Space Rocks!

According to geologists at the University of Toronto and the University of Maryland some of the rocks beneath earths surface maybe from space. James Brenan, of the Department of Geology at the University of Toronto, says "The extreme temperature at which the Earth's core formed more than four billion years ago would have completely stripped any precious metals from the rocky crust and deposited them in the core." 
So far the current results say that there is no way that mine-able platinum and rhodium would exist from just 
internal processes alone, and the only way is they could exist is a 'rain' of extraterrestrial debris spreading the rar minerals over the surface of earth. The resurch was funded with the support of the Natural Sciences and Engineering Research Council of Canada and a NASA Cosmochemistry grant. And you can read the full article here: http://www.sciencedaily.com/releases/2009/10/091018141608.htm

It would be really interesting if most of our rare minerals came from outer space. And it would explain somewhat why these minerals are so rare and how they only happen in some areas even though the same conditions can occur somewhere else and not have the mineral come out.