310 DEPARTMENT OF THE INTERIOR 



2 GEORGE V, A. 1912 



' On account of its superior freshness the rock from the chilled zone (speci- 

 men No. 493) was selected for chemical analysis. Mineralogically it resembles 

 the coarser phase except that hornblende is scarcely more than accessory and 

 that here minute biotite and augite crystals with the dominant alkaline feldspar 

 form the ground-mass. Its chemical analysis yielded Mr. Connor the following 

 proportions : — ■ 



Analysis of hornblende-aiugite minette. 



Mol. 



SiOo 



TiO, 



ALA 



Fe 2 3 



FeO 



MnO 



MgO 



CaO 



SrO 



BaO 



Na 2 



K s 



H 2 at 110°C. . 

 H 2 above 110°C. 

 P.O., 



53-68 



•895 



•90 



•Oil 



16-89 



•166 



1-28 



•008 



5-53 



•076 



•11 



•001 



3-70 



■092 



6-08 



•109 



•10 



•001 



•38 



•003 



4-03 



•065 



4-32 



•046 



•10 





1-85 





1-05 



•007 



100-00 





Sp.gr 2-723 



The calculated norm is: — 



Orthoclase ' 25-58 



Albite 32-49 



Nephelite , -85 



Anorthite.. 15-29 



Diopside 8-47 



Olivine , 9-29 



Ilmenite 1-67 



Magnetite 1-86 



Apatite 2-17 



Water 1-95 



99-62 

 According to the Norm classification the rock enters the sodipotassic sub- 

 rang, monzonose, of the domalkalic rang, monzonase, in the dosalane order, 

 germanare. The analysis doubtless represents also the composition of the main, 

 unchilled part of the dike, in which hornblende is more abundant. 



Olivine-augite Minette. — A fourth variety of the porphyritic minettes 

 -forms a two-foot sill cutting the Wolf grit on the main summit of the Sel- 

 ] kirks, and one mile north of the Dewdney trail. It appears itself to be cut off 

 by the long east -west granite dike shown on the map as occurring at this 

 locality. The granite is perhaps contemporaneous with the Bayonne batholith 

 : and it is thus possible that this minette injection antedates the batholithic 

 :intrusion. 



