Vol. 4] 



Re id. — The Comstoek Lode. 



181 



not yet removed by atmospheric agencies. The cross-section of 

 the upper portion of the lode, figure 1, shows this structure. 



2. There is no stream worn material of any sort, except very 

 locally, in these ravines, nor any outside their mouths where a de- 

 posit would take place by stream action. The whole region is re- 

 markable in the lack of all such material. 



No faults from Bullion Ravine in the hanging wall under- 

 ground have been seen, because this area is not accessible. But 

 on the surface, east of the lode, there are many very well defined 

 east-west faults, some of which are filled with caleite. A few have 

 been prospected and considerable ore extracted. The ridge run- 

 ning east from Bullion and Crown Point Ravines is a locus of 

 these movements. 



Cedar Ravine and Cedar Hill Canon — These are the large 

 gulches on the north end of the lode. Cedar Ravine is due to the 

 surface effects of the east-west motion exposed underground in 

 the Sierra Nevada mine, as is Ophir Ravine the surface effect of 

 the fault shown in the Mexican mine. Cedar Hill Caiion is rather 

 beyond the limits of the lode, yet deserves mention because it is 

 the sharpest cut of all the fault ravines, and, like Bullion Ravine, 

 shows the faulting by the stratigraphic relations of diorite and 

 andesite. In both instances the andesite abuts against the diorite 

 in a plane which occupies approximately the center of the gulches. 

 In Bullion Ravine the andesite is south of the diorite ; in the 

 northern fault canon, the andesite is north of the diorite. This 

 andesite is *Becker's "earlier hornblende andesite," which has 

 been shown to be identical with the porphyritic facies of the di- 

 orite mass.t Hence, an abutment of one of these rocks upon 

 the other indicates a fault plane. 



There appears even yet to be a doubt in the minds of some 

 geologists, for instance, Lindgren,$ as to the correlation of the 

 Comstoek rocks. The evidence for this correlation is, of course, 

 of two kinds: (1) microscopical, and (2) macroscopical, includ- 



*G. F. Becker, op. eit. 



fHague and Icldings, Bull. No. 17, TJ.S.G.S. "On the Development of 

 Crystallization in the Igneous Bocks of Washoe Co., Nevada. 



% W. Lindgren, in one of his numerous papers, states that he believes the 

 Comstoek rocks to be sejjarate flows. 



