354 



Dresser — Geology of Brome Mountain. 



Hornblende is green in ordinary light and shows pleochroism. 

 It is in so small amounts, however, that the scheme of its absorp- 

 tion could not be satisfactorily determined. . 



The other minerals require no special note. Where quartz 

 enters into its composition this rock is identical with the Nord- 

 markose (Nordmarkite) of Shefford Mountain. In other phases 

 it closely resembles the Laurvikite of Southern Norway 

 described by Prof. W. C. Brogger. Its resemblance to both 

 is shown in the following analyses. 





VII. 





VIII. 





IX. 



X. 



Si0 2 



.. 61*77 





58-88 





65-43 



59-96 



A1 2 3 



. . 18-05 





20-30 





16-96 



19-12 



Fe 2 O s 



.. 1-77 





3-63 





1-55 



1-85 



FeO 



.. 1-75 





2-58 





1-53 



1-73 



MnO 



•08 











•40 



•49 



CaO 



_. 1-54 





3-03 





1-36 



2-24 



MgO 



•89 





•79 





•22 



•65 



Na 2 ..... 



.. 6-83 





5-73 





5-95 



6-98 



K 2 



. . 5-21 





4-50 





5-36 



4-91 



P 2 6 



•15 





•54 





•02 



•14 



Ti0 2 



•74 





- - - - 





•16 



•66 



H a O 



.. 1-10 





1-01 





•82 • 



1-10 





99-97 



100-99 



99-74 x 



99-83 



xS0 3 



— 



•06 



a 



BaO 



so, 





— •12 



.. —'08 



CI 



— 



•04 





CI 





.. —'14 



VII. Nordmarkose, Brome. Analysis by M. F. Connor. 

 VIII. Laurvikose, Byskoven, near Laurvik, Norway. (" Chemi- 

 cal Analyses of Igneous Rocks," by H. S. Washington.) 

 IX. Nordmarkose, Shefford. Analysis by M. F. Connor. 

 X. Laurvikose "" " « " 



The norm of VII is as follows : 



Orthoclase _ 31-14 



Albite 57-11 



Anorthite _ 2-78 



Nepheline -28 



Olivine _ -62 



Diopside 3-16 



Apatite _ -34 



Ilmenite ,. 1*37 



Magnetite 2-55 



t 



100-45 



