What is the difference between moissanite and diamond?

Short answer: moissanite is lab-created silicon carbide; diamond is carbon. Moissanite is more brilliant (refractive index 2.65–2.69 vs 2.42) and has more than twice the “fire”, the rainbow flashes. It is slightly less hard (9.25 vs 10 on the Mohs scale) and costs a fraction of a diamond.

To the naked eye they are very hard to tell apart; the most visible difference is moissanite's livelier colored flashes in direct light. Read more in our moissanite bridal guide.