GOLD AJTD SILVER DEPOSITS LUSTDGEEN. 167 



here, as elsewhere in South American literature, andesite, dacite, 

 and rhyolite are names often nsed for intrusive Tertiary rocks, a 

 survival of the old view that any Tertiary volcanic rock must belong 

 to one of these rock types. 



Some gold-bearing veins are found in rhyolite and allied flow 

 rocks, for instance, at Guanaco, southeast of Antofagasta, prol^ably 

 also at Sierra Overa, southeast of Taltal, and at Andacollo, south- 

 west of Coquimbo. Other veins carrying both silver and gold occur, 

 according to Moericke.^ in andesite flows, in part tuffaceous, for 

 instance, at Batuco and Cerro Blanco. According to Moericke all 

 veins of this type seem to have a tendency to play out at a depth of 

 a few hundred feet. 



Much more numerous are the gold quartz veins connected with 

 intrusives, such as granites and quartz diorites. We find them at 

 Canutillo,^ north of Taltal, in diorite intrusive in Cretaceous lime- 

 stone. Others are found associated with tourmaline and copper ores 

 at Remolinos in Atacama, at Tamaya and La Higiiera in Coquimbo, 

 and at Las Condes in Santiago. Another gold belt extends from 

 Coquimbo down to Santiago, and to Rancagua and Talca, south of 

 this city.^ These quartz veins occur mostly in granite near the con- 

 tact of schist. 



Wliile silver is sometimes associated with gold, the richest silver 

 mines of Chile, which yielded great amounts of the metal in the 

 nineteenth century, occur as a rule separate in Mesozoic limestone, 

 intruded by or interbedded with greenstones of various kinds. They 

 are characterized by extremely rich ore and antimonial and arsenical 

 silver minerals; some of them also contain silver amalgam. Their 

 genesis is doubtful. The gangue is mainly calcite. In depth these 

 veins also are disappointing and the silver production of Chile is 

 now only a fraction of what it was when these mines were in 

 l)onanza. 



Among these celebrated districts, mainly situated along the coast, 

 are Huantajaya and ChallacoUo near Iquique, Chanarcillo (50 miles 

 south of Copiapo), and finally a group of districts including Ar- 

 queros and Condoriaco (100 miles south of Copiapo). 



The great low-grade copper deposits, such as Braden and Chuqui- 

 camata, appear to contain very little of the precious metals. 



In remarkable contrast to the northern half, so rich in precious 

 metal deposits, the southern part of the Republic appears to be 

 amazingly poor in mineral deposits. Scarcely any mines are ro- 



* W. Moericke : Einige Beobachtungen ueber Chilenlscbe Erzlagerstatten (Tschermaks 

 Min. u. Pet. Mitteilungen, vol. xii, pp. 186 to 198 (1891)). 



* S. n. Loram : Notes on tbe Gold District of Canutillo, Chile (Trans., vol. xxxv, 

 p. 696 (1906)). 



' E. D. Pope: Gold Mining in Chile (The Mining Magazine (London), vol. xiil, No. 1, 

 pp. 33 to 36 (July, 1915)). 



