246 PROCEEDINGS OF SECTION C. 



officers of the Geological Survey, who have reported on the 

 district, hold diametrically opposite opinions as to its structure. 

 If Mr. S. H. Cox is right in supposing that these limestones, &c., 

 rest uncomformably on the auriferous series,* then that series will 

 probably be Cretaceous, and the volcanic rocks of Coromandel and 

 Kennedy's Bny, may be much younger. If, however, Mr. A. 

 McKay should be right in saying that the auriferous volcanic series 

 lies uncomformably on the sedimentary series,! then the whole 

 volcanic formation must be considered as not older than Miocene 



PEE-JURASSIC ROCKS. 



These consist chiefly of dark coloured sandstones, greywackes, 

 and slates, in which no fossils have as yet been found. The only 

 rock belonging to this formation that I wish to notice is the 

 so-called felsite at Waiohanga Point, north of Graham's Town. 

 This rock was described by me in 1867, as a felsite-tufl". Afterwards 

 I called it a felstone, meaning thereby an altered eiuptive rock. 

 By Mr. E. H. Davis it was considei-ed as a clay-stone " cut through 

 by a broad band of pyritous quartz sandstone." Mr. S. H. Cox calls 

 it a felsite, but is uncertain whether it is intrusive in, or interbedded 

 with the slate rocks. When I first visited the locality in 1867-69 

 the junction between the felsite and the blue slates was hidden by 

 sand ; but last year I found the f^and washed away and the 

 junction exposed. It could then be seen distinctly that the felsite 

 was interbedded with the slates. Above the slates comes a 

 bed of felsite five feet thick, then four ieet of pale slates, and 

 then the main body of the felsite which forms the point. Both 

 the blue slates, and the white felsite, ai^e largely impregnated with 

 pyrites in places, in other places they are free from it. 



I'he felsite is creamy white with an earthy fracture and a 

 hardness of about three. It is irregularly jointed in three directions, 

 and the joints are so numerous that it is difiicult to get good 

 specimens shewing a fresh fracture. To the naked eye it is dis- 

 tinctly vesicular, the vesicles being minute and irregularly scattered. 

 It is not laminated, but occasionally there are bands of a coarser 

 material in it. "Where it is vesicular there is no pyrites, and the 

 vesicles are probably due to the removal of the latter. Under the 

 microscope, with an inch objective and ordinary light, it is seen to 

 be very finely granular, with minute specks of an opaque white 

 mineral like leucoxene. In places there are rather sharply-defined 

 clouds of lighter and darker, but no distinctly crystalline forms. 

 Occasionally narrow pale bands run thi'ough it, in which larger 

 masses of the opaque white mineral are collected. The vesicles 

 are either rounded or angular, and are no doubt due to the 

 decomposition of pyrites. With polarized light and crossed nicols 



* Reports, Geological Explorations, 1882, p. 19, 



t Reports, Geographical Explorations, 1885, p. 98, &c. 



