There's a vein that appears as iron or silver up the hill to the right as you enter Angerfang Encampment in Wetlands. Head right as you enter through the gap nearest Menethil. Found it up 3 times now - 2 x iron, 1 x silver. Level 26/27 orcs there, so you may need to wait a couple of levels.
If you carry on to the top, there are a couple of lvl 28 orcs that sometimes have a treasure chest with them.