46 - The Patio and Cazo Process. 



silver varies from 20 to 25 per cent, of the assay value of the ore. 

 Some amalgamators claim that they can save as much as 80 or 

 even 85 per cent., but this is doubtful, even with the ores most 

 easily treated. When the ores contain much blende and galena 

 the loss easily reaches 25 to 30 per cent., and if in addition to 

 this there is any amount of antimonial or arsenical sulphides, it 

 will reach as high as 40 per cent. A part of this loss is, of 

 course, counted with the loss of the amalgam, which is carried 

 off in fiae particles. It could easily be reduced by better appli- 

 ances for catching the mercury, and better washing and concen- 

 tration, to catch a larger part of the pulp not acted on. But 

 there is a mechanical loss as well as a chemical one, which must 

 in any case be large. Just as soon as it is possible to introduce 

 all the modern methods of concentration, the conditions will 

 be such that other processes will take its place. Although 

 much has been done to improve it, no process with large 

 losses in the precious metal and excess of labor, can hope to 

 stand before increased facilities for transportation. When 

 gold is contained in the ore as a sulphide, not more than 40 per 

 cent, is recovered; when it is free, 75 per cent, is often saved.* 

 The cost of the process will of necessity vary in different local- 

 ities under dissimilar circumstances, and with ores whose compo- 

 sition is not the same. The results vary from year to year. 

 Phillips gives the mean cost per ton for reducing these ores as 

 follows:f 



Cost of Treating Ores. 



Coarse crushing in dry stamps and subsequent fine grinding in 



arrastra, - - - - - - - $1.90 



Manipulation in patio, - - 4.50 



General expenses of management, - 1.20 



Kepairs, - - - - - - - j 1.20 



Sulphate of copper, - - $3.20 



Salt (1.6 quintals per ton), .... 6.50 



Quicksilver (11 oz. per 8 oz. of silver), - - - 6.50 



-$17.00 



$25.00 



* Eng. and Min. Jour., Vol. 33, p. 104. 

 f Phillips's Gold and Silver, 1867, p. 357. 



