Luthorite
From superman.nu: Supermanica
A fabulous "new metal"—described as the "hardest and strongest [metal] of all"—that is created by Lex Luthor in November-December 1946. "Luthorite resists friction-heat!" explains Luthor. "[With it] I can build irresistible weapons and impenetrable space ships to dominate the universe!" Luthorite contains iridium and possibly osmium, but its chief ingredient is "the unknown Element X," available only from certain rare meteorites. (S No. 43/3: "The Molten World!")
