how does mining limonite or iron ore affect the enviroment ?

The biggest problem associated with this is something called acid mine drainage, or AMD.

When iron bearing minerals are exposed to air, they begin to oxidize. They are also exposed to bacteria that act on the minerals creating a chemical reaction that produces acidic waters when it rains and there is run off.

The problem is more severe with iron sulfide minerals, but is also found with iron oxides and hydroxides.

Of course, the typical mining problems are there too, such as landscape damage, soil erosion, habitat destruction, etc.