Sarge wrote:Can an Ore Smelter be built in a mine? If so, as is, or paving is required first and...?
no they can't ...
You get the some error as the OP received (indicating that, probably, the ground must be paved), and you can't pave in a mine.
Honestly, this'd be awesome! Imagine house/smelters/stamps/mills underground!
Guess it's pretty obvious why this is not allowed

private instance mines would make any upkeep for a claim pointless, since anyone who is certain he can protect the mine entrance will just put everything underground.
Question (semi-connected): does anyone know whether mine holes are persistent ? (i.e. when you destroy a mine entrance, and rebuild it, is the mine you enter then the same as before the entrance was destroyed, or does it start afresh? )