﻿BENGUET PETROGRAPHY. 



239 



The rock is a quartz diorite. 



Constituent. 

 SiO a 

 FeO 

 Fe.fi, 

 A1A 

 ]\IgO 

 Na,0 

 CaO 

 H,0 



Calculated 

 from min- 

 eral con- 

 tents. 



Calculated 



by chemical 



analysis. 



Per cent. 

 56.89 



Per cent. 

 57.06 



} 8.58 



6.04 



17.52 



20.00 



2.9 



3.27 



7.32 



2.95 



3.97 



7.18 





3.06 



97.18 



100.00 



Plate II, fig. 1, is a photomicrograph, taken with polarized light, of this rock. 



Remarks. — A greater number of measurements would doubtless raise the silica 

 content by showing more quartz. In this calculation the orthoclase was taken 

 with the plagioclase. This, in close work, strictly should not be done. Making 

 allowance for orthoclase we should have a lower Na,0 figure and about 3 per 

 cent of K 2 0. 



Examination of additional sections of this rock revealed some small amount 

 of biotite. 



Table I. — Benguel No. 12. 



Constituent. 



Per 

 cent. 



Molecu- 

 lar pro- 

 portions. 



Orth. 



Alb. 



An- 

 orth. 



Mag. 



Diop. 



Hyp. 



Quartz. 



SiOo — 



57.06 

 20.00 



\ 6.04 



3.27 

 7.18 

 2.95 

 3.06 



951 

 196 



( 19 

 1 42 



82 



129 



48 



33 



198 

 33 



288 

 48 



230 

 115 





24 



91 



116 



A1«0 3 



Fe-0 3 - - 



19 

 19 









FeO _ _ 









3 



11 

 14 



29 

 71 





MgO - . 











CaO 







115 







Na.,0 - 



33 



48 







K..0 -- 



























99.56 



















Constituent. 



Norm. 



Quartz . .. - -- 



0.116 

 .033 



.04S 

 .115 

 .014 

 .011 

 .003 

 .071 

 .020 

 .019 



6.96 

 18.351 

 25. 15} 

 31. 97] 



1.631 



1.10I 



.40) 

 7.101 

 2. 64j 

 4.41 



Q 6.961 



Ualic 82. 43 

 F 75. 47J 



3.13i 



\ P 12.87i 

 a - ' 4 >Ferricl7.28 

 M 4.4lJ 



Orthoclase. — 



Albite _ — - 





Hyp 



Magnetite _ ._ _ 





|Ca„ 

 JMg- 

 Ifc - 



<Mg__ 



\Fe .. 





99.71 











Class II. 

 Subclass I. 

 Order 5. 

 Rang 3. 

 Subrang 3. 

 58011 3 



Dosalane. 



Dosalone. 



Germanare. 



Andase. 



Shoshonose. 



