because no has ever been interested in them by the sounds of it… what a Wanker. On one hand you can say it is ridiculous and on the other I can say you have absolutely no right telling people how to feel, what is right or wrong and telling these people it is wrong to wear an expensive ring… get a life.

        • http://www.seguebythesea.com/ segue

          Plenty of men wear diamonds. Of course, in your cave you might not notice them, but out in the real world they are all around.

    • Lisa 39

      Its symbolism, when I was first married and still kind of happy it was a nice reminder that someone loved me.

      Off topic, I hope everything’s ok and that you come back here regularly :)

    • http://www.seguebythesea.com/ segue

      People have been wearing jewelry since there were people. The need to decorate ourselves seems to be an integral part of the human psyche.
      Why does this offend you?
      Do explain.

  • Alex Smith

    You definitely want to be able to tell the difference between real diamonds and Zirconia. Diamonds are one of the hardest naturally-occuring surfce and should be able to scratch easily like the article says. I found this blog post that gives tips and advice on making sure you are able to tell the difference between real diamonds and not. http://www.diamond-banc.com/tell-if-diamond-is-real/ have a read!

  • Bradley Marillier

    diamonds dont chip or scratch been working with diamonds for a long time, seen uncut and cut, try hitting a diamond with a hammer