What Is Moissanite? How It Differs from a Diamond

Short answer: Moissanite is a stone made of silicon carbide that looks very much like a diamond but is not a diamond. Almost all moissanite used in jewellery is made in a laboratory. A lab-grown diamond, on the other hand, is made of carbon and is a real diamond; the two are not the same thing.

What is moissanite and where does it come from?

Moissanite is named after the French chemist Henri Moissan, who found it in 1893 in a meteorite crater in Arizona. It is so rare in nature that natural moissanite large enough for jewellery practically does not exist. The moissanite you see in jewellery shops today is silicon carbide crystal grown in a laboratory.

Moissanite is not cheap glass or cubic zirconia designed to imitate a diamond; it is a hard, brilliant stone in its own right. But its chemistry is different from diamond, so it cannot be called a diamond.

The differences between moissanite and diamond

The most visible difference in the table is the coloured sparkle. Moissanite splits light into colours more than twice as strongly as diamond, so it throws rainbow-like flashes, especially in sunlight and in larger stones. A diamond’s sparkle is whiter and crisper.

Can you tell moissanite from diamond by eye?

In small stones most people cannot see the difference. It becomes clearer as the stone gets bigger:

• Coloured flashes: Under light, moissanite flashes more colourfully, like a disco ball. In a diamond, white light dominates.
• Doubling: Moissanite is doubly refractive. Seen through a loupe from certain angles, the edges of the back facets appear doubled. This does not happen in a diamond.
• Body tone: Some moissanite, especially older production, can show a faint yellowish or greenish undertone.

Does a diamond tester detect moissanite?

Not every tester does. The simple diamond tester pens common in jewellery shops measure thermal conductivity. Because moissanite conducts heat very well, just like diamond, these testers can show it as “diamond”. For a reliable result, testers that also measure electrical conductivity and can separate moissanite are used.

That is why the surest way to know what a stone is, is a document rather than a device. We explain it in detail in how to tell if a diamond is real.

Are moissanite and lab-grown diamond the same thing?

No, and this is the most common confusion. Both are made in a laboratory, but one is a diamond and the other is not.

• A lab-grown diamond is pure carbon. Its chemistry, hardness and light are the same as a natural diamond. It tests as diamond on diamond testers and receives a diamond report from organisations such as GIA and IGI.
• Moissanite is silicon carbide. It resembles diamond but is a different stone and cannot receive a diamond report.

You can read how lab-grown diamonds are grown on our what is a lab-grown diamond page.

Frequently asked questions