The Patio anil Oazo Process, lw 



The slimes are called lama; they are brought to the patio as 

 a liquid mud. In order to keep it in the place assigned for the 

 torta, in small works a dam of sand or old boards is made to con- 

 fine it, and it is left for some time exposed to the sun and wind, to 

 hasten the separation of the water by evaporation as well as by 

 drainage. In larger works, the pulp flow T s from the arrastra into 

 circular walled spaces called cajetes or lameros, which are used for 

 the same purpose. After sufficient material has been collected to 

 treat it, and when it has acquired the consistence of thick mud, 

 the piles, called tortas, or trillas, are made. The number and 

 size of these depend on the size of the works. For ore, they vary 

 from 30 to 130 tons each ;* for tails, they are usually smaller, or 

 from 16 to 20 tons. They occasionally contain from half a ton to 

 two tons; but such tortas indicate working on a very small scale, 

 and the pile is trodden by men. As the material is still too liquid 

 to support itself, a support is made around the outside with 

 beams or stones, the joints between them being made tight with 

 clay. Within this enclosure the pulp is placed. It will usually 

 be about 0.30 m. in thickness. An assay is always taken both to 

 check the work already done by the arrastra and to know what is 

 being clone. After several days exposure, the pile will be suffi- 

 ciently thick to be worked. It is spaded over and made into a 

 regular shape of 7 to 15 meters in diameter. 



o. Introducing the Reagents. — In about twenty-four hours 

 after the shaping, from two to five per cent, of salt is scat- 

 tered over the pile, as evenly as possible. With ores con- 

 taining from 30 to 35 ounces of silver, four per cent, of 

 salt, with those containing 45 to 75 ounces, about four and 

 a half per cent, is added. The greater the amount of salt, 

 the easier the amalgamation will be, and the more rapidly it 

 will be effected ; but notwithstanding the gain in time, it is 

 generally found that the cost of the salt compensates for it, 

 so that the amount is usually restricted to between three and. 

 four per cent. The operation of putting in the salt is called 

 insahnoro. The salt which is used in the process formerly came 



* Phillips, p. 343, says that they vary at Guanaxuato from 30 to 80 mon- 

 tones, a montone there heing 1.62 tons. 



