202 Pen field and Howe — Chemical Composition 



The material for the analysis had to be selected by hand 

 picking and, when introduced into the heavy solution, showed 

 a specific gravity between the limits 3'219 and 3-258. The 

 analyses are as follows : 









First Analysis. 







a. 



b. 





SiO , 





. 37-15 



38-03 



•634 



MgO 





. 52-74 



54-00 



1-350 



FeO 





. 4-72 



4-83 



• '067 



F 





. 2-01 



2-06 



•108 



H„0- 





1-94 



1-94^- 



-9= -215 





98-56 



100-86 





eq. 



toF 



= -84 



•86 





Ratio. 



1-417 



•323 



4-02 

 900 



2-05 



97-72 



100-00 



Second Analysis. 



Ratio. 



SiO„ 

 MgO 

 FeO 

 F 

 HO . 







37-78 



53-05 



5-64 



3-58 



.. 1-33-4-9 



•629 

 1-326 



•078 



•188 



— -148 





to 



F = 







O eq. 



101-38 

 1-50 





1-404 



•336 



4'03 

 9-00 



2-15 



99-88 



In both of these analyses the ratios of Si0 2 : RO : (F + OH) 

 approximate closely to 4:9:2 corresponding to the formula 

 Mg 7 [Mg(FOH)] 2 (Si0 4 ) r In the first analysis, the ratio of 

 F : OH = 1:2 and in the second it is about 1:1. Below we 

 have given the analyses after calculating FeO as MgO and 

 bringing them to 100 per cent and, for comparison, the theo- 

 retical composition according to the above formula with 

 F : OH = 1 : 2 and 1 : 1 respectively. 



First analysis. 



Si0 2 38-87 



MgO 57-94 



F 2-10 



HO 1-98 



Theory where 

 F: OH = 1:2. 



38-75 



58-12 



2-05 



1-94 



Second analysis. 

 38-81 

 57-64 



3-68 



1-37 



Theory where 



F:OH = l:l. 



38-77 



58-16 



3-07 



1-29 



100-89 

 O eq. to F . -89 



100-86 



101-50 

 1-50 



101-29 

 1-29 



