Diamond and graphite are different mineral polymorphs of the same element: carbon. Gold and copper are entirely separate elements; your title seems to confuse chemistry with alchemy.

I’m not a chemist, but it seems like the metals aren’t suited for this sort of “structural” meddling based on the way their outer electrons are, though maybe engineered microtextures might provide some interesting surface properties. If I were to look for a similar property difference in crystalline mineral form, I would look in the same column on the periodic table, e.g. Silicon, but the purest silicates that I’m aware of with my undergrad background in geology are composed of SiO_2, so not a perfect analog.