FROM THE MAINLAND OF SOUTH VICTORIA LAND 



An analysis made by A. B. Walkom, B.Sc, gave the following : 



225 



COMPOSITION OF THE NORM 



100-25 



99-61 



Chemico-mineralogical Classification: Class 2, Order 5. Rang 4, Sub-rang 3 (Hessose). 



Specimens of a rock similar in all respects but containing less sphene were found 

 in the same moraine. 



BlOTITE-HORNBLENDE DlORITE ; NEAR MOUNT LARSEN 



A very similar rock to the preceding, though deficient in sphene. It was collected 

 from the lateral moraine near Camp Lake at the foot of the Larsen Glacier. This is a 

 fine granular grey rock exhibiting, to the naked eye, plagioclase, hornblende, and 

 biotite. 



Microscopic Characters. Hypidiomorphic granular ; average grain size in the 

 section 0-75 mm. The constituent minerals are quartz, plagioclase (andesine and 

 oligoclase), hornblende, biotite, apatite, magnetite, and sphene. 



Quartz is present as irregular grains in small quantity only ; it is the last crystal- 

 lisation product ; strain shadows are frequent. The plagioclase is zoned and ranges 

 between andesine and oligoclase ; saussuritisation is advanced. The hornblende is 

 fresh and in idiomorphic or panidiomorphic forms ; twinning is frequent ; pleochroism 

 is strong (light yellow, deep greenish-yellow, and bluish-green. Biotite is distributed 

 unequally, but always subordinate to hornblende ; the flakes are frequently bent ; 

 pleochroic (light yellow to deep yellowish -brown). Apatite is abundant as idiomorphic 

 prisms. Sphene is comparatively rare, occurring in minute grey grains. 



An analysis of this rock made by A. B. Walkom, B.Sc, gave the following figures : 



107-90 



98-69 



