140 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



FRACTION NO. 1 VEINS. 



DISCOVERY AND DEVELOPMENT. 



The No. 1 Fraction shaft was sunk blindly in the outcropping dacite of the 

 Fraction dacite breccia in the fall of 1901, and was one of the first explorations 

 outside of Mizpah Hill and Gold Hill. The shaft was sunk to the depth of 238 

 feet by means of a horse whim. The shaft passed through 150 feet of soft dacite, 

 20 feet of crushed material probably representing the later andesite, several feet 

 of breccia indicating a probable fault zone, and ended in the earlier andesite. At 

 the depth of 238 feet, the rope not being long enough to sink any farther, drifting 

 was started, which, in 20 feet, cut a body of quartz that had a width of several 

 feet and showed some rich ore. Subsequent to this a great deal of development 

 work has been done, but the results have been unsatisfactory, the vein being very 

 badly faulted and there being very little rich ore. 



NATURE AND RELATIONS OF THE FRACTION VEIN. 



By looking at the detailed map of the mining district it will be seen that 

 the Fraction workings lie close to two faults which were drawn from surface 

 indications. A study of the underground workings indicates that the faulting has 

 been so intense and complicated as to defj' working out of the smaller details and 

 as to make the mining under these conditions practically hopeless, unless the ore 

 were very rich. 



Apparently a single strong vein is represented in the Fraction workings. This 

 strikes in general east and west, but frequently north of west, and dips south at 

 varying angles. This vein is in line with the outcrops of the Valley View veins 

 across the gulch to the east on Mizpah Hill. It is possible, therefore, that it 

 belongs to the Valley View system. On the other hand, the Valley View and 

 the Fraction veins underground, when plotted on a given level, show no signs of 

 being part of the same body, following quite different lines. Indeed, the two 

 veins dip in opposite directions the Valley View to the north, the Fraction to the 

 south. The two are also separated, as shown on the map, by one or more faults 

 which makes correlation still more doubtful. If the Fraction is part of the Valley 

 View svstem, its vein, dipping in the opposite direction, might be considered as 

 making up with the Valley View vein a pair of conjugated veins. It is barely 

 possible, though perhaps not probable, that the fault movement has in the case 

 of the Fraction reversed the original dip by tilting the block in which the vein lies. 



Some of the numerous faults which cut the vein have been exposed in the 

 mine workings, and such have been shown in the accompanying detailed plans 

 and cross section (PI. XXI). 



