HurroN.—On the Thames Gold Fields. 273 
alluvial gold washed from the higher grounds. к " : On the 
slope of the hills I saw large blocks of quartz lying, which, from all appearances, 
originated from reefs or veins that—according to the statement of 
Mr. Heaphy—protrude on the top of the dividing range in various places, like 
. walls, eight to ten feet high, and ten to twenty feet thick. * * е 
The Coromandel gold fields —such was my opinion in 1859—bid fair to grow 
into importance in future years when the auriferous quartz reefs themselves 
shall have been discovered." (“New Zealand," p. 96, ez 8eq.) 
In June, 1864, and in February, 1866, Dr. Hector visited Coromandel, 
and the opinion he then formed of the structure of the country is thus given 
in his instructions to me in August, 1867 (Geological Report on the Thames 
Gold Field, by Captain Hutton, September, 1867. Extract from Dr. Hector's 
instructions, p. 2):—*« The range which separates the Thames Valley from the 
Bay of Plenty I found to consist of a nucleus of aphanite slates, interbedded 
with green brecciated and greywacke slates, being part of the upper palæozoic 
series. Flanking and capping this nucleus is a great development of the 
following members of the tertiary series :—(a.) brown coal formation, very 
local; (b.) quartzose gravels, cemented so that they break away in large 
blocks; (c.) Waitemata series (pliocene); (d.) trachytic tuff; (е.) trachytie 
breccia. The palsozoic rocks are cut by dykes of trachyte (granite of the 
miners), which is charged with auriferous and cupreous iron pyrites. They, 
moreover, contain quartz veins, which are also pyritiferous and auriferous, 
The older rocks decompose very freely to laterite, and the fissures then contain 
secondary deposits of silica, manganese, etc., especially when near the supposed 
trachyte dykes, alongside of which, in some cases, there would seem to have 
been fissures that were only gradually filled up by deposits from thermal 
waters, giving rise to the banded, irregular, and crystalline structure of the 
lodes which is so characteristic of Coromandel, * * т А third 
manner іп which quartz occurs in the district is in the trachyte tufas, but it is 
then more chalcedonic and erystalline, and associated with jasper and chert, 
and is non-auriferous, as proved by the numerous trials at Keeven's Point, 
Coromandel.” And further on he instructs me to “search for the grey 
pyritiferous rock" (i.¢., the dykes of trachyte), “in the beds of the streams.” 
Dr. Hector's opinion, therefore, agreed with that of Dr. Hochstetter, but 
he pointed out that the gold reefs (some of which had meanwhile been 
discovered and were then being worked), were not found in the slates, but in 
the grey pyritiferous rock, which he took to be dykes of trachyte. 
Hitherto gold had only been known at Coromandel, but in August, 1867, 
it was also found near Shortland; and in September of that year I was sent 
by Dr. Hector to examine the new discoveries, and I then reported that the 
country was * almost entirely composed of a huge mass of trachyte tufa 
81 
