Moissanite vs Diamond: How They Really Compare
Moissanite and diamond can look very similar at a glance, which is why moissanite has become one of the most popular stones for engagement rings and everyday earrings. They are not the same gemstone, though, and the differences are worth knowing before you buy.
The short answer
Moissanite is a lab-created gemstone made of silicon carbide. Diamond is made of carbon, and can be mined or lab-grown. Moissanite is slightly less hard than diamond, shows more rainbow-coloured sparkle, and costs a fraction of the price of a diamond of the same size.
Side by side
| Moissanite | Diamond | |
|---|---|---|
| Material | Silicon carbide | Carbon |
| Origin in jewelry | Lab-created | Mined or lab-grown |
| Hardness (Mohs scale) | 9.25 | 10 |
| Refractive index | about 2.65–2.69 | about 2.42 |
| Dispersion ("fire") | about 0.104 | about 0.044 |
| Weight at the same size | roughly 10% lighter | heavier |
Sparkle: more fire, a different look
Moissanite bends light more strongly than diamond and splits it into colour more than twice as much. In practice this means more rainbow flashes, especially in sunlight and in larger stones. Some people love that extra fire; others prefer the whiter, more contained sparkle of a diamond. Neither is better, it is a matter of taste.
Hardness and everyday wear
At 9.25 on the Mohs scale, moissanite is harder than sapphire and ruby and second only to diamond among popular gemstones. It resists scratches well, which makes it a practical choice for rings and studs you wear every day. The setting and metal matter too: a plated finish needs gentler care than the stone itself. Our guide on how to clean moissanite jewelry covers both.
Carats and millimetres
Because moissanite is lighter than diamond, moissanite sizes are usually described by their diamond-equivalent carat weight: the weight a diamond of the same diameter would have. A 6.5 mm round moissanite is commonly listed as 1 ct, and an 8 mm stone as 2 ct. Always check the millimetre size, since that is what you actually see. Our moissanite size guide has a full chart.
Price
For the same visible size, moissanite costs far less than a mined or lab-grown diamond. That is the main reason people choose it: a larger or more detailed piece, such as a halo or a bridal set, becomes affordable.
Can people tell the difference?
Most people cannot tell at a normal viewing distance. A trained eye may notice the stronger rainbow fire, and a jeweller can identify moissanite with a multi-tester or by looking for the doubled facet edges caused by its double refraction. We sell moissanite as moissanite, and you should expect any honest jeweller to do the same. More on this in does moissanite pass a diamond tester?
Which should you choose?
Choose moissanite if you want a bright, durable stone and a bigger look for your budget. Choose diamond if the material itself matters most to you. If you are leaning towards moissanite, browse our moissanite rings, moissanite earrings and moissanite necklaces, all with free shipping.
Gemstone properties are typical published values for each material. See also the Gemological Institute of America's introduction to imitation and synthetic gems.