Lab-Grown Diamond vs. Moissanite vs. Cubic Zirconia: Which Should You Buy?

A lab-grown diamond is a real diamond, moissanite is a different (and flashier) stone, and cubic zirconia is a budget stand-in that will not stay bright. Those are the honest one-line answers, and the rest of this guide explains why they are true and how to choose between the three when you are shopping for jewelry with a clear white stone in it.

Lab-grown diamond vs. moissanite vs. cubic zirconia at a glance

The three stones differ in what they are made of, how hard they are, and how they handle light. Everything else in this guide follows from these numbers.

	Lab-grown diamond	Moissanite	Cubic zirconia
What it is	Crystallised carbon, identical to a mined diamond	Silicon carbide, a distinct mineral	Zirconium dioxide, a synthetic look-alike
Hardness (Mohs)	10	9.25	8 to 8.5
Brilliance (refractive index)	2.42	2.65 to 2.69	2.15 to 2.18
Fire (dispersion)	0.044, balanced white and rainbow flashes	0.104, strong rainbow flashes	About 0.060, noticeable rainbow
How it ages	Stays bright indefinitely	Stays bright, may need occasional cleaning	Scratches and clouds within a few years of regular wear
Typical price	A fraction of a mined diamond	Lower than lab-grown diamond	A few dollars per stone

What a lab-grown diamond actually is

A lab-grown diamond is chemically, physically, and optically the same as a diamond pulled out of the ground; the only difference is where the crystal formed. It is pure carbon arranged in the same cubic lattice, grown over weeks in a chamber rather than over a billion years underground. It scores a 10 on the Mohs hardness scale, which is why diamonds are the only stone on this list that essentially cannot be scratched in normal wear.

In the United States, the Federal Trade Commission's Jewelry Guides treat lab-grown diamonds as diamonds, provided the seller clearly discloses that they were laboratory-created. That disclosure matters: a stone described only as "diamond" is understood to be mined, so an honest retailer will always say "lab-grown" out loud. If you want the full backstory, our guide to lab-grown vs. natural diamonds covers how they are grown and graded.

What moissanite is, and why it sparkles differently

Moissanite is silicon carbide, a separate mineral that happens to be very hard and very bright, but it is not a diamond and does not look exactly like one. Natural moissanite is so rare (it was first identified in a meteorite crater) that virtually every moissanite in jewelry is lab-created.

Its defining trait is fire. With a dispersion of roughly 0.104, moissanite splits light into rainbow colour more than twice as strongly as a diamond, which produces the "disco ball" flash people either love or find too much, especially in larger stones and under direct sunlight. It is also doubly refractive, so under magnification the back facets can look slightly doubled. At 9.25 on the Mohs scale it is durable enough for daily wear and will not cloud the way cubic zirconia does. One practical note: moissanite conducts heat much like diamond, so it can fool a basic handheld diamond tester. That is not a mark against the stone, but it is a reason to buy from a seller who names what they are selling.

What cubic zirconia is, and why it stops looking good

Cubic zirconia is an inexpensive synthetic crystal of zirconium dioxide that looks convincing when new and visibly dull after a year or two of regular wear. The problem is hardness. At 8 to 8.5 on the Mohs scale, CZ is softer than the airborne quartz dust that settles on everything, so everyday contact with countertops, handbags, and other jewelry gradually abrades the facet edges. Once the polish goes, the stone stops returning light and starts looking like glass.

CZ is also noticeably heavier than diamond for the same size (its specific gravity is around 5.6 to 6.0 versus 3.52), which is one of the quickest ways a jeweller tells them apart. None of this makes CZ a bad choice for a costume piece you will wear a handful of times. It does make it a poor choice for anything you intend to keep, and CZ is very often set in brass or plated base metal, which is where the green-skin and tarnish complaints come from.

Which one should you buy?

Buy a lab-grown diamond for anything you want to wear for years, moissanite if you want maximum sparkle per dollar in a larger stone and do not mind that it is not a diamond, and cubic zirconia only for a one-off costume look. A few more specific situations:

• Accent stones in pearl jewelry. When a white stone is a small accent rather than the centrepiece, lab-grown diamond is the clear winner. The stones are tiny, so the diamond premium is small, and you get permanent brightness next to the pearl's soft glow. Our diamond jewelry uses lab-grown diamonds in exactly this way: for example, the Halo Pearl Pendant pairs a 7 to 7.5mm freshwater pearl with a 3mm, 0.11 carat lab-grown diamond.
• Everyday earrings. Earrings take less abuse than rings, so moissanite and lab-grown diamond both hold up. For small studs and drops the price gap is modest, and the diamond's calmer, whiter flash tends to read more refined beside a pearl. See our diamond earrings.
• A large solitaire on a budget. This is where moissanite earns its following. A one- or two-carat moissanite costs a small fraction of the equivalent lab-grown diamond and will still look crisp in a decade.
• A stone for a single event. CZ is fine here, but check the metal it sits in. A sterling silver setting will outlast the stone; a brass one may leave a mark on your skin before the night is over.

How to tell them apart when you are shopping

You usually cannot tell the three apart from a product photo, so read the listing and, if you can, look at the stone in daylight. Reliable tells: a description that says "diamond" with no qualifier should mean mined, "lab-grown diamond" or "laboratory-created diamond" means exactly that, and vague words like "simulated," "diamond-look," or "crystal" almost always mean cubic zirconia. Moissanite is usually named proudly because it is a selling point. In person, tilt the stone under a lamp: strong rainbow flashes point to moissanite, softer mixed white and colour flashes point to diamond, and a stone that looks slightly glassy or shows tiny surface scratches is likely CZ that has been worn.

Ask about the metal as well. Whatever the stone, a setting in 925 sterling silver or solid gold will keep its finish and stay comfortable on sensitive skin; base-metal settings will not. Every Pearl Luna piece is sterling silver with 18k gold plating, nickel-free, and never brass, and the lab-grown diamonds, sapphires, rubies, and emeralds we set are disclosed as lab-grown on every product page.

Caring for each stone

All three clean the same way: warm water, a drop of mild dish soap, a soft toothbrush around the setting, then a rinse and a lint-free cloth. Diamond and moissanite can be cleaned as often as you like. Cubic zirconia should be cleaned gently and stored on its own, because contact with harder stones is what wears it down. If the stone sits beside a pearl, skip ultrasonic cleaners and anything acidic; our guide to cleaning silver and gold-plated jewelry at home walks through the safe method.

Frequently asked questions

Is a lab-grown diamond a real diamond?

Yes. A lab-grown diamond has the same carbon crystal structure, hardness, and optical properties as a mined diamond; only its origin differs. The US Federal Trade Commission's Jewelry Guides recognise lab-grown diamonds as diamonds as long as the seller clearly discloses that they were created in a laboratory rather than mined.

Is moissanite better than cubic zirconia?

Yes, by a wide margin. Moissanite is far harder (9.25 versus 8 to 8.5 on the Mohs scale), so it keeps its polish and sparkle for decades, while cubic zirconia scratches and clouds within a few years of regular wear. Moissanite also has much stronger brilliance and fire. CZ's only advantage is its very low price.

Can you tell moissanite from a diamond?

Often, yes, especially in larger stones. Moissanite throws noticeably more rainbow-coloured fire than a diamond and is doubly refractive, which a jeweller can see under a loupe. In small accent stones the difference is subtle. Moissanite conducts heat like diamond, so it can pass a basic thermal diamond tester; an electrical tester separates them.

Does cubic zirconia lose its sparkle?

Yes. Cubic zirconia is soft enough that everyday contact with dust, countertops, and other jewelry slowly scratches its facets, and the stone also picks up skin oils readily. Both effects reduce the light it returns, so a CZ that looked bright when new usually appears dull or cloudy after one to three years of regular wear.

Which is the best value for everyday jewelry?

For small accent stones, lab-grown diamond is the best value because the premium over moissanite is minor and the brightness is permanent. For a large centre stone on a tight budget, moissanite gives the most sparkle per dollar and lasts. Cubic zirconia is only worth buying for occasional costume wear.