Mine copper, subsides, oh please.

[sdholloway56]

The famous boulder was actually 3700# of pure copper. 

Since the planet is now about 99% better explored, very unlikely there's another one. The average ore grde in 1900 was 5%, now it is .5%.

Just like it it is unlikely that there's another beyond the 5 Supergiant oilfields in the world (at least 4 past peak production) 

[rickgthf]

...there's always sea floor mining of polymetallic nodules.  The sea floor copper reserves  alone are estimated to be 3x the terrestrial copper reserves.

  Besides, before long we'll be using carbon nanowires for conductors and won't need that heavy  copper.