text: At the high temperatures for Earth, no volatiles would be in the solid state, and the dust would be made up of silicate and metal.
  The continental crust and lower mantle have average K/U values of about 12,000.  mid-ocean ridge basalt (MORB) or upper mantle have more volatiles and have a K/U ratio of about 19,000.
  Volatile depletion explains why Earth's sodium (volatile) content is about 10% of its calcium (refractory) content, despite the similar abundance in chondrites.