18fi9.] MACPARLANE — GEOLOGY OF LAKE SUPERIOR. 461 



modified, hyperjte. Four difierent specimens, tested as to specific 

 gravity, gave respectively 3.061, 3.034, 3.009 and '^.922. 



The explorations made upon the location during the summer 

 and fall of 1869 did not result in the discovery of any new veins 

 of much economic value. A few very narrow and unimportant 

 veins, noted on the map, were found on the face of Thunder 

 Cape clifi's, and at a few other points in the interior of the 

 location. Much more important, because of great width, are the 

 veins noted as occurring on Shangoinah Island, and running 

 parallel with its length. In places this network of veins has a 

 width of forty feet, enclosing, however, much rock, the greatest 

 width of pure veinstone being about three feet. The veinstone 

 consists of large-grained calcspar, accompanied by saponite and 

 iron pyrites. Several days were spent in blasting on the vein 

 and searching for silver in it, but without result ; nor did the 

 iron pyrites contain any, except the merest traces. It is to be 

 remarked that the general course of this suite of veins is N. 

 50^E., consequently almost at right angles to that of the Silver 

 Islet vein. On this account, and because of the coarse grain of 

 of the veinstone, and because also of its similarity to that of the 

 dyke veins, in which nothing of value has been hitherto dis- 

 covered, it is not anticipated that the veins of Shangoinah Island 

 will ever turn out to be of much value. 



Pyritic Island, which lies inside of Shangoinah Island, was 

 also carefully explored. No veins were detected anywhere upon 

 it, but a baud of reddish weathering rock runs through its length 

 from north-east to south-west. It contains finely disseminated 

 plumbago, copper, iron and magnetic pyrites, and also 0.02 per 

 cent, of silver, a quantity, however, too small to be economically 

 available. 



The continuation of Silver Islet vein, across Burnt Island, and 

 upon the main laud, was carefully explored for a distance of 

 about one mile from the lake. On Burnt Island a large quantity 

 of earth was removed, and excavation done on the vein, which 

 was found to be irregular at the point where it intersects the 

 most southerly dyke. Here calcspar, quartz and fluorspar form 

 the veinstone, with small grains of galena, blende, iron and copper 

 pyrites, but no silver. The vein was uncovered at numerous 

 points inland without obtaining any better result 



The situation of the rich vein at Silver Islet is such that work 

 was only possible upon it on the calmest days, when neither wind 



