And it seems that Superman has never heard of Adamantium That's okay, Spider-Man has never heard of kryptonite.
All-New All-Spectacular Spider-Man/Superman by Brad Metlzer and Pepe Larraz
Even though you know, it came up last month.
Superman/Spider-Man by Mark Waid and Jorge Jimenez
But everyone else definitely knows what adamantium is Roy Thomas introduced the idea of adamantium in Avengers[...]
