COMPARISON WITH SIMILAR ORE DEPOSITS ELSEWHERE. 281 



copper minerals, zinc, and iron pyrite. Twenty-seven miles from Cerro de Pasco 

 are veins in quartz-porphyry (rhyolite?). The ore contains, besides silver min- 

 erals, various copper minerals, galena, sphalerite, bismuthinite, and stibnite." 



In view of the presence of selenium at Tonopah, the occurrence of this 

 element at other places along this Pacific petrographic province in America is 

 of interest. At Guanajuato, northwest of the city of Mexico, selenides, including 

 a sulpho-selenide of silver, occur in argentiferous veins in hornblende andesite. 6 

 At Tasco, 180 miles southeast of Guanajuato, crystallized selenide of silver 

 occurs/ In the South American Andes selenides occur at the Cacheuta silver mine, 

 province of Mendoza, Argentina, whose vein is in "trachyte."'' They include the 

 selenide of lead and copper, that of copper and silver, and others. The latter selenide 

 occurs also in the Chilean Andes, at Copiapo and Flamenco, and elsewhere/ 



It is also interesting, in regard to the speculations of the author above quoted 

 concerning the Asiatic prolongation of the petrographic province, to note that in 

 Japan veins of argentiferous quartz are being worked, which occur in the midst of 

 Tertiary eruptives, and which belong to the Comstock type.-'' Explicit information 

 concerning these has lately come to hand.* Tertian* and Quaternary volcanic rocks 

 are widely distributed in northern Japan. The Tertiary rocks include rhyolite 

 (as old as the beginning of the Tertiary), andesite, and basalt. Metalliferous veins 

 in Tertiary andesite and rhyolite are among the most important mineral resources 

 in Japan. The older andesites have often suffered alteration by mineral waters 

 and gases. 



The Hoshino mines, in Hoshino-mura, Chikugo province, are in augite-andesite. 

 The deposits are quartz veins containing pyrite, blende, gold, and silver. The 

 Serigano mine, in Satsuma province, is in augite-andesite; the gangue is quartz, and 

 the metallic minerals are pyrite, chalcopyrite, gold, and silver. The Yamagano 

 district, between Satsuma and Osuini, is at present the most promising in the 

 country. Here are numerous veins in augite-andesite. The gangue is quartz, often 

 containing calcite and pyrite. The ore is native gold associated with argentite, and 

 rarely with chalcopyrite. The proportion of gold to silver is about 5 to 1. At the 

 Ponshikaribets mine, Shiribeshi province, the country rocks are Tertiary tuffs, cut 

 by andesite dikes. The gangue is rhodochrosite and quartz, the ores are auriferous 

 argentite, galena, chalcopyrite, and blende. The mine of Aikawa, in Sado province, 

 has had an enormous production. The veins are in augite-andesite and Tertiary 



o Mason, Russell T., Eng. and Min. Jour., June 8, 1905, p. 1092. 



fcTrans. Am. Inst. Min. Eng., vol. 32, p. 501. Dana, System of Mineralogy, 6th ed., p. 1025. 



cDana, op. cit., p. 52. 



<*Fuchs et de Launay, GHes m^talliferes, vol. 2, p. 832. The "trachyte" is probably andesite. 



Dana, op. cit., pp. 53, 54. . 



/ Fuchs et de Launay, op. cit., p. 832. 



a Geology of Japan, Geol. Survey, Tokyo, 1902, pp. 18, 19, 118, 124-171. 



