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How to Know the Difference Between CZ Stones and Diamonds

How to Know the Difference Between CZ Stones and Diamonds

Not all people can distinguish between cubic zirconia (CZ) from a natural diamond. But you don’t need to be a jewelry expert to learn how to recognize the difference between the stones. In fact, there are telltale signs to know whether you are holding CZ stones or diamonds.

As wholesale fashion jewelry experts, we at CeriJewelry, created this article to help you tell the difference between CZ stones and diamond.

Cubic Zirconia vs. Diamond

Cubic zirconia crystals are a popular diamond simulant. However, cubic zirconia is made of synthetic material, which means it is not as hard as a natural diamond. And although the two look similar, CZ and diamonds are made of different mineral structures. Cubic zirconia is made from zirconium dioxide, while diamonds are carbon.

Below is a list of detailed characteristics to help you distinguish between a cubic zirconia stone and a diamond.

CZ Stones and Diamonds
Photo Source: Sell Your Jewelry

Appearance & Color

The best way to determine whether a stone is a diamond or cubic zirconia is to look at its appearance. You may see subtle differences when you observe the two stones closely. While many people think diamonds have a clear appearance, a white diamond can still have different underlying tints, such as faint yellow, very light yellow, and light yellow. In fact, diamond experts use a diamond color scale to determine its value. The higher the value of a diamond, the lesser color it has.

Cubic zirconia, on the other hand, is entirely colorless. However, CZ stones can also be manufactured in different colors.

Light Dispersion

Dispersion refers to the way the light reflects on an object. When you flash or shine a light on a diamond, the light will split into tiny bits of the color spectrum called the rainbow effect. 

Dispersion is measured by a rate. Diamonds have 0.044, while cubic zirconia has a dispersion rate between 0.058 to 0.066. This means that CZ stones can show a more significant rainbow effect when flashed with light than with diamonds.


Aside from the color spectrum, another factor you need to check to know the difference between cubic zirconia and a diamond is its brilliance. A stone’s brilliance is measured through the depth of its brightness instead of its colors.

The measurement of a stone’s brilliance is called the refractive index. Diamond’s refractive index of 2.42, while cubic zirconia stones have 2.16. So diamonds shine brighter than CZ crystals.


While diamond and cubic zirconia may look the same, their composition differs. Hardness is another thing to consider when checking the difference between the two stones. A diamond is slightly more durable than CZ because, on the Mohs scale of hardness, a diamond’s value is 10, while CZ has an 8.5.

Another thing you should look into is the weight of the stone. Although a diamond and a cubic zirconia stone may have the same size, diamonds are made of carbon and thus weigh lighter than CZ. Considering the two stones, you will notice that a CZ stone weighs twice as heavy as a diamond.

Diamonds are also more heat-resistant because they have a higher thermal conductivity. However, CZ stones can be a better thermal insulator than diamonds.

An easy test to know whether the stone you have in hand is cubic zirconia or a diamond is by breathing on the crystal. A fog from your breath will disappear right away if it’s a diamond. However, the stone will remain foggy for a longer time on a CZ stone.


Diamonds come at varying prices depending on their size and quality. However, diamonds will always cost more than cubic zirconia stones. Cost-wise cubic zirconia offers a more affordable option if you want to wear jewelry adorned with brilliant clear crystals.

If you’re considering cubic zirconia because it’s affordable but you’re worried about its quality, there are jewelry stores that offer top AAA-grade cubic zirconia like us at CeriJewelry.com. We have an extensive selection of exquisite jewelry and accessories with top-AAA-grade cubic zirconia in different colors aside from clear. You can check our website to see our collection.