 Cobalt @-@ based blue pigments ( cobalt blue ) have been used since ancient times for jewelry and paints , and to impart a distinctive blue tint to glass , but the color was later thought by alchemists to be due to the known metal bismuth . Miners had long used the name kobold ore ( German for goblin ore ) for some of the blue @-@ pigment producing minerals ; they were so named because they were poor in known metals , and gave poisonous arsenic @-@ containing fumes upon smelting . In 1735 , such ores were found to be reducible to a new metal ( the first discovered since ancient times ) , and this was ultimately named for the kobold . 
