He gets the choicest places, and keeps them.

His salary is not based upon what he would get in America, but apparently upon what a whole family of him would get there.
The successful mines pay great dividends, yet the rock is not rich, from a Californian point of view.

Rock which yields ten or twelve dollars a ton is considered plenty rich enough.

It is troubled with base metals to such a degree that twenty years ago it would have been only about half as valuable as it is now; for at that time there was no paying way of getting anything out of such rock but the coarser-grained "free" gold; but the new cyanide process has changed all that, and the gold fields of the world now deliver up fifty million dollars' worth of gold per year which would have gone into the tailing-pile under the former conditions.
The cyanide process was new to me, and full of interest; and among the costly and elaborate mining machinery there were fine things which were new to me, but I was already familiar with the rest of the details of the gold-mining industry.

I had been a gold miner myself, in my day, and knew substantially everything that those people knew about it, except how to make money at it.