Diamond consists of carbon atoms in a face-centered cubic lattice, creating the hardest known natural material (Mohs 10). It forms in the mantle at depths of 150–200 km under extreme pressure and temperature, then ascends rapidly via kimberlite or lamproite magmas. Most natural diamonds are 1–3.5 billion years old.
Key properties include the highest thermal conductivity of any material, high refractive index (2.42), and strong dispersion (0.044), producing exceptional fire. Type classification (Ia, Ib, IIa, IIb) based on nitrogen or boron impurities explains color and conductivity differences. These attributes make diamond ideal for both gem and industrial uses.