Cubic Zirconia vs. Diamond: Differences You Should Know

a wedding diamond jewelry set

Diamonds and cubic zirconia stones look similar, especially from a distance. The clear and sparkling gems have significant differences in quality, durability, and value. After learning about the differences between the two stones, it becomes easy to identify them. Looking at them side by side, there are ways to tell them apart. 

It’s always best to have a professional ensure your jewel’s authenticity. Still, there are simple you can check gem authenticity on your own. When comparing prices, it’s smart to know you are getting what to expect, especially if you think you are buying a diamond.

What Is a Diamond?

A diamond is a naturally occurring mineral made of a carbon atom surrounded by four more carbon atoms. Its structure makes diamond the hardest natural substance on the planet. 

Diamonds are chemical-resistant and have high thermal conductivity, making them popular tools in manufacturing. Because diamonds also have a beautiful luster and refraction, they have become iconic gemstones, too. 

These beautiful gemstones are durable, customizable, and fashionable. Their beauty and versatility are why they adorn engagement rings and serve as the April birthstone. Designers cut diamonds with facets to reflect the light. They also cut them into a variety of shapes, from round to heart-shaped.

Diamonds come in several varieties, including naturally mined, lab-grown, treated, and fancy-colored. 

Natural diamonds come from mines, while lab-grown diamonds are manufactured but have the same atomic composition as natural diamonds. There are also colored diamonds, though they are rarer. 

How to Tell If a Diamond Is Real

Close-up of a jeweler using a loupe to check the quality of a diamond

The easiest way to determine if your diamond is genuine is to take it to a certified jeweler or a gemologist. The jeweler will use a loupe to look closely at the diamond to see if it is legitimate. They also have diamond testers that check the heat that passes through the diamond. They touch the tester to the diamond then the tester lights up to share whether the diamond is natural. 

Diamonds won't scratch, so you can test the stone by trying to scratch it. If the stone is not a diamond, you’ll be able to see any scratches it may have. To double-check your stone, you can look for a scratch under a microscope. Under a microscope, you can see if the diamond is genuine if the facets are scratch-free. 

Another test involves heating the diamond for 40 seconds, then dropping it in a bowl of cold water. You’ll need a flame from a candle or lighter and fire-proof gloves to hold the diamond. If it is a faux diamond, it will break. 

Diamonds are the hardest natural substance on Earth and will not shatter under these conditions. Of course, do not do this if you don’t want to risk breaking your jewelry.

You can also test diamonds with a bright light. Hold the diamond up to bright light, like the flashlight on your smartphone. If you have a diamond, it should sparkle brilliantly. Cubic zirconia will emit a rainbow of light, but not at the extreme that diamonds show light. 

All About Cubic Zirconia

Cubic zirconia (or CZ) is an affordable, lab-created alternative to diamonds with a different chemical composition. They are not synthetic diamonds. They are heavier but not as hard. 

They are comparable to diamonds because they are clear stones that reflect light well. Cubic zirconia produces more rainbow flashes of light compared to diamonds. Fortunately, more jewelers are covering cubic zirconias with protective coatings. As a result, they are more durable and scratch-resistant. 

Cubic zirconia is not a naturally occurring stone. Instead, manufacturers produce them in labs using zirconium dioxide. Manufacturers melt zirconium oxide with stabilizers and heat it to nearly 5,000º F. After heating zirconium oxide, crystals form. Then, artisans cut and polish them. 

They first hit store shelves in the 1970s, providing consumers an affordable option for diamonds. They do come in several colors, and they can be cut into the same geometric shapes as diamonds. However, cubic zirconia can have more clarity than naturally occurring diamonds that often have occlusions (internal flaws). 

Cubic zirconia and lab-made diamonds are different. Lab-made diamonds are made of carbon, while CZ stones are made of zirconium. They have entirely different properties and similar appearances. 

Cubic Zirconia and Diamonds Compared

A diamond and a cubic zirconia on lighted holders

While the two stones look similar, they are rather different when it comes to properties and costs. 

Cubic Zirconia vs. Diamond – Clarity and Color

When shopping for diamonds, experts recommend looking for the Four C’s: cut, clarity, carat, and color. Consumers can choose the cut and carat (weight) they prefer. The clarity involves how clear the stone is, as many of them have some subtle flaws on the inside. The color can range from completely clear to black. 

Jewelers also grade cubic zirconia with the Four C’s, but they have a slightly different grading system that includes five tiers. The lowest grade CZ is rated A, while the highest quality is AAAAA. Because jewelers that sell a high volume of CZ jewelry buy in bulk, they don’t usually share the grades.

A diamond gives off a white light, while CZs show more colorful light. The clarity of the stone can affect how much light they emit. Usually, CZ looks flawless, giving them a look that many diamonds cannot replicate. A clear diamond will have a rating of VS1 or VS2, meaning that you cannot see any flaws with the naked eye.

 When shopping for a CZ, you’ll be hard-pressed to find anything other than clear. Diamonds have color rated between D to Z, with D being perfectly colorless and Z having a yellow tone. Most jewelers carry G to I with a colorless quality and an imperceptible tinge of yellow. 

Cubic Zirconia vs. Diamond – Refractive Index (RI)

Diamonds and CZ have a refractive index reflecting how much light bends as it passes through the stone. The CZ has a 2.15 to 2.18 RI, while diamonds have a 2.42 rating. The diamond has more brilliance because it reflects more light to the eye. Light travels faster through the stone. 

Cubic Zirconia vs. Diamonds – Brilliance and Sparkle

Both stones have a flash of lovely brilliance and sparkle, but they show different lights. Diamonds reflect white light, while CZ radiates a rainbow of color. 

The sparkle depends on the cut, as the number and position of facets create more sparkle under bright light. When light enters the diamond, it disperses it back in all colors, creating a diamond’s fire. If you see an excess of dispersion, it might mean that you found a fake diamond, as CZ has more dispersion, which is why they are known for reflecting rainbows of color. 

Cubic Zirconia vs. Diamonds – Origin & Sustainability

Two diamonds back-to-back on white background

Both gemstones have environmental issues that need to be fixed. Lab-created diamonds require surprising amounts of energy. Mining for diamonds also comes with several concerns, from human rights to environmental impact.

Heating zirconium to excessively high heat requires immense amounts of energy. So while they are considered a more ethical choice than mined diamonds, they also harm the environment.

Cubic Zirconia vs. Diamonds – Durability and Density

Diamonds are the hardest substance on Earth, so they are more durable than CZ. On the other hand, CZ is denser than diamonds and weighs more as well. If you wear your gems daily, diamonds will last longer and are less likely to chip than CZs. 

Cubic Zirconia vs. Diamonds – Value

Diamonds are significantly more expensive than cubic zirconia. The Four C’s affect the price of diamonds, as clearer diamonds with better cuts and more carats cost more than yellow diamonds with inferior cuts and fewer carats. 

Jewelers who sell discounted diamonds might be trying to trick consumers with cubic zirconia or inferior diamonds with internal flaws and other undesirable issues. A one-carat diamond with lovely facets and clarity can cost more than $10,000. A one-carat CZ is often worth less than $100. 

When shopping for diamonds, it is smart to buy only from reputable jewelers. Remember that diamonds generally do not appreciate, as they often drop in value by at least 50% as soon as you bring the stone home. Lab-grown diamonds cost about 40% less than mined diamonds.


Always check for authenticity to determine whether you are getting a diamond or cubic zirconia. Scammers who sell jewelry online try to pass off cubic zirconia as diamonds at low prices. Still, you’ll be paying much more than you typically would for cubic zirconia. 

Diamonds are a good choice for buyers who want brilliance and fire in a genuine stone that comes from a mine. They are popular engagement ring stones because diamonds last forever. However, if you want a lovely stone at an affordable price, cubic zirconia is a good choice. When choosing the perfect gem, what matters most is that you love the jewelry piece.