422 Transactions. 



The Sumner rock is known to other geologists, but has not been reported 

 in literature so far as the writer is aware. It contains abundant iron- 

 stained idiomorphic olivine crystals, which are frequently enclosed in the 

 coarser pale-green augite. The hornblende is quite fresh and unresorbed ; 

 it is greenish-brown, and lacks the deep absorption tints of the usual basaltic 

 hornblende. 



Andesites in Mid-Mesozoic Eocks at Port Waikato. 



At a point on the south bank of the Waikato River about a mile and 

 a half up-stream from Port Waikato a well-marked conglomerate with 

 rounded pebbles up to 5 in. in diameter outcrops amongst finer plant- 

 bearing mid-Mesozoic sediments. The pebbles include many sedimentary 

 rocks, such as quartzite, shale, and greywacke, and several varieties of 

 andesite. Similar pebbles are frequent in irregular bands along the 

 " strike " coast south of the mouth of the river. 



There are several highly feldspathic types of andesite, one with perfect 

 trachytic groundmass and practically no ferro-magnesian mineral, though 

 magnetite is fairly abundant in specks in the groundmass. There are also 

 augite andesites and one hornblende type rich in fresh greenish-brown horn- 

 blende and with very coarse plagioclase. 



Andesitic, rhyolitic, and other pebbles are found in the basement sedi- 

 ments of Coromandel Peninsula,* and in the " Maitai " shales on the east 

 shore of Palliser Bay, Wellington, f and thus in rocks, so far as we know, 

 roughly coeval with those at Port Waikato. 



In the Mount Somers district, Canterbury, the varied rhyolites and 

 andesites are Jurassic, according to Marshall,! though other statements 

 about them conflict with this view.§ 



Another well-known occurrence of pebble-beds of igneous rocks in sedi- 

 ments belonging to the same Trias-Jura succession is in the hills near- 

 Nelson ; the included pebbles there are largely derived from plutonic rocks. || 



GrNEISSIC DlORITES, ALBANY, NEAR AUCKLAND. 



An interesting occurrence of gneissic diorites or dioritic gneisses was 

 made known recently to the writer by some specimens collected at Albany 

 by Mr. G. B. Battersby from boulders up to several feet in diameter which 

 were unearthed by farming operations. As they are located a moderate 

 distance from the water's edge it is very unlikely that they have been brought 

 thither by vessels trading up Lucas Creek, and they more probably come 

 from a boulder-bed, belonging to the Miocene Waitemata series, known 



*W. J. Sollas and A. McKay, Rocks of Cape Colville Peninsula, vol. 1, 1905, 

 p. 52 : C. Eraser and J. Adams, The Geology of the Coromandel Subdivision, N.Z. 

 Geol. Surv. Bull., No. 4, 1907, pp. 45 and 52. 



t W- J. Sollas and A. McKay, Eocks of Cape Colville Peninsula, vol. 2, 1906, 

 pp. 178 et seq. 



1 P. Marshall, Distribution of the Igneous Rocks of New Zealand, Rep. Austral. 

 Assoc. Adv. ScL, vol. 11, 1907, p. 6 of reprint. 



§ Cf. J. Park, Geology of New Zealand, Wellington, 1910, pp. 82-S3. 



|| P. Marshall, Boulders in a, Triassic Conglomerate, Nel«on, Trans. N.Z. Inst.. 

 vol. 36, 1904, pp. 467-71. Since the above was written Professor Marshall has informed 

 me that a thick conglomerate with similar pebbles of even greater variety outcrops in 

 the Mesozoic rocks at Kawhia. 



