196 KEMP'S ORE DEPOSITS. 



form of deposit. According to this view, the chambers were 

 formed before the ore was brought in. It is also possible that the 

 ore bodies have been deposited by replacement of the limestone 

 with sulphides, as is known abundantly elsewhere, and that the 

 alteration of these to oxides has occasioned the apparent caves. 

 The products of the mine afford but 5 to 1% lead, but are valuable 

 as an iron flux to the neighboring smelters. The mines are in the 

 Granite range, seven miles southeast of Mil ford. 1 



NOTE. Although the larger part of the Utah mines are for 

 lead and silver, several others of great importance will be taken 

 up under " Silver " itself. 



NEVADA. 



2.08.29. Example 36. Eureka. Bodies of oxidized lead-sil- 

 ver ores in much faulted and fractured Cambrian limestone, 

 with great outbreaks of eruptive rocks near. The Eureka geo- 

 logical section is one of the most interesting in the entire country, 

 and involves some 30,000 feet of Paleozoic strata, divided as fol- 

 lows : Cambrian quartzite, limestone, and shale, 7700 feet ; Silu- 

 rian limestone and quartzite, 5000 feet ; Devonian limestone and 

 shale, 8000 feet ; Carboniferous quartzite, limestone, and conglom- 

 erate, 9300 feet. These have afforded some extremely valuable 

 materials for comparative studies with homotaxial strata in the 

 East. The ore occurs especially in what is called the Prospect 

 Mountain limestone of the Cambrian, one smaller deposit being 

 also known in Silurian quartzite. The limestone has been crushed 

 and shattered along a great fault, and through its substance 

 ore solutions have circulated, replacing it in part with large 

 bodies of sulphides which have afterward become oxidized to 

 a depth of 1000 feet. The ore bodies were puzzling as regards 

 their classification, and a famous mining suit, with many interpre- 

 tations from various experts, resulted. The alteration of the ore 

 has caused shrinkage and the formation of apparent caves over it. 

 But there are many empty caves, formed by surface waters long 

 after the ore was deposited, and Mr. Curtis very clearly shows 

 that the ore bodies originated by replacement. All are connected 



1 O. J. Hollister, "Gold and Silver Mining in Utah," M. E., 1887. 

 D. B. Hunt ley, Tenth Census, Vol. XIII., p. 474. J. S. Newberry, School 

 of Mines Quarterly, March, 1880. Reprint, p. 9. Cf. also J. P. Kimball, 

 "The Silver Mines of Santa Eulalia, Chihuahua," Amer. Jour. Sci , ii., 

 XLIX. 161. 



