Lab-Grown Diamond vs. Cubic Zirconia: How to Avoid Confusion

When looking for an alternative to natural diamonds, two options often come up: lab-grown diamonds and cubic zirconia. They look similar at first glance. But they are two very different materials — and the confusion can be costly in the long run.

Here's what you need to know before choosing.

Cubic Zirconia: What exactly is it?

Cubic zirconia is zirconium dioxide (ZrO₂), an entirely synthetic material created in the 1970s as a diamond simulant. It has no chemical connection to diamond — it is a fashion stone, not a gemstone.

It is found in many low-cost fashion jewelry items, precisely because it resembles diamond at first glance and is very inexpensive to produce.

Composition: Two unrelated materials

A lab-grown diamond is composed of pure crystallized carbon — exactly like a natural diamond. This is what gives it its maximum hardness (10/10 on the Mohs scale) and permanent durability.

Cubic zirconia is composed of zirconium dioxide. Its hardness is 8 to 8.5 on the Mohs scale — which may seem close, but represents a significant difference in daily use. Common materials like quartz (found in dust and sand) have a hardness of 7: a cubic zirconia ring worn every day will eventually scratch and gradually dull.

Brilliance: Brilliant at first, aging over time

Out of the box, a cubic zirconia can be very brilliant — sometimes even more sparkling than a diamond, because its light dispersion is higher. Some find it too bright, with a rainbow effect sometimes perceived as artificial.

But the real problem appears after a few months of wear. Cubic zirconia dulls, gradually loses its brilliance, and becomes lackluster. A diamond — lab-grown or natural — maintains the exact same brilliance.

Price: An apparent saving

A cubic zirconia costs a few euros. An IGI-certified lab-grown diamond represents a more significant investment — but incomparably lower than an equivalent natural diamond.

The real question is not the purchase price, but the total cost over time. A cubic zirconia that degrades will need to be replaced. A lab-grown diamond has no expiration date.

What cubic zirconia cannot be

Cubic zirconia cannot be certified by IGI or GIA. These organizations certify only diamonds — natural and lab-grown. Therefore, there is no "IGI certificate" for cubic zirconia: if a seller offers you one, it's a red flag.

At Diamelys, every diamond comes with its IGI certificate with an online verifiable report number. This is the guarantee that you are purchasing a real diamond.

In summary

If you are looking for an inexpensive fashion jewelry item without expectations of long-term durability, cubic zirconia may be suitable.

If you are looking for jewelry to wear every day, to give for an important occasion, to keep and perhaps pass down — the IGI-certified lab-grown diamond is the option that will not disappoint you.

Frequently Asked Questions

Is cubic zirconia a real diamond?
No. Cubic zirconia is zirconium dioxide, a completely different material from diamond. It is a simulant, not a gemstone.

How do you distinguish cubic zirconia from a lab-grown diamond?
Visually, it's difficult at first glance. But an IGI-certified diamond has a laser-engraved report number on its girdle, verifiable online. Cubic zirconia has no equivalent certification.

Is cubic zirconia suitable for an engagement ring?
Not in the long term. It dulls and scratches with daily wear. For a ring meant to last, a lab-grown diamond is much more suitable.

Why do we still see cubic zirconia jewelry?
For fashion or costume jewelry worn occasionally, cubic zirconia is a valid option.

Discover our IGI-certified lab-grown diamonds — see our collections →