APPENDIX. 529 



In addition to these masses of native copper, an ore of that 

 metal has long been known to the lake traders as the green rock, 

 in which the characteristic substances are the green and blue car- 

 bonates of copper, accompanied by copper black. It is situated 

 upon Keweena Point, 280 miles above the falls of the Ste. Marie. 

 The ore is embraced by what is apparently a recently formed 

 crag; and, although it is of a kind and so situated as to make an 

 imposing appearance, there is little certainty of its existence in 

 large quantities in this formation. The ore forms a thin cover- 

 ing to the pebbles of which the body of the rock is composed, 

 and is rarely observed in masses separate from it. The crag is 

 composed of angular fragments of trap-rock, and the formation is 

 occasionally traversed by broad and continuous belts of calc. spar, 

 here and there tinged with copper. Although the ore was not 

 observed in any considerable quantity, except at one point, it 

 apparently exists in minute specks through a greater part of the 

 crag formation, which extends several miles, forming the shore 

 of the lake. 



This examination of the crag threw new interest upon the trap 

 formation, which had been first observed to take the place of the 

 sandstone at the bottom of a deep bay, called Montreal Bay, on 

 the easterly side of Keweena Point. The trap-rock continues for 

 a few miles, when the crag before noticed appears to lie directly 

 upon it, and to form the extremity of the point ; the crag, in turn, 

 disappears, and the trap-rock is continued for a distance of six or 

 eight miles upon the westerly side of the point, when the sand- 

 stone again reappears. 



The trap-rock is of a compact granular texture, occasionally 

 running into the amygdaloid and toadstone varieties, and is rich 

 in imbedded minerals, such as amethystine quartz, smoky quartz, 

 carnelian, chalcedony, agate, &c., together with several of the ores 

 of copper. Traces of copper ore in the trap-rock were first 

 noticed on the easterly side of Keweena Point, and near the com- 

 mencement of the trap formation. This ore, which is an impure 

 copper black, was observed in a vein of variable thickness, but 

 not in any part exceeding two and a half inches. It is sufficiently 

 compact and hard to receive a firm polish, but it is rather disposed 

 to break into small irregular masses. A specimen furnished, 

 upon analysis, 47.5 per cent, of pure copper. 

 34 



