﻿On a Neiv Alkali Hornblende. 



87 



is perfectly 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.^ 



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 



Kerric oxide 15 996 



Ferrous oxide 3-852 



Manganous oxide : 1 -301 



Lime 29-306 



Magnesia 1 '384 



Loss on ignition 



The atomic and quantivalent ratios 

 the above analysis are as follows : 



•285 



99-577 

 deduced 



from 



Atomic, 



Si 610x4 = 2440 



52 

 576 

 600 

 106 



36 



Ti 13x4 = 



Al 192x3 = 



Fe"^ .... .... 200x3 = 



Fe" 53x2 = 



Mn 18x2- 



Ca 523x2 = 1046 



Mg 35 X 2 = 70 



H 32 32 



\) 



Quantivalent. 



2492 2492 



1176 



1290 



2466 



1 " Ueber das Nephelinsyenitgebiet auf der Iiisel Aln6," von A. G. Hogbom. 

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



Geol. 



