Mithril

Also called 'true-silver', and many other names besides; the remarkable metal that the Dwarves discovered in the mines of Khazad-dûm. It was supple and easy to work, and could be polished to shimmer like silver that never tarnished, and it was stronger than steel. In Middle-earth, mithril was found nowhere but the Dwarf-mines of Khazad-dûm, though there are indications that it was also found in Númenor and in Aman.

The metal held a value almost beyond price. In Númenor, King Tar-Telemmaitë became so greedy for mithril that it gave him his name - Telemmaitë means 'silverhand'. In Middle-earth, meanwhile, the Dwarves' discovery of mithril drew the Noldor to found the kingdom of Eregion in the lands immediately westward of Khazad-dûm. As the years passed, the seams beneath the Dwarf-city began to be worked out, and the Dwarves dug deeper and deeper. It was their deep mining for mithril that would awake the Balrog, Durin's Bane, and bring about the downfall of their kingdom.

Of all the mithril artefacts, the most famous is surely the coat of mail given to Bilbo Baggins by Thorin Oakenshield, that was held for a while in the Michel Delving mathom-house before being worn by Frodo during the Quest of Mount Doom. Many other of the world's most important items were made of mithril, too. The symbol of High Kingship worn by Elendil and Isildur was the Elendilmir, a diamond bound to the brow by a mithril fillet, and Nenya, one of the Three Rings of the Elves, was also made of the metal, again bearing a diamond. Greatest of all, according to legend, was the ship of Eärendil in which he sailed into the sky, making the gleam of truesilver visible to the world as the Morning and Evening Star.