Moissanite vs Lab Grown Diamond: Why We Don't Sell Moissanite

Moissanite is a real gemstone and a perfectly good one. It is not a diamond. It is silicon carbide, it is 9.25 on the Mohs scale rather than 10, and it throws noticeably more rainbow fire than a diamond does, which some people love and some people spot instantly across a dinner table. We do not sell it. Not because it is bad, but because lab grown diamonds now cost so little that moissanite's one real advantage, the price, has mostly evaporated. Here is the honest comparison, including the parts that favour moissanite.

In this article

• What is moissanite, actually?
• Moissanite vs lab grown diamond at a glance
• Does moissanite look like a diamond?
• Is moissanite durable enough for daily wear?
• The honest case for moissanite
• Why we chose not to sell it
• FAQ

What is moissanite, actually?

Moissanite is silicon carbide. It was discovered in 1893 by Henri Moissan in a meteorite crater in Arizona, which is where the marketing line about "born from the stars" comes from. Natural moissanite is vanishingly rare, so every moissanite you can buy is laboratory grown, exactly like a lab grown diamond. The difference is not where it was made. The difference is what it is made of.

A diamond, mined or lab grown, is pure carbon. Moissanite is a different mineral entirely, with different optics, different hardness and different behaviour in light. Calling it a "moissanite diamond", as some sellers do, is simply wrong.

Moissanite vs lab grown diamond at a glance

	Moissanite	Lab grown diamond
Composition	Silicon carbide	Pure carbon, identical to mined
Hardness (Mohs)	9.25	10
Refractive index	2.65 to 2.69	2.42
Dispersion (rainbow fire)	0.104, roughly 2.4x a diamond	0.044
Is it a diamond?	No	Yes
Certification	No universal grading standard	IGI / GIA, same 4Cs as mined
Resale value	Very low	Low

Two numbers in that table do most of the work. Refractive index governs brilliance and dispersion governs the rainbow flashes. Moissanite scores higher on both, which sounds like a win until you see what it actually looks like on a hand.

Does moissanite look like a diamond?

At a glance, in a photograph, yes. In daylight, on a moving hand, less so.

Because moissanite disperses light roughly two and a half times as strongly as a diamond, it throws pronounced rainbow flashes of red, green and blue rather than the crisp white brilliance a diamond returns. Jewellers call this the disco ball effect. Under bright light and above about one carat, it becomes hard to miss.

Moissanite is also doubly refractive, meaning each ray of light entering the stone splits in two. View it under magnification through a crown facet and the back facets appear doubled. Diamonds are singly refractive and never do this. It is one of the tells gemmologists use, and it takes about three seconds.

Whether any of that matters is a personal question, not a moral one. Some people genuinely prefer the fire. But if the goal is for the ring to read as a diamond, be aware that it does not, quite.

Is moissanite durable enough for daily wear?

Yes, for practical purposes. At 9.25 on the Mohs scale, moissanite is harder than sapphire and vastly harder than the softer stones people are sometimes talked into for engagement rings. It will not scratch easily, and it will not cloud.

But the Mohs scale is not linear. A diamond at 10 is significantly harder than moissanite at 9.25, and only a diamond can scratch a diamond. For a ring worn every day for fifty years, that gap is the difference between a stone that stays pristine and one that can gradually accumulate wear on the facet edges.

The honest case for moissanite

We would be doing exactly what we criticise if we only listed the drawbacks. Moissanite genuinely wins in three situations:

Budget below the diamond floor. If your total ring budget is a few hundred pounds, moissanite gives you a hard, brilliant, colourless stone at a size no diamond will match. That is a real advantage and we will not pretend otherwise.

Travel and replacement rings. A moissanite copy of an expensive ring for holidays, festivals or the gym is a sensible, practical thing to own.

You actively like the fire. Some people see the rainbow dispersion and love it. If that is you, buy the moissanite and enjoy it. It is your ring.

What moissanite does not do is give you a diamond. And that is fine, as long as nobody is telling you otherwise.

Why we chose not to sell it

The economics have changed. A decade ago, moissanite was the only way most people could put a large, brilliant, colourless stone on a hand without spending five figures. Lab grown diamonds have since fallen 60 to 80% below mined prices, which means an actual certified diamond, D colour, VVS+ clarity, Ideal cut, now sits within reach of most engagement ring budgets: our rings start at £1,795.

Once that is true, moissanite's case narrows to "it is cheaper still". And at that point we would rather sell you a real diamond, with a real IGI or GIA certificate, that will look right in every light for the rest of your life, than save you a few hundred pounds on a stone that is not what people will assume it is.

That is the whole reason we exist: no mining, no marketing myths, no substitutes. Just the real stone, honestly priced. Our guide to whether lab grown diamonds are worth it sets out that value case in full, including the parts that are not flattering.

Frequently asked questions

Is moissanite a real diamond?

No. Moissanite is silicon carbide, a different mineral from diamond, which is pure carbon. It is a real gemstone, but it is not a diamond. Any seller describing a "moissanite diamond" is using a term that does not exist.

Can a jeweller tell moissanite from a diamond?

Instantly. Moissanite is doubly refractive, so under magnification through a crown facet the back facets appear doubled, which never happens in a diamond. It also shows far stronger rainbow dispersion. Your friends may not notice; any jeweller will.

Is moissanite cheaper than a lab grown diamond?

Yes, usually by a significant margin. But the gap has narrowed sharply as lab grown diamond prices have fallen. For most UK engagement ring budgets, the question is no longer "can I afford a diamond" but "is the remaining saving worth not having one". Compare diamond rings from £1,795 →

Does moissanite get cloudy or scratch over time?

It does not cloud. At 9.25 on the Mohs scale it resists scratching well, though not as well as a diamond at 10. Over decades of daily wear, facet edges can show more wear than a diamond's would.

Is moissanite good for an engagement ring?

It is durable enough, and if you like its fire and the price suits you, it is a legitimate choice. If you want a stone that reads as a diamond, you want a diamond, and lab grown makes that affordable.