BY D. MAWSON. 587 



In a few cases, slight parting along the walls suggested that 

 contraction consequent perhaps on cooling had taken place in 

 the vein subsequent to the consolidation of invading magma. 



iii. Descriptions of the Minerals. 



iEgirine is found as stumpy crystals with splendent black faces, 

 in association with arf vedsonite. 



A typically developed crystal measured 75 cms. in the c to c 

 direction, with a cross-section of 0-44 cms. from a to a, and 

 0'31 cms. from b to b'. The prism zone is alwaj^s well formed, 

 and several accordant readings were made &A»i = 42° 38'. No 

 satisfaction was obtained by measurements on several irregular 

 vestiges of pyramid faces closing the crystal. Internally these 

 large crystals are often quite uniform in character, though in 

 some of the veins they are invariably zoned. 



Result of analysis. — Colour of the powder yellowish-grey. 

 Specific gravity determined on pure material, employing similar 

 methods to those adopted in the case of the amphibole — 3 -70 at 

 26°C. 



Si0 2 



Ti0 2 



A1 2 3 



Fe~0 3 



FeO 



MnO 



CaO 



MgO 



Na,0 



Notes on the analysis. — Only one complete analysis was 

 attempted owing to scarcity of the pure mineral. The material 

 was carefully selected from the debris of the rock by hand-picking. 

 Each of the fragments was separately crushed, and the streak 

 noted as a means of deciding on its final inclusion amongst the 

 chosen material. 



A petrographical study revealed the fact that, no matter how 

 carefully the material for analysis be chosen, it would likely not 

 represent a distinct species on account of many of the crystals 



49-49 



K 2 





T)-18 



0-S9 



Li 2 





nil 



trace. 



Zr0 2 





1-80 



27-76 



H 2 O + (110°C) 





95 



4-71 



H 2 O-(110'C) 





035 



0-60 



FLCI.SO3. P.,0 5 . 



I 



nil 



3-28 



V 2 5 . Cr 2 3 



J 



0-30 









10-10 







100-41 



