The price of rare earth metals, which are used to build super-strong permanent magnets, have soared this year, as China further reduced export quotas and closed down illegal mines.

Traders sought to take advantage of the tightening supply, investing heavily in the metals and driving prices to record levels, says Vivian Pang, an analyst at Asian Metal in Beijing.

Neodymium, the main rare earth used in the industry, hit a peak of 1.79m