The hardest natural material is diamond. Diamonds are formed deep within the Earth under extreme pressure and temperature conditions, crystallizing carbon atoms in a tetrahedral structure. This unique arrangement not only gives diamonds their remarkable hardness but also contributes to their exceptional brilliance when cut and polished. Due to their hardness, diamonds are widely used in industrial applications for cutting, grinding, and drilling, as well as in jewelry, where they symbolize luxury and commitment. Their high refractive index and dispersion of light make them valuable in the gem industry.