Black metal of meteoric origin, used for the most powerful weapons and armour, crafting secrets lost with Elverandil
The secret of working adamantite was maintained by the elves until the fall of Sildor, and rediscovered with the recovery of the Journals of Elverandil. Since then copies of the Journals have been traded to the dwarves of Kobur, and the Library of Aderra in Thornal, meaning in theory that the dwarves and the Erlyid share with the elves the secret of working the star-steel.
The Panserbørnë also have the secret, taught by Elverandil in exchange for guarding the Valca Gate.