The Patio and Cazo Process. 



15 



added just before the clean-up, are saved for concentration or 

 treatment. 



After a number of charges have been ground, the process of 

 grinding is stopped to allow of collecting the amalgam, which is 

 done by scraping the inside of the arrastra with great care. 

 This operation is called raspando. In the most primitive 

 arrastras it is performed as often as twice a month, or perhaps 

 not oftener than twice in three months. In those of the best 

 construction it is done from two to four times a year. As a prop- 

 erly made pavement lasts about a year there is no necessity for 

 doing it oftener. It is done by carefully scraping the stones and 

 the intervals between them with a curved tool, in order to be cer- 

 tain to remove every particle of ore and amalgam; the amalgam 

 so collected is called raspa or raspadura. In case the pavement 

 is worn out, each stone is carefully scraped and washed, and the 

 earth for a slight depth as well. In some places the raspa 

 is simply washed with the addition of fresh mercury in a wooden 

 bowl, boliche, Fig. 4, where most of the amalgam is collected. 

 This operation is called bolichar. The tails are then washed 

 on the planillo, Fig. 3, a masonry platform erected for the pur- 

 pose of concentrating them. The operator here is called the 

 planillero. When the ore contains gold, or in the more mod- 

 ern works as at San Dimas, 

 3 it is washed in a pit called a 

 cliuza, Fig. 1, which is also 

 used for the treatment of con- 

 centrated tails from the patio. 

 The cliuza* is an excava- 

 tions m. diameter and 0.5 m. 

 deep, lined with cement, 

 with a conical wooden bowl 

 0.35 m. in diameter, and 

 0.30 m. deep, whose sides 

 rise 0.05 m. above the ce- 

 mented bottom on one side. 

 Fig. 1. Directly above it at A, Fig. 1 



iCHUZA . (Settler) 

 Scale 200:1 



Patio Process at San Dimas, 



