3S Allen, etc. — Diopside and its Relations 



Table VIII. 



Composition 

 % MgSi0 3 



a 



1-616 

 1-609 



1-612 

 1-620 



1-670 



1-664 

 1-664 

 1-662 

 1-660 

 1-654 



1-650 



1-645 

 1-641 



1-628 



:: 



1-630 



1-671 



-" 



1-647 

 1-648 



7 



1-632 

 1-650 



1-654 

 1-634 



1-694 



1-694 

 1-692 

 1-684 

 1-684 

 1-678 



1-660 



1-655 

 1-663 



y— a* 



y-a 



•016 

 •041 



•042 

 •014 



•024 



•030 



•028 

 •022 

 •024 

 •024 



•oYo 



Y-P 



•004 



•o"o"4 

 •02~3 



•015 



7-/3' 

 •012 



•o'fo 



•007 

 •007 



Si 



o 



c 

 + 



+ 

 + 

 + 



+ 

 + 



+ 

 + 



Optical 



axial 



angle 



2 V 



Dis- 

 per- 

 sion 



Extinc- 

 tion 

 angles 



c : c' on 

 110 





 



I 



5 



7-95 

 7-95 



10 



10-74 



28 



28 



40 



44-5 



45 



46-12 



50 



55 



60 



65 



665 



68 



70 



72 



75 



80 



90 



95 



97 



98 

 100 

 100 



Wollastonite 



Pseudo-wollastonite 



a 



Wollastonite 



Pseudo-wollastonite 

 Wollastonite 



a 



Diopside 



■ a 



\\ 



a 

 a 

 i i 

 (< 

 a 

 a 

 <( 

 a 

 a 



/?-MgSi0 3 



a-MgSiOs 



•014 

 •043 



•043 

 •014 



•030 



•030 



•027 

 •024 

 •022 

 •023 



•023 



38 c 



7° 



10° 



10° 



38° 

 41° 

 7° 

 40° 

 40° 

 41° 

 57° 

 58° 



58° 

 59° 

 58° 

 57° 

 56° 

 54° 

 53° 

 53° 

 52° 

 51° 



52°" 



53°" 



53° 

 53° 



60° 



8 

 5 

 



5 

 

 

 

 8 

 2 

 5 

 5 

 1 



5 



8 

 5 

 5 





 

 6 

 2 

 5 

 7 



5 



4 



5 



5 

 R 



p > V 



p > V 



p > V 



-32 V -4 

 -32° -5 

 -32°-4 



-82°~8 



-31°'7 

 -30° -2 

 -28°-4 

 -27°-9 



-27"°"-4 

 -27° -4 



..27°"-4 























* y— a in this column was determined directly by measurements on plates in the thin 

 section. 



rations between 40 and 45 per cent peculiar phenomena were 

 observed and no satisfactory tests of homogeneity could be 

 made. — Between diopside and pure magnesium metasilicate 

 mixed crystals extend from diopside up to about 66 or 67 

 per cent MgSi0 3 of the series. The appearance of all prepa- 

 rations between pure diopside (46*12 per cent MgSi0 3 ) and 67 

 per cent MgSi0 3 is that of diopside in the thin section so far 

 as the optic properties are concerned. The refractive indices, 

 the birefringence, the extinction angles and the optic axial 

 angles all decrease gradually but noticeably, and the sections 

 appear homogeneous under the microscope except for the 

 minute air spaces. The crystallized melt changes noticeably 

 moreover in appearance from the large, bright and glistening 



