HuTTON. — On the Thames Gold Fields. 273 



alluvial gold washed from the higher grounds. * * * q^ ^j^q 



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. * * * 



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, et seq.) 



In Jvine, 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 palaeozoic 

 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 3 (c.) Waitemata series (pliocene); {d.) trachytic tuff; (e.) trachytic 

 breccia. The palaeozoic 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. * * * ^ third 



manner in which quartz occurs in the district is in the trachyte tufas, but it is 

 then more chalcedonic and crystalline, 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.e., 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 



Si 



