Grant H. Smith The History of the Comstock Lode 1850-1920, Geology and Mining Series No. 37, University of Nevada Bulletin: Reno, Nevada, vol. XXXVII. 1 July 1943, no. 3, (revised 1966), Ninth printing, 1980. 305 pp., 1880
[p. 249] Chapter XXV Fire in the Stopes-Low-Grade Operations in the Bonanza Mines-The Comstock Milling Monopoly-The Last Washoe Process Mill-Losses in Tailings-Tailings Reworked
[p. 256] Losses in Tailings and Quicksilver
"The Comstock mines produced a little over $300,000,000 from 1859 to 1880, excluding returns from tailings, and it has been said repeatedly that an additional $100,000,000, or 25 percent, escaped in the tailings and were irretrievably lost. But that estimate appears to be excessive.
"The total loss up to 1880 is estimated at $70,000,000, and could not have exceeded $75,000,000. The total amount recovered from [p. 257] tailings saved up to that time is estimated at $23,000,000, including some that were reworked later. Hague, in 1870, estimated the average recovery from tailings as $5.50 a ton. Until the cyanide process was introduced the millmen did not expect to recover more than 50 to 60 percent of the values of the "tailings," or sands and the slimes. Some rich tailings were reworked twice, or even a third time after cyanide came into use.