272 AUSTRALASIAN ANTARCTIC EXPEDITION. 



pre-existing crystals. These contain numerous inclusions of magnetite and amphibole 

 The magnetite appears to have been a separation product, accompanying the 

 formation of the talc. It is distributed as fine particles along traces of former cleavage 

 planes, and along a system of cracks more or less at right angles to the cleavage. In 

 many places these particles have coalesced to form irregularly -shaped inclusions of 

 magnetite. The arrangement of the discharge of magnetite suggests that the original 

 crystals were olivine, though the nature of some of the included amphibole indicates 

 the possibility of pre-existing pyroxene, partly altered to hornblende before the 

 curious alteration to talc. The amphibole is the most abundant mineral, and 

 includes green hornblende and anthophyllite. The latter has developed in long 

 prismatic crystals, which possess faint pleochroism from colourless to very light 

 brown. The cross sections show the usual hornblende cleavage and outline, and the 

 prismatic sections possess straight extinction. Sometimes there is a green core of 

 hornblende, with a colourless border zone of anthophyllite. Sometimes the hornblende 

 is decolourised, and there appears to be a gradation from hornblende to anthophyllite. 

 In addition to these minerals, the rock contains a minor amount of biotite, with 

 pleochroism from a pale-straw brown to a bright green, and of magnetite with 

 accessory grains of pyrite, apatite and quartz. The rock is an anthophyllite-schist, 

 on which has been superimposed some of the features of the Epi division. These 

 features include the development of talc, the bent and crushed appearance of some 

 of the biotite crystals, and the occasional fracturing and mortar structure in the 

 amphibole. 



Specimen No. 516 is another representative of the anthophyllite-schists, and, 

 as in No. 513, there are only occasional grains of felspar. It is a dark-green schistose 

 rock, showing a brownish tinge on the weathered surface, due to the slight oxidation 

 of anthophyllite. In thin section, the green hornblende is the most important 

 mineral, and the colourless to light-brown anthophyllite is intergrown with it. The 

 talcose areas of the preceding specimen are absent, but some of the anthophyllite 

 crystals show decomposition around their edges and cleavages to a talcose material. 

 Brown biotite is much more abundant than in No. 513, and helps to produce the 

 schistose structure. Accessory grains of apatite, ilmenite, pyrite and quartz are 

 present. 



Another representative of the anthophyllite-schists is Specimen No. 109, in 

 which the green hornblende is absent. This specimen is a light-brown rock, in which 

 the prisms of anthophyllite are arranged with their long axes in the plane of schistosity. 

 Some of these crystals are over 2cm. long, and they lie in all positions in this plane. 

 Plagioclase can be observed in the hand specimen in a proportion which makes the 

 inclusion of this specimen in this group doubtful. In section the anthophyllite is 

 slightly pleochroic from colourless to pale brown, showing the well-developed cleavage 

 and outline of the amphiboles. The plagioclase is labradorite, and there are odd 

 flakes of biotite and a few grains of magnetite (or ilmenite). The rock could possibly 

 be placed in the group of the amphibolites. 



