Will Cubic Zirconia Scratch Glass?

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Cubic zirconia (CZ) is a beautiful stone often used as a diamond alternative. It has many of the same properties as diamonds but is much cheaper. So, what happens when you scratch glass with cubic zirconia? And how does it compare to diamonds?

Cubic zirconia is harder than glass and will scratch or cut it just as diamonds do. So, scratching glass isn’t reliable for testing if a stone is a diamond or cubic zirconia. Also, cubic zirconia has a colorful sparkle, while diamonds have a white brilliance since they bend light differently.

Let’s look at what cubic zirconia consists of and how it ranks on the Mohs hardness scale. You’ll also find out why cubic zirconia and diamonds can scratch glass and ways to tell the difference between the two stones.

What is Cubic Zirconia?

American Dimond or Cubic Zirconia

Cubic zirconia is a synthetic material created in 1937 from zirconium oxide (ZrO2), which is then polished and cut into the shape of a diamond. 

Cubic zirconia is widely available and affordable, making it a popular choice for costume jewelry and engagement rings.

Although there is naturally occurring cubic zirconia, it’s so rare that it’s not used for jewelry. However, jewelry-quality cubic zirconia is an affordable diamond alternative with optical properties similar to diamonds.

Cubic zirconia is sometimes confused with zircon, a natural stone, and a diamond alternative with a similar brilliance, but it’s not the same as cubic zirconia.

However, zircon is much softer than cubic zirconia and ranks at only 7.5 on the Mohs hardness scale, making it more susceptible to scratching and chipping.

Cubic Zirconia vs. Diamond: What’s the Difference?

Cubic zirconia (CZ) is an affordable diamond alternative often used in jewelry. But what exactly is cubic zirconia, and how does it compare to diamonds?

Diamonds are natural minerals mined from the Earth. They’re composed of carbon atoms arranged in a specific way, giving them incredible hardness.

Diamonds are the hardest naturally occurring material on Earth, which is why they’re often used in industrial applications like computer chips and drilling.


There are some significant differences in physical properties between cubic zirconia and diamonds.

For starters, cubic zirconia is about 1.7 times denser than diamonds so a cubic zirconia stone will appear smaller than a diamond of the same weight.


Under a microscope, a diamond will have inclusions or minor imperfections because of the natural formation process.

For example, cubic zirconia stones are optically perfect with zero inclusions, whereas cubic zirconia stones are near flawless.


Diamond is also harder than cubic zirconia on the Mohs scale of hardness. The Mohs hardness scale measures how well a material resists scratching. Cubic zirconia ranks eight on the Mohs hardness scale, while diamonds rank 10, so diamonds are technically more scratch-resistant.

Optical Properties

In terms of optical properties, cubic zirconia and diamonds are pretty similar. They both have a high refractive index, which means they sparkle brightly.

However, cubic zirconia has a higher dispersion rate than diamonds, meaning it breaks light into colors more efficiently. The result is a rainbow-like sparkle of color, whereas diamonds have a brilliant white sparkle.


There is also a significant difference in cost between cubic zirconia and diamonds.

Cubic zirconia is much more affordable, making it a popular costume jewelry choice. For example, a one-carat cubic zirconia stone can cost as little as $10, while a one-carat diamond can cost upwards of $1,000.

Can Cubic Zirconia Scratch Glass?

The Mohs hardness scale rates glass at 5.5, which is softer than cubic zirconia, which has an 8 rating, so cubic zirconia can scratch glass.

Because cubic zirconia is harder than glass, testing whether it can scratch glass is not a good way to determine if a material is a cubic zirconia or diamond. 

How to Tell the Difference Between Cubic Zirconia and Diamond

Gold Ring with Cubic Zirconia (CZ) on the Ground with Green Plants

If you’re trying to tell the difference between cubic zirconia and diamond, there are other tests you can do, like the newspaper test.

Hold the stone close to a newspaper and see if you can read the print through the stone. If you can, it’s cubic zirconia because diamonds refract light differently.

The best way to tell the difference between cubic zirconia and diamond is by consulting with a jeweler. They will examine the stone and tell you for sure what it is.

Can Diamond Scratch Glass?

Glass is softer than many other materials, so anything with a hardness equal to or greater than glass can scratch it.

Diamonds are one of the most durable materials on Earth, and they can scratch glass and other materials. So, there are better ways to determine whether a stone is a diamond than scratching glass. 

Other ways to test whether a stone is a diamond include analyzing the refractive index, specific gravity, and hardness. But, a certified gemologist or jeweler will have the most definitive methods for determining whether a stone is a diamond.

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