The deposits of the useful minerals & rocks; their origin, form, and content . At Nagyag the lodes occur within an eruptive throat or chimney con-sisting of propyhtized dacite, though andesite also appears. Within an area THE YOUNG GOLD-SILVER LODES 545 about 1000 m. long and 950 m. wide an extraordinary number of steeplyinclined and approximately north-south lodes are found, these being generallybut 10 cm. wide and seldom as much as 30 cm. The occurrence is illus-trated in Fig. 295. In addition to gold telluride/ native gold, thoughseldom, is also found. Its derivation from the telkuide may b
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The deposits of the useful minerals & rocks; their origin, form, and content . At Nagyag the lodes occur within an eruptive throat or chimney con-sisting of propyhtized dacite, though andesite also appears. Within an area THE YOUNG GOLD-SILVER LODES 545 about 1000 m. long and 950 m. wide an extraordinary number of steeplyinclined and approximately north-south lodes are found, these being generallybut 10 cm. wide and seldom as much as 30 cm. The occurrence is illus-trated in Fig. 295. In addition to gold telluride/ native gold, thoughseldom, is also found. Its derivation from the telkuide may be explainedin the same way as the silver horns upon argentite at Kongsberg.^The lodes themselves may be divided into three divisions : 1. The quartz-telluride lodes, containing quartz with sylvanite andmore seldom with nagyagite ; and pyrite and tetrahedrite. 2. The pink manganese - telluride lodes, with rhodochrosite ; somequartz, alabandite, and nagyagite ; and tetrahedrite, pyrite, bournonite, asprimary minerals ; and with arsenic, sulphur, etc., as secondary minerals.. Fig. 295.âIdealized section at Nagyag. B. v. Inkey, 1885.A, (lacite ; P, propylite; K, kaolinized dacite immediately along the lodes ; V, lodes ; m, surface weathering 3. The base-metal lodes, containing galena, sphalerite, and pyrite, with calcite and dolomite. With many of the lodes a breccia occurs ^ wliich doubtless, both inregard to its fragments and matrix, is the result of friction and tritura-tion along the fissure walls. The most productive ore-bodies, somebeing occasionally very rich, are found where many lodes intersect toform a chimney or shoot.* In 1883 or 1884, for instance, one such bodyin three days yielded gold to the value of £2300 from an area of twosquare metres on the lode plane and a thickness of about 0-20 metre. Mining at Nagyag began in the year 1747. The element telluriumwas discovered at this place. The mines at present are worked from theFranz-Joseph adit which has a length of 5