Usually, refineries are located very close to mines, such that raw ore doesn't spend much time being shipped around — because most of it's going to be slag, any

Usually, refineries are located very close to mines, such that raw ore doesn't spend much time being shipped around — because most of it's going to be slag, anyway, and it's a waste of money to ship that. Often ore is delivered into a refinery "directly" on a minecart; or, if not, then on a railcar loaded from buffer hoppers at the mine; but either way using point-to-point rail service between the two sites (i.e. not part of the rail network.)