218 On the Principles Involved in the 



For details upon all the methods of working iron ores, the reader 

 is referred to Hassenfratz's Siderotechnie. 



II. On the extraction of silver from its ores. 

 Processes. 



Silver is separated from its ores, either by smelting, or by amalga- 

 mation. The most important points, in determining to which of these 

 processes they shall be subjected, are, 



1. The nature of the ore. 



2. The comparative facilities for obtaining lead and mercury. 



3. The abundance of fuel. 



4. The abundance of water. 



Generally speaking, it is most advantageous to anjalgamate ores in 

 which the silver is in a metallic state, or when it is combined with 

 substances of little value. 



When the ores are very much disseminated in their gangue, so as 

 to render stamping necessary, it is more advantageous to amalgamate. 

 Pyrites are generally contained in abundance in such ores, and sul- 

 phur is necessary to the success of the amalgamation process. 



When silver ores are rich in lead or copper, it is advisable to 

 smelt them. 



Ores, of difScult fusion, may also be amalgamated with advantage, 

 for the nature of the accompanying materials is not important in the 

 amalgamation process. 



Ores containing from seventy to eighty ounces of silver to a ton, 

 have been found best adapted for amalgamation, but when they con- 

 tain more than eighty ounces to the ton, it is difficult to extract all 

 the silver, by this method. It is generally most economical to smelt 

 ores containing less than sixty ounces of silver to a ton of ore. Rich 

 ores of silver are always smelted.* 



1 . Smelting of Silver Ores. 



The silver smelting processes are very simple, and the ultimate 

 separation of the silver from the materials, combined or mixed in the 

 ore, depends upon the strong affinity of lead for the precious metals. 



* For minute details of the various operations of smelting and amalgamating silver 

 ores, the reader is referred to Clemson's memoir in the American Journal of Sci- 

 ence, vol. xix, p. 105 ; Taylor's Records of Mining, vol. i ; Annales des Mines, 

 tomes xxix and xxxi ; Humboldt's Essai sur le Nouvelle Espagne, tomes iil and ir. 



