MONTANA TONOPAH VEIN SYSTEM. 



177 



NORTH STAR WORKINGS. 



SECTION PASSED THROUGH. 



The North Star shaft was started in white rhyolite on the slope of Mount 

 Oddie (fig. 67). Below the rhyolite comes the later andesite, the contact being 

 practically horizontal and indicating the later age of the rhyolite. From this 

 contact down to a depth of about 720 feet the shaft is in the later andesite, 

 largely soft and decomposed. It is sometimes brecciated, indicating considerable 

 movement, and in places contains much secondary pyrite. At depths of about 



KIG. 07. Section on plane of Desert Queen and North Star shafts. 



720 to 740 feet the shaft cuts the zone of the Mizpah fault, which is characterized 

 by 20 feet or more of clay, formed by trituration and decomposition along the 

 fault. Beneath the fault the earlier andesite comes in. 



Just above the bottom of the shaft, which is 1,050 feet deep, the Tonopah 

 rhyolite-dacite comes in. It is the same sheet which is encountered on the 814- 

 foot level of the Desert Queen. 



The developments in the North Star consist of two drifts, at 950 and 1,050 feet. 

 The lower one of these levels is the more extensive, having a drift to the north 

 of over 500 feet. On the 950-foot level and on the north drift of the 1,050-foot 

 16843 No. 4205 12 



