140 



AUSTEALASIAN ANTARCTIC EXPEDITION. 



The lamellar twinning is generally exceedingly fine, and the small extinction angle 

 and low refractive index indicates an albitic plagioclase. Sometimes the felspar includes 

 rounded blebs of quartz, and sometimes there is incipient diablastic structure. A 

 certain amount of sericite has been produced from the felspar. The hypersthene 

 is partly altered, and the same greenish, feebly pleochroic mineral (delessite ?) is 

 present as before. It is also partly altered to enstatite. Brown biotite and ilmenite 

 are also again associated in a significant manner with the hypersthene. Colourless to 

 pale-pink garnet is present, and may be associated with the hypersthene. The garnet is 

 found both in small and large crystals, which are partly idioblastic. Inclusions are not 

 abundant in the garnet, but biotite, quartz, and ilmenite appear as such. Accessory 

 grains of monazite or zircon are present. 



Chemical Characters. 



The following analysis of No. 754 was made by J. C. Watson in the Victorian 

 Geological Survey Laboratory : 



SiO a 6942 



A1 2 3 15-03 



Fe 2 3 1-66 



FeO 2-65 



MgO MO 



CaO 345 



Na 2 4-50 



K 2 1-39 



H 2 + 0-65 



H 2 - 0-07 



C0 2 nil 



Ti0 2 0-35 



P 2 5 tr. 



S0 3 nil 



Cl tr. 



MnO 0-06 



I-JzO strong tr. 



100-33 

 Specific Gravity 2-685 



75-2 



A. 



5-7 



C. 



3-8 



Group Values. 



F. 



5-8 



M. 



0-2 



T. 



K. 



1-6 



Projection Values. 



a. 



7-4 



c. 



5-0 



7-6 



