GOLD AND SILVER DEPOSITS LINDGREN. 163 



Esmeraldas near the coast and the Colombian boundary there are 

 placer deposits which have not so far been successfully worked; the 

 eastern ranges are also said to contain placers which may be derived 

 from deposits of pre-Cambrian age. 



PERU. 



The conditions in Peru are very different from those in Colombia. 

 There are relatively few gold deposits — some veins are being worked, 

 and a certain amount of placer gold is obtained from the montana 

 region of southern Peru. The annual production of gold is rarely 

 over $500,000; thanks, to the careful work of the Cuerpo de Ingenieros 

 de Minas it is possible to gain an exact idea as to its derivation. 

 Half of the production comes from the copper of Cerro de Pasco. 

 One-sixth is derived from placers and one-fourth from gold-quartz 

 mines proper. 



On the other hand, Peru is the leading silver-producing country 

 in South America, the present annual output being about 9,600,000 

 ounces or 300,000 kilograms. Of this again more than one-half is 

 derived from the copper mines of Cerro de Pasco, a small amount 

 from lead bullion, and the remainder from silver or gold-silver 

 deposits. 



It is well known that Peru has yielded an enormous amount of 

 silver. Professor Vogt has estimated 35,000,000 kilograms as the 

 production from 1533 to 1910. Whether this is accurate or not, it is 

 certain that Cerro de Pasco has contributed the greater part of the 

 silver of Peru. 



The silver districts are very numerous and generally situated in 

 the western cordillera in the Departments of Cajamarca, Libertad, 

 Ancachs, Huanuco, Juin (Cerro de Pasco), Lima, Huancavelica, and 

 Arequipa. It would seem that the silver production could be con- 

 siderably increased. 



Geologically there is also a great difference from conditions in 

 Colombia. In Peru and Chile we find along the coast and central 

 Cordilleras a strong development of Jurassic and particularly Cre- 

 taceous sediments, folded and in part overturned toward the east. 

 These Mesozoic sediments contain embedded lava flows of the same 

 age, which, however, do not appear to be of importance as regards 

 mineralization. 



According to Prof. G. Steinmann, 1 the great majority of Peruvian 

 deposits are undoubtedly in close genetic connection with numberless 

 small intrusive masses of " andesite," " dacite," or " liparite." These 

 names are confusing for the rocks are really deep-seated dioritic or 



1 Gebirgsbildung und Massengesteine in der Kordillere Sudamerikas (Geologische 

 Rundscbau, Bd. 1, Heft 1-3 (1910)). 



