Tfans. N.Z. Inst., Vol. LI I. 



Plate XXVIIT. 



Fia. 1. 



Fio 



Fig. 1. — Quartz-norite, Cleddau-Hollyford Saddle, illustrating the structure and the 

 mineral relationshijjs. The field of the photograph coincides with a portion 

 of the diagrammatic sketch of the text-figure, and the identification of the 

 minerals is possible from the labelling of that sketch. The enclosure of 

 hypersthene by augite is evident at the left-hand end of the horizontal 

 diameter, whilst the jienetration of the same augite crystal by zoisite (dark) 

 is also recognizable. The interstitial quartz is very obvious. In the lower 

 right-hand quadrant it is just possible to recognize some fine lamellae of 

 augite intergrown with a crystal of hypersthene-like pjTOxene (dark). Crossed 

 nicols. Magnification, 35 diameters. 



Fig. 2. — Dolerite, Silverdale, Auckland. The general ophitic structure can readily be 

 recognized, as also the bar-like growths of iron-ore. Crossed nicols. Magni- 

 fication, 20 diameters.! 



'V ft*,* ^- • 



-1 ''> '• 





\1 .• #:. M 



Fig. 3. 



Fig. 4. 



Fig. 3. — Basalt, near old wharf, Ti Point, Whangateau Harbour. A typical olivine 

 phenocryst. fringed by a rim of oxidation, set in a groundmass in which 

 augite plays an important part. Ordinary light. Magnification, 35 diameters. 



Fig. 4. — Basalt, Ohakune ballast-pit. A central crj'stal of olivine (dark) with wide 

 celyphitic rim of augite (mainly white). Some feldspar laths show up in the 

 groundmass, but the olivine laths are here inconspicuous owing to clouding 

 by haematite, whilst abundant vesicles also render the slide dark. Crossed 

 nicols. Magnification, 21 diameters. 



Face p. 416.] 



