Cobalt ( Co )
Cobalt has been in use since at least 2250 BC, when the Persians used it to color glass. It was not until 1735, however, that Swedish scientist G. Brandt first isolated metallic cobalt and it was not until 1780 that it was recognized as an element.
Today, cobalt is used mainly in high-temperature steel alloys, magnetic alloys and hard-facing alloys resistant to abrasion. Alloys containing 25 percent cobalt have been developed for use as fasteners in gas turbine engines.
Cobalt is a silver-white, lustrous, hard, brittle metal. It is a member of group VIII of the periodic table. Like iron, it can be magnetized. It is similar to iron and nickel in its physical properties. The element is active chemically, forming many compounds.