Cobalt

Cobalt is a hard, silvery-blue metal that, like iron and nickel, is naturally magnetic. Its name comes from kobold, a goblin of German folklore, because miners blamed its arsenic-laced ores for making them sick while yielding no useful metal. Georg Brandt identified it around 1735. Most of today's cobalt is mined in the Democratic Republic of the Congo, usually alongside copper.

Cobalt is a key ingredient in the cathodes of many lithium-ion batteries. It also goes into superalloys for jet engine turbines, hard cutting tools and strong magnets. Cobalt compounds have colored glass and pottery a deep blue for thousands of years.