Cubic Zirconia: What It Is and How It Differs From Diamond

Cubic zirconia is the most widely used diamond alternative in the world, and it is a genuinely good material rather than a poor substitute. It is not glass, it is not fake diamond, it is its own crystal with its own properties. Here is what it is, how it behaves, and what to expect from a piece set with it.

Key facts

What cubic zirconia is

Cubic zirconia, usually shortened to CZ, is a lab-grown crystal of zirconium dioxide. It was developed as an optical material and turned out to make an excellent gemstone.

Two things it is not. It is not glass, which is soft, amorphous and dull by comparison. And it is not a lab-grown diamond, which is chemically identical to a mined diamond. CZ is a different material entirely with its own character.

How it compares with diamond

• Hardness. CZ is 8 to 8.5 on the Mohs scale. Diamond is 10, and that scale is not linear, so diamond is very much harder. CZ will pick up surface scratches over years of hard wear.
• Fire. CZ actually disperses more coloured light than diamond, which is why it can look showier. To a trained eye that extra rainbow flash is the giveaway.
• Weight. CZ is substantially denser, so a CZ stone weighs noticeably more than a diamond cut to the same dimensions.
• Colour. CZ is grown colourless, and it is also grown in colours, which is why coloured stone settings are easy and affordable in it.

Why designers use it

Cost is the obvious reason, but it is not the only one. Because CZ comes in reliable colours, a designer can set a piece with green, blue, red and yellow stones without hunting matched natural gems at unreachable prices.

That is exactly what happens in Alexandra Hakim’s Canter collection. The Large Golden Horseshoe Earrings are set with square-cut stones in green, blue, red and pink, and the Silver Horseshoe Earrings with yellow. That palette would be prohibitive in natural stones on a piece at this price.

How to care for it

CZ is durable in normal wear, and the usual caveat applies: the setting and the metal around it are more fragile than the stone.

• Store separately. CZ scratches other CZ, and diamond scratches everything.
• Clean gently. Warm water, a drop of mild soap, a soft brush, dried thoroughly. On a plated piece, keep even that to a minimum and stick to a dry cloth.
• Avoid ultrasonic cleaners on plated settings, since they strip plating even when the stone is fine.
• Expect a little dulling. Skin oils and cosmetics film over stones. A wipe after wear keeps the sparkle.

Should it change your buying decision?

Only if you are buying for material value. A CZ piece is bought for design and for how it looks, not as a store of wealth, and the price reflects that honestly.

For a handmade designer piece at a few hundred dollars, CZ is exactly the right material. It lets the design carry the value and keeps the piece something you actually wear rather than something you insure.

How to tell cubic zirconia from diamond

There are a few reliable tells, and none of them require equipment.

• Fire. CZ throws more coloured flashes. A stone showing strong rainbow sparkle across the whole surface is usually CZ.
• Weight. CZ is substantially denser, so a CZ stone feels heavier than a diamond of the same dimensions.
• Edges. Under magnification, CZ facet edges soften with wear where diamond edges stay crisp.
• Flaws. CZ is grown near-perfect. A stone with no inclusions at all, at a low price, is not a diamond.

The context usually answers it before any of this. A handmade designer piece at a few hundred dollars is set with CZ, and reputable retailers say so plainly rather than leaving it vague.

Coloured stones

This is where CZ is genuinely better than the alternative rather than merely cheaper.

Natural coloured gemstones are hard to match. Sourcing eight small stones in the same green, at the same clarity, at a price that works on a 570 dollar earring is close to impossible. CZ is grown to specification, so a designer can set a precise palette and repeat it.

That is exactly what the Large Golden Horseshoe Earrings do with green, blue, red and pink, and what the Silver Horseshoe Earrings do with yellow against cool silver.

Frequently asked questions

What is cubic zirconia?

A lab-grown crystal of zirconium dioxide, used as a gemstone. It is not glass and it is not a lab-grown diamond, which is a different material chemically identical to mined diamond.

Does cubic zirconia look like a diamond?

To most eyes, yes. It actually disperses more coloured light than diamond, so it can look showier, and that extra rainbow flash is one of the giveaways to a trained eye.

Does cubic zirconia scratch?

It can. CZ is 8 to 8.5 on the Mohs scale against diamond at 10, so it picks up surface scratches over years of hard wear. Storing pieces separately prevents most of it.

Does cubic zirconia lose its sparkle?

It films over with skin oils and cosmetics rather than degrading. A wipe after wear and an occasional gentle clean restores it.

Why do designers use cubic zirconia?

Cost, and colour reliability. CZ is grown in consistent colours, so a designer can set green, blue, red and yellow stones in one piece without sourcing matched natural gems at unreachable prices.

How can I tell cubic zirconia from a diamond?

CZ throws more coloured flashes, is noticeably denser so it feels heavier for its size, and is grown near-flawless. The price and context usually answer the question first.

Are coloured cubic zirconia stones worse than natural gems?

For a designer piece at this price they are better suited. Natural stones are almost impossible to match in colour and clarity at small sizes, while CZ is grown to a specification and can be repeated exactly.

Read next

• Gold plated brass, explained
• The Canter horseshoe collection
• The care guide
• Is Alexandra Hakim a luxury brand?

Sources

• Alexandra Hakim, About the designer
• Alexandra Hakim, Jewellery care
• Arab News, Lebanese designer using natural resources to make jewelry
• FashionUnited, Career Q and A with Alexandra Hakim

Prices and stock are as listed on Coveti at the time of writing and change with availability.

Written by Gemma Deeks, Fashion Editor at Coveti.