LITTLE TONOPAH SHAFT. 199 



VEINS. 



The quartz stringers found along the edges of the rhyolite dikes near the 

 edge of the shaft are stated by Mr. Stock to run as high as $13 in gold. These 

 consist of dark, rather dense quartz, carrying a great deal of pyrite. In the 

 shaft also small stringers have been found up to the time of the writer's visit, 

 generally striking parallel with the slips but dipping in the opposite direction, 

 and affording assays running up as high as $18, being all in gold. Mr. Stock 

 reports that at a depth of 440 feet a stringer was cut which gave an assay of 

 $39.60 in gold and $3.80 in silver, while at the bottom of the shaft (460 feet) 

 another stringer 2 inches thick gave an assay of $4.14 in gold and $6 in silver, 

 the latter being the first which showed preponderating silver values, the other 

 assays from the shafts of the neighborhood showing chiefly gold. This minerali- 

 zation is therefore comparable with the low-grade pyrite-bearing quartz veins, 

 with the values chiefly in gold, which occur at various other points in or near 

 the glassy Tonopah rhyolite-dacite near its contact. It is due to the action of 

 heated waters circulating along the contact, subsequent to the intrusion of the 

 rhyolite-dacite, and is of a different and later period from that of the veins in 

 the earlier andesite. 



The abundance of pyrite in the altered later andesite seems to indicate that 

 the pyritization here, as probably in the case of similarly altered later andesite 

 on Mizpah Hill, is associated with present water courses. The pyrite, like that 

 of the later andesite on Mizpah Hill, is barren of gold and silver values. 



SHAFTS AT THE UNMINERALIZED CONTACT OF THE TONOPAH 



RHYOLITE-DACITE. 



BUTTE TONOPAH SHAFT. 



The Butte Tonopah shaft, at the eastern base of Ararat Mountain, was 35 

 or 40 feet deep at the time of the writer's visit. It was in the Tonopah 

 rhyolite-dacite, at the contact of this rock with the later andesite. This con- 

 tact, apparently vertical, is plainly and continuous!}- shown about 30 feet east of 

 the shaft. The rhyolite-dacite contains many inclusions of the andesite, and is 

 intrusive into it. 



LITTLE TONOPAH SHAFT. 



This shaft is located about 150 feet from the edge of the area mapped and 

 about one-half mile west of the Golden Anchor shaft. It is situated at the 

 contact of the glass}' Tonopah rhyolite-dacite with the later andesite. The shaft 

 starts in the rhyolite-dacite and runs down about 50 feet to the contact with the 

 andesite. The rhyolite contains fragments of the later andesite, and the contact 



