Moissanite
Moissanite is a lab-grown stone that sits just below diamond for hardness but throws far more colourful sparkle, and it costs a fraction of the price. Here's how it actually compares to a diamond, and how we tell them apart on our bench.
Key Takeaways
- Moissanite is lab-grown silicon carbide (SiC). It scores 9.25 on the Mohs hardness scale, second only to diamond at 10, which makes it hard enough for daily-wear engagement rings (source).
- It has more "fire" than diamond. Moissanite's dispersion (the rainbow flash) is about 0.104 versus diamond's 0.044, so it throws noticeably more colour (source).
- Moissanite is doubly refractive; diamond is not. That difference is the main way a jeweller tells them apart under a loupe (source).
- It typically costs a small fraction of a comparable diamond, which is its biggest practical advantage.
- The trade-off is look: some people love the extra rainbow sparkle, others find it reads less like a diamond, especially in bright light and at larger sizes.
Moissanite vs diamond: the honest comparison
The short answer to "moissanite vs diamond" is this: moissanite is nearly as hard as diamond, it sparkles with more colour, and it costs a fraction of the price, but it is a different stone with a different look, not a cheaper diamond. Both are excellent choices for an engagement ring. Which one is right depends on whether you want maximum durability and the classic white sparkle of a diamond, or a tougher budget and a livelier, more colourful flash.
Moissanite is silicon carbide, chemical formula SiC. The mineral was first identified by French chemist Henri Moissan in 1893 in rock from a meteor crater near Canyon Diablo, Arizona — he initially thought the crystals were diamonds (source). Natural moissanite is vanishingly rare, so every moissanite you'll see in jewellery is grown in a lab. That's not a knock on it. Lab growth is exactly what lets it be made clean, colourless, and affordable.
Hardness: second only to diamond
On the Mohs scale, which runs from 1 (talc) to 10 (diamond), moissanite sits at 9.25 and diamond at 10 (source). For comparison, sapphire and ruby sit at 9. That puts moissanite above every coloured gemstone we sell. In plain terms, it resists scratching extremely well and holds a crisp facet edge over years of daily wear. You can wear a moissanite ring while you do the dishes, garden, and travel without babying it.
For context on where everything else lands, see our Gemstone Guide: Durability, Colour & Care, Stone by Stone, which lines up every stone by hardness and explains what the Mohs number actually means for a ring you wear every day.
Why moissanite sparkles differently
This is where moissanite and diamond genuinely part ways, and it's worth understanding before you buy.
Fire (the rainbow flashes). Fire is dispersion — how much a stone splits white light into spectral colours. Moissanite's dispersion is roughly 0.104, well over double diamond's 0.044 (source). In real life that means moissanite throws bigger, more obvious flashes of rainbow colour, especially under spotlights and sunlight. Some people love it. Some find it a touch disco. It's a matter of taste, not quality.
Brilliance (the white sparkle) and refractive index. Moissanite's refractive index is about 2.65, higher than diamond's, which the International Gem Society measures at 2.417–2.419 (source). High refractive index means more light bounces back to your eye, so moissanite is very bright. But because so much of that return reads as coloured fire rather than white light, the overall impression is different from a diamond's cleaner, whiter sparkle.
Double refraction. Diamond is singly refractive — light passes through on a single path. Moissanite is doubly refractive, meaning light entering the stone splits into two paths (source). At larger sizes you can sometimes see a slight doubling of the back facets through the top of the stone if you look closely. It's subtle, but it's there.
How a jeweller tells moissanite from diamond
You can't tell reliably by eye in a shop, and the old "diamond tester" pen doesn't help — those measure thermal conductivity, and moissanite conducts heat much like diamond does, which is exactly why early testers were fooled. On our Coquitlam bench we rely on a few honest methods:
- Double refraction under magnification. Looking down through the table of the stone with a loupe, the doubled back facets give moissanite away. Diamond shows single, crisp edges.
- A moissanite tester. Modern combination testers measure electrical conductivity, which separates moissanite from diamond cleanly. This is the quick, reliable check.
- Fire and tint. Side by side with a diamond, moissanite's extra rainbow flash and, in some stones, a faint warm or greenish tint under certain light can be a clue. On its own it's not proof, but it's a flag.
If you ever want a stone identified, bring it in. We're happy to put it under the loupe and tell you straight what it is.
Moissanite vs diamond at a glance
| Property | Moissanite | Diamond |
|---|---|---|
| Material | Lab-grown silicon carbide (SiC) | Crystalline carbon (natural or lab-grown) |
| Mohs hardness | 9.25 | 10 |
| Dispersion (fire) | ~0.104 | 0.044 |
| Refractive index | ~2.65 | 2.417–2.419 |
| Light behaviour | Doubly refractive | Singly refractive |
| Relative price | A fraction of a diamond | Highest of the two |
| Best for | Maximum sparkle on a budget | Classic white brilliance, top durability |
Hardness from naturaldiamonds.com; optical values from Wikipedia and the International Gem Society.
The honest pros and cons
What's great about moissanite: It's tough enough for daily wear, it's brilliant and full of fire, and it costs a fraction of a diamond, so you can have a much larger stone for the same budget. Because it's lab-grown, sourcing is clean and supply is reliable.
What to keep in mind: It doesn't look identical to a diamond. The extra fire is lovely to some eyes and too flashy to others, and that difference grows with carat size. A few stones can show a slight tint in certain light. And while resale value isn't really a factor for diamonds either, moissanite has effectively none, so buy it because you love wearing it, not as an investment.
Care
Moissanite is low-maintenance. Warm water, a drop of dish soap, and a soft toothbrush bring back the sparkle. It shrugs off everyday knocks better than any coloured gem. The setting around it (gold or platinum prongs) will need the same occasional check a diamond ring does, so have the prongs looked at once a year. We do that check for free when you're in.
If you're weighing your options
Moissanite is one of several strong diamond alternatives. If you want a coloured stone instead, our hardest coloured options are sapphire and ruby at Mohs 9, while emerald is softer and needs more care. For a fuller rundown of every non-diamond centre stone and how they wear, read Beyond Diamonds: Alternative Stones. Whatever you lean toward, we design and set it in-house here in Coquitlam, so you can see the stones side by side before you decide.
Frequently Asked Questions
Is moissanite a real gemstone or a fake diamond?
It's a real gemstone in its own right — lab-grown silicon carbide, not an imitation diamond. It's a distinct mineral with its own properties. Calling it a "fake diamond" is misleading; it's its own stone that happens to look diamond-like.
Will moissanite scratch or cloud over time?
No. At Mohs 9.25 it's second only to diamond for hardness, so it resists scratching extremely well and won't cloud. It stays bright with nothing more than soap, warm water, and a soft brush.
Can people tell it's not a diamond?
Usually not in everyday wear. The giveaway is the extra rainbow fire, which is more obvious in bright light and at larger carat sizes. Side by side with a diamond a careful eye may notice it; on its own, most people won't.
How much cheaper is moissanite than a diamond?
Substantially — a moissanite typically costs a small fraction of a comparable diamond of the same size and grade. That's the main reason people choose it: a far larger or higher-quality centre stone for the same budget. Exact savings depend on size and the diamond you're comparing against.
How do you tell moissanite from a diamond?
Under magnification, moissanite is doubly refractive and shows slightly doubled back facets, while diamond is singly refractive. A modern moissanite tester that reads electrical conductivity confirms it instantly. An old thermal "diamond pen" won't work, because moissanite conducts heat much like diamond. We can identify any stone for you on our Coquitlam bench.
Is moissanite good for an engagement ring?
Yes. It's hard enough for daily wear, very brilliant, and lets you put your budget into a bigger stone or a nicer setting. The only real question is whether you prefer its livelier, more colourful sparkle or the classic white brilliance of a diamond.