296 



Lindgren and Melville — Sodcdite- Syenite 



clase and 16 per cent albite. If it is further assumed, for the 

 purposes of a calculation of the rock analysis, that the compo- 

 sition of the two minerals is 



Orthoclase. Albite. 



SiO 6S 66 



A1„0 3 21 19 



Na o 11 13 



K„0 .. 2 



100 



100 



the composition of the rock may be calculated as follows 

















Rock 









Horn- 



Ortho- 





Soda- 



Anal- 



Calc. 



analysis. 









blende. 



clase. 



Albite. 



lite. 



cite. 



comp. 



V. 



Difference. 



VI. 



H 2 0* 



























0-26 







HoOf 



0-06 



.... 







0-16 



0-29 



0-51 



1-51 



+ 1-00 



3-49 



SiOo 



883 



33-00 



10-88 



3-00 . 



1-65 



57-36 



56-45 



— •91 



55-76 



Po0 5 



























0-13 









CI 















0-48 







0-48 



043 



-•05 







TiO» 



0-28 















0-28 



0-29 









Al a Os 



3-77 



9-50 



3-36 



2-52 



0-66 



19-81 



20-08 



+ •27 



21-61 



Fe 2 3 



0-86 

















0-86 



1-31 



+ •45 



1-65 



FeO 



5-00 





.... 











5-00 



4-39 



-61 



4-09 



NiO 





















trace 









MnO 



004 



1 















0-04 



0-09 



+ •05 





CaO 



2-43 

















2-43 



2-14 



-•29 



2-26 



MgO 



0-58 



















0-58 



063 



+ ■05 



0-74 



NaoO 



069 



1-00 



1-76 



1-72 



40 



5-57 



5-61 



+ •04 



6-94 



K 2 



0-46 



6-50 



---- 



0-08 



0-03 



7-07 



7-13 

 100-45 



+ •06 



5-34 





23-00 



50-00 



16-00 



7-96 



303 



9999 



101 88 













Excess O. 



•10 







100-35 



The complete analysis of the rock is inserted under Y in 

 the third column from the right. The analysis agrees fairly 

 well with the calculated composition in all except Si0 2 and 

 H„0 ; the former is very uncertain on account of no complete 

 analysis having been made of the feldspars ; the latter is too 

 low in the calculated composition and the rock evidently con- 

 tains more analcite than 3 per cent. A part of that amount 

 which is not accounted for in the calculated composition 

 doubtless fell together with the feldspars in the separation and 

 some per cent of analcite should be substituted in the 16 per 

 cent of albite. This would bring the calculated analysis closer 

 to the actual composition, as the only effect would be to lower 

 the Si0 2 and increase the H 2 0. The analysis further shows 

 that no plagioclase except albite is contained in the rock and 

 also that there is about 03 per cent of apatite present. 



*At 100°. 



f Above 100°. 



