A rare metallic element (S No. 68/1, Jan/Feb 1951: "The Six Elements of Crime!"; and others) that is discovered by Superman in July-August 1949 and named in his honor by the members of The Super-Saved Club. Superman refers to it as "the hardest substance in existence" (WF No. 41, Jul/Aug 1949: "The Discovery of Supermanium!") and as "my invulnerable new element" (S No. 68/1, Jan/Feb 1951: "The Six Elements of Crime!"), and the texts describe it as "the strongest metal known" (Act No. 289, Jun 1962: "The Super-Practical Joker!") and as "the strongest metal known to science" (S No. 167, Feb 1964: "The Team of Luthor and Brainiac!" pts. I-III: â€"The Deadly Duo!"; "The Downfall of Superman!"; "The Hour of Kandorâ€™s Vengeance!").
In July-August 1949, after an "eminent chemist" has reported the probable existence of a "super-hard" element, as yet undiscovered, whose unique properties would make it "extremely valuable for all sorts of industrial purposes," the members of the Super-Saved Club, acting at the urging of James Harvey Thorben, decide to pool their financial resources and scientific and engineering expertise in order to locate and refine the new element. If successful, they plan to name it "supermanium" as a surprise tribute to Superman.
Officially, it is the members of the Super-Saved Club who locate the new element in a remote mountain region and refine the worldâ€™s first sample of supermanium ore. In actuality, however, it is Superman, working behind the scenes with his superpowers so as not to spoil the club membersâ€™ surprise for him, who locates the vein of supermanium ore and refines it, for the new substance is so unbelievably super-hard that it literally shatters the machinery with which the club members attempt to grind it, forcing Superman "to apply his full colossal strength" in order to refine the ore by hand. "Heat and pressure," thinks Superman as he bends to the task, "â€¦ I can supply more of them with my hands than any machine can!"
Having secretly refined the rare ore himself while contriving to make it appear that the Super-Saved Clubâ€™s machinery has somehow done the job for them, Superman graciously allows the clubâ€™s members to present him with the element they have named in his honor, promising that he will see to it that it is put to work in a multitude of ways "to save human drudgery!" (WF No.41: "The Discovery of Supermanium!").
In January-February 1951, Superman fashions a vault out of supermanium for Metropolisâ€™s "famous radium institute" in order to prevent its priceless radium stockpile from being stolen by Lex Luthor. He also makes the bars of Luthor's cell out of supermanium so he can't use his scientific genius to escape. (S No. 68/1: "The Six Elements of Crime!")
In June 1962, Superman employs invisibly fine wires fashioned out of supermanium to enable him to manipulate gigantic replicas of mythical monsters as though they were colossal marionettes (Act No. 289: "The Super-Practical Joker!").
In February 1964, when Lex Luthor arrives on the "prison planet" Kronis to liberate Brainiac, he finds the notorious space villain locked in a "mighty cage", fashioned by Superman from "an isotope of supermanium", which his powerful "atomic torch" cannot even scratch. It is while Lex Luthor is attempting to free him from his supermanium prison that Brainiac remarks, incorrectly, that supermanium "is named after Superman because it was forged by him from the heart of a mighty star!" (S No. 167: "The Team of Luthor and Brainiac!" pts. I-III—"The Deadly Duo!"; "The Downfall of Superman!"; "The Hour of Kandorâ€™s Vengeance!").