Adamantite

Adamantite (金剛岩, Kongougan; Literally meaning Adamantine Rock) is a type of metal that's found occurring in most nations, though large amounts of it are found in the Land of Chasms. The metal is reputed to be the strongest substance known, even harder than diamond.

Uses
With its extraordinary hardness. Adamantite is often made into Swords and other ninja weapons. These weapons are often reserved for people of high class such as a Kage.