Cobalt ancient glass colorant

After the discovery of phosphorus, 66 years passed before another new element, cobalt, was discovered. Cobalt compounds were known since ancient times and had been used to color glass since the sixteenth century. They were collectively known under the name kobold. Miners believed that the presence of these substances in mines was the work of malicious gnomes called kobolds, who wanted to poison the miners. 

Cobalt has been in use as a coloring agent for glass since ancient times. The metal was isolated by Brandt in 1735 and confirmed as an element by Bergman in 1780. Cobalt is widely distributed in nature, but in small concentrations. Its concentration in the earth s crust is estimated to be about 0.0025% and in the sea water is about 0.02 pg/L. Cobalt minerals with their chemical formula and CAS Registry numbers are tabulated below ... 

---