Park. — On the Geology of the Kuaotunu Goldfield. 363 



points to the Post-eocene age of the Thames and Kuaotunu 

 tuffs, which can be traced almost continuously to Coromandel 

 on the west and Te Aroha on the south. 



In connection with their economic importance, it is in- 

 teresting to note that they are the youngest gold-bearing rocks 

 in the Southern Hemisphere, being younger than the gold- 

 bearing rocks of Otago, Eeefton, and the different goldfields of 

 Australia, by the whole of the Secondary epoch and the upper 

 part of the Palasozoic. Even in composition and origin they 

 stand unique, and their homologues are found only in two 

 countries in the Northern Hemisphere— namely, Transyl- 

 vania, in Hungary, and the Pacific States of America ; and 

 in these countries the similarity extends also to their gold and 

 silver contents, which are frequently as refractory and difficult 

 to treat as ours, while their free-milling bullion is alloyed with 

 silver to the extent of about 30 per cent., as it is throughout 

 the Hauraki Peninsula. 



PalcBOZoic Bocks. 



(a.) Greywackes and Slaty Breccias.- — These rocks occupy 

 the wooded spurs and ridges on the west side of the Kuaotunu 

 Eiver, and form the broken rocky headlands and islets between 

 Kuaotunu and Matarangi, and the steep precipitous sea-cliffs 

 north of the mouth of the river. 



They consist of hard siliceous greenish and grey-coloured 

 sandstones, interbedded with hard blue slaty breccias and 

 occasional bands of slaty shale. They are always much 

 jointed and shattered, and often streaked with thread-like 

 veins of quartz or haematite. Up to the present time no vein 

 containing payable gold has been found in them. 



(b.) Clay-shales, Diabase-ash and Breccia Beds. — The clay- 

 shales occupy the lower slopes of the spurs on the east side of 

 the valley, and are well exposed in many of the road-cuttings. 

 Their strike varies from north to north-east, and their dip is 

 always, so far as can be made out, to the eastward. They 

 are soft and crumbling, and form red, yellow, and brown clays. 

 In many places on the spurs behind the township they contain 

 large irregular segregated masses of grey chalcedonic quartz, 

 often streaked or brecciated. On the range between Kuaotunu 

 and Otama there are several very large deposits of this kind 

 of quartz cropping out and forming conspicuous objects in the 

 landscape. 



At Otama and Opito the clay-shales are intruded by large 

 masses or dykes of black hornblende-andesite, forming high 

 isolated hills with rounded outlines and steep black sides. 



Besides chalcedonic quartz, the clay-shales also contain 

 veins or reefs of crystalline quartz which in many places have 

 been proved to contain payable gold. Among these may be 



