Moissanite vs Diamond: How to Tell the Difference

Moissanite is the most popular diamond alternative in the world — it’s brilliant, durable, and costs a small fraction of a diamond. But it is not a diamond, and the differences matter whether you’re buying, selling, or just curious about a stone you already own.

What moissanite actually is

Moissanite is silicon carbide. It was first discovered in a meteor crater, but virtually all moissanite sold today is lab-created. A diamond is pure crystallized carbon. So while they can look similar, they’re entirely different materials with different optical properties.

The sparkle is different

Moissanite has more "fire" than a diamond — it splits light into rainbow flashes more intensely. To some that extra sparkle is the appeal; to others it looks slightly "disco" compared with a diamond’s balance of white and colored light. In larger sizes the rainbow effect is easier to notice.

The quickest visual tell is the flash: if a stone throws off unusually strong rainbow fire, especially when it’s large, suspect moissanite.

Hardness and durability

Diamond is the hardest known natural material at 10 on the Mohs scale. Moissanite is close behind at about 9.25 — harder than almost any other gem, so it resists scratches and wears beautifully for everyday rings. For durability, both are excellent choices.

How testers tell them apart

Old "diamond testers" measure heat conductivity — and moissanite can fool them because it also conducts heat well. That’s why jewelers use a combined tester that also checks electrical conductivity, or look at doubling: through a loupe, moissanite’s facets can appear doubled because the material is birefringent, while a diamond’s don’t.

Price and resale

Moissanite costs roughly a tenth of a comparable diamond, give or take, which is its biggest draw. The trade-off is resale: diamonds hold value far better, while moissanite has little secondary market. Choose based on budget versus long-term value.

Material

Silicon carbide (vs carbon)

Sparkle

More rainbow fire than diamond

Hardness

~9.25 vs diamond’s 10

Tell-tale

Facet doubling under a loupe

Resale

Low (diamond holds value better)

The takeaway

Moissanite is a brilliant, tough, budget-friendly diamond look-alike — but a different stone with more fire, slightly less hardness, and little resale value. Know the tells (extra rainbow flash, facet doubling) and you can tell the two apart and choose the one that fits your priorities.

At a glance

Moissanite vs diamond

Property	Moissanite	Diamond
Material	Silicon carbide (SiC)	Carbon (C)
Hardness (Mohs)	9.25	10
Refractive index	≈2.65–2.69 (doubly refractive)	≈2.42 (singly refractive)
Dispersion (fire)	≈0.104 — more rainbow flashes	≈0.044
Thermal tester	Often reads as diamond	Diamond
Price	A small fraction	Much higher

Frequently asked questions

Can you tell moissanite from diamond by eye?

Sometimes. Moissanite throws more rainbow fire, especially in sunlight, and its double refraction can make facet edges look doubled through the side of the stone under a loupe.

Will moissanite pass a diamond tester?

It passes most basic thermal testers because it conducts heat well. Testers that also measure electrical conductivity, or lab instruments, separate the two.

Is moissanite a fake diamond?

It is a diamond simulant — a different gemstone that looks similar. It is legitimate when sold as moissanite, and fraud only when sold as diamond.

Does moissanite have resale value?

Very little. Buy moissanite for its look and durability, not as an investment.

Sources and further reading

1. Moissanite — Wikipedia
2. Diamond simulant — Wikipedia
3. 16 CFR Part 23 — Guides for the Jewelry, Precious Metals, and Pewter Industries — U.S. Electronic Code of Federal Regulations

Links checked September 14, 2026.