Lithium and other elements that the U.S. needs for vital defense, energy and other applications could become harder to obtain if the Trump administration goes ahead with tariffs and other protectionist policies aimed at China.

China refines more than 90% of the global supply of so-called "rare earth elements," which include neodymium and dysprosium. Not actually rare, these 17 elements are difficult to mine and refine because they're not often found in concentrated deposits. Some elements, like Lithium, are usually mentioned along with rare earth elements, because they are also critical for the tech sector.