174 AUSTRALASIAN ANTARCTIC EXPEDITION. 



A small portion of the hornblende is very pale in colour, and has the appearance 

 of uralite rather than that of the normal green hornblende. The uralite has green spots 

 of normal hornblende, and the cleavage passes indiscriminately through both. The 

 uralite is evidently passing into hornblende, or vice versa. Sometimes there are bluish 

 glaucophane borders on the hornblende crystals. 



The biotite is intergrown with the hornblende as before. There are occasional 

 small blebs of garnet usually set in the felspar. Similar in outline and situation are 

 occasional small blebs of calcite, and these are probably the remains of former garnet 

 from which the A1 2 3 and the Si0 2 have been withdrawn, and the excess lime has been 

 converted by carbonation into calcite. Small dusty ilmenite areas have been found, 

 and suggest that some of the ilmenite has formed by the aggregation of this dust. 



The rock is a true amphibolite, which has formed under meso zone conditions, 

 and its presence is noteworthy among a large number of recrystallised basic rocks in which 

 garnet and pyroxene predominate. 



No. 935. This specimen was obtained from a broad band about 20ft. wide with ill- 

 defined boundaries. The rock is dark coloured and massive, with a vitreous lustre, 

 but without any suggestion of schistose texture in the hand specimen. The doleritic 

 character is suggested by the presence of felspar laths and large black augites, which can 

 be seen with the naked eye. With the aid of a pocket lens small garnets are found to 

 be numerous. 



In thin section we find abundant garnet, pyroxene, hornblende, ilmenite, and felspar. 

 Pyrite and apatite are also found. The mineral proportions in slide No. 935 (2) have 

 been determined as follows : 



Felspar 25-4 



Pyroxene 21-3 



Hornblende 25-3 



Garnet 15-9 



Ilmenite 5-7 



Biotite 6-0 



Apatite 0-4 



The transformation of augite and its reactions with the felspar are very plain. 

 There are large plates of augite crowded with the minute dusty ilmenite inclusions 

 which we know are a relic of the pre-existing dolerite. We can trace the following 

 changes in this primary augite : 



(1) There are parasitic clumps of small, interlocking, granular pyroxene crystals 

 which are clear and have been formed in the recrystallisation of the dusty pyroxene. 

 The primary schiller inclusions have been thrown out, and have coalesced to form large 

 ilmenite crystals. This is the same change as was observed in No. 773 from Cape Gray. 

 Partial aggregations of the minute ilmenite dust are often seen (Plate VII., fig. 2). 



