USEFUL METALS 



153 



little sphalerite. Tin- percentage of chalcopyrite is higher in th<; 

 alternating bands of sulphide copper ores and schist than it is in 



the more massive material (Fig 92). 



1 ; : ft*/*/.'/. \ -, ^pJSg 



feMggt V 



^;fe^^^ 



:./:?.-.-- .-: : \: .-;-;;: 



"/ . // A* f v ^-^ 



f ?::'::iy-:^\'Av'.-;'V : \ 



FIG. 92. Diagrammatic cross section through the Old Dominion mine 

 showing the occurrence of a mass of limestone in the diabase of the foot 

 wall, Globe district, Arizona. Scale 1 in. =200 ft. approximately. (After 

 F. L. Ransome, U. S. Geological Survey.) 



(5) The Mineral Creek District: The terranes are pre-Cam- 

 brian and the ore is chalcocite widely disseminated through the 

 schistose rocks. 



(4) The Pacific Coast Belt. California is the largest producer 



