600 



GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



REMARKS ON TABLE VIII. 



Consideration of Analysis I shows that the carbon dioxide is insufficient for com- 

 bination with all the lead oxide, and that the chlorine (entirely soluble in nitric acid) 

 and the phosphorus pentoxide bear to one another the exact ratio of chlorine and 

 phosphorus pentoxide in the mineral pyromorphite; 3(3PbO, P 2 O 5 ) + PbCl 2 .) Calcu- 

 lating from the chlorine there is found to be 9.75 per cent, of this mineral. The carbon 

 dioxide is, then, somewhat more than sufficient for the remaining lead oxide, forming 

 86.CO per cent, of cerussite, PbCO 3 . 



The silver exists in the state of chloride, as shown by extracting it from a large 

 amount of ore with ammonia. 



A portion of the ferrous oxide is present as magnetite. The slight excess of car- 

 bon dioxide above that required for the lead is probably combined with ferrous, man- 

 ganous, and calcium oxides. 



Analysis II shows plainly that pyromorphite is practically absent from the spec- 

 imen of ore from the Little Chief mine. The lead exists mainly as carbonate, with a 

 little sulphate, and probably a small amount of antimoniate. A yellow substance left 

 unattacked with the silica and silver chloride ore, on treating with nitric acid, gave 

 reactions for lead and antimony. The silver exists altogether in the state of chloride 

 and could be completely extracted by ammonia. The total chlorine, found by fusion 

 with alkaline carbonates, extraction with water, and subsequent precipitation with 

 silver nitrate, is slightly in excess of that required by the silver, but it was found that 

 a few hnndredths of 1 per cent, was present in a combination soluble in water. 



Only the chief constituents from the ore in the Waterloo mine (Analysis III) 

 were estimated. Starting from the chlorine, which represents that soluble in nitric 

 acid alone, the ore is found by calculation to contain 32.07 per cent, of pyromophite 

 and 61.78 per cent, of cerussite, the carbon dioxide exactly sufficing for the lead oxide 

 left after combining the elements of pyromorphite. An excess of 1.44 per cent, phos- 

 phorus peutoxide is probably combined with alumina, of which a considerable amount 

 was found to be present. 



TABLE IX. Chloro-bromo-iodides ofiilrer. 



