THE METAMORPHIC ROCKS OF ADELIE LAND. 8TILLWELL. 59 



The chemical composition of this rock is found by J. C. Watson to be 



Si0 2 43-12 



A1 2 0, 12-74 



Fe 2 8 1-35 



FeO 10-14 



MgO 17-13 



CaO 4-70 



Na 2 0-26 



K 2 6-08 



H 2 + 3-07 



H 2 - 0-02 



C0 2 nil 



Ti0 2 1-35 



P 2 5 trace 



SO S nil 



Cl 0-06 



MnO 0-13 



NiO, CoO trace 



CoO p. 



Li 2 nil 



Total . 100-15 



Sp. Gr. at 4 C 3-012 



If this composition is compared with that of the normal amphibolite, No. 629, 

 strong points of difference are noticed, and these correspond with the mineralogical 

 differences. There is 5 per cent, less silica, but the most striking differences are found 

 in the percentages of CaO, MgO, and K 2 0, and NajO. The amount of K 2 is more 

 than seven times greater, and the Na 2 about seven times smaller. There is two and 

 a half times as much MgO, while the CaO has decreased by a half. The large percentages 

 of MgO and K 2 correspond with the high percentage of biotite. There is no important 

 difference in the alumina, total iron, or titanium. 



The Ozann group values are S = 4-60, A = 4-3, C = 3-5, F = 37-4, M = 1-8, 

 T = 0, K = -6. 



The projection values are a = 1-9, c = 1-5, / = 16-6. 



These values, considered collectively, place the rock among the magnesium silicate 

 schists, Group V., though the high value of A is exceptional for this group. The position 

 in the triangular diagram is shown in fig. 6. 



The composition of these biotite hornblende schlieren seems impossible for any 

 primary magma tic xenolith that can be postulated. Neither augite nor olivine can 



