Short answer. Moissanite is silicon carbide, grown in a lab, harder than every gemstone except diamond and with more fire than diamond. Diamond is crystalline carbon, mined or grown, the hardest material known and priced on rarity as much as on beauty. Side by side, moissanite throws more coloured flash; diamond throws whiter light. In a ring or a stud worn under ordinary light, most people cannot tell them apart. What you pay for with a natural diamond is scarcity, grading and a century of marketing; what you pay for with moissanite is the stone and the cut.
What moissanite is
Natural moissanite was first identified in 1893 by the French chemist Henri Moissan, in fragments from a meteorite crater in Arizona. It is silicon carbide, and it is so rare in nature that every stone used in jewellery is grown. That is not a compromise; it is the only way the material exists in a size you could set.
Grown moissanite is cut like a diamond, graded like a diamond for colour and clarity, and sold by size. It is not an imitation in the way that glass or cubic zirconia are imitations. It is a gemstone in its own right that happens to share a diamond's colourlessness and most of its hardness, and to beat it on fire.
The numbers
| Moissanite | Diamond | |
|---|---|---|
| Composition | Silicon carbide | Carbon |
| Hardness (Mohs) | 9.25 | 10 |
| Refractive index (brilliance) | 2.65 to 2.69 | 2.42 |
| Dispersion (fire) | 0.104 | 0.044 |
| Origin | Lab-grown, always | Mined, or lab-grown |
| Colour | Modern stones graded colourless to near-colourless; older stones carried a faint yellow or green tint | Graded D (colourless) to Z; most jewellery stones sit in the near-colourless range |
| What sets the price | Size, cut, colour grade | Carat, cut, colour, clarity, and for natural stones, rarity |
| Cleaning | Warm soapy water and a soft brush | Warm soapy water and a soft brush |
What you see
Two optical properties do the work. Refractive index is how sharply a stone bends light, which reads as brilliance: white flash. Dispersion is how far it splits white light into colours, which reads as fire: rainbow flash. Moissanite is higher on both, and more than twice as high on dispersion. That is why it looks livelier than a diamond of the same cut, and why, in bright sunlight, a large moissanite shows more colour than a diamond would.
Whether that is a virtue is taste. Some people want the extra fire; some find it too much in a big stone and prefer diamond's cooler light. In smaller stones, studs and halos, the difference narrows to almost nothing, and under indoor light at arm's length it disappears. It is the setting that people notice first: a well-cut stone in a well-made setting reads as good jewellery whichever stone it is.
How each one wears
Hardness is resistance to scratching. Diamond is 10 on the Mohs scale; moissanite is 9.25; sapphire, the next stone down, is 9. In practice both moissanite and diamond will scratch anything they meet and be scratched by almost nothing. Both can be worn every day for decades.
Toughness is resistance to chipping, and it is a different property. Diamond, for all its hardness, has cleavage planes: a sharp knock at the wrong angle can chip it, which is why diamond rings are set with protected corners. Moissanite has no cleavage planes and is, on that measure, the tougher stone. Neither should be treated as fragile; neither should be hit with a hammer.
Does moissanite go cloudy?
No. The crystal does not change with age, light or wear. What people describe as cloudiness is a film of skin oil, soap and cosmetics sitting on the stone and behind it, which happens to diamond just as readily. Warm water with a drop of mild soap and a soft brush removes it, and the stone is hard enough to take that as often as you like.
Where the money goes
Natural diamond. You are paying for a stone that was mined, sorted, cut and graded on four scales, and for the scarcity of the ones at the top of those scales. You are also paying for the century of marketing that made a diamond the expected stone for certain occasions. That expectation is real and has value to many people; it is simply worth knowing that it is part of the price.
Lab-grown diamond. Chemically and optically identical to a mined diamond: carbon, hardness 10, the same grading. The difference is origin and price. Lab-grown diamond prices have fallen sharply over recent years as production has scaled, and a lab-grown stone now costs a fraction of its mined equivalent at the same grade. Resale value tracks the falling price, which matters if you think of a stone as an asset and does not if you think of it as jewellery.
Moissanite. Priced on size and cut, and commonly a small fraction of the cost of a natural diamond the same size. Because it is always grown, there is no rarity premium and no mining question. What you are paying for is the stone in front of you: its cut, its colour grade, and the setting it sits in.
The honest comparison is not "which is better" but "what am I paying for". A natural diamond buys scarcity and tradition. A lab-grown diamond buys the diamond without the scarcity. Moissanite buys more fire per dollar than either, in a stone that is a gemstone in its own right.
How we use each
Étoilée is brilliant-cut moissanite set in solid 925 sterling silver. Each page names the stone size, carat weight and clarity grade; the Prélude Moissanite Studs, for example, list VVS1 clarity and come with a certificate of moissanite authenticity, and the Équinoxe Halo Ring sets a 2 ct centre inside a halo on the same sterling core. Moissanite suits the silver world of Amaurine because it reads as light rather than sparkle, and because it is hard enough to be worn rather than kept for best.
Each page says exactly what the stone and the metal are, in the same words we use on the Standards page.
A last note on settings. The metal around a stone matters as much as the stone for how a piece wears, and the words used for that metal are looser than the words used for stones. Our guide to gold-plated, vermeil and solid gold in Australia covers what to look for.
Questions
Is moissanite a real diamond?
No, and it does not claim to be. Moissanite is silicon carbide, a gemstone in its own right that is colourless, nearly as hard as diamond and higher in fire. Diamond is carbon. They are different stones that look alike from across a room.
Can you tell moissanite from diamond?
Side by side in bright sunlight, yes: moissanite throws more coloured flash. In a stud, a halo or a ring worn under ordinary light, most people cannot. A jeweller can tell with a gemmological tester; the eye at arm's length usually cannot.
Does moissanite get cloudy?
No. The crystal does not change with age or wear. Any cloudiness is a film of oil, soap and cosmetics on the surface, which diamond collects just as readily. Warm soapy water and a soft brush bring it back.
Does moissanite pass a diamond tester?
Most handheld testers read thermal conductivity, and moissanite conducts heat much as diamond does, so it will often read as diamond on one of those. Testers that also check electrical conductivity separate the two. This is why moissanite is sold with its own certificate rather than passed off as diamond.
Is moissanite better than a lab-grown diamond?
Different, rather than better. A lab-grown diamond is a diamond: hardness 10, diamond's light, at a fraction of the mined price. Moissanite is harder-wearing against chipping, has more fire, and costs less again. If you want the word "diamond", buy the diamond. If you want the most light per dollar, moissanite wins.
How should I clean moissanite jewellery?
Warm water with a drop of mild soap and a soft brush, then rinse and dry. The stone is hard enough to take it as often as you like. Care for the metal around it according to what that metal is: a silver cloth for plain sterling, a dry cloth only for anything with gold on top.
