Cubic Zirconia VS Diamond – 6 Key Differences & A Few Alternatives

Cubic zirconia and diamonds are two of the shiniest, most sparkly stones you could every find in jewelry. Both appear radiant, brilliant, and they can make any engagement ring pop. But, they have some pretty clear differences which are not exactly easy to spot by the untrained eye.

Today we’re taking a closer look at cubic zirconia vs diamond. We’ll take a look at they key differences, and whether it truly matters which stone you have. Let’s take a look.

diamond cubic zirconia

Cubic zirconia vs diamond

Cubic zirconia is a softer gem than diamond, and it will scratch and lose its sparkle in time. A diamond has a higher refractive index so it will show equal parts white and colored light, while cubic zirconia shows mostly colorful light (especially orange-blue). Diamonds are usually natural diamonds, while cubic zirconia is always a lab-grown gem, and this creates a steep price difference between the two.

In terms of appearance, at first glance diamonds and cubic zirconia look the same. Their price, sparkle, and how well they hold up over time is what will really make a difference in the long run.

Both stones look beautiful in jewelry, and both can be a great option for an engagement ring. But let’s take a closer look at their differences, so you know what you’re wearing (or planning to wear).

1. Cubic zirconia is always a synthetic gem

Diamonds have always been natural gemstones, as they were mined from the earth since the dawn of time. They’re valued for the amount of labor that is put into digging them up and then transforming them into what now sparkles on many hands. There are lab-grown diamonds but those tend to have much lower sales than natural diamonds.

Cubic zirconia is always a lab-grown gemstone. This comes with a host of perks such as being conflict-free, and also having better color, or rather a better control over what color will be produced.

One of the key grading factors for diamonds is color. The whiter the diamond, the higher the price. Diamonds range from white (as in colorless) to yellow in their natural state. Any natural diamond has at least a slight yellow tint, even the ones that appear colorless. But you can only se what with a jeweler’s loupe or a microscope. To the untrained eye it appears white. Lab grown diamonds are able to achieve a perfect color without too much trouble, but they are considered less desirable, since they’re lab grown.

Cubic zirconia has a much easier time getting the perfect color, as it’s a lab-grown diamond simulant, and can thus produce any color the client wants.

Read also: Black Diamond Engagement Ring Meaning

2. Diamonds have a higher refractive index

And why does a diamond’s color matter ? It influences the final sparkle of the diamond, which in turn is dictated by its refractive index. Diamond has the highest refractive index for a natural gem – 2.42 – and this gives it brilliance and fire, the white and colored light show. The only other gem that has a higher index than diamond is moissanite (2.62), but this is a lab-grown diamond simulant.

Cubic zirconia has a refractive index of 2.15, which is still pretty nigh but light will not behave in the exact same way it would in a diamond. Why does this index matter ? It’s a way of seeing how well light travels through a material.

When the round brilliant cut was patented, it was produces especially and directly for diamonds, because it took into account the gem’s refractive index. This means each facet was cut in such a way as to optimize the amount of light that went in and traveled through the diamond. The result is the best fire and brilliance possible for a diamond.

A different material cut in the same way would not offer the same light play, because it cannot handle light the same way. So a diamond and a cubic zirconia of the same carat and the exact same shape and cut would appear to sparkle differently.

3. Cubic zirconia is significantly softer than diamond

One of diamond’s selling points is how tough it is. This gem doesn’t scratch at all, and it’s pretty much the toughest material known to man. Cubic zirconia on the other hand is a much softer material, and this mean it can wear down in time, and lose its sparkle.

Take a look at a piece of glass with lots of scratches on it. Where there are abrasions and scratches, the light doesn’t go through as it normally would, it’s diffused. This happens to cubic zirconia as well, and over time it will become dull.

These are all things measured by the Mohs scale of hardness. Where a diamond scores a perfect 10, cubic zirconia scores 8.5. This is a logarithmic scale, meaning 8.5 is much, much, much smaller than 10.

So what does this mean if you’re looking for a big rock to propose with ? Anything over 1 carat will begin to show some clear signs of wear and tear if it’s cubic zirconia. Because of this, we recommend working with smaller stones and providing a better setting, such as pave or bezel.

4. Diamonds have equal parts sparkle and fire

Diamonds have a different light show than cubic zirconia, which in turn is dictated by its refractive index. In short, cubic zirconia will offer more colorful flashes and less white flashes, otherwise known as fire and brilliance. This is not necessarily a bad thing, if you’re looking for any sparkle at all.

Diamonds offer equal parts white and color flashes, adding to its general appeal. So that’s one way to tell the difference between cubic zirconia and diamond. But this only works if you’ve got both gems next to each other.

The gem’s cut also influences this heavily. Any brilliant cut will bring out more flashes than a step cut, regardless of the material used.

So if you’re just looking for a sparkly gemstone, both diamond and cubic zirconia will do. If you don’t mind a very colorful sparkle, then cubic zirconia will do just fine.

5. Cubic zirconia is more affordable than diamond

Due to cubic zirconia’s tendency to offer more colorful light, the fact that it’s lab-grown, and its softness compared to diamond, CZ is actually much more affordable than diamond.

This doesn’t mean it’s a cheap stone by any means. But it’s within the lower hundreds, which doesn’t even begin to compare to how much a diamond would cost. If you’re shopping on a budget, or if you really just want a ring and don’t mind what kind of stone it has, a cubic zirconia will not put you in debt.

6. Diamonds appear larger than cubic zirconia

Diamonds have a density of 3.5-3.53 gr/cm3, while cubic zirconia has a density of 5.6-6.0 gr/cm3. That’s nearly double ! So a 4×4 mm diamond is usually around 0.50 carats, while a 4×4 mm cubic zirconia is about 0.35 ct. 

Diamonds and cubic zirconia have different densities, which means the same amount of diamond and CZ will weigh differently. One of the ways to establish a price for a diamond is carat weight. The keyword here is weight, because a 1 carat diamond will appear larger in millimeters than a 1 ct cubic zirconia.

This means that you should take a very close look at what you’re buying. A 5 ct cubic zirconia ring won’t be as large as a 5 ct diamond ring, but it will be far, far more affordable. Which is fine because you can easily buy a larger CZ ring without much of a price difference.

Can you sell or pawn off cubic zirconia ?

Cubic zirconia has no resale or pawn value. This means if you ever find yourself in the position to sell your jewelry the cubic zirconia in it will not be worth anything. By comparison a diamond is always worth more than the metal in whatever jewelry you’re selling.

Will anyone notice it’s not a diamond ?

The vast majority of people won’t notice you’re wearing cubic zirconia instead of diamond. Unless you’re talking to a gemologist or jeweler, who have sharp eyes and have seen these stones every day. But regular people can’t easily tell the difference, if you’re worried about that.

In the end it’s really your opinion that matters the most, since this is your jewelry. If you’re in love with that pair of cubic zirconia earrings then no amount of side-eye should be able to make you stop wearing them because they’re not diamonds.

Take for example this pair of snowflake earrings off Amazon.

They’re cubic zirconia set in sterling silver, and they’re just the cutest pair of earrings we’ve ever seen ! Would anyone fault you for wearing CZ when they saw the earrings ? We don’t think so. These would make a really beautiful Christmas gift.

White gemstone alternatives to diamond

If you really, really just want a true, natural gemstone to wear but can’t afford a diamond, then there are a few other gems you can look at. In this case cubic zirconia and moissanite are out of the picture, because both are lab-grown. There are at least 4 versions of white gemstones you can wear instead.

White sapphire. Sapphires are usually blue, that’s true, but they are also white (or colorless). A sapphire does not sparkle as brightly as a diamond, no gemstone comes close. But does have some white flashes, and in some cases it might appear slightly cloudy since sapphires do tend to have inclusions in them.

White morganite. Morganite is generally pink, but you can sometimes find versions that are such a light shade of pink they appear almost white. These are very beautiful gemstones that are highly popular at the moment.

Goshenite (white beryl). Goshenite is a type of beryl, which is the same family as emerald and aquamarine. This is an incredibly clear gemstone and it can easily sit in place of a diamond. It won’t sparkle as much, but it’ll make for a very beautiful center stone.

White topaz. Like goshenite and white sapphire, white topaz doesn’t have as much sparkle as a diamond but it’s definitely a more affordable alternative to diamond, that is also natural.