Pirsson and Washington — Geology of Bed Hill, N. H. 435 



Minerals mm. 



Orthoclase 4*20 



Albite "3-70 



Nephelite 1*80 



Sodalite -60 



Aegirite -55 



Biotite 1-05 



Magnetite -05 



Zircon . _ '05 



Total . 



12-00 



Vol. % 



Sp. G. 



Wt. % 



35-00 



2-55 



33-5 



30-83 



2-62 



30-4 



15-00 



2-55 



14-4 



5-00 



2-30 



4-3 



4-58 



3-50 



6-0 



8-75 



3-00 



99 



•41 



5-00 



0-8 



•41 



4-70 



0-7 



99-98 



100-0 



vlgO 



CaO 



Na 2 



K 2 H 2 



Ti0 2 











16-4 



5-1 ... 







4-0 



9-5 



8-5 



0-5 ... 



1-0 



1-0 







1-5 



8-0 4-5 



2-0 



position of the rock may now be deduced from the mode 

 given above. For this purpose the following mineral com- 

 positions are assumed: 



Si0 2 A1 2 3 Fe 2 3 FeO 



Nephelite 45-1 33-3 ... ... 



Aegirite 50-0 5-0 16-0 5-5 



Biotite 32-0 17'0 19-0 14-0 



The biotite is that of the green lepidomelane from the nephe- 

 lite syenite of Litchfield, Maine* with correction for TiO, ; 

 that of the aegirite-augite one from nephelite-syenite of Sarna, 

 Dalecarlia, Swedenf and the nephelite the average of a num- 

 ber of closely agreeing analyses of nephelites. The presence 

 of the potash in this mineral is to be noted ; it is wrong in 

 such calculations to consider it as pure NaAlSi0 4 , as in the 

 norm, the modal nephelite contains considerable potash. The 

 results of the calculation are as seen in No. I of the table. 



Si0 2 



Al O, 



I 



57-08 



20-20 



II 



58-30 



21-38 



1-05 



2-04 



0-22 



0-95 



8-66 



6-06 



•80 



•10 



•02 



•04 



none 



•35 



III 



59-01 



18-18 



1-63 



3-65 



1-05 



2-40 



7-03 



5-34 



•65 



•81 



tr. 



tr. 



•12 



IV 



•951 



•198 



Fe O 



3-39 



•021 



FeO 



MgO ;. 



CaO 



NaO 



1-97 

 •34 

 •57 



7-70 



•028 

 •008 



•011 



•124 



K 2 



7-21 



•077 



HO 



-45 





TiO, 



ZrO, 



-36 



-47 



•005 

 •004 



PO 



... . tr. 





cb, 5 . 



CI 



tr. 



-31 



•009 



0=C1 



100-05 



•07 



100-05 

 •08 



99-98 

 •03 



* 



Total 99-98 99-97 99-95 



* Bull. 168 U. S. Geol. Surv. , p. 21. f Rosenbusch, El. Gesteinslehre, p. 122. 



