How to identify moissanite

How to identify moissanite

You do not have to own a piece of expensive technology to identify moissanite, just a 10X loupe and good lighting.

The dispersion of moissanite is twice that of diamond, making the stone much more fiery. The hardness (resistance to scratching) of 9.25 is measured on a scale that is not absolute. In fact, diamond is many orders of magnitude harder than any other gem, natural or created.


Almost all diamond simulants share one property with diamond. They are singly refractive. The term, singly refractive means that a ray of light passing through the gem is slowed but otherwise unaffected by the medium. Glass is a singly refractive material, as are cubic zirconia, garnet and diamond itself.

Synthetic moissanite, however is doubly refractive. This means that a ray of light passing through this sort of gem is slowed, bent and split in two as it passes though the medium. Sapphire is a doubly refractive material, as are peridot, tourmaline and zircon.

The effect of double refraction becomes visible, for example in peridot or zircon, when the back facets of the stone are viewed through the table. There seem to be two of every facet and the culet. This effect is called doubling. One aspect of doubly refractive material is that every doubly refractive gem has at least one direction in which the material appears to behave like a singly refractive gem (called the optic axis), and does not break light into two rays. Synthetic moissanite is cut so that this direction of single refraction is though the table. This means that the doubling is not apparent when the stone is viewed though the table. Moissanite must be viewed through any other crown facet (e. g. star, or bezel) to see the doubling. The doubling seen through these other facets is very strong, almost fuzzy in appearance.

Therefore, when examining a "diamond" after testing it with the thermal probe, tilt the stone slightly and look at the culet and the other pavilion facets through one of the crown facets other than the table. No doubling, it's a diamond. If you see doubling it is not a diamond. 

The faceted moissanite we have seen is quite yellow (K and lower) in colour and it (sometimes) may have inclusions (whitish, VS and lower in appearance). It is now also cut in princess and radiant cuts as well as round. It is the kind of gem that one would not think twice about, it has to be diamond: it has colour, it may have marks. Well, what you have to do now is look just a bit more carefully at the stone you are accepting for repair or appraisal. Before you write diamond on the job bag or take-in form don't simply use the diamond probe. Look at it too. If there is apparent doubling seen through the crown facets, or of you are unsure about what you are seeing, please call, send or bring it in, we will be happy to identify the stone for you (fees may apply).