Does Moissanite Pass a Diamond Tester?

It is one of the most searched questions about moissanite. The honest answer: it depends on the tester.

Basic thermal testers: usually yes

The classic diamond tester pen measures how quickly a stone draws heat away from the tip. Diamond conducts heat extremely well, and so does moissanite. Because their thermal readings are so close, a basic thermal tester will often report moissanite as diamond.

Multi-testers: no

Moissanite (silicon carbide) conducts a small amount of electricity, while nearly all diamonds do not. Multi-testers measure electrical conductivity as well as heat, so they flag moissanite as moissanite. Most jewellers today use a multi-tester or a dedicated moissanite tester for exactly this reason.

What a jeweller sees

• Double refraction. Moissanite is doubly refractive, so looking through the stone at an angle can show doubled facet edges. Diamond is singly refractive.
• More fire. Moissanite disperses light into colour more than twice as much as diamond, giving stronger rainbow flashes.
• Weight. A moissanite is roughly 10% lighter than a diamond of the same size.

Why it matters

People choose moissanite for its brilliance, its hardness and its price, not to pass it off as something else. If you are buying or selling a stone, always ask what it is and how it was identified. At JUSMIR every piece is described as moissanite, with its size in millimetres and, where the supplier lists one, its carat weight.

Read next: moissanite vs diamond, or explore our moissanite rings and moissanite earrings.