 Cobalt compounds have been used for centuries to impart a rich blue color to glass , glazes , and ceramics . Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC , in the ruins of Pompeii ( destroyed in 79 AD ) , and in China dating from the Tang dynasty ( 618 – 907 AD ) and the Ming dynasty ( 1368 – 1644 AD ) . 
