Co

Cobalt, symbol Co, is a transition metal with atomic number 27. It is a hard, silvery-gray to bluish metal that is ferromagnetic at room temperature. Cobalt occurs in minerals together with nickel and is often recovered as a byproduct of copper and nickel mining. It is essential in trace amounts for certain biological processes.

Cobalt was discovered in 1735 by the Swedish chemist Georg Brandt. The name derives from the German kobold, meaning goblin or elf, a reference to troublesome ore miners encountered in cobalt-bearing minerals. Cobalt and its compounds have a long history in pigments and alloys, and the metal is valued for its stability at high temperatures and its magnetic properties.

Occurrence and production are dominated by byproduct mining from copper and nickel operations. The largest producers include the Democratic Republic of the Congo, Russia, Canada, and Australia. In nature, cobalt is found in several minerals, such as cobaltite and erythrite, and is often refined to metal or used directly in alloys and compounds.

Applications of cobalt are diverse. It is a key component of lithium cobalt oxide cathodes in lithium-ion batteries and is used in other battery chemistries as well. Cobalt is also employed in high-performance superalloys for turbines, catalysts in petroleum refining, and pigments such as cobalt blue. Cobalt compounds serve in magnetic materials and in various chemical processes.

Isotopes and biology: the only stable isotope is cobalt-59; cobalt-60 is a radioactive isotope used in cancer radiotherapy and sterilization. Biologically, cobalt is a central element in vitamin B12 (cobalamin) and is essential for red blood cell production in many organisms. Safety concerns include toxicity from cobalt compounds and inhalation exposure in occupational settings.