1867.] macfarlaNE — geology of lake superior. 193 



Siliceous Slate. — In many places bands of such dark coloured 

 slate as that just described are interbedded with others which 

 are lighter coloured and more siliceous. Such banded slates may, 

 for instance, be observed on the north-east shore of Goulais Bay. 

 Here the darker slate is very evenly foliated, of a dark greenish- 

 grey colour, and has a specific gravity of 2-685. Its powder is 

 light green, changing on ignition to light brown, and losing 2*02 

 per cent, of its weight. It yields to sulphuric acid 16*75 of bases. 

 The rock of the lighter bands is highly siliceous, and in fusibility 

 equal to orthoclase. The powder has a reddish grey colour, 

 which changes on ignition to brownish grey, 0-54 per cent, of loss 

 being at the same time sustained. Hot sulphuric acid removes 

 only 3-79 per cent, of bases. A similar association of slates is 

 found at a point bearing 41° 30' E.from the east end of Michipi- 

 coten Island. Here, a series of lighter and darker coloured bands 

 of very decided slate occur, striking N. 78° to 86° W., and 

 dipping 50 ° to 52 ° northward. They are overlaid by a band 

 of dark green slate, which contains granitic pebbles, and this band 

 is again overlaid by light coloured slates. Small bands may be 

 observed to leave the dark green slates and to join with those of a 

 lighter colour. The latter are not only lighter in colour, but harder 

 and less dense, and occasionally show on their cleavage planes a 

 silky lustre. A specimen gave a specific gravity of 2-681, and its 

 powder, which was almost quite white, lost 1-12 per cent, on 

 ignition, becoming slightly brown. It fuses only in fine splinters, 

 and, generally, the fusibility of these slates is the greater the 

 darker their colour. 



Chlorite Schist. — Some of the greenstone slates occasionally 

 contain an unusually large quantity of chlorite, and sometimes so 

 much as to form chlorite schist. This schist forms the side rock 

 of the Palmer Mine on Goulais Bay. 



Quartzite. — This rock is of less frequent occurrence than I had 

 anticipated. It is most frequent on the west and south-west side 

 of the hills between Bachewahnung and Goulais Bay, and in the 

 district north-eastwards from Sault Ste. Marie. 



Hematite. — This mineral often occurs in such quantity as to 

 constitute rock masses. It will however be referred to under the 

 economic minerals of the series. 



Greenstone Breccia. — The occurrence of angular fragments of 

 other rocks in the greenstones above described is by no means rare, 

 and the resulting breccias are common between Bachewahnung 

 Yol. III. ST No. 3. 



