Cubic Zirconia vs. Diamond What's the Difference

If you’re looking for a sparkling white stone to add some magic to your jewelry, diamonds are the classic choice. But they’re not the only option.

One of the most frequently used alternatives is cubic zirconia. But what is it? How similar or different is it to a diamond? And what are the benefits and drawbacks of choosing it for your jewelry?

We’re going to look at all these questions as we investigate cubic zirconia versus diamond. So if you’re ready, step this way to find out everything you need to know!

What is cubic zirconia (CZ)?

What is cubic zirconia (CZ)
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Unlike natural diamonds, which are mined, cubic zirconia is a man-made substance. It has a cubic crystalline molecular structure like diamonds. But where diamond is a form of pure carbon, cubic zirconia is made of a substance called zirconium dioxide.

And cubic zirconia isn’t the same as a laboratory-grown diamond either. Lab-grown diamonds have exactly the same physical composition as natural diamonds, being made of pure carbon.

The crystalline structure of melted zirconium dioxide was discovered in the 1930s. But it wasn’t until the 1960s that a single cubic zirconia stone was produced.

The creation was nothing to do with jewelry. The scientists who produced it were looking for an alternative to rubies to use in producing lasers. But the crystals that were formed were too small to be used in jewelry.

That changed in the 1970s. Russian scientists figured out a way to grow the crystals, producing a stone they called Djevalite. The stones were marketed as an alternative to diamonds, but at first they weren’t commercially successful.

It wasn’t until Swarovski, already a renowned manufacturer of lead crystal, developed its own product that the stones became a hit. It was Swarovski who also coined the term “CZ” as an abbreviation for cubic zirconia.

Although we’re used to thinking of cubic zirconia as white, it can be made in different colors too. Pink, green, yellow and purple stones are popular. And it’s even possible to find multicolored cubic zirconia.

How similar is cubic zirconia to diamond?

We’ve already seen that the chemical composition of cubic zirconia is quite different to that of diamond. But does that mean you can tell the difference between them with the naked eye?

Well, at first glance the two stones look very similar. But a closer inspection will usually enable you to tell which is which. Let’s take a look at how to do just that.

Cubic Zirconia vs. Diamond – Hardness

Cubic Zirconia vs. Diamond - Hardness
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One of the main differences between cubic zirconia and diamond is how hard the stones are. Diamond is that hardest substance on earth, which is why it’s used in drilling equipment as well as jewelry. For that reason, it scores a perfect 10 on the Mohs’ scale, which measures hardness.

Cubic zirconia, in contrast, scores about 8 on the Mohs’ scale. That means it isn’t quite as robust.

That can be particularly important if you’re looking for a stone for jewelry you’ll wear often or every day. And it’s especially likely to be an issue for jewelry worn on or near the hands, like rings and bracelets. A ring set with cubic zirconia will be more vulnerable to damage from knocks and bumps.

The difference in hardness is also behind other visual differences between cubic zirconia and diamonds. The softer stone will have less sharp facets, with a more rounded look. And cubic zirconia will show marks of polishing on its surface, which won’t be present on a diamond.

Cubic Zirconia vs. Diamond – Weight

Cubic Zirconia vs. Diamond - Weight
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Cubic zirconia also differs in its density to diamond. Despite being softer, it’s a denser material – about 1.7 times as dense, in fact. That means that if you have two stones of equal size, the cubic zirconia will be noticeably heavier than the diamond.

That poses a problem for some simple, traditional diamond-testing techniques. One approach to testing whether an unmounted stone is a genuine diamond is to drop it in water. If it sinks, the story goes, it’s the real thing.

That may be the case for lightweight diamond substitutes, such as those made of glass or quartz. But many artificial stones, including cubic zirconia, will also sink to the bottom.

If you like a ring with more presence on your finger, the heavier cubic zirconia can be a good option. Note, however, that your setting will also make a difference to the overall weight. Platinum – often used with diamonds but rarely, if ever, with cubic zirconia – is much heavier than gold or silver.

Cubic Zirconia vs. Diamond – The play of light

Cubic Zirconia vs. Diamond - The play of light
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One of the most distinctive characteristics of real diamonds is the way they reflect the light.

One aspect of this is what’s known as refraction – the way light is reflected from the sides of the stone. Different materials refract light differently. Cubic zirconia has a refractive index of between 2.15 and 2.18. That compares to an index of 2.42 for diamond.

That difference means that when light enters a diamond, it will slow down much more than when it enters a cubic zirconia. But that in itself doesn’t necessarily make much difference to what you see.

What makes more difference is the dispersion of light. This is the extent to which the stone splits the light that passes through it into its constituent colors.

Dispersion is what gives you the flash of rainbow colors in both a diamond and a cubic zirconia. And it’s why you’ll often hear people talking about diamonds having “fire”.

Dispersion can be measured too, and it’s much higher for cubic zirconia than for diamond. A cubic zirconia has a dispersion of between 0.058 and 0.066. That’s much higher than the 0.044 of diamond. What this means is that you’ll get more rainbow flashing with cubic zirconia than with diamond.

For some people, this is a giveaway that it’s not the real thing. And there are disparaging comments about the “glitter ball” look of cubic zirconia – mostly from the diamond industry. But if you like a bit of flash and sparkle, cubic zirconia offers more color into the bargain.

Cubic Zirconia vs. Diamond – Color

Cubic Zirconia vs. Diamond - Color
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White diamonds are graded on a color scale that surprisingly runs from D to Z. (It replaced earlier scales that used multiple As and ran to C, so this was intended to avoid confusion.)

Each grouping of letters signifies a gradation on the color scale. So diamonds graded D to F are colorless and those from G to J are “near colorless”. These are the ones generally used in jewelry.

The closer to colorless a diamond is, the more expensive it is too. But that isn’t an issue when it comes to cubic zirconia.

Because CZ is manufactured, it can be made colorless relatively easily. So if you’re looking for a crisp white stone that will work with a white metal setting, it’s a good bet.

Cubic Zirconia vs. Diamond – Price

Cubic Zirconia vs. Diamond - Price
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The major advantage of cubic zirconia over diamonds is its price. The stones can be produced inexpensively and on demand. That translates to a price that’s about 90 times lower than that of diamonds.

That means you can get a great looking piece of jewelry at a fraction of the cost. But it also means that the resale value of cubic zirconia jewelry is negligible. And it doesn’t make as impressive a gift as a real diamond.

Unless you’re spending time with a qualified gemologist, however, it’s unlikely anyone will know the difference.

Some people choose cubic zirconia jewelry as temporary replacements for pieces featuring diamonds. You may not want to take a very expensive ring on holiday, say. And if your budget is tight, a cubic zirconia ring can make an excellent stand-in until you’ve saved up for a diamond.

Watch out for grading of cubic zirconia

Watch out for grading of cubic zirconia
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We all know that diamonds come in different grades. We’ve already talked about color, but there’s also clarity and carat (weight).

All white cubic zirconias are virtually colorless, so there’s no grading there. And as man-made stones, they’re also free of flaws and blemishes – so clarity is perfect too.

You may nevertheless come across some retailers offering different grades of cubic zirconia. We’ve seen some examples touting AAAAA stones as the best quality, with A grades the lowest. So what do those grades mean?

The short answer is, very little! It’s essentially a clever marketing tactic, designed to get people to spend as much as they can afford on the product. But whether you opt for a five-A CZ or a single A stone, the chances are the only difference between them will be the price.

Impact on people and the planet

Diamond mining has a significant environmental and social impact. The sale of “conflict diamonds”, mined from countries like Angola and Sierra Leone, has helped fund murder and oppression. Conditions in some diamond mines are dangerous, and forced labor has been used.

The Kimberley Process was designed to remove conflict diamonds from the market. There are, however, differing views on how successful that has been. In 2011 the human rights organization Global Witness left the scheme, saying it had failed to break the link between violence and diamonds.

Diamond mining also has a significant environmental impact. Poor mining practices can lead to soil erosion, drought and deforestation.

But it is also an important source of income and employment in some developing countries. Some programs, such as DDI@RESOLVE, aim to promote responsible diamond sourcing. The aim is to support economic development without harming human rights or the environment.

These complex issues don’t apply in the same way to cubic zirconia. There are, however, some environmental impacts from the production of cubic zirconia to be aware of.

The process of creating and growing the stones requires heat. And depending on where the laboratory is located, that can mean drawing power from fossil fuels.

How to tell the difference between diamond and cubic zirconia

When you’re buying a piece of jewelry, a key giveaway is price. If it’s a few dollars, that white stone will be cubic zirconia (or another diamond substitute).

But don’t assume that a piece of jewelry contains diamonds just because it’s expensive! If you’re spending real-diamond-money on your item, ask for certification for your stones. That certification should come from a respected body such as the Gemological Society of America.

The right documentation will give you confidence that you’re paying a fair price for your jewelry. And it will tell you about the stones it contains – their color, clarity, carat and cut.

There are other tests you can do to get a better idea of whether your stone is a diamond or cubic zirconia. We’ve already seen that dropping them in water won’t do – both cubic zirconia and diamond will sink to the bottom.

Some tests will tell you which is which, but risk damaging or shattering the stone if it’s cubic zirconia. Rubbing sandpaper across the surface, for example, will scratch CZ but not diamond. And heating it in a flame can cause cubic zirconia to shatter, while a diamond will be unaffected.

But for a less brutal way to check your stone, invest in a heat probe tester. These are readily available online and don’t cost a lot of money.

They work because cubic zirconia conducts heat much more slowly than a diamond. The heat probe measures the length of time it takes for a substance to heat up. It matches the rate against the known thermal conductivity of diamonds and cubic zirconia.

If the rate of heat transfer matches that of a diamond, an LED will be illuminated on the tester.

Ready to choose between diamond and cubic zirconia?

That brings us to the end of our look at cubic zirconia versus diamond! We hope it’s helped you understand the similarities between the two stones, as well as their differences.

Cubic zirconia may not have the traditional cachet of diamond, but it has plenty to recommend it. It’s a great choice to add sparkle to an inexpensive substitute ring, or for a temporary ring while you save up for a diamond.

But cubic zirconia jewelry is also beautiful and elegant in its own right. And you won’t have to worry about its production funding conflict or oppression.

Whether you choose diamond or cubic zirconia, you’ll be getting sparkling jewelry to love. Enjoy wearing it, and happy shopping!

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