320 AUSTRALASIAN ANTARCTIC EXPEDITION, 



to the pyroxene fingers in the transfer of material mentioned in the previous paragraph. 

 These rims of felspar, with hornblende and sometimes biotite, are the reaction zones 

 between the hornblende and the garnet nucleus. The possibility of felspar being 

 potential hornblende to some degree at least is thus emphasised, and an indication is 

 given that the relationship is reversible under suitable conditions. 



Such masses of ilmenite, as previously referred to, are as frequently found 

 associated with garnet as they are with hornblende. The fingers of the dactylitic 

 intergrowth are still alternate bands of felspar and green pyroxene, but this time there 

 is evidence that the pyroxene is a diffusion path of titanium as well as lime. It is quite 

 usual to have the following serial relationships, hornblende connected to ilmenite nucleus 

 by dactylitic felspar and pyroxene in a narrow rim, and then, the ilmenite nucleus 

 connected to the garnet crystal by another such dactylitic rim, but this time, wider. 



The garnet crystals have not assumed their perfect crystal outline, an indication 

 that they are still undergoing the process of formation. They are remarkably embayed, 

 and contain a large number of inclusions which include quartz, ilmenite, hornblende and 

 biotite which produce the unusual effect of poikiloblastic garnets. 



The other main minerals developed are hornblende, biotite, andesine and quartz. 

 Accessory minerals include sphene, zircon in minute crystals, and apatite. 



Rock No. 976 is merely a duplicate of this (No. 977). 



No. 978. Garnet-Plagioclase-Amphibolite. 



This rock, which was collected near the boat moorings, looks very much like 

 No. 977, except that together with an increased micaceous content there has developed 

 a more pronounced schistosity. This feature, however, has not been developed to such 

 a degree as would warrant calling the rock a schist it is still a gneiss. Another factor 

 which favours a reduction in the gneissic nature of the rock is the smaller amount of garnet 

 present, but, even so, garnet is still one of the most important minerals in the rock. 

 Other minerals which can be recognised by the naked eye are hornblende and felspar. 



Weathering has converted the biotite of the superficial layers into a golden 

 coloured mica and has set free considerable quantities of oxidised iron compounds with 

 the result that the exposed surfaces have assumed a deep yellow-brown colour. 



The microscopic examination confirms the conclusions formed from the study 

 of the hand specimen. Except for a slight increase in the amount of biotite present the 

 rock differs in no material respect from No. 977. There is the same green, compact 

 hornblende, garnet, ilmenite and hornblende in the same relations as before, and 

 leucocratic areas of quartz and plagioclase. 



