How Cubic Zirconia (CZ) and Lab Diamonds are Different

You might think that a cubic zirconia gemstone is the same as a lab-grown diamond, but there are actually some pretty big differences between the two. Here’s what you need to know about cubic zirconia vs lab-grown diamonds.

The difference between Cubic Zirconia and a Lab-Grown Diamond is in the composition. Cubic zirconia is made of zirconium oxide, while lab-grown diamonds are made of carbon. The way they’re made is also different. Cubic zirconia is grown in a lab using a method called skull-melting method, while lab-grown diamonds are created through chemical vapor deposition (CVD).

Technically, they are both man-made, and both grown in a lab, but cubic zirconia is considered a synthetic gemstone or diamond simulant, while lab-grown diamonds are considered to be real diamonds. That’s right, lab-grown diamonds have the same chemical and physical properties as natural diamonds!

Lab-grown diamonds are not cubic zirconia. They are two completely different types of stones. Keep reading and I’ll show you the major differences between these two types of gems.

Lab-Grown Diamond Explained.

Natural diamonds are usually formed through mining in the earth, but lab-grown (also referred to as lab-made, lab-created, laboratory-grown, laboratory-created, man-made, artisan-created, or cultured diamond) are produced through a process that’s controlled by human technology. This type of diamond is different from other types of diamonds because it’s not produced through a traditional geological process.

Unlike imitations of natural diamonds, which are commonly referred to as diamond simulants, synthetic diamonds are made from the same exact materials. They share the same physical and chemical properties as earth-mined diamonds.

The two most common methods used to create lab-grown diamonds are high-pressure high temperature (HPHT) and chemical vapor deposition (CVD).

HPHT methods recreate the natural conditions that occur deep within the Earth. It involves taking a small diamond seed and placing it into a chamber where it’s exposed to intense heat and pressure. Over time, the diamond seed grows into a full-sized diamond.

CVD methods involve using a small diamond seed as a catalyst for the growth of a larger diamond. In this process, gasses are used to deposit carbon onto the surface of the diamond seed. The temperature and pressure in the chamber are carefully controlled

HPHT methods can take anywhere from a few weeks to a few months to grow, while CVD methods can take up to a year to grow.

Cubic Zirconia Explained.

The term cubic zirconia refers to a type of crystal that is made from the mineral known as zirconium dioxide (ZrO2). Although it is usually colorless, it can be produced in various colors. It is different than zircon, which is a type of mineral known as zirconium silicate (ZrSiO4).

Since its commercial production in 1976, synthetic cubic zirconia has been regarded as the most economically and technically valuable competitor to diamonds. Its low cost and close visual resemblance to the natural diamond makes it an ideal choice for jewelry.

Cubic zirconia is regarded as one of the best simulants for diamonds (or fake imitation diamonds).

The Difference Between Cubic Zirconia and Lab-Grown Diamonds.

Are you curious about the difference between lab-grown diamonds and cubic zirconia? Here’s what you need to know. I broke them down into a few key categories: Physical Properties, Chemical Composition, Durability, Clarity, Carat, Quality Grade, Color, Cut, and Price.

Physical Properties:

One of the main ways to tell cubic zirconia and lab-grown diamonds apart is by their physical properties. The most obvious difference is in their appearance. Cubic zirconia is typically found in a wide range of colors, while lab-grown diamonds are usually clear or near-colorless.

Cubic zirconia has a greater specific gravity (5.95) than lab-grown diamonds (3.52). This means that a cubic zirconia stone will feel heavier than a lab-grown diamond of the same size.

Chemical Composition:

Cubic zirconia and lab-grown diamonds also have different chemical compositions. Cubic zirconia is made with zirconium dioxide (ZrO2), while lab-grown diamonds are made of carbon (C).


In terms of durability, cubic zirconia is softer than lab-grown diamonds and is therefore more susceptible to scratching and chipping. However, both materials are considered to be very durable and long-lasting.


When it comes to clarity, lab-grown diamonds can have inclusions or blemishes. Inclusions are imperfections that can be found within a stone, and they can affect a stone’s clarity. Cubic zirconia is completely flawless, having no imperfections.


The term “carat” is used to describe the weight of a gemstone. One carat is equal to 200 milligrams. Cubic zirconia and lab-grown diamonds can be found in a wide range of sizes, but a cubic zirconia stone will feel heavier than a lab-grown diamond of the same size. This is because cubic zirconia has a higher specific gravity than lab-grown diamonds.

Quality Grade:

They are not graded in the same way. The 4C’s (cut, color, clarity, and carat weight) are used to grade natural diamonds and Lab-grown diamonds. Cubic zirconia has a different system to measure quality. There are six different categories are used to describe the cubic zirconia’s characteristics. The highest quality cubic zirconia is usually regarded as an AAAAA quality stone. On the other hand, the lowest quality is referred as AB. (AAAAA is the highest quality, followed by AAAA, AAA, AA, A, and AB which is the lowest quality.)


If a diamond is lab-grown or mined, a color grade D is considered to be completely colorless, which is extremely rare. Most couples avoid buying a completely colorless diamond because it’s extremely expensive. Instead, they prefer to look for diamonds that are either near-colorless or graded J through G. Even if the stone has a yellow tint, it wouldn’t be noticeable to the naked eye.

Cubic zirconia is 100% colorless. The form of cubic zirconia is a flawless, colorless stone. However, it’s also possible to find modified cubic zirconia in a wide range of colors, from yellow and orange to pink and blue.


Compared to a diamond, cubic zirconia has a lower refraction index, which means that when it’s polished or cut, it doesn’t have the same level of brilliance, fire, or scintillation a diamond has. This is because the light that passes through it doesn’t go through the same path as it does through a diamond. Also, when exposed to light, it produces more vibrant flashes than natural diamonds. So, in general, a diamond will appear to be more sparkly than cubic zirconia.


Now, we get to the big question, how do lab-grown diamonds compare in price to cubic zirconia?

The price of a lab-grown diamond depends on the size, quality, and clarity of the stone. A one carat, lab-grown diamond can cost anywhere from $2,000 to $4,000.

On the other hand, the price of a one-carat, cubic zirconia stone can cost anywhere from $10 to $100.

Cubic zirconia is a fraction of the price of a lab-grown diamond because they are much cheaper to make. But lab-grown diamonds are still much cheaper than natural diamonds!

The Technical Differences

The chart below shows a comparison of the two materials’ properties. You can see that they are quite different.

Cubic Zirconia Lab-grown Diamond
Composition Zirconium dioxide (ZrO2) Carbon (C)
Hardness (Mohs) 8.5 10
Refractive Index 2.15-2.18 2.417 – 2.419
Specific Gravity 5.6-6.0 3.52
Dispersion 0.060 0.044
Florescence None Blue, yellow, orange, red, green, pink
UV Reaction Fluoresces No reaction
Cost per Carat $10-$100 $2,000-$4,000

As you can see, there are quite a few differences between cubic zirconia and lab-grown diamonds.

How to Tell the Difference Between a Lab-Grown Diamond and Cubic Zirconia.

The differences between a lab-made diamond and a cubic zirconia gemstone can be quite obvious to spot. Some of the differences that you can spot even if you are not a qualified gemologist are:

1. Look for Imperfections

If the stone does not have any common traits of a real diamond such as black spots, lines, or any other imperfections, then the likelihood is it’s cubic zirconia.

2. Light produces a Bright Rainbow Color

If you were to shine light through a cubic zirconia gemstone, it would produce a bright and colorful rainbow color. When light passes through a real diamond, it does not produce a rainbow of colors.

3. The Breath Fog Test

One way you can determine whether a diamond is real or a cubic zirconia gemstone is when you breathe against the diamond, a real lab-grown diamond will not leave fog from your breath on the diamond. However, a cubic zirconia will remain foggy for some time.

4. Ask a Jeweler

If you are still unsure whether your gemstone is a real lab diamond or cubic zirconia, the easiest path to take is to visit a diamond jeweler for a small fee. They will have an electric device that can test for real or fake diamonds. This will be accurate and able to tell you if your gemstone is a real diamond or not.

5. Buy a Diamond Tester

For as little as $20, you can buy a diamond tester to see if your diamond is real or not. I reviewed the best diamond testers a few weeks ago. Once you have a diamond tester, you can go wild and test all your jewelry. It’s kind of fun.

READ MORE >> Cubic Zirconia Versus Diamond: How to Tell Which is Real

People also ask

Are lab diamonds better than cubic zirconia?

I would say that lab-grown diamonds are better than cubic zirconia. This is because they are just like a mined diamond and hold value. Cubic zirconia is somewhat worthless.

Compared to cubic zirconia, man-made diamonds are also more durable. This is because the difference in the hardness of the two types of stones is significant. For instance, while synthetic diamonds have a rating of 10 on the Mohs scale, cubic zirconia has an 8.5.

How do you tell a CZ from a lab diamond?

Compared to diamond, cubic zirconia is slightly heavier. Also, since cubic zirconia slightly denser, a lab-grown diamond with the same weight will not be the same size (it will be smaller) as one with the same amount of weight.

Are lab-grown diamonds like cubic zirconia?

No, they are not. Cubic zirconia is made from synthetic materials in a lab, while lab-grown diamonds are made completely of carbon. Lab-grown diamonds are real diamonds and cubic zirconia is not.

Although imitations of natural diamonds, such as cubic zirconia and moissanite, are commonly referred to as diamond simulants, lab-grown diamonds are actually not. They are physically, chemically, and optically indistinguishable from natural ones. Since diamonds are made of carbon, they’re considered to be the toughest types of stones on the market.

Can a jeweler tell if a diamond is lab created?

Yes, a jeweler has specialized equipment that can determine if a diamond is lab-grown or natural. Here is a video that explains the process.

Are lab-grown diamonds worth money?

I would say that lab-grown diamonds are worth money. I like that they are environmentally friendly and that they hold value. Compared to natural diamonds, lab-grown diamonds are less valuable. However, unless you’re planning on spending a lot of money on a large, fancy-colored diamond or a rare blue diamond, a natural stone will not appreciate much anyway. I do like the idea of supporting the future of diamonds, which are lab-grown, over mined diamonds, but it’s ultimately up to you.

Are cubic zirconia real diamonds?

A cubic zirconia gemstone is human-made from synthetic materials, not carbon like real diamonds. Because of this, cubic zirconia is not considered a real diamond. It is instead what you could classify as a cheap imposter, a fake diamond. It does look like a diamond but has a lot of differences.

Is cubic zirconia a synthetic diamond?

Cubic zirconia is produced from synthetic zirconium dioxide in its crystalline form. Despite them being made from a synthetic material, they are not classed as diamonds. This is because they contain zero-carbon. Both earth-mined and lab diamonds are made entirely from carbon.

Lab diamonds are identical to mined diamonds, something which a cubic zirconia gemstone isn’t due to all the differences we explained above.

The Bottom Line: Cubic Zirconia vs. Lab-Grown Diamonds.

Cubic zirconia is not a real diamond. It is made of synthetic materials in a lab and does not have the same value as a mined or earth-grown diamond. Lab-grown diamonds are made completely of carbon and are identical to mined diamonds. They are more durable and hold their value better than cubic zirconia.

So, there you have it! These are the main differences between lab-grown diamonds and cubic zirconia. I hope this helped to clear things up for you. Thanks for reading!

Carl A. Jones, GIA GG

Carl A. Jones is a GIA Graduate Gemologist with over 20 years of experience in the diamond industry. He is an independent jewelry appraiser. He specializes in determining the value of diamonds and advising consumers on how to buy quality diamond jewelry.

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