226 KEMP'S ORE DEPOSITS. 



under Examples 30</, 33#, and 32&. The great iron mines of Iron 

 County will be found under Example 14. In Piute County, near 

 the town of Marysvale, around Mount Baldy, are a number of 

 mines with lead-silver or milling ores in quartz porphyry (copper 

 belt), or between limestone and quartzite (Deer Trail, Greeneyed 

 Monster, etc.). Selenide of mercury is found in the Lucky Boy. 1 



2.11.05. Example 41. Silver Reef, Utah. Native silver, cerar- 

 gerite, and argentite, impregnating Triassic sandstones, and often 

 replacing organic remains. These deposits were earlier referred 

 to under Example 21, p. 80. They were discovered in 1877. At 

 Silver Reef there are two silver-bearing strata or reefs, with beds 

 of shale between. Above the water line the ore is horn silver ; 

 below, it is argentite. At times it replaces plant remains ; at other 

 times no visible presence of ore can be noted, although the rock 



xxxxx.xx x^- ^^ 

 x 



/ 



% 

 I 



Runs into. 

 barren rock 



FIG. 56. Two sections of the argentiferous sandstone at Silver Reef, 

 Utah. After C. M. Rolker, M. E., IX., p. 21. 



may afford $30 to the ton. The silver always occurs along certain 

 ore channels, distributed through parts of the sandstone. The 

 origin of the deposits has given occasion to a vigorous discussion. 

 J. S. Newberry holds that the silver was deposited in and with 

 the sandstone from the Triassic sea, although it may have been 

 concentrated since in the ore channels. F. M. F. Cazin holds that 

 the organic remains were deposited in and with the sandstone, and 

 that these were the immediate precipitating agents of the ores. 

 R. P. Rothwell explained them much as does Rolker, below. C. M. 

 Rolker, who was for some years in charge of several of the mines, 

 has also written about them, and is probably nearest to the truth. 

 Rolker argues that the impregnation was subsequent to the forma- 

 tion of the sandstone, and was caused by the igneous outbreaks in 

 the neighborhood, and probably runs along old lines of partial 

 weakening or crushing that afterward healed up. Eruptive rock& 



1 G. J. Brush, " On theOnofrite, etc.," Amer. Jour. Sci., iii., XXI. 312. 



