Adamantine was mentioned in Percy Jackson's Greek Gods, alongside the three magical ores. There's no other information that, though. Also, the search bar is your friend.
Edit: I did some research on adamantine and in Greek mythology it's used to describe any material whose composition was that of a very hard material. Although not only referring to metals, the adamantine was also known as the metal of the gods.
I don't own the book making reading difficult without illegal methods. the search bar doesn't exactly help much either. it gives brief mentions of basically nothing other than existing and maybe something to do with Tartarus.