Ever wonder how much gold was left in the old placer mine tailings, and why? How do you wash gold using a sluice? Author John S. Hittell's 1864 book answers this and many other questions.
Hittel explains: "The general estimate in California is that one-twentieth of the gold in the dirt which is washed is lost." "The miner does not grieve about that which he cannot catch. He is not careful to catch all that he could. His purpose is to draw the largest possible revenue per day from his claim." "If his claim contain a dollar to the ton, and he can save five dollars by slowly washing only six tons in a day, while he might make ten dollars by rapidly washing fifteen tons in a day, he will prefer the latter result, though he will loose twice as much of the precious metal by the fast as by the slow mode of working. The object of the miner is the practical dispatch of work, and his success will depend to a great extent upon the amount of dirt which he can wash within a given space of time."
If you want to know the how and why of mining this book answers the questions. The techniques explained are still in use. It is easy to read and if you are interested in gold mining or its history this book is a must.