too 



Measured Mean Calculated 



(loTo) (oiToi = 60°—' 60° 13' 60° — ' 



59° 54' 59° 55' 59° 58' 60° —'60°—' 



(ЮТЗ) : (OOOl) = 27° 5' 27° 26 27° I5V2' 27° 41' 



(IOT2) : (0001) = 37° 48' 37° 57' 38° 5' 37° 57' 38° 12' 



(lOTl) : (0001) = 57° 13' 57° 25' 57° 3' 57° 20' 57° 34' 



(2021) : (0001) = 72° 1' 72° 16' 72° 11' 72° 9' 72° 22b'2' 



As was the case with the foregoing types, all the measured 

 angles show lower values than those calculated. It is, there- 

 fore , evident that the geometrical constant for the cata- 

 pleiite from Narsarsuk differs somewhat from that of the mineral 

 from Langesund. The Greenlandian mineral is pure soda- 

 catapleiite. At the Langesund locality occur both soda- and 

 hme-soda-catapleiite. However, no divergency in the axial 

 relations seems to have been found between the two Norwegian 

 varieties, and it seems to be from the measurements made on 

 the soda-catapleiite that the axial ratio has been calculated. 

 Difference in chemical composition, therefore, can hardly be 

 the cause of the discrepancy between the minerals from the 

 two localities with regard to the dimensions of their angles. 



From the mean value 



-p-.c = 57° 20' 



the following axial ratio is calculated for the Greenlandian ca- 

 tapleiite : 



a:c= 1 : 1,3509. 



According to this axial ratio the relation between measured 

 and calculated values becomes as follows: 





Measured 



Calculated 



У 



:c = 27°15V2' 



27° 28' 



V 



■.c = 37° 57' 



37° 57' 



■p: 



:c = 57° 20' 



57° 20' 



X : 



с = 72° 9' 



72° 14' 



