Geological and other Reports
Manawatu, October 21, 1862
As an examination of the rocks of the Province of Wellington has hitherto only resulted in the discovery of small samples of gold, and has failed to discover that metal in workable quantities, the question arises in what line, or direction, we ought to expect to find gold in the Northern Island.
Some years ago and before the opening of the Otago Gold Diggings, but subsequent to the discovery of those at the Buller river, I pointed out in a letter to the newspapers, that a continuation of a line, through the Gold districts of the Middle Island to Coromandel, would intersect the country lying between the Whanganui river and Taranaki and that on that line, supposing the tertiary rocks did not entirely cover the country, the gold bearing rocks would probably be found.
This line is in a bearing of about N.N E, and S S.W., nearly the line of the Magnetic Meridian.
Subsequent observations and discoveries, tend to confirm the probability that this is the true line, or rather zone, in which to look for the gold bearing rocks.
From the specimens which I have seen from Otago, from the Buller river, and elsewhere in the Middle Island, micaceous and talcose schists and micaceous rocks generally, associated with quartz, seem to be those most favourable for the finding of gold. Now the rocks of the Western ranges of the Middle Island are very micaceous, while those of the Eastern Ranges, minerologically the same as the main range of the North Island, contain little mica, and are principally silicious slates and crystalline sandstones, associated with serpentinous rocks.
There appears to be a remarkable parallelism in the ancient New Zealand rocks. The main range of the North Island, in which Wellington is situated, traverses the Island in a N.N.E. direction from Cook's Strait, and reaches the sea in the Bay of Plenty about six miles from the East Cape. This range, having rocks of similar mineralogical character, crosses the Strait, and proceeds in a curve into the Canterbury Province, and so on to the Southward. Behind it, in the Otago Province, the gold bearing mica schists would appear to curve round somewhat to the Eastward. The Eastern range, composed principally of silicious slates, and crystalline sandstones, all highly inclined, appears to contain some gold, but none has yet been found in payable quantities.
As far as my examination extended in the Taupo country and at the head waters of the Whanganui, the few ancient cocks which I found there, either “in situ” or as boulders, consisted only of siliceous slutes, or semi crystalline sandstones,—no mica schists, nor gneiss, nor granites; but the line of my journey was still to the Eastward of what may be the gold bearing zone.
As evidence of a gold bearing zone running through the North Island, taking the Coromandel as a starting point, we hear of gold quartz being discovered at the Wairoa, not far from Auckland,—next, I am credibly informed. that gold quartz is common in e Hangawera range, which separates the Waikato from the Thames valley and next, I have the authority of Sir George Grey for stating, that a rich piece of gold quartz was brought to him by a native from Titi Raupenga, a place distant a journey of a day and a half N.N.W. from Pukawa on Lake Taupo. I have also to add to this, information which I have received from Mr. Fitzherbert, that samples of the iron sand of Taranaki, sent by him to be analized, were reported to contain traces of gold.
Should the above view of the line of the gold bearing rocks seem theoretically good, the question arises in which way the existence of gold can best be proved. I believe that point can be most satisfactorily arrived at by traversing the gold bearing rocks in the Province of Auckland, from the Coromandel towards the Waikato and Waipa districts, and finding how far they can be traced to the South.
I would here point out, that although volcanic regions are generally considered unlikely for metals, yet immense areas of the Gold Fields of Victoria are covered by a sheet of trap, and as yet I know no reason why the age of eruption of Mount Egmont should not be the same as that of the extinct volcanic region of Victoria, and therefore infer the possibility that the Trachytes of Taranaki may cover gold bearing drifts.
Again, with regard to gold drifts, Mr. Selwyn reports three distinct gold drifts in Victoria, the oldest being of miocene age. Now although the West Coast of this Island is covered to a considerable thickness with sedimentary tertiary rocks, the oldest of which is probably of miocene age, there is no impossibility that a gold bearing drift of about the same age, should underlie these marine formations. For supposing the gold bearing rocks to lie beneath, they are likely to have been much abraded, during the depression preceeding the deposition of the tertiaries.
The supposed gold bearing zone, commencing at Coromandel, will cross the courses of the rivers Thames and Waikato, pass through Otawhao and through the Waipa valley, traverse the country lying between the Whanganui river and Taranaki, and so on to the Nelson Gold Fields across the Strait. The southern part of this zone in the North Island is very much, perhaps entirely, covered by tertiary rocks, but I have reason to suppose from the evidence previously given, and from other information, that in the Auckland Province the older rocks may be more exposed.
I have the honor to be,
Your Obedient Servant,
James C. Crawford,