Mountain Pass Materials, the premier rare earth producer in the United States, has announced that the Pentagon will invest $400 million in convertible preferred stock, thereby becoming the company's largest shareholder with a 15% stake. This investment also grants the Pentagon the potential to further increase its ownership. As the sole U.S. enterprise possessing a comprehensive rare earth production chain, Mountain Pass Materials boasts the world's second-largest rare earth mine and processing facility. Its primary client is General Motors, and the company anticipates commencing the supply of rare earth magnet products later this year.