Mithril: The Empire’s so awash in exotic materials of the future (see: Unobtainium) that there’s almost certain to be one that matches mithril’s hypothetical properties pretty much one for one.
I mean, sure, it’s some hideously complicated nanoformed metallic-glass composite, but “does the same, is the same”, right? Right? (Or at least close enough that that’s how the first-contact team’d program the translator when they got around to pillaging our fantasy and SF for linguistic close-fits.)
Makes a damn fine mail shirt, too.
Mithril always seem to me to “merely” be ordinary metallic titanium, which made it unobtainium when JRRT was writing, but today the only really difficult part of it would be the astounding pain in the ass it is to machine mail rings of it together.