Duranium/Legends

Duranium was a substance much stronger than either Transparisteel or Bronzium. It was extremely durable, light, and was capable of withstanding a glancing blow from a lightsaber; however, it also had a very high melting point, making it difficult to shape. It was however, fool proof against blasters and slugthrowers, only the continuous heat of a lightsaber able to melt through it, and this would take up to half an hour. It was often used in making prison cells and cages.

Behind the scenes
"Duranium" is also a strong substance in Star Trek, used in the construction of starship hulls in that universe; it was first used in the Original Series episode "The Menagerie," predating Star Wars itself by nearly eleven years.

Appearances

 * The Betrayal of Darth Revan
 * Labyrinth of Evil
 * Star Wars Episode III: Revenge of the Sith novel
 * The Last of the Jedi: Against the Empire
 * Coruscant Nights I: Jedi Twilight
 * The Force Unleashed II novel
 * Star Wars Galaxies
 * A Boy and His Monster: The Rancor Keeper's Tale