Moissanite is the best substitute for Diamond due to very similar appearance.
Most of the commercially available Moissanite is man made/synthetic, but small traces of Natural Moissanite have been found on Earth. These traces of Natural Moissanite are believed to have come from meteorites.
Moissanite Physical & Optical Properties are very close to that of Diamond.
Hardness of diamond & Moissanite is 10 and 9.25 respectively.
Moissanite is Doubly Refractive stone unlike diamond, which is Singly Refractive.
Moissanite has more Brilliance and Fire than Diamond due to its higher RI & Dispersion value.
Moissanite is liked for its very close resemblance to Diamond and much lower price.
Moissanite Price is as per its size; Diameter in mm, Color & Clarity.
Broadly speaking, Moissanite is almost 1/10 the price of Diamond.