Adamantine

Described as a super strong metal, Adamantine glitters translucent white, sort of like a cross of silver and diamonds. Adamantine was used when Hephaestus made Hera's throne. Curiously, most of the weapons made out adamantine that appeared in the series have Imperial Gold in they too.

Percy Jackson's Greek Gods
To be added

Notable Adamantine Weapons

 * Perseus's sickle (half Adamantine, half Imperial Gold)
 * Hermes's Sword (half Adamantine, half Imperial Gold)
 * Kronos' Scythe (according to some myths)