692 



SUBANTARCTIC ISLANDS OF NEW ZEALAND, 



[Geology. 



Analyses. 







Mount Honey. 



Mount Lyall. 



Filhol. 



SiO^ .. 





. 63-34 



63-56 



65-50 



AL,03. 







. 1524 



15-32 



10-50 



Fe.O,. 







5-15 



4-29 



13-30 



FeO . 







2-06 



2-85 



, , 



CaO . 







3-30 



1-90 



3-32 



MgO . 







0-82 



0-21 



0-05 



TiO, . 







0-53 



0-40 



, , 



Na/O . 







6-28 



6-48 



6-50 



K,0 . 







2-38 



209 



1-71 



H2O . 







1-78 



1-21 



, , 



Loss . 







- . . 





1-02 



100-88 



100-83 



100-00 



The third analysis given is quoted from Filhol, p. 168. It represents the com- 

 position of his " andesitic basalt with anorthite." From the localities he mentions 

 for his andesite, it appears to be the same rock as that here called trachjrte. 



On the western cliffs, jnst beyond 

 St. Col Peak, there is a peculiar type 

 of rock, which appears to form an in- 

 trusion. The stormy weather which 

 prevailed when this locality was visited 

 prevented a close examination from 

 being made. From what could be 

 seen, the rock appears to occur along 

 a line of fracture which separates the 

 limestones from the tuffs. The down- 

 throw of this fault appears to be about 

 500 ft. to the north. The following 

 three specimens are from this locality : — 



352. Hand-specimen pale grey, 

 with a flinty appearance. Section : 

 Perfectly clear and transparent glass. 

 A few minute microlites of feldspar 

 and one or two plates of biotite are 

 imbedded in the glass. There are 

 numerous extremely minute spherulitic 

 bodies. 



353. This specimen is pale grey, 

 with a distinct lamellar structure. In 

 section quartz is plentiful, but the 

 grains are irregular and angular. In 

 places the quartz forms small plates enclosing feldspar which recall the micro- 

 poecilitic structure, Arfvedsonite occurs rather abundantly, in highly irregular 



Fig. 7. — Summit of Lyall Pyramid, Campbell Island 

 (1,273 ft. high). 



