The hardest naturally occurring substance on Earth is diamond. Composed of carbon atoms arranged in a crystal lattice structure, diamonds are renowned for their exceptional hardness and resistance to scratching. They form under high-pressure and high-temperature conditions deep within the Earth’s mantle over millions of years. Due to their hardness, diamonds are not only prized as gemstones in jewelry but are also used in various industrial applications, including cutting, grinding, and drilling tools. The unique optical properties of diamonds, including exceptional brilliance and dispersion of light, contribute to their appeal in the jewelry market.