284 AUSTEALASIAN ANTARCTIC EXPEDITION. 



remains of large crystals which have been mostly altered to chlorite, quartz, and mag- 

 netite. This is a common alteration in the suite of specimens and will be dealt with 

 later. The colour scheme of the- biotite is X, light green, Y and Z, dark green. 

 Sometimes it has altered to chlorite, frequently showing the indigo blue polarisation 

 colours of clinochlore, and magnetite. Quartz is abundant and shows cataclasis and 

 strain polarisation. Orthoclase felspar is common but much kaolinized and sericitised. 

 Epidote occurs in numerous granular aggregates, usually almost opaque, and a very 

 strong light is necessary to observe its characteristic polarisation colours. Apatite is 

 common as small rounded grains. The rock is Micaceous-Magnetite-Gneiss. 



No. 912. This is a schistose type, dark-coloured, and easily cleaved. It is 

 extremely fine grained and it possesses a lustrous appearance owing to the presence of 

 white mica. Flakes of the rock are strongly magnetic. 



Microscopically, the structure is lepidoblastic. Magnetite crystals, which 

 constitute nearly a third of the rock, are xenoblastic in outline, especially in the larger 

 grains. Occasional minute flakes of micaceous hematite (eisenglimmer) are recognised 

 and ilmenite is intergrown with the magnetite. Garnets are moderately abundant but 

 they are small and much fractured and contain inclusions of magnetite. Green biotite 

 is common and sometimes exhibits pleochroic halos which are too indistinct to measure. 

 Quartz is an important constituent and contains fluid and magnetite inclusions. The 

 fluid inclusions generally have an arrangement parallel to the schistosity. Scaly 

 sericite, chlorite, epidote, and accessory apatite form the remainder of the rock, which 

 may be called a Magnetite-Schist. 



No. 296. This is a dark greasy-looking rock, extremely fine grained and 

 traversed by a few lenticular bands composed mostly of quartz and epidote. It possesses 

 a very definite crystallisation schistosity. 



The structure is both granoblastic and lepidoblastic. Magnetite is extremely 

 abundant, occurring in little xenoblastic individuals with linear development and also 

 in larger porphyroblastic grains (up to 0-3 mm.). It is disseminated through the rock 

 as well as segregated in thin bands. Small red flakes of micaceous hematite also occur. 

 Garnets are very small and idioblastic, their averages absolute diameter being about 

 0-4 mm. Quartz 'is the most abundant constituent and reduces the specific gravity 

 (2-93) below the average. Biotite is present as small flakes, while epidote is restricted 

 to certain bands as xenoblastic grains. Felspar is absent. The rock is Quartz- 

 Magnetite-Schist. 



No. 989. Macroscopically the rock is dense and dark-coloured, being traversed 

 by a few epidotic bands. Little porphyroblasts of magnetite can be seen in the ground 

 mass of the rock. 



The structure is granoblastic and the texture is schistose. In most respects the 

 rock is similar to the preceding quartz-magnetite-schist, No. 296. The garnets, 

 however, show two kinds of alteration, one of which has produced chlorite and the 



