Geological Survey Branch.
During the year the following extensions of the survey have been made, the special reports on which are printed in the annual progress report of this department (Fifteenth Annual Report, 1880–81):—
On the Chrome Deposits in the vicinity of Nelson.—The discovery of several new applications of chrome salts in the arts, and notably the proposal to use it for tanning leather, having, revived an interest in this ore, various lodes, some of which have recently been discovered, were carefully examined with a view of determining if they could supply the market successfully at the present prices. The result shows that there are lodes of chromic iron ore in ten different localities, containing from 36 to 64 per cent. of chromic oxide, but that many of them are in such inaccessible positions that they would not pay the expense of carriage. As to this must be added the freight to London, which is 15s. per ton, Mr. Cox is of opinion that, instead of shipping the crude ore, works should be established for the local production of the bichromate of potash. Mr. Cox also examined the further exploratory works that have been made for opening up the copper lodes in Aniseed Valley, and reports that, as a mining venture, its prospects are still somewhat speculative, as for want of capital the exploration of the lodes has not been carried on in a sufficiently satisfactory manner.
The Richmond Hill Silver Mine was also re-examined as far as possible, considering that the main shaft is full of water. It is pointed out that an expenditure of £100 should be sufficient to repair the water-race, and that the present water-wheel would be then sufficient to pump the mine, and afterwards to compress air for working rock-drills, the past failure of the mine being evidently due to the use of hand-drilling alone, which is not suitable for following patchy ore shoots in such hard ground. As besides silver varying from 21 to 179 ozs. per ton, the ore contains lead, copper, antimony, bismuth, nickel, and zinc, it is certainly worth following up, but it is considered that it would not be advisable to commence with a less paid-up capital than £10,000.
The Collingwood Coal Mine was examined with the view of advising on the most judicious manner of extending the workings.
Mr. Cox spent three months in continuing the survey of the North Auckland District, and in examining certain mineral deposits at Kawau, Coromandel, and the Thames; also Drury and Waikato Coal Fields; and he obtained valuable results that are detailed in his reports. Two months were
next occupied by Mr. Cox in the examination of the geology of the mountains lying between the Takaka and Aorere Valleys in the northwest part of Nelson District, and, in his report, he points out the importance of the mineral deposits which occur in the Lower Devonian rocks.
From September to April, Mr. McKay was engaged in geologically mapping a section between the east coast at the mouth of the Waitaki River, and the main watershed lying west of the Wanaka Lake. In the course of this survey, he examined in detail the structure of a strip of country about 10 miles in average width, and extending for a distance of 120 miles inland from the east coast. In the Waitaki Valley he completely cleared up the evidence on which the subdivision of the Lower Tertiary and Upper Cretaceous strata had been proposed, and obtained, a large addition to the collection of fossils. He also proved the existence in the first-named range of mountains of the Permian and Upper Devonian formations, and refers the highly-altered slates and sandstones of the Kurow Mountains to the Lower Devonian group, identifying them with the rocks of the Walter Cecil Peaks south-west of Wakatipu Lake. He further found that the silicious rocks charged with mineral veins, at the source of the Arrow and Shotover Rivers, overlie the older schists of Central Otago, and in the higher points of the Black Peak Range found them to be traversed by dykes of igneous rocks, and to afford other indications of their being probably intersected by rich mineral lodes. In the Devonian formation in South-east Canterbury he found a local development of white felspathic rocks charged with auriferous pyrites, which in their mineral character closely approach the auriferous rocks of Coromandel Peninsula, and which, on further examination, may prove of importance to the miner.