I did think of that, but it violates some core concepts of how I saw Dwarven Magic working, so I didn't go that way. Your last bit about nodes could work though, since there is an innately magical essence to Rune Metals, you could say they boost anything in the area if there's enough ore there. Of course getting the big of a concentration would likely be the find of a millenium, but it could be an interesting adventure hook, you'd just have to make sure the chracters didn't get a hold of it.