496- .DESCRIPTIVE GEOLOGY. 



where tliey form the syndinal, the beds on the south side dipping northwest, 

 but with the same strike as before. At Pilot Peak, there is an antichnal 

 fold, the beds striking north 15° to 20° east, and dipping 15° both to the 

 east and west; the greater part of the rock-mass inclined to the southeast. 



This quartzite body, although its age has not been definitely deter- 

 mined, has been referred to the Weber formation. This reference is based 

 upon its great thickness, at least 6,000 or 7,000 feet, its similarity to other 

 great quartzite bodies which have been regarded as of Carboniferous age, 

 and its probable relation to the overlying limestone strata found upon its 

 southern flank. It is possible, however, that further examination may show 

 that there are two distinct unconformable quartzites represented in the 

 range. In its lithological aspect, this quartzite shows but little variety. It 

 is all heavily bedded, with the divisional planes distinctly marked; it is 

 mostly a fine-grained compact mass, with a conchoidal fracture and slightly 

 arenaceous texture. Near the northern end, it has the prevailing bluish- 

 gray or brownish-gray color which characterizes the Weber Quartzite in 

 Nevada. 



At Pilot Peak, however, the rocks possess a somewhat different habit, 

 closely resembling the massive quartzites of Bonneville Peak, Aqui Mountains, 

 which have been referred to the Cambrian age, the upper beds being a pure 

 snow-white body, underlaid by others of a deep bluish tinge, which appear 

 less pure, carrying some feldspathic material, with occasional pebbles, and 

 passing down into conglomerate beds, with quartz and jasper pebbles, show- 

 ing considerable compression and flattening, and arranged with their broader 

 faces parallel with the planes of stratification. Interstratified in this 

 quartzite are narrow seams of silver-gray mica-schists composed of brown 

 mica and quartz in exceedingly fine brilliant particles. A characteristic 

 feature of Pilot Peak is seen upon the east side, where the entire slope is 

 covered with huge blocks of quartzite, which have fallen down, and now 

 completely hide the rock in place. This rock-mass is so exceedingly brit- 

 tle, that, although formed of nearly pure silica, it has, under the influence 

 of frost and ice, worn away with great rapidity, showing near the sum- 

 mit numerous rents and fissures with walls two and three hundred feet in 

 height, standing out from the main mass, shattered and partially fallen 



