166 THE PYROXENE GRANULITES COLLECTED 



The minerals present are : quartz, pyroxene, scapolite, felspar, sphene, and apatite. 



Quartz is the most abundant mineral and occurs in very ragged, elongated grains 

 which show marked shadowy extinctions. The larger grains are very much granulated. 

 Pyroxene is abundant in subidiomorphic grains, light green in colour, with fairly strong 

 absorption but little pleochroism. The D.R. is medium (about -021) and positive, 

 and the R.I. high. It is most probably augite. Scapolite (Wernerite) is present in 

 irregular grains. Felspar is present in allotriomorphic grains showing albite twins. 

 It is labradorite with composition AbiArij. Sphene is abundant and apatite scarce. 



This rock has been analysed and the analysis is given on p. 161. 



459. Scapolite-bearing Pyroxene Granulite. Erratic (Cape Royds). 



Hand-specimen. A light-greenish, fine-grained rock, fairly hard and heavy. It is 

 very siliceous and has well-marked foliation. Quartz, felspar, and a greenish ferro- 

 magnesian mineral can be recognised. Under the microscope the fabric is gramilitic 

 and the grainsize even, medium, with the grains having an average diameter of about 

 *4 mm. Foliation very noticeable both by the pyroxene and sphene. 



Minerals present are : scapolite, }5yroxene, quartz, felspar, sphene, and pyrites. 



Scapolite is perhaps the most abundant mineral. It encloses pyroxene, quartz, 

 and sphene poikilitically. Pyroxene is abundant in subidiomorphic and rounded grains, 

 colourless, nonpleochroic, and with no noticeable absorption. It is Diopside. The 

 sections are mostly longitudinal ones and the cleavages are all in a roughly parallel 

 direction. Quartz is fairly abundant, with very little evidence of strain. Felspar is 

 not abundant. It is in fairly large allotriomorphic grains twinned after the albite law. 

 It is a good deal altered, and the appearance is much the same as when a felspar becomes 

 sericitised, with the difference that the secondary mineral, instead of being sericite, is 

 scapolite. The felspar is a labradorite with the composition AbjAiij. Sphene is present 

 as numerous small lozenge-shaped crystals. Apatite, zircon, and pyrites are sparingly 

 present. 



P. 391. Scapolite-bearing Pyroxene Granulite. Erratic (Cape Royds). 



Hand-specimen missing. 



Under the microscope the fabric is gramilitic and the grainsize uneven. 



The minerals are : pyroxene, quartz, felspar, scapolite, sphene, zircon. Pyroxene 

 is easily the most abundant mineral and is present in rounded to columnar grains. 

 The rectangular cleavage is very well marked. It is colourless and quite fresh, and is 

 Diopside. Quartz is in irregular grains, some of which show shadowy extinctions. 

 Felspar is present in subidiomorphic grains twinned after the albite and pericline laws. 

 Its R.I. is less than that of quartz and greater than that of Canada Balsam. It is 

 intermediate in composition between oligoclase and andesine and probably is about the 

 composition Ab 7 An 4 . In places it is altered to sericite. Scapolite is present and 

 contains numerous small inclusions. Sphene and apatite are also present. There are 

 a few grains of colourless mineral, untwinned and with R.I. less than quartz, and which 

 may be orthoclase. 



P. 355. Scapolite-bearing Pyroxene Granulite, Erratic (Cape Royds). 



Hand-specimen missing. 



Under the microscope the fabric is granulitic and the grainsize uneven, the greater 

 part of the rock having grains of medium size and the remainder coarse. A somewhat 

 gneissic structure is exhibited. (Plate I, Fig. 4.) 



The minerals present are : pyroxene, felspar, quartz, scapolite, sphene, and diallage (?). 



Pyroxene is very abundant in medium-sized subidiomorphic grains. It is colourless 

 and a small amount of absorption is noticeable. It encloses quartz. The felspar is 

 abundant in fairly large subidiomorphic sections, twinned after the albite law. Sym- 

 metrical sections give extinctions up to 26°, and therefore it is a labradorite of compo- 



