Titaniferous Andradite from Ontario. 217 



The analyses selected by Scharizer agree remarkably well 

 with his theory, but there are aluminous hornblendes whose 

 constitution cannot be readily explained in this way and which 

 at the same time cannot be referred to the pargasite orthosili- 

 cate.* 



Garnet. — In the hand specimens the garnet is seen to possess a 

 deep reddish-brown color. In the thin sections it is a paler 

 brown although still deeply colored. It is not found in all parts 

 of the mass and where it does occur is usually present only in 

 small amount. It possesses the usual high index of refraction 

 and is quite isotropic, occurring usually in irregular shaped 

 grains but in some few cases showing distinct crystalline form. 

 It frequently holds a few large inclusions which usually con- 

 sist of calcite in single individuals, although the garnet is per- 

 fectly fresh and the calcite shows no distinct evidence of a 

 secondary origin. It moreover sometimes holds inclusions of the 

 hornblende above described, of pyrite, iron ore and even of 

 nepheline. A garnet resembling this occurs in small amount 

 associated with a similar hornblende, as above mentioned, in 

 the nepheline- syenite of the Corporation Quarry at Montreal, 

 and it also contains as inclusions most of the other constituents 

 of the rock. The same is also true of the melanite in the 

 nepheline-syenite of Alno.f 



Before analysis the garnet was purified by several separations 

 with fused silver nitrate and on careful examination with the 

 microscope the grains appeared to be entirely free from foreign 

 matter. With the pycnometer their specific gravity at 16° C. 

 was found to be 3*739. Chemical analysis gave the following 

 results : 



Silica 36-604 



Titanium dioxide 1*078 



Alumina 9*771 



Ferric oxide __. 15*996 



Ferrous oxide __ _ 3*852 



Manganous oxide .._ 1 *301 



Lime 29*306 



Magnesia... . ._ 1*384 



Loss on ignition *285 



99*577 



The atomic and quantivalent ratios deduced from the above 

 analysis are as follows : 



*See Scharizer's paper, loc. cit., p. 156. 



f " Ueber das Nephelinsyenitgebiet auf der Insel Alno," von A. G-. Hogbom. 

 Geol. Foren. i. Stockholm Forh., 1895, p. 144. 



