THE GEOLOGY OF AUCKLAND. 
15 
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 
surrounding 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 amorphous character 
—that is, not crystalline, but in the shape of chalcedony, cor¬ 
nelian, agate, and jasper—are found in numerous places on the 
shores of Coromandel. These veins occurring in trachytic tucks, 
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 docs 
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 crvstalline veins in the 
primary rocks. The surface-deposit in those creeks is very rich, 
but, as compared with Australian and Californian gold-fields, of 
limited extent and depth. I washed a few bucketsful of sur¬ 
face earth, and gravel, at a creek pointed out to me by Mr. 
Charles Heaphy, near Ring’s Mill, at the Kapanga. Every 
panful showed scales of thin gold, with small fragments of quartz 
streaked and studded with veins and spangles of gold. These 
“ specimens,” as they are called by diggers, show no—or very 
little—sign of being water-worn, but are sharp and crisp frag¬ 
ments, as if they had been broken up on the spot, or in the 
immediate vicinity. I think the quartz veins in the mountains 
should be thoroughly examined, and that, when once the day 
has come that the Coromandel gold-fields are worked, the atten¬ 
tion of the “ digger ” should be directed as well to the hills 
immediately above any rich deposits as to the alluvial workings 
below. 
