186 



THE GEOLOGIST. 



The gold which is washed out from beds of quartz-gravel in the rivers and 

 cr ^eks flowing down from both sides of Coromandel range, is derived from 

 qn irtz veins of crystalline character and considerable thickness, running in a 

 general direction' from north to south, through the old primary rocks which 

 form the foundation of the Coromandel range. In some places these veins 

 stand up like a wall on the summit of the range to a height of eight or ten 

 feet. The clay-slate rock itself is exposed only at the bottom of deep gorges 

 which form the channels of the principal streams. In almost all places it is 

 covered by large masses of trachytic tuff and breccia, of which the hills sur- 

 rounding the harbour of Coromandel are composed. The well-known " Castle 

 Hill," which can be seen from Auckland, is a characteristic example of the 

 trachytic breccia formation. The magnetic iron-sand, which, in washing, is 

 found with the gold, is derived from the same source as aU the magnetic iron- 

 sand of New Zealand, namely, from the decomposition of trachytic rocks. 

 Small vems of quartz of amorphous character — that is, not crystalline, but in 

 the shape of chalcedony, cornelian, agate, and jasper — are found in numerous 

 places on the shores of Coromandel. These veins occurring in trachytic rocks, 

 are quite different from the auriferous quartz veins in the primary formation — 

 a fact, I think, of much practical importance to state, to prevent the fruitless 

 search for gold where gold does not exist. AU the gold-bearing gravel in the 

 creeks is derived, as I have already said, not from the veins in the trachytic 

 breccia, but from the much thicker and crystalline veins in the primary rocks. 



The surface-deposit in those creeks is very rich, but, as compared with Aus- 

 tralian and Californian gold-fields, of limited extent and depth.* 



The coal beds at Coromandel occurriDg between strata of trachytic breccia 

 are too thin to be of any value, and as the coal formation is absent there is no 

 ground for hoping that a workable seam may be found. 



The primary formation occurs to a more considerable extent to the eastAvard 

 of Auckland, in ranges on both sides of the Wairoa river, attaining an altitude 

 of one thousand five hundred feet above the sea, and striking from thence 

 northwards, over Waiheki and Kawau, to the Bay of Islands. In a southerly 

 direction they extend through the Hangawera and Taupiri ranges, across 

 the Waikato, through the Hakari-mata and Hauturu range, parallel with the 

 west coast, to the Mokau district, where, at Wairere, the Mokau river falls in 

 a magnificent cascade o^ er a lofty precipice. 



The same formation occurs again in the Rangitoto mountain on the Upper 

 Wnipa, and west of Taupo lake in the Tuhua mountains. But the most ex- 

 tcDsive range of primary rocks is that which commences near Wellington, under 

 the name of T'ararua and Iluawahine, and runs in a north-easterly direction to 

 the east shore of Taupo lake, under the name of Kaimanawa, in which rises 

 the princii)al source of the VVaikato, there called Tongariro river. The range 

 colli iiincs from the shores of Taupo lake, in a nortli-ejisterly direction, to the 

 KasI Cajir, under the principal name of Tewhaiti. This lofty and extensive 

 moil ill aiii r;ingc — the true backbone of the Northern Island — with peaks from 

 six lliousaiul lo seven thousand feet, is entirely unknown. In this range the 

 philonic and mot amorphic rocks, yet unknown in the Northern Islanct, may, 

 perhaps, be found. 



* Pr. Tloclisioltor washed a few Inickots of surfiice-cartli and sravel, at a creek pointed 

 O'ltby Mr. Chaiies lle:\]thy. near Kinu-"s Mill. m. the Ka]iani-a. Every pa nfnl showed scales 

 of thin sold, with .small fra.u-nuMits oi' ((uartz streaked and studded with vems and sp.anglos 

 of _i;old. These " speeiniens," as Ihoy are called hy d'c.Licrs, show no, or very little, sign of 

 being water-worn, but are sharji and Va-isji I'vacnieni's. as if thev had been broken up on the 

 spot, or in the hnmetUate vicinity. The (|uart/. vi, ins ui the mountains should l)e thoronglily 

 cxMimned, and when once the day has rome that- the Corinuandel Gold-fields are worked, the 

 intention of the digu-cr should lu' diroctt'd as well to the hills immediately alwve any rich 

 deposits as to the alluvial workinL;s below. 



