Vol. 62.] GEOLOGY OF DUNEDIN (NEW ZEALAND). 405 



A. B. 



Per cent. Per cent. 



Si0 2 56-40 58-37 



A1,0 3 15*84 16-65 



F e ;0 3 6-48 4-09 



FeO 354 303 



MgO 0-21 0-37 



CaO 1-52 1-66 



Na 2 5-80 7-28 



K.,0 5-78 5-46 



P 0-13 008 



H 2 3-96 2-36 



Totals 99-66 99'35 



A=r]S"ephelinitoid phonolite, Mopanui, Dunedin (N.Z.). Anal. P. Marshall. 

 B = Phonolite, Mount Kenya. G. T. Prior, Min. Mag. vol. xiii (1903) p. 240. 



Except at Mopanui and Normanby, the nephelinitoid phonolites 

 do not form large rock-masses. In all the localities in which they 

 occur, it is difficult to distinguish the boundaries of the area covered 

 by the rock, because of the growth of vegetation and the depth of 

 soil that covers the ground around the outcrop. 



12. Leucitophyre. — I have found a specimen of this type 

 in one locality only, Puketeraki. It is a dark-green dense rock, 

 showing on its fractured surface a slight shimmer, due to the 

 large quantity of minute felspars. In slices the felspar is very 

 abundant ; the larger crystals are anorthoclase. The nepheline 

 is in small quantity. Leucite occurs in the finer-grained types 

 only. The crystals are almost round, and have concentrically- 

 arranged, minute, needle-shaped microliths of segirine. The 

 leucites are not sensibly birefringent. The coloured constituent 

 is a pale-green segirine-augite, with much magnetite. The minute 

 felspar-laths have an arrangement not very different from their web- 

 like arrangement in the trachytoid phonolite of the Logan's-Point 

 type (see p. 401). 



A. B. 



Per cent. Per cent. 



SiO, 52-88 48-95 



Al 2 6 3 14-44 18-43 



Fe 3 6-72 



FeO 4-56 8-19 



CaO 380 6-42 



MgO 1-68 1-43 



Na o 4-78 6-51 



K 9 7-09 6-90 



P 5 011 



H^O 4-00 1-79 



Totals 100-06 98-62 



A = Leucitophyre, Puketeraki, Dunedin (N.Z.). Anal. P. Marshall. 

 B=Leucitophyre (nosean-melanite rock), Perlenkopf, Oibriick. Eosenbusch, 

 ' Elemente der Gesteinslebre' 2nd ed. (1901) p. 292, No. 15. 



Chemically, the silica-percentage is low and the iron-percentage 

 high — a feature that recurs frequently in the Dunedin rocks. The 



