The Patio and Cazo Process. 55 



phides more or less rich in silver, which are not acted on by this 

 method. The tails vary from twenty-five to forty dollars to the 

 ton, so that the \fondon process can generally be used only as a pre- 

 liminary method, and the patio, or some other process, is usually 

 associated with it. The residues remaining in the fondon consist 

 for the most part of the oxides of lead and iron, and some sul- 

 phurets containing silver and floured mercury. These are 

 washed in large wooden bowls in a water-tight vat, adding as 

 much mercury by weight as there is material to be treated, in 

 order to collect the flour. The amalgam is treated as usual. 



In Mexico, the slimes which have been removed are put into 

 catch -pits where the excess of water evaporates. They are then 

 made into small tortas, which are trodden by men. Two to two and 

 a half per cent, of salt is added to them, but no magistral, for the 

 water coming out of the fondon contains enough copper salts to 

 do the whole of the work. The amalgamation is conducted as 

 usual, except that it is very slow, lasting often as long as three 

 months. The loss in silver is as much as 20 to 25 per cent. The 

 mercury used is 125 to 150 per cent, of the silver contained. 

 This method is one of the most rapid and least expensive of the 

 Mexican processes. The cost is given below:* 



Cazeador (amalgamator), - 



Atizador (furnace man), - 



Wood for heating the furnace, 



Salt, 75 lbs., at $6 for 300 lbs., - 



Mules, -.----- 



Mercury, two per cent. , loss, 



Cost of distillation, etc. , - - 



$4,665 



In a single operation 1,200 pounds of ore are treated, which 

 is 9.33 reals per charge. 



If to these the expenses of dressing and concentration on tho 

 planilla are added, calculating the expenses in grammes of fine 

 silver per ton, we have as follows : 



* Ibid., d. 221. 



$0,500 



0.280 



1.562 



1.500 



0.187 



0.416 



0.250 



