Rare earths at a factory in Tianjin, China. Manufacturers speak of resilience yet some keep only a week’s supply of rare earth magnets in their inventories © Doug Kanter/Bloomberg China’s weaponisatio

When China restricted rare earth exports to Japan in 2010 during a diplomatic spat, a wild west domestic industry undermined Beijing with rampant smuggling.

Low environmental standards helped China become the world’s low-cost producer of rare earths, but Beijing was also focused on helping the industry.