146 



ECONOMIC GEOLOGY 



one of the largest producers of copper in the world. Its output has 

 been approximately 2,000,000,000 Ib. of copper. It has further- 



, :-<^^^- :~rt^^ 

 $W&dS%w$-$M$^ 



H Pa/ - ALLUVIUM AND WASH PLEISTOCENE 

 75 Nri - INTRUSIVE RHYOLITE NEOCENE 

 1 OP- APLITE 



SILVER VEINS 

 COPPER VEINS 



qr- GRANITE 



POST CARBONIFEROUS 



FIG. 85. Map of the eastern part of Butte, Montana, district, showing 

 distribution of Veins and geology. (By permission of the Macmillan 

 Company, from Ries' Economic Geology.} 



more produced more than 100,000,000 oz. of silver and 500,000 

 of gold. The camp began its mining career as a gold producer 

 in 1864. It held this recognition until 1875 when it became a 





