For a while now, the Pentagon has been concerned about U.S. dependence on rare-earth metals. Precision weapons, Priuses and iPhones depend on components made from rare earths like terbium, dysprosium, yttrium and thulium. And the dependence threatens more than just national security: It's a major issue when it comes to developing renewable energy sources.

The House Committee on Science and Technology's investigations and oversight panel is holding a hearing today on rare-earth metal supplies, focusing on China's near-monopoly on the stuff. As we've reported here before, China has raised concerns by threatening to limit exports. And to make matters more complicated, U.S. mining companies are dependent on China for processing. As a recent LiveScience story points out, U.S.-based Molycorp Minerals has to ship rare earths to China for final separation.

Testimony is embargoed until the hearing begins today at 2 p.m., but you can read a hearing overview (.pdf) and watch a live webcast once the hearing begins.

The hearing will include testimony from Mark Smith, the CEO of Molycorp Minerals, which is trying to restarting a mine in Mountain Pass, California, which is the primary source for rare earth minerals in the United States. (That mining operation closed in 2002.)

It's not all doom and gloom: China has reportedly backed away from a sweeping ban on the export of some rare earths. And the United States is sitting on significant reserves of rare-earth metals (.pdf), as a U.S. Geological Survey report points out. Perhaps more importantly, policymakers and politicians are now catching on to their strategic value.

Image: Google Earth