The hardest natural substance known to humankind is diamond. Diamonds are formed under intense pressure and high temperatures deep within the Earth’s mantle over millions of years. They are made of carbon atoms arranged in a crystal lattice structure, which contributes to their renowned hardness and durability. Diamonds not only have industrial applications, used in cutting and grinding tools, but they are also prized as gemstones in jewelry for their brilliance and beauty. Their exceptional hardness makes them resistant to scratches, distinguishing them as the hardest known naturally occurring material on the Mohs scale of mineral hardness.