232 VEINS AT KEWENAW POINT. 



in to mere films of metal in many places ; and in the 

 sandstone the veins, though continuing large, are filled 

 with calc — spar, and other vein-stones — and become poor 

 in valuable mineral matter. 



The veins are of two kinds — transverse, which cross 

 the trap ridges in a direction which is N. by 26° to 30° 

 W. ; and longitudinal, which run parallel to the ridges 

 and to the strike of the red-sandstone beds. These 

 longitudinal veins, as well as the cross veins, are rich in 

 copper in the amygdaloid only ; and though in many 

 places they have the appearance of beds, they are, in 

 the opinion of Dr Jackson, probably true veins. The 

 most successful mine as yet brought into operation is the 

 Cliff Mine, in a cross vein on Kewenaw Point. The 

 vein-stone is prehnite, and the vein widens and becomes 

 richer in copper the deeper it is followed. In 1848 

 this mine shipped and sold 800 tons, and in 1849 about 

 930 tons, containing an average of 60 per cent of pure 

 copper. Next to it is the Minnesota Mhie, on the Onto- 

 nagon River. It is in one of the longitudinal veins or 

 beds, and though only a few hundred tons of metal have 

 yet been shipped, the mine is of great promise. There 

 are many others in progress, from which large supplies 

 are expected, in a few years, to be obtained. 



The only form in which the mineral has yet been 

 extracted, in marketable quantity, is in that of metallic 

 copper. When the huge masses and sheets of native 

 metal were first met with in these veins, the extraction 

 of them was found so difficult that it was doubted 

 whether it would be possible economically to remove 

 them. This is now done by clearing the face of the 

 metal, and cutting it out with cold-steel chisels. It 

 occurs in more or less extended sheets, standing on 

 edge, and following the lie of the vein. Several of 

 these are sometimes arranged side by side. They swell 

 out here and there Into ellipsoidal forms, so as to be in 



