152 Coleman — Nejpheline and other Syenites in Ontario. 



fairly fresh and in some directions have a handsome bluish 

 shimmer. No nepheline nor sodalite nor quartz was observed. 

 The dark minerals are chiefly augite with brown interior and 

 dark green exterior, but some dark green and brown horn- 

 blende, and some magnetite occur also, as well as apatite. 



An analysis of this rock made by Mr. A. H. A. Robinson of 

 the Chemical Department of the School of Practical Science, 

 Toronto University, gives the following results in column I : 



I. II. III. 



SiO, 58-81 58-88 '980 



Al^Og 13-37 20-30 -131 



Fe.Og 3-88 3-63 -024 



FeO 6-97 2-58 -097 



MnO 0-20 



MgO 0-51 0-79 -012 



CaO 3-89 3-03 -069 



Na,0 4-96 5-73 -080 



K^ 5-42 4-50 -056 



HO at 100° C -. 0-29 ) 



/o 



•75 



1-01 



H,0 above 100° C 



TiO,..._ _.-. 0- 



PO. 0-31 0-54 



Total 100-06 100-99 



Specific gravity at 17°-5 C, 2-75. 



For comparison an analysis of Norwegian laurvikite from 

 Byskoven, Laurvik, by A. Merian is given in column II.* The 

 two analyses agree fairly closely except for the relative pro- 

 portions of alumina and of ferrous iron oxide, which differ 

 greatly. The analysis shows the rock consists largely of micro- 

 cline and microperthite, the small amount of magnesia and 

 large amount of ferrous oxide that the augite must consist 

 mostly of the hedenbergite molecule. The amount of alumina, 

 though smaller than in the laurvikite, is that which is required 

 by the soda and potash to turn them into feldspars and is 

 therefore correct, as shown in the molecular ratios given in 

 column III. 



Associated with the dark augite syenites with plate-like feld- 

 spars are numerous other varieties in much smaller amounts, 

 some merely having the red color of the ordinary syenite, due 

 to diffused hematite particles, but with the same ingredients 

 and the same' shape of the feldspars; others differing more 

 widely in appearance and composition, but all more weathered 

 and less satisfactory for study with the microscope. It will be 

 sufficient to refer to the kinds having granitic structures, 



* Ibid., p. 30. 



