Stone Guide
Moissanite, Zircon, Lab-Grown: What Actually Sets Them Apart
They are three separate materials, not grades of one. Lab-grown diamond is chemically a diamond (Mohs 10). Moissanite is silicon carbide (Mohs 9.25) and throws more coloured fire than a diamond. Cubic zirconia is zirconium dioxide (Mohs 8-8.5), the cheapest of the three, and dulls with years of daily wear.
| Moissanite | Cubic zirconia | Lab-grown diamond | |
|---|---|---|---|
| Material | Silicon carbide | Zirconium dioxide | Carbon (a real diamond) |
| Mohs hardness | 9.25 | 8 - 8.5 | 10 |
| Refractive index | 2.65 - 2.69 | 2.15 - 2.18 | 2.42 |
| Brilliance | More coloured fire than diamond | Softer, less fire | Diamond, by definition |
| Holds up to daily wear | Yes | Edges abrade over a few years | Yes |
| Relative cost | Mid | Lowest | Highest of the three |
| Best for | Daily wear on a budget | Occasional pieces, trying a look | Diamond optics and permanence |
If you have shopped for a diamond alternative recently, you have met all three of these names — usually with very little explanation of how they differ. They are not grades of the same thing. They are three separate materials with different chemistry, different durability, and different reasons to choose them.
Moissanite
Moissanite is silicon carbide. It occurs naturally in meteorite fragments, but in practically every piece of jewelry you will encounter it has been grown in a lab — natural deposits are far too small and rare to cut.
Two properties define how it looks. It sits at 9.25 on the Mohs hardness scale, just under diamond at 10, which makes it genuinely suitable for daily wear. And its refractive index is higher than a diamond's, so it throws noticeably more coloured flash. Some people want exactly that fire; others find it reads as brighter than a diamond. Look at a larger stone in daylight before you decide — the effect is subtle at 1ct and obvious at 3ct.
Cubic Zirconia
Zircon in the jewelry trade almost always means cubic zirconia — zirconium dioxide, a fully synthetic material. It is the most affordable of the three by a wide margin, and a well-cut stone looks excellent when new.
The trade-off is durability. At around 8 to 8.5 on the Mohs scale it is softer than the other two, and the facet edges gradually abrade with everyday contact. Over a few years of constant wear a CZ tends to lose its crispness and cloud slightly. That makes it a strong choice for occasional pieces, statement earrings, and trying a silhouette before committing — and a weaker one for something you never take off.
Lab-Grown Diamond
A lab-grown diamond is a diamond. Same carbon lattice, same 10 on the Mohs scale, same optical behaviour — the only difference from a mined stone is the growth environment and the price, which typically runs well below a mined equivalent of the same specification.
If you want the exact optical character of a diamond rather than something adjacent to it, this is the only one of the three that delivers it. Reputable lab-grown stones are laser-inscribed and certified, so the provenance is documented rather than assumed.
How to choose
Pick a lab-grown diamond when you want diamond optics and diamond permanence. Pick moissanite when you want maximum brilliance per dollar in a piece that will take daily wear. Pick cubic zirconia when the piece is occasional, the design is the point, or you are testing a look.
Whichever you choose, the setting matters as much as the stone. A well-made bezel or a secure prong protects the girdle from the knocks that dull any stone over time.
