6415 



GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



Analyses of dolomites mails tn the Grant Smelting Works by Vr. M. W. lies. 



NOTE. Analyses XIV and XV, locality not given; XVI. Glass mine dolomite ; XVII, Carbonate mine dolomite, 

 said to contain from two to six ounces of silver to tbc toil ; X VIII and XIX, Glass-Fendery dolomite, said to contain from 

 one to two ounces of silver to the ton. 



The superintendents in Leadville do not like dolomite as a flux. It is probable that 

 before long limestone will be substituted for it. Already Messrs. Billing & Eilers have 

 experimented at their smelter with perfectly pure arragonite from the Duncan quarry, 

 Arkansas Valley, close to Leadville, and the results have been most satisfactory. 



Limestone Should limestone be used instead of dolomite, it might be brought 

 from Kobiusou, in the Ten-Mile District, 1C miles distant, or from Cafioii City, about one 

 hundred and thirty miles south of Leadville, on the Eio Grande Uailroad. These linn-- 

 stones are similar in appearance to lithographic limestone. That from Hobinsou (Upper 

 Carboniferous) contains 97.11 per cent, of carbonate of lime, as determined by Dr."\V. F. 

 Hillebrand. The following analysis of the Cafiou City limestone (Cretaceous) was 

 made by Dr. M. W. lies. 



ANALYSIS XX. CASOS CITY LIMKSTONE. 



Carbonate of liiuo 83.90 



Carbonate of magnesia 6. 30 



Silica 3.10 



Alumina and oxide of iron 1.50 



9<J.80 



Hematite The hematite used as a flux at the smelters is chiefly extracted from 

 the Breece Iron mine, on Breece Hill, but at one smelter some Silver Wave mine iron 

 ore is also much used as a flux. This ore was uot, however, examined. The sample of 

 Breece Hill hematite, which was examined in the laboratory of the Survey, was made 

 from specimens collected on the hematite heaps of the following smelters: American, 

 California, Elgin, Harrison, and Billing & Eilers. 



The following is the description of the specimens and the color of their streaks: 



1. Black, submetallic luster; red spots; reddish violet streak. 



2. Red and yellow ; silicions appearance ; deep brick-colored streak. 



3. Very compact ; submetallic luster; magnetic; black streak. 



4. Compact; dull luster; light brick-colored streak. 



5. Black ; submetallic luster ; brownish streak. 



In Analysis XXI the decimals are carried to six figures, in order to introduce 

 both gold and silver. 



