The New York Times reports:

Some of the greenest technologies of the age, from electric cars to efficient light bulbs to very large wind turbines, are made possible by an unusual group of elements called rare earths. The world’s dependence on these substances is rising fast.

Just one problem: These elements come almost entirely from China, from some of the most environmentally damaging mines in the country, in an industry dominated by criminal gangs.

This chart shows a) the extent to which production of these elements is dominated by China and b) the price volatility of the rarest of these elements:

We may need to do some rethinking of what we mean when we call an energy source or technology ’sustainable’ or ‘environmentally friendly.’