186 
THE GEOLOGIST. 
The gold wliicli is waslied out from beds of quavtz-gravel in the rivers and 
creeks lowing down from botli sides of Coromandel range, is derived from 
quartz 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 uj) 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 
wiiich form the chauuels of the principal streams. In ahnost all places it is 
covered by large masses of trachytic tuff and breccia, of which the hiUs 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 all the magnetic iron- 
sand of New Zealand, namely, from the decomposition of trachytic rocks. 
Small veins of quartz of amorohous character — that is, not crystiilline, but in. 
the shape of chalcedony, cornelian, agate, and jasper— are found in numerous 
places on the shores of Coromandel. These vems occm-ring in trachytic rocks, 
are quite different from the auriferous quartz vems 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. All 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 occurring 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 eastward 
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 Waii'ere, the Mokau river falls in 
a magnificent cascade over a lofty precipice. 
The same formation occurs again in 'the Rangitoto mountain on the Upper 
"VVaijia, and west of Taupo lake in the Tuhua mountains. But the most ex- 
tensive range of primary rocks is that which commences near Wellington, under 
the name of Tararua and Ruawahine, and runs in a north-easterly du'cction to 
the east shore of Taupo lake, under the name of Kaimanawa, in which rises 
the principal source of the Waikato, there called Tongariro river. The range 
continues from the shores of Taupo lake, in a north-easterly direction, to the 
East Cape, under the principal name of Tewhaiti. This lofty and extensive 
mountain range — the true backbone of the Northern Island — with peaks from 
six thousand to seven thousand feet, is entirely unknown. In this range the 
plutonic and metamorphic rocks, yet unknown in the Northern Island, may, 
perhaps, be found. 
* Dr. Hochstetter wa.shed a few buckets of sm-face-eaj'th and gravel, at a creek pointed 
out by Mr. Charles Heaphy, near King's Mill, at the Kapanga. Every panful showed scales 
of thin gold, with small fragments of (juartz streaked and studded with veins and spangles 
of gold. These " specimens," as they arc caUed by diggers, show no, or very little, sign of 
being water-worn, but are sharp and crisp fragments, as if they had been broken up on the 
spot, or in the immediate vicinity. The (|uart7. veins in Uie momitains should be thoroughly 
examined, and when once the day has come tliat the Coromandel gold-fields are worked, the 
attention of the digger should Ijo directed as well to the hills immediately above any rich 
deposits as to the alluvial workings below. 
