VOLCANIC NECK AT THE BASIN, NEPEAN RIVER. 



137 











Norms. 







A 



B 





A 



B 



Si0 2 



41-20 



39-13 



Anorthite 



6-39 



— 



A1 2 3 



2-85 



3-48 



Olivine 



59-89 



72-14 



Fe 3 3 



1-67 



1-83 



Enstatite 



23-80 



16-02 



FeO 



7-23 



7-58 



Corundum 



•41 



3-48 



MgO 



38-04 



42-15 



Magnetite 



2-32 



2-60 



CaO 



1-29 



•07 



Ilmenite 



— 



•30 



NaO 



trace 



— 



Chromite 



•31 



•30 



K 3 



absent 



— 



Water 



3-51 



2-88 



Ti0 3 



trace 



•16 



C0 2 



3-40 



305 



co 2 



H 2 + 



3-40 

 2-65 



3-05 



2-80 











100-09 



100-77 



H 2 0- 



•92 



•80 













NiCoO 



•45 



•04 









MnO 



•26 



•21 









Cr 2 G 3 



•21 

 100-17 



•20 











100-75 





(A) Dunite from the Basin ; Analyst G. D. Osborne. 



(B) Dunite from Dundas ; Analyst W. N. Benson. 



The correspondence of the two rocks is very evident and 

 is of course to be expected. The Dundas rock is slightly 

 more basic. 



In the case of (A) lime is higher than in (B), and owing 

 to the presence of 00 2 , most of the lime in the rock must 

 be in the form of calcite, though some of the lime is prob- 

 ably in the pyroxene molecule. 



The strict calculation of lime as anorthite uses up some 

 alumina which together with the remainder, given norm- 

 atively as corundum, is expressed mineralogically by the 

 augite and possibly picotite. 



