The Patio and Cazo Process. 17 



also to the flour formed, but more especially to the latter. Phillips 

 gives the following statement of the losses at Guanaxuato,* 

 where the ores contain gold but very little native silver, it 

 being in the form of sulphide: 



( Silver, 14 lbs. 



Composition of amalgam, - - - < 



( Mercury, 56 " 



Weight of amalgam used, - - - 70 " 



Mercury added independently of amalgam, - - - 330 lbs. 



Mercury in amalgam, - - - - - - 56 " 



Gold and silver, Plata Mixta, obtained, ( Gold ' 18 lbs " ) 



including that used in amalgam, j Silver 



84 lbs. 



06 



470 lbs. 

 ( Gold and silver, 84 lbs. 

 Amalgam produced, ] V 400 lbs. 



( Mercury, 316 " 



Loss, - ... 70 lbs. 



As the gold was metallic it probably caused no loss. This 

 loss of mercury is only a little more in weight than the silver 

 contained in the bullion. It is a received opinion among the 

 amalgamators, azogueros, that the loss in mercury will always be 

 equal to the weight of silver contained in the ore. 



The increase in the non-productive portion of the ore, owing 

 to the constant wearing of the stones of the pavement and the 

 mullers, may be as high as 8 to 10 per cent. It is a great objec- 

 tion to the arrastra, which has therefore been abandoned in all 

 the other processes; but the principle of the machine is a good 

 one, and to this principle we shall undoubtedly have to return. 

 The constant rubbing of the surfaces of the ore by the mullers, 

 and the grinding and constant rubbing in the presence of water, 

 make the metal bright, and the mixing brings it in contact 

 with the mercury. It is a notable fact that in some cases in the 

 early days of California mining, when Mexicans with their rude 

 appliances easily made $50 to $60 a day, the most efficient mod- 



* Phillips's Gold and Silver, p. 333. London, 1867. 



