36 AUSTBALASIAN ANTAKCT1C EXPEDITION. 



No. 637. This example possesses weak schistosity and approaches a massive 

 texture. Strings of white material can be seen in the hand specimen conforming to 

 the schistosity. The measured section is not quite normal to the schistosity, and this 

 is a factor in producing a slightly higher felspar percentage than is usual. Further, 

 the example is obtained from a schliere impregnated with felspar-quartz veins, and it 

 is likely that some of the visible white material is the same as in the veins. This would 

 also raise the felspar percentage above the normal, and this appears confirmed by the 

 presence of large grains of quartz in the section. The rock is granoblastic and very 

 little saussuritised felspar is present it is nearly all secondary clear felspar. The 

 hornblende percentage decreases with the increased felspar percentage, but still the 

 similarity of this rock to other examples is very obvious. The hornblende colour is 

 normal, except in an isolated grain which gives bright blue pleochroism, indicating a 

 tendency to the formation of glaucophane. This is interesting, as lawsonite has been 

 looked upon as a frequent constituent of the glaucophane schists. Brown biotite is 

 present in skeletal plates penetrated poikiloblastically by large crystals of sphene, 

 magnetite, epidote, and felspar. The biotite appears in patches throughout the rock. 

 Epidote is in small quantities, but the grains included in the biotite are well developed. 

 Sphene is more abundant in this case than in other members of the series, though its 

 average grain size is not so large. The core of magnetite is prominent and may be 

 idioblastic. The magnetite as well as the sphene attains its maximum percentage 

 here. The magnetite crystals are frequently idioblastic, and may be so large that 

 we only get a thin veneer of sphene on them, and the sphene rim may not be continuous 

 around their circumference. Minute apatites are present. The rock is an amphibolite. 



No. 634. In this example some degree of schistosity is produced by a parallel 

 arrangement of hornblende prisms. Such arrangement is almost perfect in an adjacent 

 band, No. 633, which is exceedingly fissile. No. 634 is granoblastic, and the abundant 

 rounded and embayed grains of clear plagioclase enhance this character. Though the 

 lamellar twinning is not well developed, some crystals with broad lamellae can be found 

 to give an extinction of 36, indicating labradorite. The second sodic plagioclase is 

 again present, and very occasional quartz grains can be found. The hornblende is 

 normal but with more indented outline than in No. 635. The biotite is brown, and 

 rarely intergrown with lawsonite, as the latter is very scarce. The iron ore consists of 

 scattered grains of magnetite and pyrite. Sphene is absent. The rock is an amphibolite 

 schist. 



No. 634A. This is a highly schistose specimen with abundant hornblende. 

 Glistening mica with a light golden-brown colour is noticeable on the schist surface. 

 The very large percentage of hornblende is the striking feature of this rock, and in section 

 possesses the usual characters. The felspar is mostly cloudy and saussuritised, and only 

 occasionally does a clear grain arise from it. The small amount of clear felspar in this 

 rock is in contrast to the large amount of clear felspar in the neighbouring dyke, No. 634, 

 a yard or so away from it. The mica consists of intergrown biotite and chlorite, of 

 which the former is more abundant. The biotite possesses the same curious brown 



