Lab-Grown Diamonds vs. Moissanite: What's Actually Different

Both stones are grown, not mined, and both are sold as alternatives to a traditional mined diamond — which is where the similarity ends. They are different minerals.

What each one actually is

A lab-grown diamond is carbon, arranged in the same crystal structure as a mined diamond, produced by either high-pressure-high-temperature (HPHT) or chemical vapour deposition (CVD) methods rather than formed underground over geological time. Graded on the same 4Cs — cut, colour, clarity, carat — by the same laboratories, because chemically and optically it is a diamond.

Moissanite is silicon carbide. It occurs naturally in vanishingly small quantities (first identified in a meteor crater) and is lab-created for jewellery use. It is not a diamond and is never sold as one — it's its own stone, valued for its own properties.

Where they actually differ

Hardness. Diamond, lab-grown or mined, is a 10 on the Mohs scale — the hardest natural material there is. Moissanite sits at 9.25, still hard enough for daily wear, but a step below.

Fire and brilliance. Moissanite has a higher refractive index than diamond, which means more dispersion — the flashes of rainbow colour you see when the stone moves. Some people want that. Others find it reads as slightly less like a traditional diamond's white sparkle, and prefer diamond's brilliance instead.

Price. Moissanite costs a fraction of an equivalent-carat lab-grown diamond, which is most of its appeal for a larger stone at a given budget.

How to tell them apart

A jeweller checks with a thermal or electrical conductivity tester — moissanite conducts electricity, diamond doesn't, which is the one property older diamond testers (built for spotting cubic zirconia) couldn't distinguish. Visually, under strong light, moissanite's extra fire is the giveaway to a trained eye.

Neither is a compromise. They're different stones for a different brief — and both, unlike a mined diamond, come with no mining footprint attached.