re: Martian GOLD RUSH?
We're not likely to find rich ore bodies on Mars. Mineral enrichement happens in hydrothermal systems, especially at mid-ocean rifts, though also in areas of continental volcanic activity. It's likely that some of that has happened on Mars, but between lower heat flow and less water, probably a lot less than on earth.
Gold in particular is further concentrated when gold-bearing ores are weathered, and the relatively inert gold ends up washed down streams and concentrated in gold dust and nuggets in alluvial deposits (thus, panning for gold along rivers).
As other have noted, of course, no mineral would come close to paying its transportation costs back to Earth, even if it were laying around in pre-formed ingots all over the surface.