That would be true if concretion could form metal objects but it can't.
They can form Iron Oxide, and Iron Sulfide spheres but they are usually very small like these: https://en.wikipedia.org/wiki/Klerksdorp_sphere
They can form Iron Oxide, and Iron Sulfide spheres but they are usually very small like these: https://en.wikipedia.org/wiki/Klerksdorp_sphere