When China began its crackdown on the sector some fifteen years ago, there were hundreds of miners and processors. By 2013 ten producers controlled almost all mining. Today, there are just two state-owned giants: China Rare Earth Group and China Northern Rare Earth Group High-Tech (600111.SS).

Dust and groundwater contaminated with heavy metals and radioactive chemicals pose a health threat that the authorities have been trying to address for years.

China signaled it would approve the export of rare earth minerals in a statement Friday hours after White House officials said that the US and China had signed a trade agreement to work out tensions linked to US access to the key material.