mithril

Gandalf from Tolkien's Fellowship of the Ring says: "Mithril! All folk desired it. It could be beaten like copper and polished like glass; and the Dwarves could make of it a metal, lighter and yet harder than tempered steel. Its beauty was like to that of common silver, but the beauty of mithril did not tarnish or grow dim. The Elves dearly loved it, and among many uses they made of it ithildin, starmoon, which you saw upon the doors. Bilbo had a corslet of mithril-rings that Thorin gave him. I wonder what became of it? Gathering dust still in Michel Delving Museum, I supposed." It is also referred to as Moria-silver or true-silver.

Mithril is Sindarin for "Grey Flame".

This metal was found only in Khazad-Dum (Moria). It was loved among the dwarves above all other things, and highly prized among the other races such as elves and men, and also Sauron. It was light and hard and would not tarnish like silver.

The mithril vein in Khazad- Dum was what made Durin’s folk wealthy. However, the dwarves dug too deeply and uncovered Durin’s Bane, the balrog, in TA 1980. Such was the terror of the balrog that even the orcs refused to mine the mirthil located there, so that by the end of the third age it became priceless. Indeed Bilbo’s (later Frodo’s) mirthil coat was estimated at a cost of more then the whole of The Shire and its entire contents.
The Noldor of Eregion made ithildin from mithril. Bilbo’s mail, Nenya and the helms of the Guards of the citadel were all made of Mithril.
Mithril was also called silver- steel, Moria- silver and true- silver.