Geology.] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



697 



Melilite Basalt. 



A dark-grey dense rock found at Lyall Pyramid. 



Section : A few feldspar crystals, little twinned, but one individual is distinctly 

 andesine. A few colourless augites and some olivine crystals with crusts of limonite. 

 With the olivine a few flakes of reddish-yellow mica, probably anomite. Ground- 

 mass very fine-grained. Colourless 

 augite magnetite and olivine are 

 present in about equal quantities ; 

 they are imbedded in plates of 

 a feebly bi-refringent colourless 

 mineral. The characters of this 

 mineral suggest melilite, and its 

 presence is proved by the separa- 

 tion of gypsum needles from a 

 solution in dilute hydrochloric 

 acid on the addition of sulphuric 

 acid. 



Very similar rocks occur at 

 the summits of Mount Dumas and 

 Mount Honey, but in them melilite 

 appears to be wholly replaced by 

 feldspar. 



Analysis. 



SiO, 





. 54-44 



A1,0, 





. 12-83 



Fe.,0.5 





8-32 



FeO 





5-41 



CaO 





6-90 



MgO 





2-66 



TiO^ 





2-68 



Na.,0 





4-34 



KoO 





1-58 



H2O 





1-58 



100-69 



Limestone. (Fig. 13.) 



As a rule, the limestone is 

 somewhat lamellar, but appears to 

 the naked eye to be perfectly 

 homogeneous. In section a few 

 grains of glauconite are occasionally 

 seen ; except for these, the whole 

 rock consists of extremely fine cal- 

 careous matter, in which tests of 

 Foraminifera can be seen. 



■ Basalt dykes. 



Trachyte dykes. 



Nature of dyke not 

 determined. 



Pl.AN OF FoliESHOIiE OF HeAD OF PeESEVEKAXCE 



Harbouk, Campbell Island, showing the 

 numbek and direction of d^kes. 



