678 DESCEIPTIVE GEOLOGY. 



under the hammer less readily than most basalts, with a rather sharp angular 

 fracture. Under the microscope, the thin sections reveal but little glass-base, 

 which is unusual in the basaltic rocks of Nevada, and accounts for its differ- 

 ent physical habit. It has rather a fine-grained fresh-looking groundmass 

 of augite and triclinic feldspar, the latter occurring as brilliant thin needles. 

 There is some olivine in the rock. 



One other locality of granite was observed in the Havallah Range; it is 

 possible that others may be present, but, if so, they occupy a very limited 

 area. This one occurs along the' west base of the range, rising but a few 

 hundred feet above the valley; it reaches the surface a short distance south 

 of the entrance to Clear Creek Canon in a conical hill, and from there may 

 be followed along the foot-hills for 4 or 5 miles nearly to Bardmass Pass. 

 It is characterized by a hard compact texture and a prevailing purplisli- 

 gray color. It carries as essential mineral constituents both orthoclase and 

 oligoclase, the latter less prominent, but frequently marked by very beau- 

 tiful characteristic striae, limpid quartz-grains of considerable size, and dark- 

 green hornblende, but proportionally little mica. 



The post-Archsean sedimentary beds of the Havallah Range in many 

 respects differ widely from those already described in the ranges to the east- 

 ward, but, on the other hand, are closely allied to formations found in the 

 Pah-Ute and West Humboldt Ranges to the westward, the three ranges taken 

 together forming quite a distinct geological province. Nowhere in Western 

 Nevada have the Carboniferous and Triassic strata been recognized in direct 

 connection with each other in the same uplift, and, in ranges standing as 

 isolated as they do in the Nevada Basin, it is difficult to relate formations 

 separated by broad valleys from 5 to 10 miles in width, and covered by 

 Quaternary deposits. It is possible that Carboniferous rocks may be present 

 in the Havallah Range, but they were not recognized as such, while there is 

 no doubt that, at least in one locality, Triassic limestones form the foot-hills 

 along the western base. With this exception, however, there has been as yet 

 but little direct evidence obtained as to the age of these formations in the 

 Havallah Range, and their reference to the Triassic is based more upon their 

 broader, general features and lithological comj^arisons than upon eitlier 

 palseoutological or structural proofs. In this connection, it is especially 



