276 Transactioois. — Geology. 



I think, therefore, that the following is a fair statement of the present 

 position of the case. 



Professor Hochstetter said that there is at Coromandel a tertiary trachytic 

 formation overlying vertical beds of clay-slate and lydian stone of palseozoic 

 age, and he thought that the gold would be found only in the slates and not in 

 the trachytic formation. Dr. Hector also says that there is a trachytic 

 formation overlying slates, but that the gold is principally found in neither 

 one nor the other, but in a distinct volcanic formation which is considerably 

 older than the trachytes, having partaken in the movements and foldings of 

 the clay-slates. 



Mr. Davis appears to have agreed with Dr. Hector. 



I agree with Professor Hochstetter that there is a tertiary trachytic 

 formation overlying clay-slates, but say that the gold has been almost entirely 

 obtained from the trachytic formation, and not from the slates ; and I deny 

 the existence of Dr. Hector's " greenstone tufa" formation as distinct from the 

 tertiary trachytic one. 



As it is now an undisputed fact that the principal mines are situated in 

 a felspathic rock, and not in the slates, the question at issue is reduced to this : 

 Is this felspathic rock part of the tertiary trachytic series, or is it part of a 

 distinct formation more closely related in age to the clay-slates than to the 

 trachyte tuffs, which have been deposited unconformably on its upturned 

 edges ? 



I will, in the first place, examine all the evidence that I can find in 

 Dr. Hector's and Mr. Davis' reports in favour of the distinctness between the 

 " greenstone tufa" and " trachyte tufa" formations, and then I will state the 

 evidence on which I rely for proving that they are one and the same. 



1. Lithological Evidence. — Mi\ Davis, in his report on the Shortland 

 district [I.e. passim), seems to lay stress on the great diversity of appearance 

 in the rocks found there, as proving that more than one formation must exist ; 

 at the same time he makes no attempt to trace out these different formations. 

 Dr. Hector, also, by calling his two foi'mations "greenstone tufa" and 

 " trachyte tufa" would seem to imply that, besides a stratigraphical break, a 

 difference could also be made out in the chemical composition of his two 

 formations. But to show the extreme difiiculty that Dr. Hector and Mr. Davis 

 must find in distinguishing between the rocks of their older and younger 

 formations, I may point out that Dr. Hector, in his instructions to me in 

 1867, states that Keeven's Point, at Coromandel, is composed of non-auriferous 

 trachyte tufa belonging to the younger formation {I.e., p. 2) ; while, in his 

 report of April, 1870, he calls it a tufaceous porphyry, originally a clay-stone 

 porphyry {I.e., p. 90), and again (p. 92) a grey tufaceous sandstone "like that 

 at Kapanga and Tokatea," in both cases including it now in his older 



