476 DESCKIPTIVE GEOLOGY. 



mulations of Quaternary detrital material are such that it was impossible 

 to obtain any definite ideas of the structural relations of these beds. 



Wachoe Mountains, — To the south of the Gosi-Ute and Peoquop 

 Eanges, rising out of the Gosi-Ute Desert, lie the Wachoe Mountains, an 

 isolated body of hills of considerable geological interest. In both their 

 topographical and geological features they offer a striking contrast to the 

 long, narrow, north and south lines of Palaeozoic ridges that characterize the 

 surrounding ranges, and show instead an irregular group composed almost 

 entirely of crystalline rocks, which include granites, later diorites, and 

 quartz-porphyries, followed by andesites and rhyolites. 



Of this group, granite forms all the more elevated portions, and gives 

 the character to the main topographical outlines, and is at the same time the 

 geological nucleus around which, at the southeastern end, is found a body of 

 limestone, while at its base is spread out over a considerable area one of the 

 most interesting outbreaks of Tertiary volcanic rocks of Eastern Nevada. It 

 is an irregular shaped mass some 8 or 9 miles in length, and across its broadest 

 expanse about 4 miles in width. From the w^estward, it rises somewhat 

 abruptly, but with even slopes, nearly 2,000 feet above the Gosi-Ute Desert, 

 while to the eastward it is more broken in outline, but falls away with gentler 

 spurs toward the volcanic rocks below. In its physical habit, this granite is of 

 special interest, as it presents marked differences from all the isolated gran- 

 itic bodies of the Eaft Eiver, Ombe, Gosi-Ute, and Peoquop Eanges, which 

 have many points of resemblance, and would appear to belong to the same 

 group. The Wachoe granite is a very compact dense mass, with a com- 

 paratively uniform texture, weathering in rounded forms, but with regular 

 monotonous outlines, all possessing the same gentle curves : it disintegrates 

 slowly, the greater part of the hills showing but little soil and debris. 

 Under the hammer, the rock breaks with great difficulty in irregular-shaped 

 pieces, having a very uneven fracture. The minerals composing the rock 

 show, as far as examined, no tendency to parallel arrangement, and have 

 developed no regular lines of bedding. In color, it is dark reddish-gray, 

 but with somewhat lighter tints on the northeastern spurs and foot-hills. 



In its mineralogical features, this rock presents many peculiarities, 

 and is marked by a composition as striking as are its outward physical 



