I largely agree with the general idea here. > metal structural systems for animals Something resembling this has actually been observed in a species of deep s

I largely agree with the general idea here. > metal structural systems for animals Something resembling this has actually been observed in a species of deep sea snails. Iron sulfide is incorporated into the hard bits (shell, foot armor). (https://en.wikipedia.org/wiki/Scaly-foot_gastropod https://en.wikipedia.org/wiki/Scaly-foot_gastropod)