Moissanite vs Diamond: How to Tell Them Apart
The quick answer
Tilt the stone under a light: moissanite throws far more rainbow-colored fire than a diamond, and a 10x loupe shows its doubled, blurry facet edges that a diamond never has.
Moissanite vs diamond comes down to one thing you can see: fire. Moissanite disperses light into rainbow flashes more than twice as strongly as diamond, so it looks noticeably more colorful and "disco-ball" under bright light. A diamond's sparkle is whiter and more restrained.
The deciding test is even simpler. Moissanite is doubly refractive, so under a 10x loupe you can see the back facet edges appear doubled or blurry. Diamond is singly refractive and shows crisp, single edges every time. Look down through the table at an angle and the difference is obvious. If you only have a photo, the crystal identifier can give you a fast first read on a loose stone.
| Property | Moissanite | Diamond |
|---|---|---|
| Hardness (Mohs) | 9.25 | 10 (hardest natural material) |
| Streak | Not used for cut gems; both are colorless to white | Not used for cut gems; colorless to white |
| Luster | Adamantine, slightly greasy; very high fire | Adamantine; bright, mostly white sparkle |
| Color | Near-colorless to faint yellow or green tint | Colorless to faint yellow or brown; fancy colors exist |
| Crystal habit / shape | Synthetic silicon carbide (SiC); lab-grown, not a natural gem in jewelry | Cubic carbon (C); octahedral crystals in nature |
| Density / heft | About 3.2 g/cm3 (lighter for the same size) | About 3.52 g/cm3 |
| Price | Roughly $300-800 per carat equivalent | Roughly $3,000-8,000+ per carat (natural) |
How to tell them apart
You do not need lab gear for most stones. Two checks settle nearly every case: the amount of fire you see, and whether the facet edges double under magnification. A diamond is whiter and sharper; moissanite is more colorful and slightly blurry inside.
Older diamond testers measure heat conductivity, and moissanite conducts heat well enough to pass as diamond on those. That is exactly why so many people get fooled. Use a combined moissanite/diamond tester that also reads electrical conductivity, since moissanite conducts electricity and diamond does not.
- Fire test: tilt the stone under a bright light. Strong rainbow flashes (red, green, blue) point to moissanite; a whiter, more subtle sparkle points to diamond.
- Doubling test: with a 10x loupe, look down through the table at the back facets at a slight angle. Doubled, fuzzy edges mean moissanite; clean single edges mean diamond.
- Tester test: use a dual moissanite-and-diamond tester. Moissanite reads as electrically conductive; diamond does not.
- Heft test: for the same measurements, moissanite weighs a little less than diamond because it is slightly less dense.
- Tint test: many moissanites show a faint yellow or grayish-green cast in bright light, especially in larger sizes.
What each one is
Moissanite is silicon carbide (SiC). It exists in nature only as tiny grains found in a meteorite, so every moissanite in jewelry is lab-grown. It is hard (9.25 on the Mohs scale), durable, and prized for its intense fire at a fraction of a diamond's cost.
Diamond is pure carbon crystallized in a cubic structure deep in the Earth. At 10 on the Mohs scale it is the hardest known natural material. Diamonds can be natural or lab-grown; both are real diamonds with identical properties, which is a separate question from the moissanite-versus-diamond one.
Which is more valuable
Diamond is far more valuable per carat. A natural diamond typically runs several thousand dollars per carat, while a moissanite of similar size costs a few hundred. Lab-grown diamonds sit in between, cheaper than natural diamond but still well above moissanite.
Value here is about rarity and market, not durability or beauty. Moissanite actually outshines diamond on raw fire and is nearly as hard, so for many buyers it is a deliberate, cost-driven choice rather than a fake. If you are buying, ask for a grading report; if you already own a stone, the tests above tell you which one you have.
Frequently asked questions
Can a jeweler tell moissanite from diamond?
Yes, easily. A jeweler uses a 10x loupe to spot moissanite's doubled facet edges and a dual moissanite-diamond tester that reads electrical conductivity. Moissanite conducts electricity and diamond does not, so the test is definitive in seconds.
Does moissanite pass a diamond tester?
Often, yes. Standard diamond testers measure heat conductivity, and moissanite conducts heat well enough to read as diamond. That is why you need a combined tester that also checks electrical conductivity, which separates the two reliably.
Is moissanite more sparkly than diamond?
Moissanite is more colorful. Its dispersion (fire) is more than double that of diamond, so it throws stronger rainbow flashes. Diamond's brilliance is whiter and more restrained. Under bright light the extra rainbow flash is the clearest sign you are looking at moissanite.
Does moissanite get cloudy or lose sparkle over time?
No. Moissanite is very hard at 9.25 on the Mohs scale and does not cloud or fade. It can collect skin oils and dust like any gem, which dulls its shine temporarily, but a quick clean restores the fire. It is built to last for everyday wear.
Is moissanite a fake diamond?
No. Moissanite is a real, distinct gem (silicon carbide), not an imitation made to deceive. It is sold as itself and chosen for its fire and value. It only becomes a problem when someone passes it off as diamond, which the loupe and conductivity tests quickly expose.
Last updated 2026-06-26. Educational comparison — confirm an identification with the tests described or a qualified expert before relying on it.