72 



particles as to have a whitish appearance ; the two 

 next strata are brown and are called ptnterias, the 

 two exterior ones are of a dark grey and known by 

 the name of brozas. Although the general direc- 

 tion of this vein is horizontal, it sometimes runs pe^ 

 pendicularly, and is found to increase in richness 

 in proportion to its depth. From assays which have 

 been made at Lima, on the ore of Uspallata, it ap- 

 pears that the guida yields more than two hundred 

 marks of silver the caxon the pintarías^ mixed 

 with the guida, fifty ; and the brozas fourteen ; 

 a produce not inferior to that of the mine of Potosi. 

 The mine of Uspallata was discovered in the year 

 1638, but although on its first discovery it furnish- 

 ed the strongest indication of its wealth, from want 

 of labourers, or some other cause, it was neglected 

 until 1763, but since that period has been constantly 

 WTOUght with immense profit. 



Before the arrival of the Europeans, the Indians 

 employed a very simple method to separate the sil- 

 ver from the ore, especially when the metal was in a 

 metallic form, and not mineralized or combined with 

 other substances. This method consisted in merely 

 exposing the ore to a degree of heat capable of melt- 

 ing the metal which it contained. When the ore 

 was united with other substances, or mineralized, 

 and of course more diflicult to be melted, they 



* A term made use of by tlie American nietallurgists to express 

 the quantity of ore which a single miner can dig in a day, usually 

 calculated at fifty quintals ; but, as this quantity contains more or 

 less of the matrix, it is impossible to ascertain the amount of 

 pure ore contained in each caxon. 



