TEEATMENT OF THE COMSTOCK OEES. 195 



In many of the mines the proportion of the second-class ore is so small, 

 or the character of the ore so uniform, that no such distinction is made, the 

 whole product being worked without assortment. About twenty-five to thirty 

 per cent, of whole value contained in these ores is gold, the remainder is sil- 

 ver. In the bullion produced the relative proportion of the gold is a little 

 higher, as it is more easily saved than the silver. 



The silver of the first-class ores is intimately combined with sulphur, zinc, 

 lead, iron, and other base metals, which render the extraction of the silver dif- 

 ficult. They cannot be profitably treated by the simple methods to which the 

 more docile ores of the second and third classes are subjected, but are crushed 

 dry, roasted with salt in reverberatory furnaces, and then amalgamated in barrels 

 by what is known as the Freiberg process. This will be described with more 

 detail further on. The ores of the second and third classes are treated by one 

 and the same method, known as the pan process ; the chief difierence, where 

 any exists, in the details of treatment as applied to the two classes, consisting 

 in the duration of time allowed for amalgamation and in the quantity of quick- 

 silver and other chemicals used in the operation. 



In the following pages a general description of the method of treatment 

 of these two classes of ores will first be given ; the machinery employed for 

 crushing, grinding, and amalgamating will then be described in detail ; after 

 which the costs of milling, the yield of the ore and its relation to the assay 

 value, the operations of difierent mills, the treatment of the " tailings " or resi- 

 dues, and other matters of interest will be discussed. 



Crushing. — The ore to be treated by the ordinary Washoe process^ is 

 delivered from the mine to the mill in pieces varying in size from fine particles to 

 those as large as a man can lift. It needs first to be crushed to a fine condition. 

 This operation is performed by stamps or heavy iron pestles that are lifted and 

 allowed to drop in iron mortars into which the ore is thrown. The larger 

 pieces of ore are first broken to a suitable size for feeding the stamps, either 

 by a sledge or a mechanical rock-breaker, Blake's machine being in general use 

 for this purpose. 



1 The process of pan amalgamation is commonly known as the " Washoe process," 

 having been first used in the "Washoe district. 



