260 PROCEEDINGS OP SECTION C. 



the aui'iferous formation are those at Mata and Waiohanga^ 

 already described as forming the basement of the series ; but Mr. 

 Davis states that fragments of slate occur in some of the breccias 

 in Karaka Creek.* These breccias are composed of angular 

 fragments of andesite in an andersite matrix, which is in general 

 so much decomposed that I was unable, except in one case, to 

 obtain a specimen fit for microscopic examination. The single 

 exception was the breccia exposed on the beach north of Tararu 

 Creek, just below the cemetery. Here, it is a pale greyish-white 

 rock with an earthy fracture, and largely impregnated with pyrites. 

 The microscope shews an abundant divitritied ground-mass with 

 secondary quartz and leucoxene, in which lie crystals of felspar 

 decomposed into calcite, and isotropic chlorites, probably pseudo- 

 morphs after augite, but much decomposed. I have no hesitation 

 in calling the rock a decomposed lava stream. In other places 

 the matrix of the breccia passes insensibly into evidently eruptive 

 rocks. Probably all are brecciated lavas, or perhaps some of them 

 may be the friction-breccias of dykes. Mr. Davis mentions a 

 block in a breccia in Tinker's Gnlly as being itself part of an older 

 breccia,! and this may perhaps be due to a dyke breaking through 

 an older breccia. 



These breccias are by no means limited to the base of the series, 

 but occur at many horizons and in many different places beside the 

 Hape, Karaka, and Tararu Creeks. They are all, I tliink, local 

 and of small superficial extent. Mr. S. H. Cox identifies the 

 breccias of Hape Creek with that found at the bottom of the 

 shaft of the Queen of Beauty Mine.| This may be correct, but 

 similar bi^eccias are also found in the upper part of the shaft of 

 the same mine, and others in the Waiotahi and Moanataiari Creeks. 

 Another was passed through in an early diive in the Moanataiari 

 Mine,§ and another occurs at the point north of the moutirof 

 the Kuranui Creek. I see no reason for identifying the breccia 

 at the bottom of the Queen of Beauty shaft with any one of these 

 more than another ; but if Mr. Cox's view of the structure of the 

 district should turn out to be correct, four or five additional bands 

 of breccia, at least, will have to be introduced into his section. 



A microscopic study of the other rocks of the series shews that 

 they are mostly lava streams in which fluxion-structure is rare, so 

 that they must generally have consolidated after movement had 

 ceased. Only two among my specimens shew fluxion-structure. 

 One is a hornblende andesite, probably a dyke, from the north 

 side of Coromandel Hai-bour, and the other is an augite andesite, 

 certainly a lava, from rather high up Mount Te Aroha. The total 

 absence of vesicular texture in all the lavas over so wide an area, 



* Reports Geological Explorations, 1870-1, p. 65, 



t loo. cit. p. 56, 



I Reports Geological Explorations, 1882, p. 10. 



§ Reports Geological Explorations, 18(.8-9, p, 31, fig. 1. 



