Cobalt (Co) is a hard, lustrous, silver-gray metal found in the Earth's crust and commonly obtained as a byproduct of nickel and copper mining. It has a face-centered cubic crystal structure and is known for its high melting point, good thermal conductivity, and magnetic properties. Cobalt is widely used in a variety of applications including superalloys for jet engines and gas turbines, permanent magnets, and rechargeable batteries. Cobalt-based blue pigments have also been historically significant for ceramics and glass. On a smaller scale, but of considerable technological interest, cobalt is also used as a dopant in semiconductors and in certain types of stainless steel. From an environmental standpoint, cobalt can be toxic in high concentrations, necessitating safe handling and disposal practices. Recently, cobalt has gained significant attention for its role in lithium-ion batteries, leading to efforts for ethical sourcing and recycling due to human rights concerns related to its mining. In summary, cobalt is a versatile metal essential for modern technology, whose complex supply chain has made it a focus of ongoing sustainability and human rights initiatives.