I've probably done minimal research on the mines but from what I hear it's mainly Iron ore / taconite. Of course there's nickel, copper and platinum to be found. A buddy and I think we may have found copper before but never tested it. There probably are mines too but I don't think they're currently in use. There's definitely amethyst, jade and quite a lot of quartz and granite and maybe even marble to be found. To be honest, I've never seen rocky beaches with so many different gemstones before I moved here.