PETROLOGY 



329 



I 



FeO 8.28 



MgO 9.33 



CaO 11.11 



Na 2 1.48 



K 2 0.35 



H 2 0— '. 0.53 



H 2 04- 1.22 



Ti0 2 0.69 



MnO 0.15 



P 2 5 0.11 



C0 2 0.83 



S f 0.20 



100.20 



la 



II 



.115 



8.67 



.233 



10.79 



.198 



9.91 



.024 



1.14 



.006 



0.26 



.009 



0.06 





.003 





.001 





.006 





99.56 



I. Chemical analysis of olivine diabase from Cross Keys, Augusta County, 

 Virginia. J. Wilbur Watson, analyst. 



la. Molecular ratios calculated from I. 



II. Chemical analysis of olivine diabase from near Fairmont. Davidson 

 County, North Carolina. A. S. Wheeler, analyst. (Described by J. E. Pogue 

 in Proceedings of the U. S. National Museum, vol. 37, 1910, pp. 475-484.) 



The norm as calculated from the chemical analysis given in column I 

 of the table above and the position of the rock in the quantitative system 

 are expressed as follows : 



Norm Ratios 



49 28 



48.70 



Or 3.341 



Ab 12.58 



An 33.36 



01 2 531 



Di 16.90 



Hy 23.49 



Mt 3.71 



II 1.37 



Ap 0.34 1 



Pr 0.36 J 



H. 2 1.75 



49.28 



Class, 



Fem 



1.01 = III, salfemane. 



HS.70 



Order, — 

 F 







Ram 



49.28 

 K 2 + Na 2 







30 



CaO 



120 



allare. 



= 0.25=4, auvergnase. 



CO., 



0.83 



100.56 



Subrang, 



M =1 = 0.25 

 Na,0 24 



4-5, auvergnose. 



Symbol 

 III. 5. 4. 



4-5. 



Name 



Auvergnose. 



Summary and Conclusions of the petrologic Relations of the 



Eock Types 



INTRODUCTION 



The distribution and geologic occurrence and the petrography o\' the 

 rocks having been described in some detail, il remains to summarize the 



