COLLKCTIONS IN ECONOMIC GEOLOGY AND MKTALLUUGY. "2") 



(:{) Galena, (UM'omitositioii jirodiiets, oapeciiilly copper, aiid (jiiartz. r)OG feet. 

 (r)o7:?0.) 



(4) Decomposition products in quartz. 577 feot. (557:51.) 



(5) Foot wall. (547 feet. (55742.) 



(1) Decomposition products, pyrite. From sixth level. 80 feet east of drain tunnel. 

 (55725.) 



(2) Galena, pyrite, blende, and decomposition products. From sixth level, 7l) feet 

 east of drain tunnel. (55724.) 



A section of the vein on the sixth level, about 12") feet west of tlje 

 drain tunnel, is illustrated by four specimens: 



(1) Hanging wall, stained by copper and iron. (.557IW. ) 



(2) Hanging wall. (557:«).) 



(:5) Quartz, stained by decomposition ])rodncts, especially copper and manganese. 

 (55727. ) 

 (4) Foot wall. (55741.) 



A section of the vein on the sixth level, about 1,400 feet west of the 

 drain tunnel, is illustrated by six specimens: 



(1) Hanging wall. (55740.) 



(2) Galena, decomposition products. (55734.) 



(3) Galena, blende, tetrahedrite, decomposition products. (55735.) 



(4) Decomposition products, quartz. (55736.) 



(5) Decomposition products. (55737.) 



(6) Foot wall. (55743.) 



(1) Galena, decomposition products. From the eighth level, 130 feet west of drain 

 tunnel. (55728.) 



SILVER SMELTING ORES. 



These ores consist of free silver, generally in crystalline branching 

 aggregates of immense size, with occasionally a small amountof argen- 

 tite, in a gangue, generally of crystalline calcite, the silver amounting 

 in some cases to two thirds of the weight of the ore. Along with this 

 very rich ore there is always a large amount of lower-grade ore requiring 

 a very different mode of treatment. On account of the richness of these 

 ores the actual amount ])roduced is small compared with the amount of 

 the poorer ores. One ton of the former may be worth more than 100 

 tons of the latter. 



The rich ores are simply melted, generally on a cupel, with suitable 

 fluxes, to remove the gangue and leave the pure silver behind. The 

 most common flux is litharge or oxide of lead. When argentite occurs 

 with the silver scrap iron is added to reduce the silver from it. In 

 some cases metallic lead is added and has to be removed by cupellation 

 after the separation of the gangue and metal. 



These ores are seldom treated at the mine, but are generally shipped 

 away and are treated at some central point whenever a sufficient amount 

 has accumulated. Many Mexican and South American mines have 

 produced large amounts of silver from this character of ore. Some 

 mines, notably the Kongsberg, in Norway, produce a large amount 

 of silver in the native state in considerable masses. 



