President Vladimir Putin has offered the U.S. the opportunity under a future economic deal to jointly explore Russia's rare earth metal deposits that he says are greater than those of Ukraine.

Rare earth metals are making headlines as demand rises for products from smartphones to wind turbines, and as governments seek secure supply.

Rare earth metals are making headlines as demand rises for products from smartphones to wind turbines, and as governments seek secure supply. Here are some basic facts about them: WHAT ARE THEY?Rare earths are a group of 17 elements including 15 silvery-white metals called lanthanides,