Keep in mind that thicker metal sinks will cost more, but add little, if anything, to the sink. (moneysense.ca)
The heat of its formation caused extensive melting of the planet, leading Earth to separate into two layers when the denser iron metal sank inward toward the center, creating the core and leaving the silicate - rich mantle floating above. (carnegiescience.edu)
Eventually the planet grew to such a size that denser iron metal sank inward, to form the beginnings of... (carnegiescience.edu)