THE CANADIAN NATURALIST. [Feb. 



Silica 31.78 



Alumina 15.47 



Protoxide of iron 28.87 



Lime 9.64 



Magnesia 4.37 



Water 9.87 



100.00 



In these figures the quantity of iron is much greater, and that 

 of magnesia much less than in ordinary chlorite. In its compo- 

 sition, and in being easily decomposed by acids, the mineral most 

 closely resembles the ferruginous chlorite of Delesse,* (the delessite 

 of Naumann), but differs from it in containing a considerable 

 amount of lime, and in being readily fused before the blow-pipe. 

 Assuming, nevertheless, that the chloritic constituent is delessite, 

 and that one half of the iron removed by hydrochloric acid belongs 

 to the magnetite, then the rock would be composed mineralogically 

 of 



Delessite •. 46.36 



Labradorite 47 . 43 



Pyroxene or hornblende 5.26 



Magnetite 0.95 



100.00 

 The next rock to the eastward, to which I paid some attention, 

 is that which constitutes the hanging wall of the Quincy Mine. 

 It is a fine-grained mixture of reddish-grey feldspar, and dark 

 green delessite, the former predominating. In this mixture larger 

 crystals of feldspar and larger rounded grains of the ferruginous 

 chlorite are occasionally discernible. Its sp. gr. is 2.83. The powder 

 is of a reddish-grey tint, and the magnet shews the presence in it 

 of a trace of magnetite. On ignition it changes to light brown, 



* The following is the composition of ferruginous chlorite according to 

 Delesse's analysis : 



Silica 31.07 



Alumina 15.47 



Peroxide of iron 22.21 



Protoxide of manganese. ........... traces 



Lime 0.46 



Magnesia 19.14 



Water 11.55 



Bischof ; Chemical and Physical Geology, III, 22S. 



