On the Copper Range of Lake Superior. 117 



From the above it is obvious that though many of the belts 

 of rock of the Range are persistent throughout its whole length, 

 yet the absolute contact of all the zones we have pointed out 

 should not be too rigidly expected over the whole distance, since 

 other belts or series of belts may be introduced between them, 



Yehis of the Lake Superior Beg ion.— Three classes of metallif- 

 erous occurrences have been shown to exist in the Trap Eange: 

 Fis.^'jre veins, Segregated and Compact deposits. 



Fissure Veins.— Th\s class of veins are almost entirely devel- 

 oped on Point Keweenaw. In their course they may be traced 

 across the whole width of the mineral formation, from the Bohe- 

 mian or South Eange to the north shore of the Point, cutting 

 the sedimentary beds without a deviation of course, and even 

 breaking through the pebbles of the conglomerate. They gen- 

 erally show small displacements of the beds, both horizontally 

 and vertically, although there are some marked exceptional ex- 

 amples. The largest 'heave' yet noticed is that at the Humboldt 

 mine, near Eagle River, where the "Ash bed"* is found on the 

 east side of the fissure vein, about 350 feet north of its position 

 on the west side. 



The course of these veins varies from N. 16° E. to N. 58° W., 

 ) of the seventeen principal ones now worked being 

 They are nearly perpendicular, with a slight under- 



Evidences of the existence of a later and distinct line of frac- 

 ture are to be found, the course of which was E. of N. about 15°, 

 and which has given rise to some powerful, though not highly 

 productive veins, which displace considerably the formation as 

 ^'ell as the veins of the first class. At the North American 

 Biine the Cliff vein is heaved 250 to 300 feet by the Armstrong 

 vein, which is necessarily posterior in formation. The existence 

 on Keweenaw Point of still another line of fracture, with a gen- 

 eral course of N. 65° E. has been contended for by some, but 

 Jae evidences are more from the topographical features than 

 from any direct explorations or exploitations. Certain it is, how- 

 !^ver, that one member of this system has been opened m the 

 f ortage Lake District, but presented no features to warrant any 

 f^^ther examination, so that nothing is known of its composi- 

 tion and structure. Still another has been traced for a length of 

 i200 feet on the Columbian location. In the same district a 

 ^em belonging to the second system was mined for some tinie 

 on the Quincy property, but did not prove of remarkable rich- 



J^ ',^r«^ted deposit situated north of the greenstone axis of Point Keweenaw, 



e average ( 



