The deal, announced on Tuesday, guarantees Apple a steady flow of rare earths and magnets free from China, the world's largest producer.

Shares of MP Materials gained 20%, closing at $58.22, a record closing high. Apple stock rose 0.2%, while the S&P 500 and Dow Jones Industrial Average fell 0.4% and 1%, respectively.

The iPhone maker is committing $500 million to buying rare-earth magnets from the company’s flagship facility in Texas, which Apple is helping to build out.