- wu _ | Geological Structure of Keweenaw Point. 69 
© alfeady this: mine sends to market nearly a thousand tons of 
- copper ore per annum, the ore being estimated to contain sixty 
per cent. of pure copper after it is cleansed of the adhering rock. 
. ‘This mine, it is understood, has paid for itself and made a divi- 
— dend of ten dollars per share to its owners. 
It is highly probable that other mines on Keweenaw Point, if 
_ Wrought with the same energy and skill, would prove equally 
~. valuable, but thus far no mining equivalent to that of the Boston 
and Pittsburg Mining Company has been attempted, and it is dif- 
ficult to find a miner so competent to the task as Capt. om 
the Cornish miner, who has had charge of this remarkable m 
T exhibit to you a profile and plan of the mine, in which all ihe 
preg are fully delineated. 
ong other promising mines are the North American, the 
Ginaee Falls, the Northwest, and the Phenix, all of which have 
en sufficiently proved to warrant the belief that they can be 
advantageously wrought, but still it must be remembered that 
even in the best known mineral districts, mines frequently fail 
to prove profitable from causes that are not at once foreseen. he 
North American Compan y’s mines are situated very near the Cliff 
mine, on the west branch of Eagle River, and are now wrought 
with energy, and give promise of success nearly equal to that of 
the Cliff mine before described. The veins are similar in their 
nature and in their contents, so that I need not describe them. 
e Copper Falls mines have been opened to a considerable 
€xtent, and from one of the veins a single mass of copper was 
taken that weighed eight tons. It was sawed into pieces and sent 
| to market. [ exhibit to the section a specimen sawed from this 
' _Mass. It is perfectly pure copper, and as dense as the purest ham- 
mered copper of commerce, showing its perfect fineness. ‘There 
isa rae proportion of native silver mixed with the cop- 
per of this mine, and in the green veinstone, a specimen of which 
I lay before you. Silver is found also in most of the copper 
ines of the lake, and frequently in suflicient quantities to be of 
commercial value. It is most curiously united with the copper, 
and in some of the pieces I lay before you, the metallic copper is 
actually porphyritic with masses of silver, and yet the silver is 
utely pure, and the copper is also pure, there being no alloy- 
ing or chemical union, but a mere metallic cementation at the 
line of contact. This phenomenon is seen in all the localities on 
the lake where native copper and silver occur together, and this 
State of the metals must have arisen from a common cause acting 
| in every one of the veins. It is not capable of being explained 
in the present state of chemical and geological knowledge, and is 
4 subject for experimental research. ‘The solution of this ques- 
tion will lead to an explanation of the origin of the native cop- 
per Schott silver veins, the rationale of which we have not yet 
