They'd have to be rarer, though, and deep within mines. I wouldn't want to be able to wander into any old mine and snatch up all the glass/ebony/mithril/adamantine I want right off the bat.
This.
Silver and Iron might be a bit more common, but then Gold, Glass, Ebony, Mithril and things like adamantine should be [u][i]extremely[i][u] rare, unless there is a legitimate excuse for there being stacks of the minerals.
I can't wait to see how they implement mining, and if you are able to turn the things you mine into armour, that'd be such a fantastic feature.