HURONIAN EOCKS OF LAKE SUPERIOR. 67 



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Silver Mines, along Kaministiquia Eiver below Kakabeka Falls, at the Pays Plat 

 Islands in Nipigon Bay and other places. 



The Animikie cherts and jaspers, black, red and green, are to a great extent charac- 

 terised by a peculiar internal oolitic structure, such as I have not seen within the Huro- 

 nian rocks. I have noticed this feature along the strike of the formation for over one 

 hundred miles, or from Silver Lake to Gunflint Lake. 



Again, none of the chloritic, talcoid, actiuolitic, micaceous, or dioritic schists, that 

 are so plentiful in the Hurouiau folded schists, are found among the Animikie beds ; nor 

 are any of the obscure conglomerates, so plentifully developed throughout, and so charac- 

 teristic of, the Huronian of Lake Superior, to be seen in the Animikie. These conglo- 

 merates or agglomerates, which are made up of oblong or lenticular masses of various 

 sizes, from a few inches up to twenty feet and more in length, are generally arranged 

 parallel with the bedding. Usually they are thickly packed, and show a gradual 

 transition from the massive central nucleus to the more fissile schistose matrix, the latter 

 being also deeper or darker in color, than the former. It is only on weathered, smooth, 

 wet surfaces that they are well seen. They have been described by Logan, Bell, Macfar- 

 lane and others, and different theories have been given for their formation. 



The rocks of the Animikie group, as a general rule, have a tendency to break at right 

 angles to the bedding, while the Huronian rocks show a strong tendency to break at acute 

 angles into lenticular fragments, characteristic of crystalline schists. The Animikie strata 

 are conspicuously slaty or flaggy, not schistose ; and the Huronian rocks are as conspi- 

 cuously schistose by reason of the development within themselves of leafy minerals. 

 Again, with the exception of the crystalline trap, chert, dolomite and iron ore, the 

 constituent minerals of the remaiuder or major portion of the Animikie strata are frag- 

 mentai, and of exotic origin as shown above in the case of the mica in the clay-slate. 

 Those of the Huronian rocks, on the other hand, have been developed in place by 

 metamorphism. The trap, of course, was crystallised from the molten state. The cherts, 

 jaspers, dolomites and iron ores, have probably been chemically formed, as suggested by 

 Prof Irving and others. In the Huronian folded schists, chlorite, mica, hornblende, etc., 

 in fine grains, are plentifully developed in places, constituting great thicknesses of the 

 different schists characterised by these minerals, while in the Animikie, I believe, none 

 of these minerals are developed within the sedimentary beds, except perhaps in close 

 proximity to eruptive trap. It would appear that the Animikie strata are not sufficiently 

 metamorphosed for the differentiation of these minerals. 



The prevailing greenish aspect of the Huronian folded schists seems to be caused by 

 the partial development of a chloritic ingredient as shown by Prof Irving. "When des- 

 cribing (p. 22V) some of the typical Huronian strata, he states, " Most all of the kinds, 

 except those that are nearly purely quartzose, have undergone a considerable amount of 

 metasomatic change, the principal result of which has been the production from the feld- 

 spars of chloritic ingredients ; whence, chiefly, the dark and often greenish hue presented 

 by these rocks." This dark and greenish hue is a prevailing characteristic with the bulk 

 of the Huronian strata, and is entirely absent from the Animikie. This distinguishing 

 feature alone should, I think, be sufficient to separate the two formations, especially as 

 it is so marked, and where only a line, as it were, separates them for some two hundred 

 miles or more along their northern contact or boundary. 



