142 



ECONOMIC GEOLOGY 



to $6 in gold. Some of the veins on the eastern coast of New- 

 foundland are true fissure veins traversing sandstones and con- 

 glomerates. Intrusive diabase appears to be the home of the 

 copper ore. Chalcopyrite and pyrite are the chief minerals. 



Chalcopyrite occurs in considerable quantity at Capleton, 

 Province of Quebec, in a sheared amygdaloid. The mine has 

 been a steady producer for a number of years. 



(2) The Lake Superior Region. This region was discovered by 

 Douglas Houghton in 1830. It has since that time produced more 

 native copper than all other localities put together. In fact it 

 has become one of the most famous copper producing districts 

 of the world. The rocks, known as the Keweenaw series, consist 



FIG. 83. Dump piles of the Ely mine, Copperfield, Vermont. (By courtesy 



of the Vermonter.) 



of interbedded lava flows, sandstones and conglomerates. The 

 conglomerates consist of rounded fragments of a reddish quartz 

 porphyry of igneous origin. 



The ore is native copper occasionally associated with native 

 silver. It occurs, according to H. Ries: (1) As a cement in 

 the conglomerate, or replacing the conglomerate; (2) as a filling in 

 the amygdules of the lava beds; and (3) as masses of irregular 

 and often large size in veins with calcite and zeolitic gangue. (See 

 Fig. 84.) 



According to A C. Lane, the original lava flows was the home 

 of small percentages of copper, and while these basaltic rocks 

 were still heated they absorbed sea waters charged with sodium 



