BETWEEN BALL MOUNTAIN AND WESTON FAULTS. 228 



replaced by limonite resulting from the leaching out of the pyrites. The 

 Weber sandstones at the contact with the porphyry are often brecciated 

 and so impregnated with pyrites as to be scarcely distinguishable from the 

 porphyry. To understand the distribution of the various bodies of this 

 porphyry and their supposed continuation below the limits of exploration 

 it will be necessary to refer to Section G, Atlas Sheet XX. According to 

 this it will be seen that there are three distinct sheets of porphyry above 

 the Weber Shales, while a fourth occurs beyond Weston fault, between the 

 Weber Shales ?nd White Porphyry, which connects with a fifth body 

 found in California gulch, where it crosses the White Limestone and White 

 Porphyry along the cross-cutting zone already mentioned. It is supposed, 

 as shown in the section, that it is in this vicinity that the porphyry came 

 up through the Archean. 



Northwest slope of Bail Mountain. The bodies of Pyritiferous Porphyry thin 

 out towards the north, and on the upper part of Breece Hill, or the north- 

 west slope of Ball Mountain, all except the upper one disappear before 

 reaching the Colorado Prince and Ball Mountain faults. No trace of Pyri- 

 tiferous Porphyry has yet been found east of the latter fault. To the north 

 the lower sheet is stratigraphically replaced by the main sheet of Gray 

 Porphyry, since farther west they are each underlaid by the main body 

 of White Porphyry. In the few cases where underground explorations have 

 disclosed the relations of the Pyritiferous and Gray Porphyries the former 

 is found to overap the latter. 



In this region the beds whcih have been assigned to the Weber Shales 

 horizon are found to have a much larger proportion of sandstone than the 

 corresponding beds on Little Ellen Hill, but in either case the data are 

 somewhat meager, as no shafts are so situated as to afford a complete or 

 continuous section. The Antelope shaft found 100 feet of white quartzite 

 immediately above the Gray Porphyry. The Quandary shaft found mi- 

 caceous sandstone ; the Garbutt, sandstone and shale ; and the shafts of 

 the Ontario (F-50 and F-51), a coarse sandstone. The Capitol (F-57) 

 and the Highland Queen (F-56) shafts passed in depth into a body of 

 quartz-porphyry of different character from the Pyritiferous Porphyry. 

 It were too long to enumerate all the other shafts on this slope, the infor- 



