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Cubic Zirconia or Diamond? How to Tell if a Diamond is Real

May 1, 2019

Today we’re going to talk about how an experienced jeweler can tell the difference between a cubic zirconia and natural diamond. Let’s get started.

 

What we have here are 2 asscher-cut stones that are the same physical size (measured in millimeters). One is a natural diamond (not lab-grown which we’ll talk about later) and one is a cubic zirconia (commonly known as a CZ in the industry).

Let’s look at the attributes of both stones and learn something new.

 

Using a stone’s weight to determine if it is a real diamond

First, we’ll weigh the stones on the scale. Remember that they are the same size in millimeters.

This stone weighs 4.85ct.

 

This stone weighs 3.06 ct.

Clearly, one is lighter than the other. Diamonds are always lighter and less dense than cubic zirconia of the same size. That’s our #1 tip.

 


What is a cubic zirconia?

Cubic zirconia is a form of zirconium dioxide that takes on a crystalline shape. To the untrained eye, it’s quite similar to a diamond. Interestingly, natural cubic zirconia is incredibly rare. All of the CZ used in jewelry was made by humans in a laboratory. Because of its appearance and abundance, man made CZ are commonly used to create jewelry.

CZ jewelry is much less expensive than a similar piece made with diamonds.


 

Using a diamond tester to identify a real diamond

Here’s another tip that isn’t quite as technical. What you see above is called a diamond tester. It uses the thermal and conductive properties of a diamond to determine if it’s a real diamond or a CZ.

As you can see in the video, it beeps when it touches a diamond and doesn’t beep when it touches a CZ.

But of course, there are some more technical factors a jeweler can consider when evaluating a stone, like facet junctions and visible wear on the facets. Sometimes you can even see a rainbow-colored tinge in a cubic zirconia that’s just not present in a real diamond. And when tested for hardness, CZ will rate about an 8 on the Mohs scale, compared to a 10 for a diamond. But because of our years of experience at Samuelson’s, we often just “know” the real thing when we see it.

 

What about lab-grown diamonds?

Lab-grown diamonds are a big concern in our industry. Diamonds can be synthesized in the lab to look very similar to natural diamonds. They even react the same way as a natural diamond when checked with the diamond tester.

In our next video, we’ll talk more about lab grown diamonds and what you need to know if you’re investing in a piece of diamond jewelry.

 

Buying or selling a diamond?

Contact Samuelson’s to schedule a private 1-on-1 appointment to browse our selection of diamonds and luxury timepieces or to sell your diamond jewelry to us. We’re happy to talk to you about your piece, evaluate it, and make you a great offer.

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