"This deal and subsequent deals around the globe have allowed China to come closer to cornering the market in rare earth minerals," Commission in a 2005 report.

"Of equal concern is the transfer of technology, including patents, allowing China to control development of next-generation products using rare earth minerals," the report said.

Mark Smith, CEO of Molycorp Minerals, told the congressional committee this week that "while the U.S. still possesses the technical expertise, we have lost the necessary infrastructure to manufacture the rare earth metals and magnets that fuel next generation technologies."

Along with high-tech uses, rare metals are heavily used by defense and, increasingly, for clean energy.

China has acquired 100% of the associated rare earth metal production. This is causing much concern because, Smith said, "China's national consumption of rare earth resources is growing at an intense pace, consistent with their meteoric GDP growth, and it is leaving the rest of the world with less of these critical materials just as the clean energy economy is beginning to gain momentum."