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Cubic Zirconia (CZ) Vs. Diamond: Know the Differences

Rajib Singha Oct 23, 2018
Cubic Zirconias (CZ) and diamonds share very close resemblances with each other, so much so that, they look identical. It becomes almost impossible for the naked eye to identify the difference between CZ and a real diamond.
Cubic zirconia (CZ) is a synthetic cubic crystalline form of zirconium dioxide (ZrO2), fashioned as a diamond simulant (non-diamond material)
At times, even trained gemologists, can be fooled by its imitations. However, the difference between CZ and diamond can be revealed through a careful gemological inspection, using equipment such as a microscope or loupe which is a small magnifying glass, used by jewelers and horologists.
CZ holds certain properties that are very close to a diamond. That's the reason it was developed by the Russians to be used in the optics of their lasers. However, the two differ widely on many parameters. Let us see the differences between the two.

The Distinguishing Factors

Hardness and Weight

Diamonds are known to be the hardest natural substance on earth, however, CZs, do not hold this property. CZ are more prone to normal wear and tear, and chip and break easily.
They have a rating of 8.5 to 9.0 out of 10 on the Mohs' hardness scale. Diamonds have a 10 out of 10 rating. Although, not as hard as a diamond, it weighs 1.75 times more than a diamond of the same size.

Prismatic Dispersion

Diamond is known for its brilliance or 'white' flashes of light.
CZ on the other hand possesses colored flashes of light, due to higher dispersion of prismatic light, which can be seen by the naked eye. Diamond has a dispersion (breaking up of light into its spectral colors) of 0.04, while CZ has 0.06.

Color and flaws

Most diamonds are naturally impure and have flaws or inclusions, like a remnant of an original crystal face, say, trigons. One typical feature  of diamonds is a yellow shade in their appearance and those without any color are rarely found.
Production of CZ is virtually flawless, and since they are composed of synthetic matter, they are absolutely colorless.The flaws in a diamond or a CZ can be identified by using an instrument that can magnify the stone, 10 times its size.
In a CZ, the facets' direction is not properly pointed and the intersection point or the edges where the facets meet are smoother and more rounded off, than that of a real diamond. In case of a diamond, the point of intersection will form a sharper edge like that of a knife ― clean and crisp!

Thermal or Heat Resistance

Diamonds are one of the best conductors of heat. This property allows jewelers to size diamond rings.
Cubic Zirconia is a thermal insulator, i.e, it cannot withstand the same amount of heat that a diamond can endure. A jeweler's torch can easily burn and shatter it into pieces.


The refractive index of both the stones play a crucial role. Refractive index is defined as the ratio of the velocity of light in a vacuum, to that in a medium. In the case of dispersion by gemstones, the refractive index is simply the measure of the degree by which a beam of light bends, when it traverses between two mediums of different optical densities.
For example, a beam of light when traveling between air and CZ would bend by a degree, different from the degree while traveling between air and real diamond.So, the refractive index of diamond (2.417), being higher than that of CZ (2.176), diamond presents brighter appearance than cubic zirconia.
Cubic zirconia remains a favorite piece of jewelry with some people.
While some still like to awe diamond jewelry.The difference between CZ and diamond can never be recognized with a simple glance, unless it is inspected by special instruments.
The choice between the two entirely depends on the consumers' perception. They can go for cubic zirconia ― inexpensive and gives the same feeling as that of a diamond. And, for those who admire real beauty, they can always go for diamonds as a part of their jewelry.