Jerry,
I know you know the difference between smelters and mills. Maybe someone would like to take a shot at describing their differences.
When I was young, my parents and some friends staked claims in the upper Mojave desert north of Randsburg, CA. Over about ten years it was their hobby and part of my young adventures. We did both dry placer and re-worked the tailings from a number of large hard rock mines.
Believe it or not, this area is loaded with mountains of at least 1000' elevation. In the early part of this century some big mines operated huge tunnel complexes, some purported to be a half mile deep and 20 miles in length. To my knowledge, these claims are still vacant. Their is gold to be had. You just gotta want it!
Brian Barr