582 Metalliferous Veins. paet n. 



latter case, it is said that if the vein ceases to contain 

 iron-pyrites, it is yet worth while to continue the 

 search, but if the iron-pyrites, when it reappears, is not 

 auriferous, it is better at once to give up working the 

 vein. Although I believe copper and gold are most 

 frequently found in the lower granitic and metamorphic 

 schistose series, yet these metals occur both in the 

 porphyritic conglomerate formation (as on the flanks of 

 the Bell of Quillota and at Jajuel), and in the superin- 

 cumbent strata. At Jajuel I was informed that the 

 copper-ore, with some gold, is found only in the green- 

 stones and altered feldspathic clay-slate, which alternate 

 with the purple porphyritic conglomerate. Several 

 gold veins and some of copper-ore are worked in several 

 parts of the Uspallata range, both in the metamor- 

 phosed strata, which have been shown to have been of 

 probably subsequent origin to the Neocomian or gyp- 

 seous formation of the main Cordillera, and in the 

 intrusive andesitic rocks of that range. At Los Hornos 

 (NE. of Illapel), likewise, there are numerous veins of 

 copper-pyrites and of gold, both in the strata of the 

 gypseous formation and in the injected hills of andesite 

 and various porphyries. 



Silver, in the form of a chloride, sulphuret, or an 

 amalgam, or in its native state, and associated with 

 lead and other metals, and at Arqueros with pure 

 native copper, occurs chiefly in the upper great gyp- 

 seous or cretaceo-oolitic formation, which forms pro- 

 bably the richest mass in Chile. We may instance 

 the mining districts of Arqueros near Coquhnbo, 

 and of nearly the whole valley of Copiapo, and of 

 Iquique (where the principal veins run NE. by E. and 

 SAY. by TV.), in Peru. Hence comes Molina's remark, 

 that silver is born in the cold and solitary deserts of 

 the upper Cordillera. There are, however, exceptions 



