Cobalt's name comes from the German Kobold, a goblin or malicious spirit of the mines. Miners applied the word to the troublesome ore because it looked like valuable silver or copper ore but yielded no useful metal, and worse, being an arsenical mineral, it gave off poisonous fumes when roasted that sickened the workers. The metal was, in effect, blamed on a mine-spirit's mischief. This makes cobalt one of a small pair, with nickel, whose names preserve the demon-haunted folklore of European mining. The blue it lends to glass and ceramic, seen in ancient Egyptian and Chinese wares and in the pigment smalt, was prized long before Brandt proved a real metal, rather than a goblin, lay behind it.
Georgius Agricola's sixteenth-century mining treatises record the broader folk belief in the Harz Mountains and Erzgebirge that malicious spirits called kobolds or Berggeister haunted deep workings, sabotaging tools and leading miners astray, a belief situated alongside similar tommyknocker legends later carried by Cornish miners to America. Cobalt has acquired a very different, entirely secular controversy in the present day, since a large share of the world's supply comes from artisanal mines in the Democratic Republic of Congo linked to child labour and unsafe conditions, an ethical shadow now attached to the element's central role in lithium-ion battery cathodes.