On the Copper Range of Lake Supei 





opened have shown an amount of this metal sufficient to war- 

 rant exploitation. However, on account of the very great ex- 

 tent linearly to -which these beds are developed over the coun- 

 istence in thickness, and their well marked and 

 cters, they become a valuable guide in explora- 

 tions, and a convenient reference in the location of the various 

 metalliferous deposits. 



On a closer examination of the trappean range at Portage 

 Lake it would appear to be divisible into certain zones, the rocks 

 of which are bounded by the conglomerate and sandstone belts, 

 and present features which characterize and separate them from 

 the members of the other series. More especially is this observ- 

 able in the copper-bearing amygdaloidal beds. The cupreous 

 deposits of the several series differ so greatly in mineralogical 

 composition that no diflQculty exists in referring the materials 

 from any one of them to its source, they being almost as well 

 characterized as the vein-matter of the different districts of this 

 mining region. 



A complete section of the range at this point has not yet been 

 obtained, as the explorations have not been extended to the ex- 

 treme east and west boundaries of the trappean rocks. For a 

 ^'dth of about two miles all the belts have been exposed, and 

 ^he examinations have developed four distinct zones of rocks, 

 jwch we shall name from the main metalliferous deposit m each. 

 passing from the east to the west these are : the Isle Eoyale, 

 i'ewabic, Hancock and the South Side series, or, as they are 

 locally styled, formations. 



isfe Hoyale Zone.— The rocks we shall include in this zone cover 

 a width of about one and one half miles, and are limited on each 

 Side by belts of conglomerate. Within this distance, fourteen 

 'topper-bearing deposits have been opened at various times, all 

 ?..OA-,ng analogous features, though but two have as yet been 

 'J'^tematically laid open to any great extent. They all have a 

 ]erv large amount of epidote, massive as well as crystalline, en- 

 ^'j;ng mto their composition, and a comparative paucity of crys- 

 !^"^sa carbonate of lime. The other minerals in the eonstitu- 

 jon of the so-called lodes of this series, and usually denommated 

 '^e vein-stones, are more crystalline in structure than the same 

 ^Peciea found in the other zones, but the abundance of the epi- 

 IC ^^- ^*^^t3'"s, and the almost total absence of this mineral m 

 ^neighboring zones, must be regarded as the mam distinction. 

 ^■^■nother point of importance in its economical bearings, is the 

 ^'^aracter of the copper produced from the mines in this zone, the 

 th,??,^^^°° ^^ ^^e heavier description of copper being greater in 

 ''i^ than in the other series. 



^ Jock. Sci._Secosd Series, Vol. XXXIY. No. IOO.-Jllt, IS6?, 



