How Is Moissanite Made? Inside the Lab That Grows It

Moissanite looks like a stone that came out of the ground. It did not. Every moissanite you can buy and wear was manufactured on purpose, and the way it is manufactured explains almost everything buyers find confusing about it — why it is so clear, why it costs what it costs, and why it still is not a diamond.

The short answer: moissanite is silicon carbide, and gem-quality moissanite is grown from vapor inside a sealed high-temperature chamber. Source material is vaporized, and the vapor settles onto a small seed crystal, building a solid crystal upward atom by atom. That rough crystal is then sawn, faceted to a set millimeter size, and set into jewelry. There is no mine, no deposit and no natural supply — growing it is not the cheap option, it is the only option.

Here is what actually happens between the furnace and your ear, and what the process does and does not change about the finished stone.

Why it has to be grown rather than mined

Natural moissanite is real. The French chemist Henri Moissan found it in 1893 in rock from the Canyon Diablo meteorite crater in Arizona, and in 1904 the material was correctly identified as silicon carbide. Since then it has turned up as microscopic grains in meteorites and trapped inside a handful of unusual rocks and other minerals.

The problem is scale. Every known natural occurrence is measured in fractions of a millimeter and scattered thinly through its host rock. Nobody has ever cut a wearable gemstone from natural moissanite, and no deposit exists that would justify digging. If a seller tells you their moissanite was mined, they are wrong, and that tells you something about the rest of what they say. The full discovery story — stars, craters and a Nobel Prize — is worth reading on its own, and we tell it in Where Does Moissanite Come From? The Space Gem Origin Story. This guide stays with the furnace.

How a moissanite crystal is actually grown

The method has a name

Large silicon carbide crystals are produced by physical vapor transport, sometimes called sublimation growth or seeded sublimation. The principle is simple even though the engineering is not:

• A sealed growth chamber holds silicon carbide source powder at the bottom and a thin seed crystal at the top.
• The chamber is taken to extreme temperature under a controlled atmosphere. The source material sublimates — it goes straight from solid to vapor without melting.
• The seed is held slightly cooler than the source. Vapor migrates toward the cooler end and condenses onto the seed.
• Layer by layer, the seed grows into a solid cylinder of silicon carbide called a boule.

Nothing is being faked or coated here. What comes out of the chamber is the same mineral, with the same chemistry, as the grains Moissan pulled out of a meteorite. The difference is that this one is big enough to cut.

How slow is "slow growth," really

You will read a lot of confident numbers about this online. Here is one that comes from a published gemological source rather than a product page: in a Gems & Gemology lab note, the Gemological Institute of America describes physical vapor transport producing bulk silicon carbide crystals up to 50 × 25 mm at a rate of about 1.2 mm per hour.

That is useful because it sets the scale honestly. Growth is measured in hours and days for a boule of that size — not in the months you will sometimes see claimed, and not in the minutes people imagine when they hear "lab-made." Individual growers do not publish their exact run times, furnace temperatures or yields, so treat any very specific timeline you read on a jewelry site, including a reassuringly round one, as marketing rather than fact.

Polytypes, and why two stones from one furnace are not identical

This is the part almost nobody explains, and it is the reason moissanite quality varies between sellers at the same price.

Silicon carbide can stack its atoms in several different repeating arrangements. Same chemistry, different crystal structure. These variants are called polytypes, and they have names like 6H, 4H, 3C and 15R. Holding the growth energy steady enough to produce one clean polytype throughout a whole boule is genuinely difficult, and GIA has documented a single large synthetic moissanite specimen that contained four polytypes at once, along with graphite inclusions breaking the surface and a mosaic pattern of lighter and darker grey regions under magnification.

For a buyer, that is the whole story behind a familiar complaint. When somebody says a cheap moissanite looks slightly grey, hazy or "oily" next to a better one, they are usually describing growth that did not stay clean — not dirt, and not the stone wearing out. That distinction matters enough that we wrote it up separately in does moissanite get cloudy.

It is also why the colorless, eye-clean end of the market costs more. Big clean crystals are harder to grow than small ones, so stone size and clarity are both priced off growth difficulty. We explain how those grades are described in what VVS moissanite means.

From boule to loose stone

Once a boule is out of the chamber it is treated like any other gem rough:

1. Sawing. The boule is cut into sections and preforms, working around inclusions and cloudy zones.
2. Orienting. Moissanite is doubly refractive, which means light entering it splits into two rays. A cutter orients the stone so the table faces down the optic axis, because that minimizes the visible doubling of facet edges when you look straight into it.
3. Faceting and polishing. Stones are cut to standard shapes — round brilliant, princess, marquise, baguette and so on — and finished to precise millimeter diameters so they drop into standard settings.

That last point is why moissanite is sold by millimeter rather than carat. A 6.5 mm round moissanite weighs less than a 6.5 mm round diamond, because moissanite is less dense, so quoting carats would make the stone sound smaller than it looks. Millimeters describe what you actually see. If that still feels backwards, we untangled it in the mm to carat size guide.

From loose stone to finished piece

The last stage is ordinary jewelry making. A setter mounts each stone by hand into prepared seats in the metal and closes the prongs or beads over it. On a cluster or pavé face that means dozens of tiny stones, each individually seated, which is where most of the labor in a finished piece goes — and why the price of a finished earring has far more to do with setting work than with the stone.

Our pieces are set in .925 sterling silver, with some finished in rhodium and some plated in gold or rose gold over the silver. If you want to know what that alloy actually is and why it is used rather than fine silver, start with what .925 sterling silver actually means.

What growing it changes, and what it does not

Lab origin is responsible for the good parts of moissanite. It is not responsible for turning it into a diamond, and no honest seller will tell you otherwise. Moissanite is its own mineral with its own measurable properties:

Property	Moissanite	Diamond	What you notice
Chemistry	Silicon carbide	Carbon	Different materials, not grades of one thing
Mohs hardness	About 9.25 to 9.5, depending on the reference	10	Both are fine for daily wear; diamond is still harder
Dispersion (fire)	0.104	0.044	Moissanite throws noticeably more colored flash
Refractive index	About 2.65	About 2.42	More light bent back at you
Optical character	Doubly refractive	Singly refractive	Facet edges can look doubled under a loupe
Density	About 3.21	About 3.52	Same size, slightly lighter stone
Thermal conductivity	Close to diamond	Very high	Basic thermal testers cannot separate them

Two of those rows are worth sitting with. The dispersion figure is why moissanite reads as livelier than diamond in moving light — some people love that and some people find it too much, and it is the single most common reason a buyer prefers one over the other. The thermal conductivity row is why a cheap pen-style diamond tester will call moissanite a diamond; a proper multi-tester will not. We covered that in full in does moissanite pass a diamond tester.

Growing a stone also does not make it a lab-grown diamond. Those are carbon, made by a completely different process, at a completely different price. If you are cross-shopping the two, moissanite vs lab-grown diamond is the comparison you want. And if what you are really trying to avoid is cubic zirconia, the difference shows up over time rather than on day one — see moissanite vs cubic zirconia.

How to check what you are actually buying

Knowing the process gives you a short, practical checklist:

• The listing should say lab-created or lab-grown. That is the correct description for all jewelry moissanite. "Mined moissanite" and "natural moissanite jewelry" do not exist.
• Expect millimeter sizing. A seller quoting only carats for moissanite is either careless or hoping you will compare it to a diamond in your head.
• Treat clarity and color grades as producer specifications. Moissanite is not routinely graded stone by stone by an independent laboratory the way diamonds are. Ours are producer specifications too, and we would rather say so than imply a certificate exists.
• Be skeptical of growth-time claims. A precise figure nobody can verify is a sales line, not a specification.
• Look at the setting, not just the stone. Thin prongs, uneven stone heights and visible glue are what actually fail. More on that in what makes iced-out jewelry look real.

If you are buying from somewhere new, our 6-point checklist for buying jewelry online safely covers the rest.

Where to start, if you are buying

The stones in our pieces are VVS lab-grown moissanite, hand-set in .925 sterling silver. A few places to begin:

• 9mm cluster earrings — $140 in silver or gold, a tight cluster around a raised center stone, rhodium finished, on screw-back posts. The everyday size.
• 12mm cluster earrings — $170 in silver or gold, the same build with more presence. If you are undecided, read 9mm vs 12mm.
• Luxe princess cut studs — $140, square stones with crisp corners, for anyone who finds a round stud too soft.
• Timeless heart pavé earrings — $120 in silver or rose gold, the smallest step into stone-set jewelry we make.
• 4mm round-cut tennis bracelet — $350, in 7" or 8", silver, gold or rose gold.
• 4mm tennis chain — $500 at 18" and $550 at 20", dozens of calibrated stones set shoulder to shoulder.

Browse the full earrings collection, the cluster earrings, or everything we make. US shipping is free and insured, unworn returns are open for 30 days, and every piece carries our Lifetime Guarantee.

Frequently asked questions

A stone with a manufacturing date

Most gemstones ask you to take their story on trust. Moissanite does not: it was grown deliberately, to a specification, so that it could be clean and colorless rather than merely lucky. That is not a compromise to apologize for. It is the reason the stone exists at all — and the reason a $140 pair of studs can look the way it does.

Related guides: Where Does Moissanite Come From? The Space Gem Origin Story | Why Is Moissanite So Cheap? | What Is VVS Moissanite? | Moissanite Size Guide: MM to Carat | Does Moissanite Pass a Diamond Tester? | Moissanite Earrings Buying Guide