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The Pamphlet Collection of Sir Robert Stout: Volume 70

(2) Copper

(2) Copper.

Copper has been known in New Zealand since 1842, when a lode of chalcopyrite, or copper pyrites, was worked on the island of Kawau, page 43 Auckland Province, It occurs elsewhere in various forms, as native metal in the Nelson serpentine belt; near Lake Wakatipuin, Otago; at the Great Barrier Island, in Auckland; in the Perseverance Mine, Collingwood; at Maharahara, near Woodville, North Island; and in small quantities distributed in basaltic dykes traversing trachy-dolerite breccias, near the Manukau Heads, Auckland.

In addition the following ores are found:—Cuprite or red copper ore, occurs in the serpentine belt of Nelson, where it is found yielding from 10 per cent. to 88.9 per cent. It is also found at Bligh Sound, in Otago; at Tokomairiro, Otago; and at the Thames. With it is frequently associated copper glance, or chalcocita. Chalcopyrite, or copper pyrites, which has already been mentioned as having been found at Kawau, was worked for several years, with a yield of metal at first of 16 per cent., then of 8 per cent., and finally, at the deepest point, of 5 per cent. When the mine was abandoned, principally on account of the high price of coal, consequent on the recent gold discoveries, the lode was said to be 15 feet thick. The same ore has again been worked at the Great Barrier Island, Auckland, in conjunction with peacock ore, malachite, azurite, and mela-conite. At Moke Creek, near Lake Wakatipu, Otago, a lode 4 feet wide is found, consisting of 5 inches to 8 inches of chalcopyrite, and 3 feet 8 inches of gangue, with a little metallic copper scattered through it. Another locality is the Paringa River, Westland, and specimens have been obtained from the Thames, where it is associated with gold; from the Moorhouse Range (Canterbury), near Mount Cook; at Dusky Sound, on the west coast of Otago; and at Lake Okou.

The neighbourhood of Nelson has been the site of some of the most recent attempts to produce copper, and the Champion Company, though not now in operation, erected works on a scale of considerable magnitude, The lodes seem to be of the nature of contact deposits, and occur where the red and green Maitai slates, of Lower Carboniferous age, abut on massive beds of diorite and greenstone, changing on the east into compact serpentine, with large intrusive masses of the olivine rock charged with chrome iron, and known (from the Dun Mountain) as dunite.

There are in the Champion property three lodes, known respectively as the Champion, the United, and the Maitai. The first-named consists, so far as is known, of a vein of rather soft serpentine, about 4 feet thick, between walls of compact serpentine, and contains, near the hanging wall, irregular lumps of metallic copper, with various adhering sulphides and oxides. Towards the footwall are masses of magnetite and pyrrhotine, and in some portions of the lode kernels of yellow sulphide and copper page 44 glance (grey sulphide). In the United lode metallic copper does not occur, and the body of the lode is almost entirely composed of yellow sulphide. In the Maitai lode, which has not been much explored, the ore is mostly grey sulphide.

A large amount of dead-work was carried out, expensive roads were constructed, reducing works, with elaborate appliances, and laboratories were built, and everything laid out for complete copper mining and smelting. In all, the expenditure was about £34,000, and the average yield of all the ore produced, including native metal, was 7½ per cent., but owing to the decrease in the value of copper, the undertaking failed to pay. The estimated cost of producing fine copper was £28 to £29 per ton.

The Nelson mineral belt which has been alluded to extends from the Dun Mountain to D'Urville Island, and is covered by the Maitai series, which consists of green and purple slates (highly cleaved) and then calcareous slates, traversed by veins of calcspar, and passing eventually into a regular bed of limestone, beyond which the slates (still calcareous in character) again come in, and are succeeded by the serpentine which may be traced from the Dun Mountain to the Croixelles, reappearing at D'Urville Island. At this last-named locality an attempt to mine was made in 1878 and 1879, the deposit consisting of a true but patchy lode of copper glance. The average return from 50 tons shipped to Melbourne was 10 per cent., but the ore was imperfectly picked.

In the early fifties an English company expended large sums of money in an attempt to work the Dun Mountain copper deposits, near Nelson, The mine was 2,500 feet above the sea, and was connected with the port by a railway, 12½ miles long, with a gradient (for a large proportion of the distance) of 1 in 18, This and other extravagances, which were committed before sufficient ore was proved, caused failure. The company expired, and for many years the property lay idle. Of late years, however, an attempt has been made to re-start it, and evidence has been obtained that the original company did not pay so much attention to the indications of the lodes as would have been prudent. While these were being followed, rich deposits of chrome ore were met with, and money, which should have gone towards proving the copper-bearing lodes, was diverted, When the price of chrome fell the available capital had been expended, and operations ceased.

Near Nelson, in the Aniseed Valley, is an interesting occurrence of native copper, interspersed in minute grains through a matrix of granular serpentine. On analysis it was found to contain from 2 per cent, to 6 per page 45 cent. of copper. A similar deposit has been found in the Serpentine Valley, lying to the south-west of the above locality, but in neither case has much been done towards proving the continuity of the bed. In the same valley redruthite or copper glance, cuprite or red oxide, and native copper occur in bunches at the Aniseed Valley Mine, but no well-defined lode is known, and at the Red Hill Mine, near Collingwood, a dark ore with resinous lustre has been found, which proved to be an intimate mixture of zinc blende, chalcopyrite, and galena.

So long ago as 1870, a discovery was made on a claim in Bedstead Gully, Collingwood, of fine specimens of chalcopyrite, and though the prospects were at the time considered to be excellent, nothing has since been done.

In Wellington Province, copper is noted as occurring at Porirua, and at Maharahara, near Woodville, and has been for some years worked. The deposit, which was first found on the slope of the Ruahine Range by Mr. Price, and consists of the native metal with various ores, is associated with red cherty rocks and h æmatite. The writer is unaware of the precise nature of the company's operations, but the March, 1892, newspapers stated that rich ore was at that time being mined.

The west coast of the South Island contains several deposits of the metal under consideration. On the Buller River, copper was found in 1874, and on the Paparoa Range in 1886; also at the Haast River a deposit is known 2 feet in thickness, and yielding 85 per cent, of copper; this is on the face of the Okura-Matakitaki Range, and within 6 miles of coal outcrops; and it is known to occur at Paringa, None of these, however have been worked, but at Dusky Sound, in the south, mining operations have been carried on. The lode here, which is 5 feet thick, consists of chalcopyrite, with pyrrhotine and magnetic iron pyrites, and yielded from 23.5 per cent. to mere traces. The associated rock is hornblende-gneiss, which varies from hornblende-rock to felspathic-gueiss, and is traversed by veins of granite. The site is only about half a mile from the shore, where there is good anchorage, but the explorations so far have gone to prove the non-existence of any well-defined lode.

In the Province of Canterbury there are, with the exception of a deposit in the Moorhouse Range, near Mount Cook, no copper ores, but in Otago—besides those occurring on the west coast, and already mentioned—are several deposits, some of which have been worked to a small extent.

About 1865, £2,000 was expended near Waipori, Otago, in a futile effort to discover a well-defined lode, and in 1862, pyritous ore containing page 46 24 per cent. of copper was found near Ben Lomond, between Late Wakatipu and Moke Creek, This is a true lode 1½ feet thick, dipping at an angle of 15 degs. Specimens have been found at Tokomairiro, and on the Car rick Range, near Cromwell.

It will have been observed that copper ores and the native metal are widely distributed in New Zealand, at several places in Auckland, in Wellington, through the Nelson mineral belt, at Collingwood, scattered through the west coast of the South Island, in Canterbury sparingly, and in Otago at various places. Also that the yield varies from pure metal downwards. In hardly any of these places has the working been earned out with any degree of perseverance, and in many cases, no doubt, what energy has been expended was misdirected, and the difficulties attendant upon copper smelting have militated against the success of the industry. Possibly, in future years, more skilled and determined efforts will be made.

The export of copper ore has been exceedingly variable. It commenced in 1858 with 351 tons, valued at £5,000, and has never again reached anything like the same figure. For several years, as will be seen on reference to the table (see Appendix), little or none has been exported.