672 DESCRIPTIVE GEOLOGY. 



from the adjacent outbreaks, with the same colors and texture. In one or 

 two localities, well-developed plates of black mica are abundant. 



In the extreme southeastern corner of the mountains occurs a body of 

 basalt which projects out in a prominent manner toward Reese River Val- 

 ley. It fonns a distinctly bedded, compact mass of a fine-grained black 

 rock, in which, without the aid of the microscope, it is almost impossible 

 to recognize the individual mineral constituents. 



Near the entrance to Elder Canon is found a small unimportant out- 

 crop of diorite. It appears to be an isolated exposure, and derives its main 

 interest from its relations to, and in some measure explaining the occur- 

 rence of, the cross-ridge connecting the Battle Mountains with the Havallah 

 Range. It is of a dirty light-gray color, with a fine-grained crystalline 

 groundmass, carrying but few well-developed minerals, and is by no means 

 a characteristic diorite. Both monoclinic and triclinic feldspars are present, 

 and, in the specimens collected, have a dull earthy appearance. Hornblende 

 is abundant in long fibrous needles. Bronze-colored mica plates may also 

 be detected. 



