i6 



J. SCHETELIG. 



M.-N. Kl. 



From the figures in No. 3 I have calculated the following approximate 

 mineral composition, taking into consideration the microscopical examination : 



100.26 % 



Calculating the orthoclase as perthite (Or72Ab28) and the plagioclase 

 as oligoclase (AbgAnj) the mineral composition of the rock is approximately 

 the following, calculated to 100: 



Quartz 2 1. 1 % 



Perthitic orthoclase . . . 52.3 » 



Albite 12.4 » 



Oligoclase AbsAni . . 8.3 » 



Mica and other constituents 5.9 » 



loo.o % 



The comparison of the analyses of the common granite from Scott's 

 Nunataks with the granite-aplite from Mt. Betty shows the connection 

 between the granites from the two localities to be very close. The 

 percentage of AI2O3 in the analysis of the granite from Scotts Nunataks 

 seems to be a little low, as the calculation of the felspars and mica gives 

 a deficit of above 2 o/^ . On the contrary SiOg, NaoO and KoO are 

 practically identic in the two analyses. The differences in the other 

 components are shown in differences in the mineral composition. In the 

 strongly leucokratic granite-aplite from Mt. Betty only traces of biotite are 

 found, but on the other hand the content of plagioclase is considerable. The 

 granite from Scotts Nunataks contains about 5 % biotite, and the amount 

 of plagioclase is less prominent. Hence the differences in the percentage 

 of Fe-oxides, MgO and CaO. 



