Diamond vs Moissanite: An Honest Guide for Modern Buyers

In 1893, the French chemist Henri Moissan was examining fragments from a meteorite crater in Arizona when he found tiny crystals he initially believed were diamond. They weren't. They were silicon carbide, a mineral that occurs naturally only in vanishingly small quantities, mostly delivered to Earth by meteorites, and it now carries his name. Natural moissanite is essentially never used in jewellery, because there isn't enough of it. Almost every moissanite stone sold today is lab-created, grown specifically to be worn, not mined and hoped for. Charles & Colvard, the company that first patented lab-created moissanite for jewellery, remains one of the best-known names in the category, though the original patent has since expired and moissanite is now widely produced by other houses too.

That history matters because moissanite gets talked about almost exclusively as diamond's budget stand-in, and that framing undersells what it actually is: a genuine gemstone with its own chemistry, its own optical behaviour, and in one specific respect, more sparkle than diamond has. This is a guide to what's actually different, honestly, including the parts most moissanite retailers don't lead with.

In Brief: Diamond is harder (Mohs 10 versus moissanite's 9.25) and holds resale value far better. Moissanite has a noticeably higher refractive index and more than double diamond's dispersion, meaning more visible rainbow flashes, and costs a fraction of the price, roughly 5 to 15 percent of an equivalent natural diamond. Neither is a compromise; they're different trade-offs, and which one is right depends on what you're actually optimising for.

What's actually different

The two stones are close enough in appearance that most people can't tell them apart across a room, and different enough under close inspection that a trained eye rarely mistakes one for the other.

Diamond sits at 10 on the Mohs hardness scale, the hardest natural material there is; nothing scratches a diamond except another diamond. Moissanite sits at 9.25, still harder than sapphire or ruby and entirely suitable for daily wear, but it can be scratched by diamond dust or certain abrasives that a diamond would shrug off entirely. In practice, for a ring worn every day, both are durable enough that this rarely becomes a real-world problem; the gap matters more in theory than in a decade of ordinary wear.

Where moissanite actually outperforms diamond is brilliance and fire. Its refractive index runs from about 2.65 to 2.69, against diamond's 2.42, and its dispersion (the property responsible for rainbow flashes, not white sparkle) is roughly double diamond's. This is the detail that surprises people: moissanite isn't a dimmer version of diamond, it's a more colourful one. Some buyers love this. Others find it reads as slightly too much for a stone meant to look classic, and it's worth seeing both in person before assuming you know which camp you're in.

Telling them apart

Under normal light, at typical viewing distance, most people cannot reliably tell diamond and moissanite apart, which is precisely why moissanite has become a popular choice. Under magnification, a trained eye can. Moissanite exhibits double refraction, meaning light splits into two rays as it passes through the stone, which shows up under a loupe as a subtle doubling of the facet edges opposite the one you're looking through. Diamond never does this.

One practical point worth knowing if authenticity matters to you: cheap handheld diamond testers work by measuring thermal conductivity, and moissanite conducts heat similarly enough to diamond that these basic testers can give a false positive. Reliable identification uses a dual tester that also checks electrical conductivity, since moissanite conducts electricity and diamond does not. If you're buying secondhand and want certainty, ask specifically whether the seller tested with a dual thermal-and-electrical device, not just a basic pen tester.

The price gap, honestly

This is where the comparison usually gets framed as a landslide in moissanite's favour, and the raw numbers support that: a good-quality one-carat moissanite typically runs somewhere in the £250 to £500 range, while a comparable one-carat natural diamond can run anywhere from roughly £2,000 to £8,000 or more depending on cut, colour, and clarity. A lab-grown diamond sits between the two, generally cheaper than natural but still a meaningful multiple of moissanite's cost. Our guide to lab-grown versus natural diamonds covers that specific comparison in full if a genuine diamond at a lower price point, not a different stone entirely, is what you're actually after.

The gap widens further at larger sizes, since diamond price increases sharply, not linearly, as carat weight climbs. A two-carat diamond of good quality can run into five figures; a two-carat moissanite of comparable visual size typically stays under a thousand pounds.

The part most guides leave out: resale

Here's the honest complication. Moissanite's resale value is weak, typically recovering only 5 to 15 percent of its original retail price on the secondary market. Natural diamond fares considerably better, typically holding 30 to 50 percent of retail, though still well below what many buyers assume going in. If part of your reasoning for either stone includes future resale or the ring functioning as a store of value, that assumption deserves scrutiny regardless of which stone you choose, and it applies with particular force to moissanite. Our guide to jewellery that holds its value covers what actually retains worth over time, and it isn't primarily about the centre stone.

Which one is actually right for you

Resale value matters to you, or tradition and convention carry real weight in the decision: natural diamond. Nothing else in this comparison changes that calculation.

You want maximum visual size and sparkle for the money, and resale isn't a consideration: moissanite. The price gap is large enough to fund a noticeably bigger stone, a better setting, or simply a lower total cost for the same visual impact.

You want a real diamond specifically, but the ethical or budget case against a natural stone matters to you: lab-grown diamond. It sits between the other two options on price and gives you diamond's exact optical signature instead of moissanite's more colourful one.

You're drawn to more fire and rainbow flashes over diamond's cooler white brilliance: moissanite, on its own merits, not as a diamond substitute. It's a real, distinct look, and for some people it's simply the one they prefer.

Quick reference

Frequently asked questions

Can jewellers tell the difference between diamond and moissanite?

Yes, reliably. Under magnification, moissanite shows a subtle doubling of facet edges caused by double refraction, a property diamond doesn't have. A dual tester checking both thermal and electrical conductivity also distinguishes the two definitively, since basic thermal-only testers can be fooled by moissanite's similar heat conductivity.

Is moissanite a fake diamond?

No. Moissanite is a genuine, separate mineral, silicon carbide, with its own chemical structure and optical properties. It isn't an imitation of diamond's. It occurs naturally in extremely small quantities, almost entirely from meteorite sources, and virtually all moissanite sold in jewellery today is lab-created specifically as its own gemstone.

Does moissanite lose its sparkle over time?

No. Moissanite's hardness and chemical stability mean its clarity and brilliance don't degrade with normal wear. Any dulling in appearance over time is almost always surface dirt or oil buildup, which cleans off with normal jewellery care. It isn't a change in the stone itself.

Is a lab-grown diamond better than moissanite?

Better is the wrong frame; they're different stones with different trade-offs. A lab-grown diamond gives you diamond's exact hardness, optical properties, and resale profile at a lower cost than a natural stone, while moissanite is a different mineral entirely, cheaper again, with more fire and lower resale value. Our guide to lab-grown versus natural diamonds covers that comparison specifically.

Why is moissanite so much cheaper than diamond?

Primarily because it's produced efficiently in a lab specifically for jewellery use, without the mining, rarity, and grading infrastructure that shapes diamond pricing, and because the market and resale infrastructure around it is far less established. The production cost gap alone doesn't fully explain the price difference; the absence of a strong secondary market and the lack of the cultural weight diamond carries both play a real part too.

Sources: mineralogical data on moissanite's discovery and properties; Gema&Co and Brilliant Earth technical comparisons of hardness, refractive index, and dispersion; industry reporting on moissanite and diamond resale value trends, 2026.