 The word cobalt is derived from the German kobalt , from kobold meaning " goblin " , a superstitious term used for the ore of cobalt by miners . The first attempts to smelt those ores for copper or nickel failed , yielding simply powder ( cobalt ( II ) oxide ) instead . Because the primary ores of cobalt always contain arsenic , smelting the ore oxidized the arsenic into the highly toxic and volatile arsenic oxide , adding to the notoriety of the ore . 
