It's very likely to be iron because of nuclear binding energy

Iron sits at the maximum of the binding energy curve (see e.g. User Posted Link ) - if you start with small atoms and fuse them - as happens at end-of-life for stars - you keep making bigger and bigger atoms until you hit iron, then it takes more energy to fuse two iron atoms together than you get out, so in the early universe after the first tranche of stars died out you ended up with a lot of iron.

Or at least that's one fairly plausible explanation as to why it might be iron and why there might have been enough of it around to coalesce into the centre of our planet.

Posted By: Partial Angler, Jun 30, 09:28:33