130 AUSTRALASIAN ANTARCTIC EXPEDITION. 



The hornblende is green and has a granular shape. It is clearly developed from 

 the pyroxene because the passage can be observed. That the hornblende developed 

 before the crushing is evident from the presence of crushed borders on the hornblende 

 crystals. Very rarely the normal hornblendisation of the pyroxene is replaced by 

 glaucophanisation. Small amounts of the blue pleochroic glaucophane have been 

 detected and are associated with the pulverised augite rather than with the large 

 crystals. It is interesting to note that such change is recorded by Grubenmann* in the 

 alteration of the pyroxene of eclogites during transition from one metamorphic zone 

 to another. 



The iron ore percentage is greater than in any of the Cape Denison amphibolites. 

 The major portion is ilmenite, which is frequently associated with a reddish-brown 

 mineral, probably rutile. Pyrite is also present. The lustre of the pyrite is bronzy 

 red, and is suggestive of pyrrhotite. Large ilmenite crystals show crushing and 

 pulverisation along the borders like the pyroxene. The reddish-brown biotite is scarce, 

 but is always associated in curious aggregates with ilmenite. It is probable that these 

 aggregates are produced here, as in other cases, by the interaction of hypersthene and 

 felspar. The hornblende may be similarly associated with the ilmenite. The biotite 

 flakes are sometimes bent, and were probably formed before the cataclasis. 



The mechanical effects which are typical in the epi zone of metamorphism are a 

 dominating feature of this rock, and mark the final metamorphic impress. Hence we 

 name the rock an epi plagioclase pyroxene gneiss. 



* Op. cit., vol. II., p. 84. 



