Moissanite is silicon carbide — a compound of silicon and carbon with the chemical formula SiC. That's the short answer. But the longer story is genuinely fascinating, and understanding what moissanite actually is helps explain why it looks the way it does, costs what it costs, and behaves differently from both diamond and cubic zirconia.
Here's everything you need to know.
The Discovery: A Meteorite and a Mistake
Moissanite gets its name from Henri Moissan, a French chemist who won the Nobel Prize in Chemistry in 1906. In 1893, while examining rock samples from a meteor crater in Canyon Diablo, Arizona, Moissan found microscopic crystals he initially believed were diamonds. Closer analysis revealed they were silicon carbide — a material that had never been found in nature before.
Moissan initially thought he had found diamonds because the crystals were extraordinarily hard and had a very high refractive index. He was wrong about the identity, but right about the rarity: natural moissanite is so rare on Earth that gem-quality pieces essentially don't exist in nature. The few natural occurrences are found in meteorites and in tiny quantities near volcanic rock formations. Every moissanite gemstone you'll find in jewelry today is lab-grown.
This is an important distinction from "fake" — moissanite is not a fake version of anything. It is a distinct material with its own identity, origin, and chemical properties.
The Chemistry: Silicon Carbide (SiC)
Silicon carbide in its gem form is a crystalline structure where silicon and carbon atoms alternate in a lattice. This arrangement gives moissanite several exceptional properties:
Hardness: Moissanite scores 9.25 on the Mohs hardness scale. For reference, diamond is 10 (the hardest known natural material), corundum (sapphire, ruby) is 9, and quartz is 7. At 9.25, moissanite is hard enough that nothing in everyday life will scratch it — including contact with other jewelry, metal surfaces, or normal wear.
Refractive Index: Moissanite's refractive index is 2.65–2.69, compared to diamond's 2.42. A higher refractive index means light bends more as it passes through the stone, producing more brilliance. This is why moissanite appears to sparkle intensely — it bends and reflects light more dramatically than diamond.
Fire Dispersion: Moissanite's dispersion value (the degree to which it separates white light into spectral colors) is 0.104, compared to diamond's 0.044. That's more than twice diamond's fire. In bright or direct light, this produces the rainbow flashes moissanite is known for.
Thermal Conductivity: Moissanite conducts heat at approximately 500 W/m·K — high enough that basic thermal diamond testers often read moissanite as diamond. This is a physical property, not a trick.
Lab-Grown: How Commercial Moissanite Is Made
Because natural gem-quality silicon carbide is essentially impossible to source, all moissanite jewelry uses lab-grown stones. The process involves: growing from a seed crystal (a tiny silicon carbide seed placed in a growth chamber under high temperature and controlled conditions); crystal growth (silicon and carbon atoms bond to the seed, gradually building a larger crystal over weeks); and cutting and polishing (the rough crystal is cut by gemologists using specialized equipment, as standard diamond-cutting techniques work because moissanite is nearly as hard as diamond).
The result is a chemically pure, optically perfect stone that is structurally identical to the rare natural mineral found in meteorites. Lab-grown does not mean inferior — it means consistent, traceable, and ethical.
How Moissanite Differs from Diamond
Diamond is pure carbon arranged in a cubic crystal structure. Moissanite is silicon carbide — a different element, a different structure. The key differences: moissanite has a hardness of 9.25 vs diamond's 10; a refractive index of 2.65–2.69 vs diamond's 2.42; fire dispersion of 0.104 vs diamond's 0.044; and thermal conductivity of approximately 500 W/m·K vs diamond's 1,000–2,200 W/m·K. Moissanite is lab-grown while diamond can be natural or lab-grown.
From across a room, moissanite and diamond are visually similar. Under close examination, moissanite shows more fire (rainbow sparkle) and double refraction (facet edges appear doubled when viewed at an angle under a loupe) — properties unique to its crystal structure.
How Moissanite Differs from Cubic Zirconia
CZ is zirconium dioxide (ZrO₂). It has a much lower hardness (8–8.5 Mohs), scratches in normal wear, clouds over time, and fails thermal diamond testers. CZ has a refractive index of approximately 2.15 and low dispersion. Moissanite significantly outperforms CZ on every durability and optical metric. The confusion between them is common but unjustified — they are completely different materials.
FAQ: What Is Moissanite Made Of?
Is moissanite a real gemstone? Yes. Moissanite is a genuine gemstone — silicon carbide that occurs naturally in meteorites and is commercially produced in labs. It is not an imitation or simulant in the way CZ is; it has its own distinct identity.
Is lab-grown moissanite lower quality than natural? No. Lab-grown moissanite is chemically identical to natural moissanite found in meteorites. The lab process allows for greater consistency and purity than natural formation would produce.
Why is moissanite so brilliant? Its high refractive index (2.65–2.69) and high dispersion (0.104) cause light to bend dramatically as it passes through the stone, producing intense white sparkle and rainbow fire.
Can moissanite scratch? At 9.25 Mohs, moissanite is extremely scratch-resistant. Only diamond and a few lab materials harder than moissanite can scratch it. In normal jewelry wear, moissanite will not scratch.
Does moissanite come from space? Natural moissanite was first discovered in a meteorite crater and trace amounts are found in some meteorites. Commercial moissanite is lab-created — but the meteoritic origin is part of moissanite's unique history.
Is moissanite ethical? Lab-grown moissanite has no mining impact. It is one of the most ethically traceable gemstones available — the entire production chain is controlled in a lab environment.
Moissanite is silicon carbide: a material discovered in a meteorite crater, now grown in labs with precisely controlled properties. Its hardness, refractive index, and fire make it genuinely exceptional as a gemstone — not because it imitates diamond, but because its own physical properties happen to produce outstanding optical performance.
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