64 C. H. Gordon. — llississipjncm Formations, etc. 



Pipe'' stratum above mentioned. The chief ore values in this 

 district consist of lead and zinc, with little or no silver. 

 With the exhaustion of the oxidized ores near the surface, 

 large bodies of sulphide are coming to light below, with 

 which is associated a considerable amount of copper. The asso- 

 ciation with the ores of certain minerals, such as pyroxene, 

 magnetite, and specularite, intergrown with quartz and calcite, 

 suggests the derivation of these deposits likewise from ascend- 

 ing hot solutions. The region is one of marked igneous activ- 

 ity, as shown by the presence in the immediate vicinity of 

 several bodies of intrusive rocks, chiefly monzonite-porphyries, 

 while extensive flows of andesite and rhyolite cover the range 

 as a whole. 



April 20, 1907. 



