LEADVILLE SILVER-BEARING DEPOSITS. 77 



Can be cut like wax, the surface of the cut part being 

 bhiny. 



Contains about 85 per cent, of silver, when pure. Not 

 soluble in acids. 



Fuses in a candle flame. Before B.F. readily yields 

 metal. The surface of a plate of iron is silvered by it when 

 moistened and rubbed. Occurs (often with carbonate of 

 lead) in the upper parts of lodes. Silver bromide and 

 iodide occasionally accompany the chloride. If a slice 

 moistened be placed on a piece of zinc foil, the latter is 

 soon stained black, and the chloride of silver partially 

 reduced to metal on the surface against the foil. Forms a 

 large portion of the South American "pacos"and "Colo- 

 rados" ores. 



Ruby Silver (pyrargyrite). 



Massive, granular, or as prismatic crystals. 



Lustre adamantine and submetallic. 



Colour Sometimes black, reddish black, or brilliant 



cochineal colour. 

 Streak lovely crimson red. 

 H. 2 to 2-5 ; S.G. 5'4 to 5'6. 



Contains about 60 per cent, of silver, the rest arsenic, 

 &c. Occurs with calcite, galena, &c. The dark red silver 

 ore is a sulphide of silver and antimony ; the light red 

 contains arsenic in the place of antimony. 



The ores of silver occur in veins traversing granitic and 

 gneissic rocks, clay slate, mica schist, limestone, &c., and 

 are usually associated with the ores of iron, copper, lead 

 (galena being always argentiferous), zinc, &c. 



At the rich mines of Leadville, Colorado, the silver is 

 found in the carbonate of lead deposit lying between a blue 

 limestone formation below and a white porphyry above 

 (Fig. 41). 



The famous Comstock lode, Nevada, consisting of quartz 

 (here and there calcite and decomposed rocks), sulphides of 

 various metals, silver ore as argentite, native silver, gold, 

 &c., lies between syenite above and metamorphic slaty rock 

 below. In Mexico deposits of silver-bearing ore are found 



