Mithril

Mithril (variously spelled mithral, mythral or mythril): a lightweight, very strong, silvery metal, similar to the real-world metal titanium. The name is Sindarin for "silvery glitter". Appeared in J. R. R. Tolkien's The Lord of the Rings as an Infinity Plus One Metal, but in later (post-Tolkien) examples it's a mid-level miracle metal only, above steel but below adamantium.