144 



KEMP'S ORE DEPOSITS. 



inches and several feet. They lie between chert seams and are 

 associated with clay and sand. The ore is thought by Nicholson 

 to have been deposited in cavities formed by dolomitization, much 



2nd._Magnes"ian Limestone 

 Roof 



Limestone 



'"> Chert seams 



>ElEEeE=~ Sulphuret ore 



2nd. Magnesian Limestone 



FIG. 32. Cross section in the St. Genevieve copper mine, illustrating the 

 relations of the ore. After F. Nicholson, M. E., X., p. 450. 



as is advocated by Schmidt for the lead and zinc deposits of south- 

 west Missouri, and as is described under Example 25. For ten 

 years the mines have not been operated. 1 



Limestone 



vi Chert and 

 ore 



]ft G< 33._ Section at the St. Genevieve mine, illustrating the intimate re- 

 lations of ore and chert. After F. Nicholson, M. E., X., p. 451. 



2.04.18. Example 20. Arizona Copper. Bodies of oxidized 

 / -copper ores in Carboniferous limestones, associated with eruptive 

 ) rocks. In addition to these, which are the most important, are 



1 F. Nicholson, "Review of the St. Genevieve Copper District," M. E., 

 X. 444. B. F. Shumard, " Observations on the Geology of the County of 

 St. Genevieve, Missouri," Trans. St. Louis Acad. Sci., Vol. I., p. 40 ; ab- 

 stract in Amer. Jour. Sci., ii., XXVIII. 126. 



