The hardest naturally occurring mineral is diamond. Diamonds are formed under high-pressure and high-temperature conditions deep within the Earth’s mantle, primarily composed of carbon atoms arranged in a crystal lattice structure. This unique structure contributes not only to diamonds' incredible hardness but also to their brilliance and clarity when cut and polished. Diamonds are extensively used in jewelry, symbolizing luxury and beauty, but their hardness also makes them valuable in industrial applications, such as cutting, grinding, and drilling. Their exceptional hardness is measured on the Mohs scale, where diamonds score a perfect 10.