COMPARISON WITH SIMILAR ORE DEPOSITS ELSEWHERE. 283 



veins are in rhyolite and Tertiary strata. The gangue is quartz with calcite and 

 amethyst; the ore is auriferous argentite, with blende; galena, pyrite, and native, 

 silver are sometimes found. At the Takadama mine, Iwashiro province, quartz 

 veins containing auriferous argentite occur in rhyolite and Tertiary strata. The 

 Kuratani mine, in Kaga province, contains veins in rhyolite and Tertiary tuffs. 

 The gangue is rhodochrosite, with barite and calcite; the ores contain argentiferous 

 galena, blende, pyrite, and jamesonite, and carry gold. At the Tagonai mine, Ugo 

 province, the veins are in Tertiary tuff, augite andesite, and rhyolite; the gangue 

 minerals are quartz and barite, the ores argentiferous galena, blende, and pyrite. 

 At the Hata mine, Ugo province, the rocks are Tertiary tutf and rhyolite; gangue 

 minerals are quartz, calcite, and barite; the ores are argentite, galena, pyrite, and 

 chalcopj'rite. At the Kuromori mine, Iwaki province, the vein is in rhyolite. 

 The gangue is quartz, often amethystine; the ore is argentite, with blende. At 

 the Kosaka mine, in Rikuchu province, the ore is an impregnation in Tertiary tutf, 

 with rhyolite and dacite intrusions; it consists of lead and copper carbonates, 

 copper sulphate, native copper and silver, and barite. At the Hatasa mine, Mino 

 province, the rocks are rhyolite (quartz-porphyry) and andesite. The veins consist 

 of quartz containing argentiferous chalcopyi'ite, galena, argentite, blende, and 

 pyrite. The Waidani mine, Bizen province, is in rhyolite; the ores are argen- 

 tiferous chalcopyrite, blende, and galena. 



Besides the examples above cited, other veins of closely related types, but 

 often containing a larger amount of the baser ores (lead, zinc, and copper) than 

 the more abundant cases above, occur in or near Tertiary andesite or rhvolite. 



Some information is available concerning certain East Indian ore deposits on 

 islands lying south of Japan along the belt characterized by similar Tertiary and 

 Pleistocene volcanics. In the whole of the Dutch East Indies, according to S. J. 

 Truscott," the gold (which is always accompanied by a larger amount of silver) 

 occurs in reefs, veins, and impregnation zones, in altered andesite (porphyrite), 

 or near the contact of such a rock with Devonian slates, in which slates there 

 are sometimes similar though less extensive occurrences. The ore deposition 

 probably took place in the Tertiary. 



One of the principal productive centers in this region is the mine Redjang 

 Lebong, in the southwest part of Sumatra. Here the ore, which occurs in altered 

 andesite, has a gangue of fine-grained silica, with often some calcite. The gold is 

 finely disseminated and is rarely visible; it exists free and in combination with 

 silver, in the proportion of 1 to 10. At depth this silver probably exists as 

 sulphide, connected with pyrites. Bullion from this mine gives the following 

 analysis: Gold and silver, 91.52 per cent; selenium, 4.35; copper, 1.82; lead, 1.65; 

 zinc, 0.48; iron, 0.14; total, 99.96. Tellurium was not found. 



a Trans. Inst. Min. Metal., vol. 10, pp. 52-73. 



