How to Tell Them Apart: Cubic Zirconia vs Diamond

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Colorless gemstones are favored for how well they pair with white metals. Cubic zirconia and diamonds are two great examples of such white gemstones.

Diamonds need no introduction. They are hard precious stones formed under high temperature and pressure by the crystallization of carbon deep inside the earth’s crust. Subsequently, they move to the surface by volcanic eruptions.

diamond ring - cubic zirconia vs diamond

On the other hand, cubic zirconia is artificial. The gemstone is marketed as a diamond simulant for its close resemblance to diamonds. However, it’s composed of zirconium oxide crystals and rarely occurs in nature.

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Cubic Zirconia vs Diamond: Side by Side

Let’s look at a side-by-side comparison of the two gemstones before we delve into the specifics.

FeaturesDiamondsCubic Zirconia
Color Usually yellow but could be white, brown, red, pink, green, or blueColorless
HardnessHardest substance on earth 10 on Mohs hardness scale8 on Mohs hardness scale
Composition 99.95% carbonZirconium dioxide
PriceBetween $1,500 and $18,000 per caratAbout $20 per carat
Density3.5–3.53 g/cm3  5.65 – 6.0 g/cm3
Brilliance and fireWhitish or grayish sparkles inside the crystal, but rainbow reflections outside in natural lightRainbow-colored sparkles in natural light
Refractive index2.4172.176
DurabilityVery durableNot as durable

What is the difference between cubic zirconia and diamond?

To the untrained eye, diamonds and cubic zirconia look the same. They’re both colorless, glittering gems, but some key differences remain. We’ll consider the differences in their origin, physical qualities, durability, and cost.


Diamonds are natural gemstones originating from deep within the earth, where high temperature and pressure make carbon atoms crystalize into the raw gem. They are transported to the earth’s surface by volcanic eruptions.

On the other hand, Cubic zirconia is a synthetic stone made in the laboratory. Manufacturers make them by melting zirconium oxide powder in the presence of stabilizers at 4982 ℉ (2750 ℃). The stabilizers used include magnesium and calcium.


Diamonds are found in various shades. The most common colors of diamonds are white and pale yellow (brown). Lower quality diamonds are often with a yellowish tinge. The rarest colors of diamonds are red, blue, pink, and green. Although colorless diamonds are highly valued, the rare-colored ones are the most expensive.

Cubic zirconia is zirconium dioxide presented in a colorless cubic crystalline form. Manufacturers can color it to give different stones new hues. However, the color variation doesn’t increase the price.


Diamonds are the hardest substances on earth, with a 10 on the Mohs hardness scale. 

Although people believe only diamonds can cut diamonds, manufacturers use laser beams as well. However, the hardness of diamonds makes them impossible to scratch unless by another diamond.

Cubic zirconia has a Mohs hardness scale rating of 8-8.5. Its hardness makes it susceptible to scratches, especially when used in making rings and bracelets.


With a carbon content of 99.95 percent, diamond is the only gemstone composed of a single element. The 0.5% of impurities include nitrogen, hydrogen, and boron atoms and account for the color. The more the impurities, the less colorless the diamond will be.

Some people believe lab-grown diamonds contain other substances, but they’re also made of pure carbon.

The hard and colorless cubic zirconia is made up of zirconium dioxide crystals.


Diamond prices are dependent on their color, cut, clarity, and carat. Based on current retail prices, a one-carat cut of a diamond will sell for anything between $1,200 and $18,000. 

Red diamonds are the rarest and often cost over $1 million per carat, while gray, brown, and yellow diamonds are the least expensive.

The more expensive diamond cuts amplify light the most. Raw diamonds are opaque with little sparkle. But manufacturers add multiple facets to increase reflection and refraction, giving you that sparkle and brilliance you see. 

The brilliant round diamond cut has the most facets, giving it the brightest sparkle and the highest price tag. However, emerald and Asscher cuts are the cheapest because they don’t give off as much sparkle.

Cubic zirconia stones are inexpensive, with a one-carat stone costing roughly $20. Some jewelers market 5A grade CZ as more expensive, but it’s just a marketing gimmick to make you spend more.


Diamonds have a density of 3.5 – 3.53 g/cm³, while cubic zirconia’s density lies between 5.6 and 6.0 g/cm3. This difference in density means a carat of cubic zirconia will look smaller than a carat of diamond.

Appearance in Light

Diamonds have a refractive index of 2.417-2.419, while that of cubic zirconia is 2.176. This means that whenever light enters a diamond, it slows down more than it would in cubic zirconia. However, this isn’t noticeable to the eyes.

What is more noticeable in these gems is the reflection of white light. 

In natural light, diamonds sparkle bright white and gray within the stone. This reflection of white light is known as “brilliance” and is influenced by the cut of the diamond. 

The brilliant round cut diamond is the most expensive because its cut brings out the maximum white and gray shine. But on the outside, diamonds reflect various rainbow colors. This outward reflection is referred to as the “fire.”

💡 Take Note: You’ll only notice rainbow-colored reflections in cubic zirconia and no brilliant whiteness. This difference in light reflection is crucial to physically tell diamonds and cubic zirconia apart.


Diamonds are hard and durable. You can wear your diamond every day without fear of scratches and damage. Your diamond will last for several years without losing its sparkle. It may get dirty, but you can always clean it with warm soapy water and a soft-bristled brush.

Cubic zirconia doesn’t stand up as well in the face of wear. It’s not as hard as a diamond and will get cloudy over time. This cloudiness comes from exposure to dirt, dust, residue, and scratches and will eventually require that you change the gemstone. 

Cubic Zirconia vs Lab Diamond

Cubic zirconia is a synthetic stone created by subjecting zirconium dioxide to high temperatures. It’s colorless and generally referred to as a “fake diamond.” 

However, its appearance is so similar to diamonds, making it an ideal diamond alternative if your budget can’t cover a diamond.

Though lab diamonds are grown in the laboratory, they aren’t fake diamonds. They’re made of carbon, and scientists create them using technology that mimics natural diamond growth processes. 

Lab diamonds compare equally with natural diamonds in all things; same hardness, same refractive brilliance, and same durability. Just as the natural diamond is far ahead of the cubic zirconia, the lab diamond is also. 

Cubic Zirconia vs Diamond: Which should you choose?

You can choose between cubic zirconia and diamonds by considering what you’re looking for. Diamonds are the hardest substances on the planet and are durable. You can wear your diamond for years and never find a scratch. If your budget can cover it, pick a diamond.

However, cubic zirconia is better for those with a smaller budget. The gemstone might not last as long or stand up to wear as much as diamonds, but it’s easier on the pocket. 

While some people don’t, you may also favor the rainbow-colored sparkle of cubic zirconia over the brilliant white of diamonds.

Frequently Asked Questions

Here are some popular questions people ask about diamond vs. cubic zirconia.

How to tell diamond vs. cubic zirconia?

Diamond has a brilliance that distinguishes it from cubic zirconia. Within the stone is a white and gray sparkle in natural light, whereas cubic zirconia has lots of rainbow colors. 

Another method of telling them apart is your ability to read through them. The high refractive index of a diamond makes it hard to read the text through it. However, cubic zirconia will not blur text enough to disrupt reading.

A final check for confirmation is a certification request from a reputable gemstone organization. 

Organizations like Gemological Institute of America (GIA), American Gem Society (AGS), and Gem Certification and Assurance Lab (GCAL) give certifications to help you know a real diamond from a fake.

Can cubic zirconia last forever?

Cubic zirconia can last five years or more with occasional wear, but they can’t hold up to daily wear. Your jewelry can get scratched and cloudy when you wear it. These gems don’t last forever and require regular cleaning or lose their sparkle.

Can I shower with cubic zirconia?

Occasional water exposure is acceptable. But getting cubic zirconia into water frequently will reduce its shiny quality. For this reason, your cubic zirconia jewelry isn’t suitable for the shower.

Can jewelers replace cubic zirconia?

Though cubic zirconia gets cloudy and can chip or fracture in use, you can replace it easily. Visit a jeweler near you and have them check the shape and size. The jeweler matches these parameters to a new one and mounts it on your jewelry. 

💡 Keep in Mind: Some jewelers might not agree to work with cubic zirconia unless the jewelry is theirs. If you meet such a jeweler, try another store.

It may also not be possible to replace cubic zirconia with a diamond. 

Jewelers typically set cubic zirconia on lower-priced metals, like sterling silver. Sterling silver is a soft metal. Over time, the prongs holding the gemstone in place can deform and you risk losing your diamond. 

Besides that, it might not be easy to find a similarly sized diamond to replace your CZ. You can’t replace a gemstone with one of a different size.

Can cubic zirconia rings lose their shine?

Yes, they can when they become cloudy. Exposure to soap, dust, scratches, residue and oxygen in the air and water can make it cloudy over time. You can clean off the residue with soapy water and a soft cloth whenever it’s dirty.

Which is better: cubic zirconia or moissanite?

Moissanite and cubic zirconia are made to mimic diamonds. However, moissanite is made of crystalline silicon carbide, while cubic zirconia is crystalline zirconium oxide. 

Moissanite is harder (9.5 on the Moh scale) and more expensive than cubic zirconia. Its hardness makes it more durable and hence, the better choice. 

But if you’re on a super tight budget or looking for a cheaper ring to wear on vacation, cubic zirconia is still your best bet.

What does a fake diamond look like in sunlight?

Fake diamonds have rainbow sparkles inside the stone itself. Diamonds should have gray or white sparkle within the stone. However, it will reflect rainbow colors outside and onto other surfaces. 

If your “diamond” has only one of the two qualities, it’s fake.

Choose Your Colorless Gemstone

Everyone values a different gem for a world of reasons. Many people love the timeless white brilliance of diamonds regardless of the price tag. Still, others appreciate cubic zirconia’s budget-friendly cost and even love the rainbow-colored sparkle it gives in natural light. We hope it adds the perfect sparkle to your jewelry with the gemstone you choose.

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