[El_Phil]

We are talking a century plus, minimum, for all major metals. One Brazilian iron ore mine, on it's own, could supply the world for over a century at current rates. Some speciality ones less, but then no-ones been prospecting for them becuase well, they're speciality.

Take Tantalum. Barely until mobiles phones and other small electronics come along, then wallop massive demand. On Australian exploration firms finds a very nice deposit, gets it going and grabs 70-80% of the market. So on paper when that runs out we run out of Tantalum, however:

1. Once Greenbushes was open everyone stopped looking because you not only had to find a deposit you had to find a really cheap one. Given it was rare to start with no-one bothered.
2. Tantalum can be subsituted with Selinium and shed loads of other sutff from the weirder parts of the periodic table
3. Worst case there's always slave labour mined Tantalum from Sierra Leone, DRC and other west/central Aftican war zones. You didn't think it was just blood diamonds did you?

So frankly I can't see asteroid mining happening.

Fossil fuels: Coal for almost half a millenium, oil/gas there's been only 35/40 years left for almost 40 years now. Whilst that can't go on forever there's still most of Siberia, Antarctic, Alaska, Rockall and the deep South Pacific basin to explore. Not even counting oil shales/sands of which the US known reserves could meet their oil needs for around 350 years.