Marshall. — Geology of North Isla?id. 85 



Park" has mentioned dolerite, phonolites, porphyritic tra- 

 chytes, and pitchstone as occurring on Kuapehu ; but neither 

 of these last two authors appears to have made anything more 

 than a field examination of the rocks. 



Rutleyf has described a large number of rhyolites from the 

 Rotorua area. Several of these suffered from geyser-action 

 and have become more or less silicified. Descriptions of rocks 

 from Tuhua (Mayor Island), in the Bay of Plenty, are included 

 in this paper. 



A different type of rock, a pantellaritic liparite lava, has 

 recently been described by F. von WolffJ from Mayor Island. 

 This is the only mention of soda-rich types from the district 

 — at any rate, in technical descriptions. 



During the presence of the " Discovery " expedition in New 

 Zealand, rocks were collected by Ferrar near the Aratiatia 

 Rapids, on the Waikato River. They have been described as 

 rhyolites and andesites by Rastall.§ Reference is here made to 

 a peculiar reddish pyroxene that it is stated may be strongly 

 soda-bearing. 



The Auckland rocks have also been described by Shrewsbury, || 

 who classed them all as basalts. 



The literature referring to the Thames rocks and those of the 

 Cape Colville Peninsula is quite extensive, but there is a very 

 general agreement as to the rock-types and the succession of 

 lavas. The most recent publication on the district appeared in 

 1905, from the pen of Professor Sollas^J, with descriptive notes 

 by A. McKay. Photographs of many of the rock-types appear 

 in this work. 



It is recognised by all workers in this field that the andesites 

 are very varied in type and structure. They range from dacites 

 to hypersthene andesites, with some olivine. Augite and horn- 

 blende types occur as well, but there are no unusual minerals 

 present. Sollas speaks in several places of the micropcecillitic 

 structure as peculiar. The mineral with which this structure 

 is most commonly associated he has identified as quartz. 

 Coarsely spherulitic rhyolites from this locality have received 

 considerable attention from Rutley** and Sollas.ff The spheru- 



* Park, Geological Reports, 1886, p. 70. 



f Rutley, Quart. Journ. Geol. Soc, vol. lvi, p. 493 et seq. 



t F. von Wolff, " Centralblatt fur Mineralogie, &c, 1904," p. 208 et seq. 



§ Geological Mag., Decade v, vol. ii, p. 403 et seq. 



|| Shrewsbury, Trans. N.Z. Inst., vol. xxiv, p. 366. 



^f Sollas, " Rocks of Cape Colville Peninsula," 2 vols. ; Government 

 Printer, Wellington. 



** Rutley, Quart. Journ. Geol. Soc, vol. lv, p. 449 et seq., particularly 

 p. 466 ; also vol. lvi, p. 509. 



ft Sollas, " Rocks of Cape Colville Peninsula," vol. i, pp. 120, 121. 



