Mithril

Fictional material from J. R. R. Tolkien's universe, Middle-earth.

Mithril is a silvery metal, as strong as steel but much lighter in weight, that was mined by the Dwarves in the mines of Khazad-dûm. Of all items made of mithril, the most famous is the coat of mail given to Bilbo Baggins by Thorin, that was worn by Frodo during the Quest to Mount Doom.

The name mithril comes from two words in the fictional Elvish language -- mith, meaning "mist", and ril meaning "glitter".

Mithril or similar spellings have been used in other fictional contests, as a strong and semi-magical metal; examples include:

the video game Hexen II, in which there is a mithril wall somewhere underwater that should be transformed into wood via a spell in order to proceed in the game,
the role playing game Dungeons and Dragons, where "mithral" is one of the special materials used to make almost magical items