These spawn occasionally in a certain store, but it's pretty much just a plain battleaxe and only marginally cheaper than the Workmill sort you can buy at any time. Maybe these could be given a bonus to the EFUSS Mining skill and their price adjusted appropriately?
Actually variables on items are wiped if they're in a store, so we can't do this even if we wanted to. But I believe they don't get damaged from hitting certain kinds of rocks, and there are other versions with +mining floating around somewhere.