a metal mine is one of the commodity industries. In normal mode these are indestructible.
It will produce iron, bauxite and copper on a monthly basis and depending on on the stone quarry next to it.
The metal mine will also upgrade itself on a higher level when their balance is enough to pay the upgrade. The base upgrade time is about 8 weeks and the industry will produce the normal amount while upgrading and when finished it will upgrade the production rate.
These industries are producing:
small steel industry[]
industry type: resource production
price: 13.500.000 $
size: 6 X 4 fields
production base amount: 30
storage size: 120
normal steel industry[]
industry type: resource production
price: 22.500.000 $
size: 6 X 6 fields
production base amount: 50
storage size: 300
large steel industry[]
industry type: resource production
price: 40.000.000 $
size: 8 X 6 fields
production base amount: 90
storage size: 900