Moissanite vs. Diamond: the honest guide

Moissanite is silicon carbide — a distinct mineral, not a synthetic diamond and not cubic zirconia. It throws roughly 2.4 times more fire than a diamond, with a refractive index of 2.65 against a diamond's 2.42. Diamonds rank 10 on the Mohs hardness scale; moissanite ranks 9.25. Moissanite has no cleavage plane, and it costs roughly a tenth as much as a comparable diamond.

The "diamond is forever" campaign traces back to 1947 — a copywriter named Frances Gerety, working for an ad agency called N.W. Ayer. Diamonds are expensive largely because of decades of controlled supply, not because they're objectively rarer or more beautiful than the alternative.

In 1893, chemist Henri Moissan discovered microscopic silicon carbide crystals in the debris of a meteor crater in Arizona. He initially believed he'd found diamonds. In 1905, George Kunz at Tiffany named the mineral moissanite, after him.

Natural moissanite is exceptionally rare — far too rare to mine at any scale. Every moissanite stone in jewelry today is lab-grown, which also means it's cleaner and more consistent than a mined stone could ever be.

Three separate things get lumped together as "sparkle." Brilliance is the white light a stone reflects. Scintillation is the flash you see as the stone — or you — moves. Fire is the rainbow of color a stone throws when it splits light apart.

Moissanite's higher dispersion means it flashes color across a room in a way a diamond simply doesn't. Some buyers love that. In direct sunlight, a large moissanite stone can read as more "showy" than they expected — worth knowing before you buy, not after.

Across a room, moissanite and diamond look nearly identical. Under a jeweler's loupe, moissanite shows "double refraction" — facet edges on the far side of the stone appear doubled, which a diamond never does.

A basic diamond tester (the kind that measures thermal conductivity) can't tell the two apart and may misidentify moissanite as diamond. A tester that measures electrical conductivity, or a professional appraisal, separates them instantly.

Diamonds are harder on paper — 10 versus moissanite's 9.25 — but hardness isn't the whole story. Diamonds have perfect cleavage in four directions, meaning a sharp, badly-angled knock can split one clean. Moissanite has no cleavage plane at all, so it resists chipping in a way a diamond sometimes can't.

Neither stone clouds, dulls, or yellows with age. A monthly clean with warm water and a drop of dish soap is all either one needs.

Moissanite runs roughly a tenth of a comparable diamond because its price reflects what it actually costs to produce — not the cost of controlling how much of it reaches the market. Most people put the difference toward a bigger stone, the wedding, or just keep it.