- by Lewis E. Aubury - A rare publication from 1910 put out by the State Mineralogist covers the districts that California's massive river dredges once mined. This Comprehensive 350 page book is jam packed full of pictures, descriptions of the deposits that were mined, the geology, and the prospecting methods that were used to determine where the dredges were to go. Great book for historians, as well as modern day prospectors. These dredges moved a lot of material but were also very inefficient leaving as much gold behind as they found... and they found millions of ounces. Now back in Print by Sylvanite Publishing.