Moissanite vs Diamond: An Honest Comparison

They are different materials. Moissanite is silicon carbide. Diamond is carbon. Everything that follows comes from that, and none of it is a matter of opinion.

The short version: moissanite is nearly as hard as diamond, noticeably brighter than diamond, and costs a small fraction of it. Whether that makes it the better choice depends entirely on what you want the ring to do.

Is moissanite as hard as a diamond?

Almost. Diamond sits at 10 on the Mohs scale and is the hardest natural material known. Moissanite sits at 9.25, which makes it one of the hardest gemstones available and second only to diamond (GIA).

In practical terms that gap does not matter much. Both will survive daily wear for decades. Sapphire, at 9, has been worn in rings for centuries without incident. Anything at 9 or above is hard enough that the setting will fail before the stone does.

Hardness is also not the same as toughness. Hardness resists scratching. Toughness resists chipping, and a hard stone with a sharp girdle can still chip if it meets a door frame at the wrong angle. That is true of diamond too.

Which sparkles more?

Moissanite, and measurably so.

Diamond has a refractive index of 2.42. Moissanite has refractive indices of 2.648 and 2.691, which is higher, so it bends and returns more light. Its dispersion, the property that splits white light into colour, is 0.104, which gives it more than twice the fire of diamond (GIA).

Whether that is a selling point is genuinely a matter of taste. More fire means more flashes of coloured light. Some people want exactly that. Others find it reads as obviously not a diamond, particularly in larger sizes, and GIA notes that at a carat and above the intense fire can give moissanite away.

That is worth knowing rather than worrying about. Nobody at a dinner table is measuring dispersion. But if the goal is a stone indistinguishable from diamond to a jeweler's eye, moissanite is not it.

How can you tell moissanite from a diamond?

This is where the two separate cleanly, and it takes a loupe rather than a gadget.

Moissanite is doubly refractive. Light entering the stone splits into two rays, so looking down through the crown at an angle you see a doubled image of the back facets, and the inside of the stone can look faintly blurred (GIA). Diamond is singly refractive and shows no such doubling.

This is the test a jeweler actually uses. It does not depend on a battery, it cannot be fooled, and it takes about five seconds once you know to look for it.

It also explains a common frustration. Older diamond testers measure thermal conductivity, and moissanite conducts heat similarly enough to diamond that it often reads as diamond on those instruments. Combination testers that also check electrical conductivity separate them correctly, but a thermal-only pen will mislead you.

Is moissanite a fake diamond?

No, and the distinction matters if you are ever selling.

A simulant looks like a diamond and is a different material. Moissanite is a simulant, as is cubic zirconia. A lab-grown diamond is chemically, physically and optically diamond, grown in a few weeks rather than found. Those are not the same thing, and conflating them is the most common error in this subject.

So a lab-grown diamond genuinely is a diamond. Moissanite genuinely is not. If lab-grown is the direction that interests you, we cover what lab-grown diamonds actually are separately.

What is moissanite worth when you sell it?

Very little, and you should decide knowing that.

Moissanite is manufactured, supply is effectively unlimited, and there is no meaningful secondary market. A jeweler buying estate pieces will price a moissanite ring at close to the value of its metal and setting, because that is what can be resold. This is not a judgement about the stone. It is what happens to any manufactured material with no scarcity behind it.

Natural diamonds hold a resale value, though usually well below retail, and people are frequently surprised by how far below. Lab-grown diamond prices have fallen substantially as production has scaled, which affects resale too.

If a ring is being bought to be worn and never sold, none of this matters. If there is any chance it comes back to a counter one day, it should be part of the decision rather than a discovery.

So which should you choose?

Choose moissanite if you want maximum size and brightness for the money, you are untroubled by the extra fire, and resale is irrelevant to you. It is a durable stone that will look excellent for a lifetime.

Choose a natural diamond if you want the material itself, want the stone to retain some value, or care that it is the thing rather than a stand-in for it.

Choose a lab-grown diamond if you want diamond specifically but would rather put the difference into size or setting, and you accept that its resale is uncertain.

There is no wrong answer here, only an uninformed one. What we would rather you not do is buy moissanite believing it is a diamond, or buy a diamond believing its resale will be close to what you paid.

Come and look at both

The fastest way to settle this is to see the two side by side under the same light, which is difficult on a screen and easy across a counter. We keep engagement rings in the case at a range of budgets and show stones loose as well as set, so you can compare before choosing a setting.

Bring whatever you are considering, including a stone you already own. We will tell you what it is.