Moissanite vs Diamond

Moissanite is silicon carbide, a completely different material from diamond, which is pure carbon. It was first identified in 1893 by the French chemist Henri Moissan in fragments from a meteorite crater in Arizona; at first he believed he had found diamonds.

Natural moissanite is extremely rare. All moissanite used in jewellery is created in a laboratory. It is not a lab-grown diamond and should never be described as one: a lab-grown diamond is diamond, while moissanite is a diamond alternative.

This is the clearest visible difference. Moissanite bends light more strongly than diamond and splits it into more colour, so it throws noticeably more rainbow flashes. Some people love that intensity. Others find it reads as a little too colourful, especially in larger stones or in sunlight, where it can look more like a disco ball than a diamond.

Diamond’s light is a balance of white brightness and coloured fire. It is the look most people picture when they think of an engagement ring.

Diamond is the hardest natural material, at 10 on the Mohs scale. Moissanite, at around 9.25, is still very hard, harder than sapphire and ruby, and well suited to everyday wear. Over decades, a diamond keeps its sharp facet edges a little better.

Moissanite is doubly refractive, so under a jeweller’s loupe, looking through the stone at an angle, the facet edges appear doubled. Diamond does not do this.

Moissanite also conducts heat in a similar way to diamond, which means a basic thermal diamond tester can mistake it for one. Jewellers use testers that also measure electrical conductivity, which tell the two apart immediately. An independent grading report is the clearest answer of all.

Moissanite costs a fraction of a diamond of the same size. It has very little resale value, and it is not graded on the 4Cs by the major diamond laboratories in the way diamonds are.

If the aim is a large, sparkling stone on a modest budget, moissanite is an option. If you want a diamond at a lower price, a lab-grown diamond is the closer choice: it is diamond in every physical sense, independently graded, and costs far less than a natural one. Our natural vs lab guide explains the difference.