If you’re just joining us, this is a follow-up to today’s day thread about the element neodymium. The rare earth metals neodymium and praseodymium are so similar chemically that they were initially believed to be one element, didymium. When they were finally separated, 40 years after the initial discovery, they were given names meaning “new twin” and “green twin.”

Praseodymium is the green twin, even though – like neodymium and, in fact, most metals – in its pure form, it is silvery-gray. The name comes from the color of the salts it forms. When Austrian chemist Carl Auer von Welsbach separated the -dymiums from each other, he was rewarded with salts that were two different colors, green and pink. (Auer von Welsbach had a pretty productive life, overall: in addition to cracking didymium, he invited the flints used in modern lighters and the metal-filament lightbulb.)

Praseodymium has various applications, but nothing like the “whoa, science!” one-two punch of lasers and magnets that neodymium has. It’s merely a thing that exists, doing good work in obscurity.