 Cobalt is a ferromagnetic metal with a specific gravity of 8 @.@ 9 . The Curie temperature is 1 @,@ 115 ° C ( 2 @,@ 039 ° F ) and the magnetic moment is 1 @.@ 6 – 1 @.@ 7 Bohr magnetons per atom . Cobalt has a relative permeability two @-@ thirds that of iron . Metallic cobalt occurs as two crystallographic structures : hcp and fcc . The ideal transition temperature between the hcp and fcc structures is 450 ° C ( 842 ° F ) , but in practice , the energy difference is so small that random intergrowth of the two is common . 
