The lockdown of Baotou in the northern region of Inner Mongolia takes China’s Covid Zero policy deep into coal country and to a crucial hub for the production of rare earths.

Baotou, home to about 2.7 million people, announced late Monday that it will lock down for a week after it reported two cases of the virus. China Northern Rare Earth Group, one of the country’s six major miners of the minerals, is based in the city and operates the nearby Baiyun Obo mine, the world’s largest rare earth deposit.

China is by far the world’s biggest producer of rare earths, and its threat to use that dominance drew global attention three years ago during the trade war with the U.S. The set of elements defined as rare earths are commonplace in components used in everything from cars to home appliances and military hardware.

Baotou is also the biggest city in China’s no. 2 coal producing region, some two hours drive from the mining hub of Ordos. Inner Mongolia accounted for about a quarter of national coal output last year, and as such maintaining its production would be critical to preventing a repeat of the power crisis that struck China in the fall.

Guest post from Bloomberg