Cobalt Metal

https://www.hsgmetal.com/products/cobalt-metal/

Cobalt is a shiny steel-gray metal, relatively hard and brittle, ferromagnetic, heated to 1150℃ magnetic disappear. The combined valence of cobalt is 2 and 3. It does not interact with water at room temperature and is stable in humid air. It is oxidized to CoO when heated to more than 300℃ in the air, and burned into Co3O4 when white hot. The fine cobalt metal minor powder produced by hydrogen reduction can spontaneously ignite into cobalt oxide in air.