Can Cubic Zirconia Pass A Diamond Tester?-Expert Answer

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There are many white gemstones that look a lot like diamonds and would easily pass for diamonds because they sparkle just as brightly as real diamonds.

So, if you are not careful about the tests for diamonds and diamond simulants, you may end up with a fake while thinking it is the real thing. One such commonly confused stone is the cubic zirconia (CZ).

While it looks much like real diamonds, it is not a real diamond, so it may not pass the detection methods commonly used for diamonds. This article lets you in on all you need to know about CZ stones and how to test this diamond-like gem.

Most importantly, we’ll answer the question, how do you know if the shiny gemstone on that ring or earrings is made of real diamonds or cubic zirconia? And can you use the conventional methods for testing diamonds to test for cubic zirconia?


How does a diamond tester work?

Can Cubic Zirconia Pass A Diamond Tester

The conventional diamond tester can be defined as a portable device used to test for diamonds.

By principle, the diamond tester’s basic principle of operation runs on the known fact that different gemstones conduct heat differently.

So, heat passes through the diamond differently through glass or cubic zirconia.

So, the diamond tester detects the heat transfer rate through the stone in question and based on this rate; you can tell if the stone is a diamond or not.

Testing for diamonds and other gems using the diamond tester is relatively easy. The diamond tester has a metallic tip that gets heated before it’s placed on the cool surface of the diamond, CZ, or any other test surface.

Can Cubic Zirconia Pass A Diamond Tester

When the metal surface touches the surface of the diamond or CZ, there is heat transference.

The heated tester tip heats the diamond, and if the temperature is read back from the tested diamond to the tester match, then the stone being tested is a natural diamond.

That said, most diamond simulants today are quite good and can mimic diamonds quite accurately and convincingly.

So, the newer testers on the market use slightly different logic to test and compare the attributes of the diamonds and the simulants.


What is cubic zirconia?

Can Cubic Zirconia Pass A Diamond Tester

The Cubic Zirconia, or CZ, is an inexpensive alternative to diamonds that carries similar qualities as the diamond. It is made of a synthetic crystalline material, which means that it is made in the laboratory.

It is, therefore, categorized as a diamond simulant, or rather, a stone that looks just like the natural diamonds.

Note, however, that unlike the lab-grown and natural diamonds made of carbon atoms, cubic zirconia stones are made of zirconium dioxide.

Another important thing to note is that cubic for the CZ name comes from the cubic crystalline structure of the cubic zirconia. This structure of CZ stones is like what is seen on natural diamonds, which is why high-quality CZ is often confused with natural diamonds.

Interestingly, the CZ material was accidentally created by scientists running experiments on different synthetic materials that they could use in the lasers.

And in the 70s, Russian scientists had perfected the techniques around the creation of single CZ crystals, and the sparkly, clear crystals would then become the most popular stones used to make the mass-produced jewelry.

Today, the CZ crystals are quite popular in the jewelry world, where they are used as diamond dupes in earrings, necklaces, rings, and bracelets, among other kinds of jewelry.


Can cubic zirconia pass a diamond tester? Why?

Can Cubic Zirconia Pass A Diamond Tester

Generally, the diamond testers are helpful tools that are often used as part of the multi-stage tests for diamonds, which means that you should not rely on the diamond tester on its own.

The cubic zirconia cannot pass the diamond-testing by the tester, although there are instances where the diamond testers cannot detect the diamonds from diamond simulants.

And because of the high conductivity of the diamonds and the simulants like the moissanite and CZ stones, this tester is not 100% reliable. In most cases, the CZ will not pass the diamond tester, hence requiring multiple tests to ensure accuracy.

Some of the reasons why the CZ stones will not pass the diamond tester testing include the fact that the CZ stones are excellent heat insulators, unlike diamonds, about 100% transparent to heat energy, meaning that the diamonds conduct heat in the same way as silver.

Can Cubic Zirconia Pass A Diamond Tester

The test machines use these elements to differentiate the diamonds from the CZ. The testers often use copper probes that are electrically heated and must maintain a specific elevated temperature controlled by a microcomputer, which then controls the thermometer and the heater.

When the tester touches the surface of the diamond, there is a rapid heat transfer into the diamond, which results in a quick reduction in the probe’s temperature, which then makes the computerized circuit elevate the power into the heater of the probe, allowing for programming of the temperature and accurate results.

This causes the LED light to go on, which tells you that the test material is likely a diamond. This doesn’t happen for CZ, though. For CZ stones, when the probe touches the stone’s surface, the heat transfer is slower because CZ is a poor heat conductor, so there will be no illumination.


The Diamond Tester: What Passes and What Doesn’t?

Can Cubic Zirconia Pass A Diamond Tester

Generally, a jeweler will run a specific series of tests to determine whether the test material is a natural diamond or another white stone.

The most common tests runs include the test for the stone’s refractive index, its conductivity, and degree of hardness (diamonds have a 10/10 hardness level).

The moissanite is different from the diamond in that its refractive index doubles under the magnification lens, separating it from other white stones like a diamond.

White sapphires, CZ, and the white topaz, on the other hand, have a lower degree of conductivity, and they don’t pass the pen tester. Then you have the little-known diamond simulants, which aren’t as hard as diamonds or CZ, and their differences can be seen under the magnification lens.

So, the pen tester can be used for diamonds thanks to the creation of diamonds out of pure carbon atoms. CZ is not made of pure carbon in the same crystalline structure, so the tester will not detect it as it does diamonds.

The moissanite has a high thermal conductivity, which means that it might give off a false-positive result with the diamond tester.


How to tell the cubic zirconia at home

Can Cubic Zirconia Pass A Diamond Tester

 Now that you know that you cannot test the cubic zirconia using the diamond tester and that you may need a professional to test the stone let’s look at some simple ways of testing for cubic zirconia at home.

The sparkle test: The sparkle test is one of the easiest ways for you to gauge the quality and features of the CZ stone at home. With the sparkle test, you would tell if the stone is a natural CZ stone or not by looking at the amount of fire and sparkle it gives off.

Reflected Light: Cubic zirconia stones can also be detected by the orange-tinted light that the stones reflect. If you look at the cubic zirconia stones under the bright sun, you will notice a bright flash of light. This isn’t the case with diamonds – they light well under the sun’s rays. CZ  will also create a rainbow effect under the sun.

Weight of the gems: The weight of the stone is also a good guide for determining the authenticity of the stones. In general, cubic zirconia stones weigh much more than real diamonds.

Can Cubic Zirconia Pass A Diamond Tester

Inclusions: Natural diamonds often have inclusions and imperfections, unlike the lab-created cubic zirconia stones, which are pretty much inclusion and imperfection-free.

Price – the other common difference between diamonds and cubic zirconia that allows you to tell the two apart is their price difference. Diamonds cost thousands more than cubic zirconia. Also, the price of colored diamonds is much higher than that of colored CZ and clear diamonds.

Fogging: CZ stones fog up, but the fog lasts longer on the CZ stones, unlike the natural diamonds with which the fogging disappears instantly. This difference comes from the differences in thermal conductivity in these stones – diamonds have a very high thermal conductivity hence the fast clearing up of the fog.



Cubic zirconia stones will not pass the diamond tester test.

So, if you have diamonds and cubic zirconia stones, you will differentiate them easily using the LED illumination from the detector.

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