508 Van Horn — Occurrence of Proustite and Argent 'dr. 



The Argentite. 



For a very short distance in the symmetrically banded vein 

 above described, proustite was replaced by argentite which in 

 two instances was reduced to wire silver. The argentite seam 

 was from 2 to 3 inches in width and generally of a massive 

 and finally granular appearance ; in some cases, however, the 

 mineral became quite coarsely granular ; in all specimens the 

 argentite was sectile and malleable but like the proustite was 

 mixed more or less with minutely divided quartz. The average 

 specific gravity of three specimens was 6*55, compared with 

 7'28 for pure argentite. The average of two analyses made by 

 Mr. R. B. Denuis, Case '07, is as follows : 



Ag _.. 83 '57 



S 12-66 



Insoluble _. 3*62 



99-85 



The insoluble matter conforms in general to the lower specific 

 gravity (6*55) and probably consisted of quartz. The analysis 

 was recalculated with the following result : 



Found 



Ag 86-71 



S 13-13 



Theoretical 

 Ag 2 S 



87-1 

 12-9 



99-84 100-0 



As far as the writer could learn, the proustite and argentite 

 have never been found previously in this locality, and the 

 occurrence of both minerals in such massive form and large 

 amounts is also considered a matter of interest. Several fine 

 vein sections were presented by The Mine Developing Com- 

 pany to the geological department of Case School of Applied 

 Science, and are on exhibition in the Museum. 



Geological-Mineral ogical Laboratory 



Case School of Applied Science, 



Cleveland, Ohio, April, 1908. 



