There are 17 rare earth elements. While almost all of them have vital industrial uses, you could be forgiven for believing, based on news coverage, that there are only four that matter: neodymium, praseodymium, dysprosium, and terbium.To be sure, those are the essential ingredients in the powerful permanent-magnet motors that go into electric vehicles, heating and cooling systems, appliances, tools, fighter jets, bombs, and many other systems. But the industrial and national-security importance of rare earth elements goes far beyond magnets. Among the 13 other rare earths are two—erbium and yttirum—whose importance is no less vital, and which are now facing a looming geopolitical deadline this November. Depending on how negotiations play out, the post-deadline framework could erode U.S. na
