Metal-working requires a furnace, heavy tools and of-course metal ore and yet nomadic Mongolians were able to obtain metal weapons, so either they worked metal or traded it. But if they worked metal how were they able to move the tools around? And surely nomads didn't mine ore, right?
About.com claims, though without any citations:
Mongolia's nomadic people have at times hungered for goods from settled cultures - things like fine metal-work, silk cloth, and weapons. To get these items, the Mongols would unite and raid surrounding peoples.
Right so this paper talks about how the Hunnu empire - which as far as I can gather are the predecessors of Mongolians - had metal working orkshops, yet it also explicitly describes them as nomadic ??
In excavations of the sites of ancient Hunnu towns[...]iron works and various kinds of cast-iron ware have been discovered.
However, the mighty empire of the nomads did not last long