"We're not finding the mother lodes of caches (insurgent military supplies) when we go out, " he says.

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While defining lodes is easy, refining the various rare earth elements is hard and each step of the process is likely to cost a billion dollars.

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On small lodes they gobble up man-hours in setup time.

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There is another challenge less emphasized in recent media coverage: The global goal rush can present dire political and physical risk as companies seek mother lodes in dangerously unstable nations.

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When two large copper lodes were discovered at mines in Calumet and Hecla in 1865, the two mine owners joined forces and the merged company became large enough to influence world markets.

BBC: Cornwall