56 



GEOLOGY OF THE EUREKA DISTRICT. 



section is numbered from the top downward, the numbers inclosed in 

 brackets coinciding witli the specimen number in the collection. Through- 

 out the section the quartzite is for the most part vitreous without partings 

 parallel to the bedding, the coloring, however, being in nearly horizontal 

 planes, passing insensibly from one tint to another. 



10 feet of white vitreous quartzite. 



10 feet grayish white, with segregation of fer- 

 ruginous material. 



30 feet white and vitreous. 



10 feet purple and white, vitreous. 



30 feet purplish white, with three narrow bauds 

 of dark gray granular quartzite. 



10 feet dark gray quartzite. 



20 feet white, banded with steel grayj dark gray 

 quartzite bands in No. 7. 



20 feet dark gray and white, banded and mottled. 



20 feet light gray, fine granular. 



40 feet white and pinkish white. 



60 feet dark gray passing into light gray, with 

 bands more or less calcareous, weathering 

 red. 



20 feet gray, having cross bedding brought out 

 by weathering. 



20 feet dark steel gray quartzite, somewhat cal- 

 careous. 



20 feet siliceous limestone. ) Pogonip 



40 feet black compact limestone. ) limestone. 



360 feet 



Fio.l. Eureka quartzite west 

 of Castle Mountain. 



The junction between the quartzite and the underlying limestone pre- 

 sents a sharp line of demarcation and indicates an abrupt change in the 

 deposition of sediments. 



Although the Eureka quartzite is probably not more than a few hun- 

 dred feet in thickness, it can be estimated only approximately, as an uncon- 

 formity exists between it and the next overlying group. Over the large 

 area covered by the exposures of the quartzite, evidences of denudation 

 prior to the deposition of the Lone Mountain limestone may be observed in 

 the mountains connecting the Fish Creek Range with Prospect Ridge, but 

 no satisfactory estimate of the amount seems possible. Again, not only 



