The hardest rock on Earth is diamond. Formed from carbon atoms arranged in a crystal structure under extreme pressure and temperature, diamonds are known for their remarkable hardness and brilliance. They are not only prized as gemstones in jewelry but also have industrial applications in cutting, grinding, and drilling due to their durability. Diamonds can be found in volcanic pipes or alluvial deposits, and gem-quality stones are often evaluated based on the "Four Cs": carat, cut, color, and clarity. This unique combination of properties makes diamonds an interesting topic both geologically and economically.