Iron – precision density-standard cube 1cm3 NEW! Iron was known and used by ancient civilizations. This is non-coherent and flakes easily to reveal fresh surfaces for attack. Gamma iron is a polymorphic form of iron which is stable between 906C and 1403C; it has a face centred cubic lattice (fcc) and is nonmagnetic (n.b. its range of stability is reduced by the presence of carbon, manganese and nickel and it is the basis of the austenite solid solutions).