Cobalt is a hard, lustrous, grey metal, a chemical element with symbol Co and atomic number 27. Cobalt-based colors and pigments have been used since ancient times for jewelry and paints, and miners have long used the name kobold ore for some minerals. Cobalt is used in the preparation of magnetic, wear-resistant, and high-strength alloys. Smalte (cobalt silicate glass) and cobalt blue aluminate, CoAl2O4 gives a distinctive deep blue color to glass, ceramics, inks, paints, and varnishes.
Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of Pompeii (destroyed AD 79), and in China dating from the Tang dynasty (AD 618–907) and the Ming dynasty (AD 1368–1644). Link Wikipedia; Cobalt