Almost every claim you will read about moissanite is made by someone selling it. So here is the plain version. Moissanite is silicon carbide: one silicon atom bonded to one carbon atom in a hexagonal lattice. Diamond is carbon alone. They are not variants of the same thing. A lab-grown diamond is a diamond, chemically and optically identical to a mined one; moissanite is a different mineral that was picked, deliberately, because its optical properties sit close enough to diamond’s to pass at arm’s length.

The mineral was found by the French chemist Henri Moissan in 1893, in rock samples from what is now Meteor Crater, near Canyon Diablo in Arizona. He initially took the crystals for diamonds; it was not until 1904 that he identified them as silicon carbide. Natural moissanite is genuinely, almost absurdly rare — it turns up as microscopic presolar grains in carbonaceous chondrite meteorites, as inclusions in diamonds, and in a handful of ultramafic rocks. Nobody is cutting gems from it. Every moissanite you can buy is laboratory-grown, and that is not a defect or a secret; it is the entire industry.

The numbers that actually describe it

Hardness. Gemmological references generally place moissanite at 9.25 on the Mohs scale; the Handbook of Mineralogy gives roughly 9.5 for the mineral. Either way it sits below diamond at 10 and above sapphire and ruby at 9. For daily wear this is more than enough. Moissanite does not scratch easily and does not chip readily.

Refractive index. Around 2.65 and upward, against diamond’s 2.42. Higher RI means more light bounces back at you rather than passing through, which is why moissanite looks emphatic even in poor light.

Dispersion — the important one. Moissanite’s dispersion is 0.104. Diamond’s is 0.044. Dispersion is the measure of how strongly a material splits white light into spectral colours, so moissanite produces roughly two and a third times the coloured “fire” of diamond. This single number explains most of what people love and most of what people dislike about the stone.

Density. Specific gravity about 3.22, against diamond’s 3.52 — moissanite is about 9% lighter for the same volume. Hold that thought; it drives the whole pricing convention.

Why it looks different, and why that is a price fact rather than a fault

Put a moissanite and a diamond of the same size side by side under a bright light and most people can tell which is which within a few seconds. The moissanite throws far more rainbow flashes — distinct bursts of red, green and blue rather than diamond’s whiter, more restrained scintillation. Under ordinary indoor light the difference narrows considerably. In sunlight, on a dance floor, or under shop spotlights, it widens.

Size amplifies it. A 4 mm moissanite in a pavé band is essentially unreadable as a simulant. A 9 mm solitaire on a hand in daylight is, to anyone who has looked at gemstones for a living, obviously not a diamond. This is not a quality problem — it is a property of silicon carbide, and it is present in the best stone as much as the worst.

The second tell is double refraction. Moissanite is birefringent: light entering the stone splits into two rays. Look down through the crown facets with a 10× loupe and you will see the pavilion facet junctions apparently doubled, like slightly out-of-register printing. Diamond is singly refractive and shows no such thing. This is the standard identification test, it takes about five seconds, and it is the reason no competent jeweller has ever been fooled by moissanite for long.

A curiosity worth knowing: moissanite is thermochromic, shifting colour slightly when heated above about 65 °C. It also conducts heat much like diamond, which is precisely why old thermal-probe “diamond testers” flagged it as diamond. Modern testers measure electrical conductivity as well and separate the two without difficulty.

Millimetres, not carats — and why the difference matters

Because moissanite is about 9% less dense than diamond, a moissanite cut to the same physical dimensions as a one-carat diamond weighs noticeably less than one carat. Most of the trade therefore sells moissanite by millimetre diameter rather than by weight, and describes stones as “1 ct equivalent” or “DEW” (diamond equivalent weight).

The reference photograph at the top of this page is a useful illustration: that stone is 9.5 mm across and weighs 2.72 carats. A round brilliant diamond of the same 9.5 mm spread would weigh roughly three carats.

This convention is sensible — buyers care about how big the stone looks, not what it weighs. But it creates two reliable sources of confusion. First, a seller quoting “per carat” prices for moissanite and comparing them to per-carat diamond prices is comparing two different things, and the comparison flatters moissanite by roughly 9% on top of everything else. Second, an unscrupulous listing can quote a carat weight that sounds impressive without stating the millimetre size. Always transact in millimetres. Ask for the diameter; ignore the carat figure entirely.

Branded or generic: what the premium buys

Gem-quality moissanite was commercialised by C3 Inc., which became Charles & Colvard and brought the stone to the jewellery market in 1998 under exclusive US patents. Those patents expired during 2015, and by 2018 the original process patents had lapsed worldwide. The market opened immediately: manufacturers in China and elsewhere began producing silicon carbide gems at a fraction of the incumbent’s prices, and quality at the cheap end improved far faster than the incumbent had publicly predicted.

The end of that story arrived this year. Charles & Colvard — the company that invented the category — filed for Chapter 11 bankruptcy protection in March 2026, citing competition, falling moissanite and lab-grown diamond prices, and the rising cost of gold. Its assets were subsequently sold to AJS Creations for $2.7 million in cash.

So what does a brand premium buy you today? Realistically: consistent colour grading, a cut executed to a stated standard rather than to whatever the factory felt like, a warranty from an entity that may still exist next year, and a returns process. Those are genuine. What it does not buy is a materially different substance. Two colourless, well-cut 6.5 mm moissanites — one branded, one generic — are the same mineral with the same dispersion and the same resale value, which is to say none. If a seller cannot articulate what the premium delivers beyond the name, the premium is the name.

Typical fair prices

Notice the last row. In a finished moissanite ring the gemstone is frequently the cheapest component. If a shop quotes you $1,800 for a moissanite solitaire, you are largely buying gold and goldsmithing — which is fine, provided you know that is what you are buying and are not paying a gemstone markup on a $90 stone.

Resale: the short section

There is essentially no secondary market for moissanite. Pawnbrokers will not lend against it, jewellers will not buy it back, and the resale listings that do exist clear at a small fraction of retail because a new stone of identical quality costs so little. This is the same structural position as lab-grown diamonds, for the same underlying reason: a manufactured good with falling production costs and no supply constraint cannot hold value, whatever it is made of.

We have set out that argument at length in our lab-grown diamond value guide, and it applies here without modification. The one-line version: the value proposition of moissanite is wear it, not hold it. Judged as jewellery it is excellent value. Judged as a store of value it is not a candidate.

The comparison that has actually changed

For roughly two decades, the case for moissanite was straightforward arithmetic. A one-carat diamond cost several thousand dollars; a one-carat-equivalent moissanite cost a couple of hundred. The optical compromise bought you a 95% discount, and for a great many buyers that was an easy trade.

Lab-grown diamond prices have since collapsed. Wholesale lab-grown rough now sits near production cost, and a well-cut one-carat lab-grown diamond in the G–H, VS range retails for roughly $700–$1,500 — with market averages reported closer to $725 for a round. Five years ago that stone was several times more expensive.

So the old comparison no longer describes the choice. A branded moissanite at $500 and a lab-grown diamond at $800 are now in the same conversation, and the lab-grown stone is actually a diamond: singly refractive, dispersion 0.044, indistinguishable from mined material, and gradeable on the standard scales. Against a generic moissanite at $90 the price gap is still real and still large — roughly eight to one — and for buyers at that end of the market, or for anyone who simply prefers the extra fire, moissanite remains a straightforward choice.

What has disappeared is the middle. Paying $600–$800 for a branded moissanite when a lab-grown diamond sits at the same number is a decision that now needs a reason beyond price, and “it’s cheaper” is no longer that reason. Plenty of people do have such a reason — they like the fire, they want the hardness at low cost, they have no interest in the word “diamond” at all. Those are perfectly good reasons. They are just different reasons from the one that built the category.

Watch-outs

The GIA covers moissanite’s separation from diamond and its optical constants. Mindat holds the mineral data for natural moissanite and its meteoritic type locality.

FAQ

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Informational only — not a formal appraisal. For insurance or resale, get a certified appraisal.