256 ANNALS NEW YORK ACADEMY OF SCIENCES 



(4) Cuzco-Cotabamba Begion. The region of Cotacamba and adjacent 

 valleys was the scene of great mining activity in the early Spanish days. 

 Many of these prospects have likewise been worked in late times. 



(5) Poti-Sandia Section (East Cordillera). This is known to con- 

 tain not only a large area of mineralized territory — gold-bearing quartz 

 veins — but also an abundance of placer on the eastern slope of the East 

 Cordillera. 



(6) Huanaco Section (East Cordillera). 



Just a word as to the distribution of the principal mining localities 

 and their relation to the geology of the Cordillera. After seeing a large 

 number of ore-bearing sections in the south, center and north of Peru, 

 the relation and association of zones of maximum mineralization with 

 certain formations becomes very clear indeed. Let us return for a moment 

 to our Huacho-Cerro de Pasco section. Near the coast, there are a few 

 intrusives which have pushed their way through the sandstones and. 

 shales. Apparently associated with these volcanics are gold-bearing 

 veins which have been prospected from time to time. Nothing of very 

 great value, however has been found here. The Spanish prospector did 

 not find this little crop of veins very attractive. He was not slow to hunt 

 more pleasing ground further to the interior. 



It is not until we pass to the zone of the West Cordillera, where there 

 are enormous intrusive bodies bordered by limestones and shales, that we 

 find ore-bodies of large dimensions. On the west side of the Cordillera, 

 we have a group of silver-copper-gold veins, some of which can be 

 traced for more than a kilometer, with widths approaching 20 meters. 

 Should we pass over the divide to the East Slope, from which we see the 

 Cerro de Pasco lowland, we will find both on the slope and in the valleys 

 leading to the crests of the Cordillera another group of veins that are 

 undoubtedly associated with the east contact of the intrusives with the 

 limestones and shales. 



Throughout this region may be seen many old plants (arrastres) and 

 the still more ancient quimbolete, where the ores were treated for the 

 recovery of gold and silver. The amount of visible tailings show to what 

 extent the early prospectors worked. Since the foundation of the repub- 

 lic, the native has likewise continued to work in this region, but, of course, 

 in the old-fashioned way. It is not at all uncommon to find Indians 

 in possession of solid silver utensils hammered out of a single piece of 

 silver. Should you visit the plazas of any of the villages in these sections,, 

 you would find the silversmith present with his little collection of silver 

 utensils and ornaments of various kinds. Most of the metal he obtains- 

 from miners of the same localitv. 



