http://physicsweb.org/article/news/7/3/7
The Earth is thought to be made of a metallic core surrounded by a
silicate shell, but the origins of this structure is one of the
outstanding unanswered questions in planetary science. Researchers at
the
Institute for Study of the Earth's Interior at Okayama University in
Japan have now used electrical conductivity measurements to show that
the
Earth may have formed from rocky bodies that had already separated into
mantle and core (T Yoshino et al. 2003 Nature 422 154).

See, research is ongoing. If you REALLY care, get off your ass, and do something besides snipe blindly from the peanut gallery.