Being one of the three ferromagnetic metals - the other two are iron and nickel - cobalt is widely used in magnetic alloys. Its compounds are used as blue pigments in the manufacture of paints and inks, and also serve as catalysts.
The scarcity of rhodium and iridium prevents their being extensively used. Extremely resistant to corrosion, iridium is employed in laboratory ware such as crucibles, and is also a constituent of very hard platinum alloys, such as those used in fountain pen points and in instrument pivots. All three members of the group are employed as catalysts.
