Not only is Moissanite significantly cheaper than diamonds, it is also guaranteed to last just as long. Moissanite is one of the hardest substances on earth. With a 9.25-9.5 rating on the Moh’s hardness scale, Moissanite is the second hardest gemstone in existence (second only to diamonds at 10). A gemstone’s hardness determines how easily it can be scratched. With such a high score, this means Moissanite is extremely scratch-resistant, making it the perfect choice for your engagement ring stone.