COBALT

(Co), chemical element, ferromagnetic metal of Group VIII of the periodic table, used especially for heat-resistant and magnetic alloys. The metal was isolated (c. 1735) by a Swedish chemist, Georg Brandt, though cobalt compounds had been used for centuries to impart a blue colour to glazes and ceramics. Cobalt has been detected in Egyptian statuettes and Persian necklace beads of the 3rd millennium BC, in glass found in the Pompeii ruins, in China as early as the T'ang dynasty (AD 618907) and later in the blue porcelain of the Ming dynasty. The name kobold was first applied (16th century) to ores thought to contain copper but eventually found to be poisonous, arsenic-bearing cobalt ores. Brandt finally determined (1742) that the blue colour of these ores was due to the presence of cobalt.