Rare-earths plants are popping up outside China

In a warehouse deep in Brazil's savanna, machines churn through piles of red clay to produce chalky rocks packed with metals critical for making electric cars, smartphones, and civilian and military technologies.

- Samantha Pearson & Jon Emont

But its 90% share of processing for rare earths mined around the world is what really concerns officials from other countries working to secure their supply.

"China is a formidable competitor," said Ramón Barúa, chief executive of Canada's Aclara Resources, which is opening a rare-earths mine to supply a processing plant it plans to build in the U.S. Aclara said it plans by August to decide where in the U.S. to build its plant for separating rare-earths deposits into individual elements.

It also has a buyer lined up. Aclara signed an agreement last year to supply rare earths to VAC, a German company that is building a factory in South Carolina with $94 million in Pentagon funding to make magnets for clients including General Motors.

"We're seeing a tsunami of demand," Barúa said. Geopolitical tension is fueling interest in Brazil's minerals. After the U.S. set new tariffs on China last month, China tightened restrictions on the export of rare-earth materials, worrying U.S. manufacturers including Tesla and redoubling their hunt for non-China alternatives. Exports of rare earths restarted this month for some companies.

"Hopefully, we'll get a license to use the rare-earth magnets," Tesla CEO Elon Musk said on the company's April earnings call.

Brazil has the world's second-largest rare-earth reserves after China, some 21 million tons, according to the U.S. Geological Survey. That represents more than a fifth of known global reserves—and more than 10 times those in the U.S.