By Oliver Pipe
The Origin of gold. Geologists are of the opinion that when the world was in a molten state the gasses and liquids were forced to the surface through fractures and faults in the earth’s crust, and in the ensuing cooling off process solidified to form reefs. These reefs contained a conglomerate of all the base metals, gold, silver, lead, iron, asbestos — you name them, they were all there. This was known as Refractory ore.
Early man was only interested in two of these metals, gold and silver. Even though it is recorded that about 6000 B.C. the Pharoahs used gold in their ornaments we can only assume that this was Alluvial Gold.
There are two types of gold, alluvial or placer, which is invariably round or smooth, and reef gold. It is thought that the smoothness of alluvial gold was caused by glacial action, but I have never met anyone who can explain how this action has managed to separate gold alone from all the other metals. As alluvial gold is almost pure, either as nuggets or dust, very little treatment is required to process it into its ultimate shape or form. The other type, reef gold, is always angular in shape, and in most cases, requires some form of treatment to separate it from other base metals.
It is recorded that about 300 B.C. (give or take a few years) quicksilver or mercury, which is extracted from antimony, was first used to amalgamate gold. The amalgum method of extraction was used for the next 2000 years, in fact up till 1889, when cyanide extraction came unto use. This was first used in New Zealand at the Crown Battery, Karangahake in that year, after extensive laboratory tests in Glasgow. The late Mr. James Noble was Battery Manager at that time.
With the amalgum method of extraction rich ore was extracted, crushed in burdans or stamper boxes, and then passed over inclined tables covered in copper or blankets which had been rubbed over with quicksilver. The gold adhered to the mercury. This amalgum was then scraped off and the gold separated out in retorts under heat. The mercury was caught as steam, solidified and then re-used. Extraction rate by this method was a little over 60% so that the treatment of residual sands around old early workings was often carried on in later years. Paeroa Treatment plant operated for years on Waihi and Karangahake sands.
Cyanide extraction is a more tortuous and complicated affair. On the other hand it is much more profitable and enables the treatment of larger quantities of low grade ore. The extraction rate is between 90% and 100%.
Gold in the Auckland Province. Charles Ring discovered gold at Coromandel in October 1852. I believe gold had been discovered in the South Island much earlier, but it was all alluvial. All the deposits discovered in the North Island were, without exception, auriferous, or reef gold.
The Thames field was opened 15 years later, in 1867. This was a very rich field and attracted within three years a population of 18,000. 1 might point out that at that time, 1870, Auckalnd's population was only 11,000, after 30 years of settlement.
The Chief Government Administrator at that time was James Mackay. It was he who had purchased from the Maoris 6 million acres of Fiordland for $600. Now he arranged for the purchase of large tracts of the Coromandel Range for mining. Several of these land transactions were so heavily loaded against the Maoris that they were loath to allow the Ohinemuri Field (which included Owharoa, Waitekauri and Waihi) to be thrown open for prospecting, with the result that this area was not opened till about ten years after the Thames Field in 1875.
Mining in Waihi. The first two men to prospect the Waihi field were Lee and McCombie. They were followed a year later by Mr. William Nichol, who struck it quite rich and named his claim after his wife. He in turn sold to an English company named the Waihi Gold and Silver Mining Coy., but the mine was always known as the Martha. It was one of the richest in the world.
The Martha and Grand Junction mines had been operating over 30 years when I was born in 1912. Thus my personal interest in mining would only start when I was in my teens. The mines were operating, so I accepted that. When I was in my middle twenties I went to work in the Victoria Battery at Waikino. I continued to work there, with a two year break at the new Dubbo at Karangahake, tributing on Karangahake mountain for a year, and then twelve months underground in the Martha, till I was called up for Military Service.
There were six shafts with winding gear operating in my boyhood days. Martha Coy. had Nos. 2,4,5, and 6. No. 2 was on top of Martha Hill, Nos. 4 and 5 were on lower slopes above Seddon Street, opposite Rugby Park, 5 alongside Old Pump House, and 4 about 150 yards north of that. No 6 was situated on the slopes above the lake. It only had skips - did not wind men. No. 1 would have been somewhere in the middle of the lake, but it had been dismantled before my time.
The Junction poppett heads were built of steel, looking like a giant Meccano set, whereas all the Martha’s were built of heavy timber. The Junction also had an air shaft, named Extended, which was on Boundary Road. There were also three other derelict shafts in the East End; the Favona beyond the East School, one out towards Golden Valley - the name eludes me - and one in Roycroft Street which I think had been sunk as an air shaft for the Junction. The foundations of another shaft were behind Union Hill, and one had been sunk up by the Hospital corner. The names of these also I cannot recall.
Mining was also done by the drive system opposite the old Central school. This area was known as the Sanatorium. I think this was owing to the fact that the prevailing westerly winds blowing into the drives kept the temperatures low. The quartz from this area was trucked down past this building.
The depths of the shafts varied from 1500 to 2000 feet, with No. 4 having 16 levels. The distances between levels was from 120 feet to 150 ft., with sub-levels in between. So with a method of extracting some sections of the quartz and leaving others for support, some form of stability enabled the Martha Hill to retain its original shape. One could almost liken this system to a honeycomb construction, or to a stack of kiddies’ building blocks.
As reef systems are really only fractures in the earth’s surface all underground streams gravitate to those fractures, so that the deeper the mines go, the greater the water problem. Added to this, a huge watershed was created by the system of back filling practised for thirty odd years.
The huge cuttings called "Smeaton’s", named after the contractor, formed a large catchment area for the 100 inches of rain per year that Waihi is blessed - or cursed - with. All of this surface and underground water had to be removed as the workings went deeper. I do not know how they coped with this problem prior to 1904, when the huge Cornish pump was installed.
Reference has been made to the Cornish pump in an earlier article, but a few facts about it are worth repeating. It weighed 52 tons, stood on a foundation measuring 50 feet by 30 feet, and was 100 feet in depth. It was driven by steam from four Babcock boilers which generated 1500 H.P. The smoke stack was 15 feet in circumference and stood 108 feet high. The capacity of this pump was 90,000 gallons per hour from 1550 feet. As the workings went deeper pumps known as Suspension, with a much greater output, had to be installed. This was about 12 years after the Cornish pump first came into use. These Suspension pumps had a combined output approaching 300,000 gallons per hour. According to my figuring, these pumps working 24 hours per day, 7 days a week, must have pumped about 50 million gallons a week, and some astronomical figure over a thirty or forty [year – E] period.
The earliest method of lighting used by miners was a single candle held in a "Spider", as it was called. It could either hang from any object or else the point could be forced into anything soft. The Company had these candles specially made and they were tinted pink.
In my days carbide lights were used, and we each had to purchase one. We were issued with a tin container to store our carbide in, and a similar one to carry our explosives in. Explosives, detonators and fuse were kept in a cupboard called a magazine, on each level. These magazines were restocked from a central one on the surface. The main magazine for the mines was situated in a depression between hills out at the East End overlooking Golden Valley. This was quite a substantial building. It is now a brick house at Waihi Beach.
Before there was any electric power, water wheels were in use, and to make this possible countless miles of water races had to be constructed. These were drains following the contours of the country, collecting the water from every possible rivulet on the way. Steam was also used, and to feed the insatiable fires the hills round Waihi were denuded of everything that would burn.
After mining had been in progress for some years a problem arose over the disposal of tailings [I don’t think so – E], and it was at this time that the treatment plant, or battery, was erected at Waikino. Operations were transferred there from the base of Union Hill [the Waihi Battery continued in operation until after 1912 – E]. Waikino was an ideal site in many respects. Ample water for power was available from the Ohinemuri, Waitawheta and Waitekauri rivers, while the Ohinemuri River was a natural sludge channel. (Many people may remember the murky water that used to flow down past Karangahake when the Battery was still working). There were, however, some drawbacks. All the quartz after crushing had to be elevated so that it could gravitate through the various treatment processes, and being of such an abrasive nature it could not be pumped. This problem was overcome by using a series of giant elevator wheels which lifted the sludge from one level to another. In one department this lift amounted to over 80 feet.
So we can see that throughout the operation of gold mining problems were always arising - and being solved. Even if to the modern engineer some of the methods and machinery may seem cumbersome, they served at the time, and enabled the business of getting out the gold to continue.
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Keywords: Martha Mine, opening goldfields, pumphouse, Ohinemuri