COLLECTED AT CAPE ROYDS 185 



In the lighter bands the actinolite appears at first sight to be granular, but between 

 crossed nicols it is shown to be optically continuous over areas of several square milli- 

 metres, so that the structure is poikiloblastic, approaching diablastic. 



The colourless interstitial material is certainly complex; the greater part appears 

 to be quartz, but quite a considerable amount of it has a refractive index decidedly 

 greater than that of quartz and is probably untwinned basic felspar. 



There are occasional flakes of colourless material answering to brucite. 



265. Fine Tremolite- Schist 



Microscopic Characters. — A very fine-grained and distinctly banded 

 lepidoblastic rock. 



It consists essentially of quartz, scaly muscovite, and prismatic tremolite, with 

 slightly larger flakes of greenish clinochlor. Some of the bands are nematoblastic on 

 account of the aggregation of the tremolite prisms. 



There are also present minute ovoid grains of a mineral, greenish to colourless with 

 a very high refractive index and strong double refraction, which, however, does not 

 seem to be epidote. 



P. 239. Spotted Schist 



Microscopic Character s. — In section the spots are quite distinct : they 

 appear to contain the same colourless constituents as the remainder of the rock with- 

 out any of the biotite which occurs in the granulitic ground fabric. 



The grainsize of the rock is very fine, which makes it very difficult to distinguish 

 the constituents. 



The colourless mineral appears to be almost all quartz. The spotted appearance 

 is strikingly suggestive of development of incipient andalusite crystals, but no distinct 

 evidence of this mineral could be observed. There is a little magnetite present mostly 

 in the ground fabric, but occasionally in the spots as well. 



602. Phyllite 



Macroscopic Characters. — Chocolate-coloured rock, with well- developed 

 slaty cleavage. On the cleavage surfaces the lustre is satiny. 



Microscopic Character s. — The rock consists of angular quartz fragments, 

 many of them showing strain effects, cemented by a fine sericitic mortar, which is stained 

 with limonite. 



464 (P. 89). Quartz Schist 



Macroscopic Characters. — A cherty-looking rock, of light yellowish-grey 

 colour and very close texture. The lustre is sub-resinous and fracture sub-conchoidal. 

 The rock is distinctly banded and its general appearance is extremely suggestive of a 

 limestone metasomatically replaced by silica. 



Microscopic Characters. — The rock is lepidoblastic, with a fine-grained 

 ground fabric (average grainsize about 01 mm.) containing " auge" of quartz up to 

 2 mm. by 1 mm. The ground fabric consists of finely granular quartz and flaky 

 sericite with a very little epidote. The constituents show a slight tendency to segregate 

 into folia. There is a very peculiar arrangement of the ground fabric with two axes 

 of schistosity, making an angle of 40° with one another, so that, between crossed nicols, 

 when both sets of mica plates are illuminated, there is a decided meshwork. Here 

 and there the sericite is segregated into moderately large patches. 



II 2 c 



