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The Pamphlet Collection of Sir Robert Stout: Volume 70

(1)—Quartz or Lode-Mining

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(1)—Quartz or Lode-Mining.

(a) Volcanic Series of Auckland.

Commencing with the northern portion of the colony the reefs of the Auckland provincial district first claim attention, and with the exception of an isolated patch near Wellington, where quartz reefs have been worked in the Maitai slates (Carboniferous), the North Island contains no other gold-field,

Gold was discovered in Auckland in the year 1852, but from the first the progress of the field was much retarded by opposition from the native owners of the soil, and the subsequent discovery of alluvial gold in great profusion in the South Island caused an exodus of the mining population, which was further intensified by the breaking out of hostilities in the year 1863. In 1867, however, peace having been restored, arrangements were made with the Maories for the opening up of the land, and on July 30th the gold-field was proclaimed. The first results were disappointing; instead of the rich alluvial deposits which had characterized the South Island, but little ground of this nature was found, and when at last a rich leader of quartz was discovered, the gold proved to be of very poor quality. This peculiarity still remains, the bullion yielding generally 54 to 75 per cent, of gold and 40 to 20 per cent, of silver, In spite of these early drawbacks the reefs have turned out fabulously rich; in some cases the yield has been for considerable distances at the rate of 600 ounces to the ton. So far from becoming poorer, as they have been worked to deeper levels, these lodes have maintained their yield, and It was the opinion of scientific men well acquainted with the fields that, as operations were continued to a greater depth, the supply of gold would not only be kept up but would probably be increased, Until recently the claims have depended principally on the rich leaders of quartz which occur, but of late years more attention has been paid to the large bodies of stone, popularly called barren or buck reefs, which exist. These are of enormous size, and give from 3 dwts. to 8 dwts. to the ton, with the possibility of opening up rich leaders, and there is no doubt that with improved appliances they can be made to pay handsomely.

The extremely complex nature of many of the ores renders their treatment very difficult, and year by year improvements in this direction are being made. The ordinary crushing battery and amalgamation processes are practically useless; before the tailings at Te Aroha were preserved for treatment the lowest estimate of the annual loss was £20,000. At Waihi the tailings were found to be worth £15 per ton, page 5 and for many years they were permitted to flow away without any regard to their value. The ones consist of a mixture of silica and various compounds of iron, copper, lead, zinc, antimony, arsenic, silver, sulphur, tellurium, and gold, and no process short of either smelting or chemical treatment will suffice to free the gold from these metals which it is not desired to extract, Unfortunately, in the locality under consideration, fuel and fluxes are scarce, and nothing therefore remains but to separate the metalliferous portion from the matrix and treat the former by a variety of processes. Many plans have, with more or less success, been tried, and at present the Oassell Gold Extraction Company appear to have grappled with the difficulty. Their process depends on the solvent action of cyanides—usually, in practice, cyanide of potassium—on the gold ore in preference to the sulphides of the base metals with which it is associated. The gold Is subsequently precipitated by the action of porous or filiform zinc. The cost of this system is somewhat heavy, and ores ranging below £2 per ton in value cannot be remuneratively subjected to it, but the percentage of bullion obtained is very high, having, during 1890, at the Crown Company's mine at Karangahake, averaged 93 per cent, of the gold and 79 per cent, of the contained silver.

Generally speaking, the machinery in this gold-field is of a class which compares very favourably with that in use elsewhere in the colony. Self-acting surface, and aerial tramways are used for bringing down the quartz, and one of the latter consists of a single span, 1,090 feet in length. At Grahamstown the claims are worked several hundred feet below sea-level, and an 82-inches bull, direct-acting, condensing engine, capable of making a 10-feet stroke, was purchased and erected by the Government, at a cost of £50,000. The pumps are 24 inches in diameter, and the height of lift 500 feet. The cost of working this engine is £320 to £330 per month, with coal from kamo, delivered at 17s. 1½d, per ton. A Drainage Board manages the concern, the Borough and County Councils contributing £35 a month, while the balance is made up by thirteen mining companies.

Water is very plentiful on the field, and is largely used as a motive power. The Pelton water-wheel is generally employed to drive machinery either for crushing, treating, or illuminating purposes. Stamper batteries are used for reducing the quartz, which is frequently first passed through a stone breaker; berdans are very common on the field. Some of the battery plants are of considerable size, that at the Waitekauri Mine consists of 40 head of stampers, and the Wailn Company has recently put up a plant which is stated to have cost about £60,000.

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Wages in the Auckland district vary from £2 5s. to £2 8s. per week for miners, and the cost of living is low when compared with other gold-fields. There were 1,387 miners employed in 1800, or 299 less than in 1889; all these were Europeans, The yield of gold for 1890 was £125,760, and for 1889 £113,191, and the number of stampers in the former year was 599, The total quantity of gold entered for export to December 31st, 1890, was 1,689,357 ounces of the value of £6,122,173.

Under The Mining Companies Act, 1886, and Amendment Act, 1890, registered companies are compelled to publish (at their own expense) certain details with regard to their position and proceedings, This return for 1890 shows that there were during that year in the Auckland district, 91 companies, having a nominal capital of £1,710,730, £1,501,088 of which was subscribed, and £106,684 paid-up, while £295,232 is returned as the value of scrip given to shareholders, and £255,765 as the total dividends paid. If we deduct from these last figures £243,141 paid by five companies there is not much left among the other 86, but most of these were only registered in 1890.

The following table gives the yield from the northern gold-fields:— District. No. of Tons of Quartz or Mullock Crushed or Sold. Yield of Gold in Ounces. Average Yield of Gold per Ton in Ounces. Coromandel, April 1st, 1880, to March 31st, 1891 20,751 66,069 Oz. Dwt. Gr 3 6 8 Thames (including Ohinemuri, up to 1886-1887) April 1st, 1878, to March 31st, 1891 503,144 594,991 1 3 15 Ohinemuri, April 1st, 1887, to March 31st, 1891 20,858 28,563 1 7 4 Te Aroha, April 1st, 1883, to March 31st, 1891 40,320 47,286 1 3 11 Totals 85,073 736.909 1 5 4

This yield is obviously extremely rich when contrasted with many other reefs in different parts of the world. In Victoria, for instance, during the years 1884-85, the average yield from all the quartz-reefing districts was less than 10 dwts. to the ton.

The geology of this neighbourhood and the occurrence of the reefs are of extreme interest. The rock forming their matrix is of volcanic origin, and of a felsitic character, decomposed in parts and freely pyritous.

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It has been called tufanite by Hector, who considers it of Cretaceo-Tertiary age. The whole formation rests unconformably upon the upturned edges of the slates which form the basenient-rocks of the Cape Colville Peninsula. Mr. Cox, who devoted great attention to the mode of occurrence of the gold, has come to the following amongst other valuable conclusions:—that the steepest parts of the reefs are usually the richest; in order that the reefs may be gold-bearing, it is impeartive for them to be passing through a certain class of ground; and a moderately hard tufaceous sandstone has been found to be the most productive.

As is usual in metalliferous mines, ventilation is not a very important consideration, but the water contains free sulphuric acid, and as ealeite is plentifully associated with the reefs, large volumes of carbonic acid gas are produced, which occasion difficulty and not infrequently danger. This free acid acting on decomposed marcasite and pyrite gives rise to the formation of stalactittc melanterite, which is an interesting feature hi the underground workings, but has not been commercially utilized.

(b) Clay-slate series of Wellington and the West Coast of South Island.

Since 1862, gold has been known to exist in the ranges near Cape Terawhiti, and between that date and 1883, occasional discoveries of small quantities have been made. In that year a considerable amount of excitement was caused by the discovery of auriferous reefs, and the country was examined and favourably reported on by experts, but the energies of the adventurers were directed more towards promoting companies than proving the ground, and the result naturally was that the field was abandoned. So far as the writer is aware, nothing has been done recently.

Before considering the great reefing country of the west coast it is necessary to mention the Marlborough gold-field, situated in the northeastern extremity of the South Island, Gold was first discovered in this province in 1860, but though a large amount of alluvial gold has been obtained, quartz-reefing has hung fire. Only two companies were at work in 1890, one a colonial proprietary, and the other with its headquarters in London.

West Coast Gold-fields.

The whole of the west coast of the South Island is auriferous, in many places richly so. Generally speaking, the country is clad with dense forests, covering the high mountain range, which runs from one extremity to the other. Traversing this range are large rapid rivers, subject to heavy and sudden floods. In consequence of these natural difficulties, the early explorers underwent great danger and privation, and, in addition, the page 8 natives showed great opposition to the intruders. It was not until 1856 that this obstacle was removed. All the rivers have shifting sand-bars at their mouths, and the early navigation was a matter of extreme risk, The first explorations were made from the Nelson base, and in 1863 a party started from Christchurch on the east coast to find a route by the headwaters of the Rakaia River, The task was almost impossible. In one day of ten hours the explorers, notwithstanding the greatest exertions, made an advance of about 200 yards. The expedition ended in disaster. Mr. Whitcombe, a surveyor, after many days of incredible hardship, was drowned while attempting to cross the Teremakau River, and his companion, a Swiss, named Louper, managed to reach a settlement of Maories. The party discovered a little gold, but alluvial deposits only, and it was not until 1864 that quartz reefs are mentioned.

For convenience it may be better to commence at the northern, or Blind Bay, portion of this large district, that being, although not of much importance from a quartz-reefing point of view, perhaps the richest mineral locality in New Zealand, so far as regards variety of ores.

So early as 1853 auriferous quartz specimens were brought from Takaka, but at the time little excitement was caused.

Since then, intermittent efforts have been made to work reefs, bat with poor success. Not that this failure is necessarily due to the poverty of the stone, for rich patches have been found, as, for instance, at the Phoenix Mines, which is stated by Dr. (now Sir James) Hector to have produced in 1877 stone yielding at the rate of 22 ounces of gold to the ton. The reef here occurs nesting on a grey tufaceous sandstone strongly impregnated with iron pyrites, and lies parallel with the junction of the dark blue slates and the overlying felspathic schists. On the western side of the range at Golden Ridge, quartz reefs occur in black slates containing graptolites.

Passing on our way the deserted districts of Mount Arthur and Owen, we arrive at the town of Reefton, where quartz-mining commenced in the year 1870, and from which large, though not uniform, returns have been obtained.

The town itself is about 50 miles equidistant from the seaports of Westport and Greymouth, and has, until recently, suffered from considerable difficulty in communication with the coast. This naturally increased the cost of stores and retarded prospecting, besides augmenting the cost of working. There was also a tendency to "boom" when "wildcat "schemes, which never had any chance of success, were freely floated and as freely sank, and it will be understood that the district has had a page 9 good deal to contend with. The country is excedingly rich and well supplied with water, timber, and excellent coal. Railway communication with Greymouth was established in February. 1892, and steady application of the natural resources of the district will no doubt eventually bring the mines into well-deserved prominence.

The quartz reefs occur in Devonian and Carboniferous slates, which are tilted at high angles, and contain (in the former formation) many characteristic fossils. Below these are metamorphic rocks, considered for stratigraphical reasons to be of Silurian age, and containing in their softer parts the auriferous reefs of the Lyell district.

Many mines are at work, some paying good dividends. The Welcome Company at Boat mans may be taken as a typical example of a prosperous concern, though for some time it has been under a cloud. To the end of 1886 the paid-up capital, in cash, was £5,750, and £7,500 was given to the shareholders as paid-up scrip. £110,250 had been paid in dividends, and the total value of gold obtained was £222,808, while the value in 1886 was £17,877, During 18U0 only five men were employed, but latest advices tend to show that prospects now are a little brighter, and even with so little attention the property yielded during 1888, 1889), and 1890 no less than £28,207.

Taking thirty-three mines which had crushed atone in this locality during the same period, the capital called up is £65,594; £96,575 has been paid as dividends, and £310,692 worth of gold has been produced.

The claims at Reefton are worked both by shafts and adits; the machinery is of first-rate description, compressed air and rock-drills being extensively used. The town is lighted by electricity, the roads and tracks in the neighbourhood are good, and the field has a great future before it.

In other parts of the west coast are auriferous reefs, as at Ross, but at present they are doing little or nothing, and time alone will show whether they are worthy of attention.

(c) Schist Series of Otago.

Leaving the west coast, covered with dense forests and blessed—so far as the gold-miner is concerned—with a very copious rainfall, the province of Otago is reached, for the most part devoid of timber and possessing a very much drier climate. The reefs occur in a great formation of contorted phyllites and schists, which occupies nearly 8,000 square miles of this province, and which is of unknown age, possibly Silurian, or—according to Hector—even its late as Lower Carboniferous.

Near the town of Palmerston the Nenthorn reefs occur. These page 10 sprang into sudden notice a few years ago, and rich but small reefs were found to exist in great profusion, and the usual craze supervened. Before proving the properties, crushing plants were erected, water races cut and expenses incurred in every direction. At very shallow depths the rich yields ceased, and disaster came upon the field, Some day, no doubt, it will receive a proper trial; and it frequently happens in cases of this kind that when a quantity of machinery has been prematurely brought upon the ground, and the reaction after a baseless excitement has caused a cessation of operations, future adventurers, who work without the expensive paraphernalia of a limited company, and with cheap machinery, reap a rich harvest.

Farther in the interior lies the Cromwell gold-field, where there is now but little reefing. An English company, with a capital of £108,000, has been engaged in re-opening the old Cromwell Quartz Mine, from which, in the early days, one private party obtained gold valued at £500,000, and a subsequent company about £100,000. The machinery is of an excellent character; electric light, compressed air, and rock-drills. Ample water-power is available, and if only some of the formerly-worked rich rock can be found, fortune will favour the spirited proprietors,

In the neighbourhood of Lake Wakatipu are several quartz mines, the most noteworthy being the Phoenix, which has been worked since 1863, when it was the first quartz mine in the South Island, So far as is known, about 20,000 ounces of gold have been taken out of the ground since the commencement-Since 1885, electric transmission of power has been in use for driving the machinery at the mine and battery, which are about two miles from a pair of 6-feet Pelton wheels, driven by water with a vertical head of about 170 feet. The current is conveyed by a copper wire to a motor in the battery building, where the machinery, consisting of thirty stampers, two air-compressors, and a rock'-breaker, is situated. From the last advices the yield of gold appeal's to be very good, and during the last four weeks of 1891, 267 ounces were obtained.

One quartz mine in this neighbourhood is worked at an altitude of 7,400 feet above sea-level.

Farther to the south are isolated reef workings, but they have not, so far, met with any conspicuous success.

In the vicinity of Dunedin is an auriferous deposit, which—not on account of the rich yield from it, for that is yet to come, but on account of its lithological character—is of considerable interest. The matrix is described by Professor Ulrich as a peculiar, hard, diorite-like rock, the structure being holocrystalline and medium coarse-grained; the mineral page 11 constituents are triclinic felspar, hornblende, and some quartz, with iron pyrites finely and uniformly impregnated, more especially through the hornblende part. He considers that a whitish mass overlying the crystalline rock is either a decomposition-product or move probably a decomposed rock of genuine trachytic type which has flowed over the other. This is indicated, he states, by the fact that on its line of continuation only a few feet distant from the shaft, there exists on the hillside a massive outcrop of hard rook, which, according to all appearance, is of trachytic origin, consisting of a very fine-grained greyish or yellowish-white base, with impregnated crystals of sanidine-like felspar, hornblende not being observable.

Several trials have been made to work the deposit, and have yielded respectively 7½ dwts. to 10 dwts., 8 dwts., and up to 1 oz. per ton, but for some years nothing has been done. Situated close to the city of Dunedin, and occurring in apparently large quantities, the deposit is, if only the lowest of the above-mentioned yields can be maintained, of great value.

In the south-west of Otago is an enormous tract of country, which is almost entirely unknown; when this is opened up and thoroughly prospected the vast quantities of hidden riches which are probably waiting there will be developed, and will afford a remunerative field for the British capitalist. Then will the colony resume its place among the great gold-producing countries of the world.