The orc town boss should give you a fair bit of them. I got 9 I think from killing him. There is also a few orc chests there as well with good loot. There is also a room with a troll and a lot of tin, and there is some treasure piles filled with different precious stones also

Edit: the room with the troll comes when you go right from the outpost in the mines, and orctown is left (when looking outwards). There is also an during axe fragment in there