What Is Moissanite? The Stone, Its Origin and How It Is Grown
Moissanite is silicon carbide (SiC), a gemstone first identified by the French chemist Henri Moissan in fragments of the Canyon Diablo meteorite in 1893. Natural moissanite is far too rare to cut into jewellery, so every moissanite sold today is grown in a laboratory, with the same chemistry and crystal structure. It is the second-hardest gem in common use (9.25 on the Mohs scale), with a higher refractive index than diamond and more than twice its dispersion, or fire.
A stone that arrived by meteorite
In 1893 Henri Moissan, who would win the 1906 Nobel Prize in Chemistry for isolating fluorine, was examining fragments of the meteorite that formed Meteor Crater near Canyon Diablo, Arizona. Among them he found tiny, brilliant crystals. He first took them for diamond. After years of analysis he concluded they were silicon carbide, and in 1905 the mineral was named moissanite in his honour.
The discovery was not straightforward. Silicon carbide had just begun to be manufactured as an industrial abrasive, carborundum, and some scientists suspected Moissan's samples had been contaminated by saw blades used to cut the meteorite. Later finds settled the question: natural moissanite exists, in microscopic grains in certain meteorites, in kimberlite and as inclusions in other minerals. It has never been found in a size that could be cut into a gem.
Silicon carbide is far more common in space than on Earth. Some of the grains recovered from meteorites are older than our Sun and formed in the outer layers of carbon-rich stars, which is where our line born from a star comes from.
How moissanite is grown today
Gem moissanite is grown from silicon carbide vapour. In a method derived from the Lely process, high-purity silicon carbide powder is heated to well over 2,000 °C in an inert atmosphere; the vapour settles on a seed crystal and builds it up, layer by layer, into a single crystal. The crystal is then sawn, faceted and polished like any other gemstone.
Colourless moissanite reached the jewellery market in the late 1990s. The Gemological Institute of America (GIA) described the new material in its journal Gems & Gemology in 1997, and early stones often had a faint grey or green tint. Growth techniques have improved since, and today's moissanite is routinely colourless.
Lab-grown or mined: what actually differs
A laboratory-grown moissanite is not an imitation of moissanite. It is moissanite: the same compound, the same crystal structure, the same hardness and optics as the grains Moissan found. What differs is origin, not substance, and the same is true of lab-grown diamond, sapphire and ruby. The meaningful questions about any stone are what it is made of, how well it is cut and how honestly it is described.
Moissanite at a glance
| Property | Moissanite | Diamond |
|---|---|---|
| Composition | Silicon carbide (SiC) | Carbon (C) |
| Mohs hardness | 9.25 | 10 |
| Refractive index | 2.65 to 2.69 | 2.42 |
| Dispersion (fire) | 0.104 | 0.044 |
| Specific gravity | 3.22 | 3.52 |
| Optical character | Doubly refractive | Singly refractive |
Values from GIA's published data on synthetic moissanite and diamond.
What the numbers mean when you wear it
- Brilliance. A refractive index of 2.65 means light is bent strongly as it enters the stone and returned to the eye as bright, white sparkle.
- Fire. With a dispersion of 0.104, moissanite splits white light into spectral colour more than twice as strongly as diamond. You see it most in sunlight, under spotlights and in larger stones.
- Durability. At 9.25 on the Mohs scale, moissanite is harder than sapphire and ruby. It is also tough, without diamond's cleavage planes, which makes it well suited to a ring worn every day.
- Double refraction. Moissanite splits light into two rays. Under a loupe you may see the back facets doubled when you look through the side of the stone. Cutters orient the crystal so that, looking straight down through the table, the effect is minimal.
- Weight. Moissanite is about 9% lighter than diamond for the same volume, so jewellers usually describe it by diamond-equivalent weight: a 6.5 mm round is sold as a 1 carat stone because that is the size of a 1 carat diamond.
Is moissanite a fake diamond?
No. Moissanite is its own mineral, with its own properties, some of which exceed diamond's. It becomes a problem only when it is sold as something it is not. At Luhusati every stone is described as moissanite and comes with a GRA report stating its colour and clarity; ours are graded D colour, VVS1.
Questions we are often asked
Does moissanite get cloudy over time?
The stone itself does not change. Like any gem, it collects a film of skin oil, lotion and soap that dulls its sparkle, and a simple clean restores it. See how to clean moissanite.
Is all moissanite lab-grown?
All moissanite used in jewellery is. Natural crystals are microscopic and of scientific interest only.
How long does moissanite last?
Indefinitely, with ordinary care. Its hardness and toughness mean it resists scratching and chipping far better than most gems; the metal around it will show wear long before the stone does.