THE GEOLOGY, PETROGRAPHY, AND MINERALOGY OF 

 THE VICINITY OF ITALIAN MOUNTAIN, GUNNISON 

 COUNTY, COLORADO 



By Whitman Cross 

 Of the United States Geological Survey 



and 



Earl V. Shannon 



Of the United States National Museum 



INTRODUCTION 



By Whitman Cross 



The minerals described by Mr. Shannon in the second part of this 

 paper were collected in 1885 and 1887 during the geological survey 

 of the Crested Butte quadrangle, which is on the southern slope of 

 the Elk Mountains in central Colorado. I was at that time assist- 

 ant to the late S. F. Emmons, specially charged with examination of 

 the igneous rocks, while the stratigraphic and structural geology 

 was the particular field of my colleague, the late George H. Eldridge. 



These minerals occur mainly in much altered sediments adjacent 

 to certain large intrusive masses. It was recognized that the occur- 

 rence was of unusual interest and deserved much more extended ex- 

 amination than could be given to it at the time of discovery. It was 

 hoped that opportunity might be found at some later date to return 

 to the area for a more thorough study of the minerals and the prob- 

 lem of their origin. But the exigencies of other work have not per- 

 mitted the carrying out of this plan. 



In the Anthracite- Crested Butte folio of the United States Geo- 

 logical Survey, issued in 1894, there is brief reference to the occur- 

 rence of these minerals, but all details, including the chemical an- 

 alyses by L. G. Eakins, here given in Mr. Shannon's description, were 

 left for some later publication. : ■■ '■ 



No. 2690.-PROCEEDINGS U. S. NATIONAL MUSEUM, VOL. 71, ART. 18 



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