40 



The Patio and Oazo Process. 



PLANILLA (Concentrator) 



SECTION 



~ Scale 100:1 ..„ . 



Fig. 5. The tails from here are con- 



centrated on the planilla* Fijj. 

 5, which is a platform of mason- 

 ry from one and a half to two 

 meters wide, and with a slope of 

 one meter in ten towards the 



Width of Planilla 2 Metres. tl'Ollgh, which SUppllCS a small 



stream of slowly-running water, f The wall at the upper side is 

 sloped, and furnishes a space to pile up the tails to be washed. The 

 workman, plafiillero, si ts on a strip of board put across the water 

 trough, and with a horn spoon containing about a quarter of a liter 

 throws the water upon the pile of tails. The operation is com- 

 menced at the lower left hand corner, and continued across the 

 planilla, going back again when the planilla has been crossed 

 to the lower left hand corner, and working always in the same 

 direction. The water is thrown in such a way as to spread out 

 as much as possible, but not to splash. When this has been re- 

 peated several times, the sand for about one meter from the 

 water-trough is thrown away. The heavy particles are thrown 

 up on the pile, and the operation recommenced. When the sup- 

 ply of tails is exhausted others are added. The result of the 

 washing is a small heap of black sulpharets, called polvillo. 



Fig. 6 . 



BOLICHE (Concentrating Bow'D 



These are further concentrated in a 

 wooden bowl called a boliche, Fig. 6, 

 which has the shape of an inverted 

 truncated cone 0.G2 m. in diameter, 

 and 0.4 m. deep, which is a hand de- 

 vice in every way similar to the 

 keeve used in dressing copper ores 

 on Lake Superior,]; and in the con- 

 centration of gold ores in California. £ 

 The boliche is sometimes made 

 as deep as 0.8 m., and correspondingly large, though this 



* Patio Process at St. Dimas. Trans, Am. Inst. Min. Eng., Yol. 11. 



f Annales des Mines, 6th series, vol. 20, plate II, Figs. 5 and 6. 



X Metallurgical Review, Vol. 2, p. 400. § Engineering, Yol. 31, p. 404. 



