MINING. 331 



main divide of the Sierra Nevada. There are five silver 

 mills in Alpine, four in Mono, and eight in Inyo County, but 

 most of them are idle, and not one of them is producing 

 much. In the production of silver by the milling process the 

 ore, after it has been pulverized by stamps, is stirred as a thick 

 pulp in a large iron pan with water, quicksilver, and some 

 chemicals for six hours, at the end of which time the pulp is 

 run into a tank, mixed with much water, and allowed to settle, 

 when the amalgam and quicksilver are found at the bottom. 



The cost of extraction usually ranges from $2 to $6 ; 

 crushing costs from $9 to $12, amalgamation from $1.50 to 

 $2.50, and other expenses may be from $2 to $10 when there 

 is a good supply of ore. But allowance must be made for 

 prospecting, dead work, and other contingencies which beset 

 every silver mine, and the cost of which is without limit. 

 Free-milling ore will not, as a general rule, pay a profit unless 

 it yields $22 per ton, and few companies can make dividends 

 at that figure. 



The most productive silver mines of California are those at 

 Cerro Gordo, in Inyo County, where the ores are of the smelt- 

 ing class, containing considerable proportions of carbonate 

 and sulphuret of lead. These mines are nearly 7,000 feet 

 above the sea. In some of the lodes the lead and silver are 

 mixed, containing sixty per cent, of the former and $60 of the 

 latter to the ton ; in others, either the quantity of one or the 

 other is very small, and the ores have to be mixed. The pay- 

 ore yields fifteen to thirty per cent, of argentiferous lead or 

 base bullion, containing from $200 to $400 per ton of silver 

 and gold. The ore is smelted at the mine in furnaces, each of 

 which produces from three to ten tons of bullion daily. The 

 base bullion is shipped to the refining works, San Francisco, 

 where it is melted at a heat so low that the silver crystal- 

 lizes in the liquid lead, and can be dipped or strained out 

 by the Pattinson process. The expense of refining varies 

 from $30 to $80 per ton. 



