My layperson understanding was that all of the surface gold (i.e. available to humans, not in earth's core) was delivered here via comets/asteroids. The explan

My layperson understanding was that all of the surface gold (i.e. available to humans, not in earth's core) was delivered here via comets/asteroids. The explanation I received was that the densest atoms (e.g. gold) migrated into the core over billions of years (because: gravity; gold is twice as dense as lead).