Where to find mithril ore on RuneScape?

Mithril Dragons are found in the Ancient Cavern. You can only enter if you have started Barbarian Training. The entrance to the Ancient Cavern is south of the Barbarian Outpost near Baxtorian Falls. You'll have to dive into the whirlpool, if you haven't completed barbarian training yet you'll get a few damage and end up near Hadley's house.