64t5 



GEOLOGY AND MINING INDUSTRY OF LEADYILLE. 



Analyses of dolomites made vt the Grant Stiicltiiiti Worl's hi/ Vr. M. Tl'. 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 the ton ; XVIII and XIX, Glass-Pendery dolomite, said to contain from 

 one to two ounces of silver to the ton. 



The superiutendeiits in Leadvillc do not like dolomite as a flux. It is probable that 

 before loug llmestoue will be substituted for it. Already Messrs. Billing & Eilers have 

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

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



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

 from Eobinson, in the Ten-Mile District, IC miles distant, or from Canon City, about one 

 hundred and thirty miles south of Leadville, on the Eio Grande Eailroad. These lime- 

 stones are similar in appearance to lithograi^hic limestone. That from Robinson (Upper 

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

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

 made by Dr. M. W. lies. 



Analysis XX. CaSon City limestone. 



Carbonate of lime 83. 90 



Carbonate of magnesia C. 30 



Silica 3.10 



Alumina and oxide of iron 1. 50 



9t). 80 



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

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

 ore is also much used as a flux. This ore was not, 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; redsiiots; reddish violet streak. 



2. Red and yellow ; silicious aiipearance; 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. 



