This has been featured in the national TV news in Japan lately. The problem is cost. It is expensive mining the sea bed at these depths. Maybe it will get cheaper if they scale it up.
The U.S. and Canada have plenty of rare earths. I expect it would be cheaper to mine our rare earths than to mine the sea floor. We cut back production because the Chinese material is cheaper, not because we ran out. The Chinese production costs are lower reportedly because labor costs are low and they ignore environmental protection regulations. (There are such regulations in China.) - Jed
