The Paliu and Cazo Process. 13 



faces for contact; a liquid one rolls around in globules and may 

 sink into the interstices ; and even if it does not, is not so 

 likely to catch the precious metal. 



In someplace?, a quarter of the arrastra* is cleaned to the bot- 

 tom, and the mixture of ore and amalgam taken out and washed. 

 This, however, is not usually done, except in very small tortus, 

 when the ores being treated are new, or, for some reason, do 

 not work well. Usually the assay is taken by probing in different 

 parts; the different probings being put together and then tested 

 in a small vessel called ajicara, by pressing the thumb or finger 

 against the side. With a very little experience the quantity of 

 mercury is quickly arrived at without so large an assay, and the 

 horn-spoon assay is sufficiently exact. "When the amalgam is 

 too dry, more mercury must be added. Generally, it is not 

 desirable that the amalgam collected should contain more than 

 20 per cent, of gold and silver. 



The quantity that a single arrastra can grind in 24 hours varies 

 with the hardness and the richness of the ore. It will generally 

 be from 400 to 600 kilos., and will require the use of from 900 to 

 1200 liters of water. When no grit can be felt between the 

 thumb and forefinger, the work of the arrastra is regarded as 

 complete. When the hands of the men who do the work are not 

 very sensitive, they sometimes make the test by rubbing some of 

 the pulp on the lobe of the ear. There is considerable differ- 

 ence in the fineness of the pulp in different sections. With 

 coarse ore, the amalgamation will not be so perfect ; but those 

 who use this practice, claim that the greater yield of fine pulp 

 does not pay the extra expense, and that the economy in pro- 

 duction and quicker returns more than pays for the loss in yield. 

 Those who grind fine, maintain the contrary, and claim that 

 their results are satisfactory, in yield, expense and time. 

 Probably the differences in the qualities of the ore have led to 

 the differences in practice in the various districts. When the 

 assay shows that the work is properly done, water is introduced 

 to thin down the mixture and allow the heavier particles to set- 

 tle. The thin slimes, lama, are either dipped out into barrels 

 and carried to the slime-pits, lameros, or into launders, from 



* Engineering- and Mining Journal. Vol. 8'd. p. 104. 



