on the Northern Shore of Lake Superior, c. == 357 
opinions of mineralogical writers can be collected on this point, 
they teach,—that large veins of native copper are seldom found, 
but that it is frequently disseminated in masses of various size in 
the rocks, and among the spars and ores of copper and other 
mines ; and when found in scattered masses upon the surface, is 
rather to’be considered as a token of the existence of the sul- 
phuret, the carbonate, and other ores of copper, within the cir- 
cle of country where it occurs, than as the precursor to conti- 
guous bodies of the same metal. ‘ Native copper,” says Cleve- 
land, ‘is found chiefly in primitive rocks, through which it is 
sometimes disseminated, or more frequently it enters into the 
composition of metallic veins, which traverse these rocks. It is 
thus connected with granite, gneiss, micaceous and argillaceous 
slates, granular limestone, chlorite, serpentine, porphyry, &c. 
It also occurs in transition and secondary rocks. Jt accompanies 
other ores of copper, as the red oxide, the carbonate and sul- 
phuret of copper, pyritous and gray copper, also the red and 
brown oxides of iron, oxide of tin, &c. Its usual gangues are * 
quartz, the fluate and carbonate of lime, and sulphate of barytes. 
At Oberstein it occurs in prehnite; and in the Faroe islands it 
accompanies zeolite. 
“© Native copper is not rare, nor is it found in sufficient quan- 
tity to be explored by itself. It sometimes occurs in loose, in- 
sulated masses of considerable size *.”” 
From all the facts which I have been able to collect on Lake 
Superior, and after a deliberation upon them since my return, [ 
have drawn the following conclusions : 
Ist. That the alluvial soil along the banks of the Ontonagon 
river, extending to its source, and embracing | the contiguous re- 
gion which gives origin to the Menomonie river of Green Bay, 
and to the Ousconsing, Chippeway and St. Croix rivers of the 
Mississippi, contains very frequent, and some most extraordinary 
imbedded masses of native copper; but that no body of it, which 
is sufficiently extensive to become the object of profitable mining 
operations, is to be found at any particular place. This con- 
clusion is supported by the facts already adduced, and, so far as 
theoretical aids can be relied upon, by an application cf those 
facts to the theories of mining. A further, extent of country 
might have been embraced along the shore of Lake Superior, but 
the same remark appears applicable to it. 
2d. That a mineralogical survey of the rock formations skirt- 
ing the Ontonagon, including the district of country above al- 
luded to, would result in the discovery of very valuable mines of 
the sulphuret, the carbonate and other profitable ores of copper; 
in the working of which the ordinary advantages of mining would 
* Cleveland's Mineralogy, p. 450. 
re 
