Pass Function Values To Global Variables

You showed very little of your actual code. As @dota already said a ref parameter might be a solution but wouldn't be a nice one. Since you use UnityScript you can't even use it so you have to use something else.

First of all static variables have the big problem that you can't reference the instance that holds the variables since static things are instance-free. Furthermore it seems a bit strange to have seperate variables for different ore types hardcoded. You usually would use a class that has an "amount" variable and an "exp" variable. For each ore type you simply create an instance of that class. That way the interaction with an "ore" is always the same. You just need to pass the appropriate reference.

I don't really use UnityScript but it might look like this:

 public class Ore extends System.Object
 {
     var name : String;
     var amount : int;
     var exp : int;
     function Ore(aName : String)
     {
         name = aName;
     }
     function mining()
     {
         amount += 1;
         exp += 1;
     }
 }
 // inside your GV script
 static var iron = new Ore("iron");
 static var coal = new Ore("coal");
 
 // in your other script
 function Start(){
     GV.iron.mining();
     GV.coal.mining();
     // or
     Mining(GV.iron);
 }
 function Mining(ore : Ore) {
     ore.amount += 1:
     ore.exp += 1
 }

Just for simplicity i stayed with the static variables. I would recommend some kind of manager class instead but that would go too far for this answer.