The Usonian Iron Mine can only be built on an Iron Mine Site that is empty. It can be upgraded to a Big Usonian Iron Mine which produces more Iron.
Functionally it is no different than Saxonian, Polanian, or Rusviet Iron Mines.
The Usonian Iron Mine can only be built on an Iron Mine Site that is empty. It can be upgraded to a Big Usonian Iron Mine which produces more Iron.
Functionally it is no different than Saxonian, Polanian, or Rusviet Iron Mines.