What is moissanite and how does it compare to diamond?

Moissanite is a beautiful stone. It is not a diamond, and I tell every client that before we go any further. The stone is silicon carbide, grown in a lab, and it was first identified by Henri Moissan in 1893 in a meteor crater outside Flagstaff, Arizona. Natural moissanite is so rare that it effectively doesn't exist for jewelry. Every moissanite you'll see in a setting today was made in a furnace, and most of it is cut to diamond angles, which is why the two get compared at all, even though they have almost nothing in common chemically.

I've set hundreds of them. Maybe half the clients who ask for moissanite walk in thinking it's a type of diamond. It isn't. Once that's clear, the conversation gets easier because the comparison stops being about imitation and starts being about what the stone actually does.

Moissanite versus diamond: the mineral facts

Here are the numbers, because the numbers do most of the work.

• Composition: moissanite is silicon carbide, diamond is carbon.
• Hardness: 9.25 on the Mohs scale, versus diamond's 10.
• Refractive index: 2.65 and doubly refractive, versus diamond's 2.42 and singly refractive.
• Dispersion: 0.104, more than double diamond's 0.044.

The hardness gap looks small on paper and mostly is. Both stones survive daily wear on a hand. Diamond has a cleavage plane, which means a hard blow at the wrong angle can split it. Moissanite doesn't cleave the same way. In a prong setting, either is fine. In a bezel, both are fine. If you're hard on your rings, moissanite is not a fragile stand-in.

The sparkle is not the same

This is where most of the confusion lives. Under magnification, the tell is double refraction. With a 10x loupe, the facet junctions in moissanite can look doubled, slightly fuzzy around the edges, and in stones above 8 millimeters the effect can read as a softness that some people pick up on without knowing exactly why. Diamond's brilliance reads mostly white with some fire. Moissanite throws more rainbow, especially above about 8 millimeters. In a 1 carat equivalent, it's noticeable but pleasant. In a 2.5 carat equivalent, it can look like a firework, which is fine if that's what you want.

Color, carat weight, and how it's sold

Older moissanite ran yellowish or greenish, often around J-K on a diamond color scale. Today's near-colorless moissanite, sold as D-E-F equivalent, is much better, though it can still read slightly gray or green under overcast skies or LED light. Moissanite doesn't get a GIA report; you'll see IGI or GCAL paperwork instead. The bigger confusion is carat weight. Moissanite is lighter than diamond, so it's sold by millimeter, not carat. A 6.5mm round moissanite weighs about 0.88 carats, but every vendor calls it a "1 carat diamond equivalent." That's not a scam; it's because the face-up size matches a 1 carat diamond. Still, if you get an appraisal, the stone's actual carat weight is not the same thing.

Price and resale reality

A round 1 carat equivalent near-colorless moissanite with a decent cut will run you roughly $300 to $700 loose. A 1 carat natural diamond, G/VS2, GIA triple excellent, is somewhere around $6,000 to $7,000. A 1 carat lab-grown diamond with the same specs, IGI certified, is maybe $900 to $1,400. So moissanite is not just cheaper than natural diamond. It's often cheaper than lab-grown, sometimes by half. One thing nobody says out loud: moissanite has almost no resale value. Neither does a lab-grown diamond, for that matter. The natural diamond is the only one that holds any meaningful fraction of what you paid.

What I tell clients

Last March, a woman named Nicole came in with a 2.8 carat equivalent moissanite oval she'd bought online for $240. The cut was shallow, the bowtie was a dark smear across the center, and the stone went lifeless in any light that wasn't direct. We sourced a replacement from a cutter I trust, a 9x7mm near-colorless oval with a proper crown, for $410. The difference was not subtle. She picked the finished ring up on a Thursday afternoon, tilted it under the bench light, and said it looked like a firework. It did. That's what moissanite does.

If you want the look of a large, clean, colorless center stone for a few hundred dollars instead of several thousand, moissanite is a legitimate choice. But don't buy it as a fake diamond. Buy it because you like the fire and the price. It's not a placeholder. It's a different gem.