Ohinemuri Regional History Journal 6, October 1966
By CYRIL GWILLIAM
There is little one can add to the early history as already recorded in regard to the opening of the Ohinemuri District as a Goldfield. It is well though to remember the fact that primarily it was considered to be an alluvial field.
In the scheme of Nature, gold occurs in two forms:-
1. Veins or Reefs in rock formations. In these the precious metal is at tines visible as grains, or in irregular patches.
2. Alluvial deposits. These have been placed in position by Ancient streams and glaciers. Hence the term Placer gold.
These two forms of gold are easily recognisable. Reef gold is angular, that is, it has sharp edges. Alluvial gold is almost invariably smoothly rounded.
How far back does man's quest for gold date?
5000 years ago the Egyptian Pharaohs were finding it and using it.
3000 years ago King Solomon and the Queen of Sheba were gathering it.
Thus there must have been vast quantities of alluvial gold round about their countries at that period, for it was not until 13 B.C. that the first mention of the reduction of quartz for gold occurs. Quicksilver or mercury is first mentioned about 300 B.C. but was not used for amalgamation until the beginning of the Christian era.
Notwithstanding the fact that in 1888 specimens of rock containing gold had been shown to certain prospectors, the contours and river flats around Mackaytown presented some physical resemblance to similar gold-bearing country elsewhere, not only in the South Island, but also as far afield as the Yukon in Alaska, the Californian diggings, and the various early fields in Western and South Australia and Victoria.
You will remember that the proposed opening of the Ohinemuri field had taken a lengthy period of negotiation with the various Maori tribes whose lands bordered the Ohinemuri, Waitawheta, Rotokohu, and Waihou rivers.
Final proclamation of the opening of the field was made in early l875, by which tine the news had travelled far, and many men who had been less fortunate in more distant fields began to congregate at the Port of Paeroa and at Mackaytown. To them no doubt it was the gateway into the unknown, for here was the springboard into possible wealth, or maybe, as eventually proved, a continuance of a way of life to which they were accustomed.
The first rush on the day of the Proclamation was across the river opposite the big square residence which was built for John McCombie an early Mine Manager and where that grand old lady Mrs. Ritchie lived for so many years. On the other side of the river, lying between Tapu Arikki (Te Moananui's Hill) and the long spur that runs down from the Trig to the old railway station is a fairly flattish area that no doubt to the old gold seekers reminded them of the physical features of other rich fields at the foot of mountain ranges. We have it on record that the going was rough — tangled fern and undergrowth. Two small streamlets drained the area. The water from these could be passed through their "cradles" into which they would shovel the material from their respective claims.
Loose gold was found in this area - and still can be panned off, but there was no rich bed of nuggets such as men had found in the Southern river flats, where the action of glaciers had ground off the mountain ridges.
These men knew that because of its weight gold must move down from higher levels. That is the reason that a prospector when testing a creek or water course works upstream, panning as he goes. If he finds colour he does not immediately peg out that spot, but continues to follow upstream until he loses colour. Then he can be reasonably certain that somewhere between those two points is an area worth working.
Scores, possibly hundreds of men were disillusioned by the poorness of the returns and left the district. Others more hardy struck out for the higher ridges round about. Here they found a vastly different concept of gold-winning. The gold was there alright, but it was embedded in hard rock of reef formation - and it was associated with other minerals, iron, silver, copper, lead etc. The cradle and sluice-box had no place here. This was a new phase, and marks the transition stage from Alluvial gold-winning to Reef gold-Mining. It was no longer a "one man and his mate" show. Machinery, buildings, and most of all, money for these was needed.
Various groups merged into Companies, and with the propaganda that there was "Gold all over N.Z." money poured in - mainly from overseas sources. Several small prospectors erected their own plants - rather primitive, but which to a degree worked successfully for a year or two. Amongst the earliest of these were the Le Monte which was situated slightly downstream from Mr. Bob Ellis's hut. This plant was used mostly for the recovery of silver, but it did not operate over a very long period.
Another treatment plant was in operation at river level on the bank of the Waitawheta River at the foot of a long spur running down N.E. of the Trig. This plant (? Reilley's [Railey - E]) is reported to have treated a quantity of rich ore which was transported by way of an incline tram - not an aerial. This site is now overgrown, but about forty-five years ago was easily discernable.
Next came the bigger Companies: Crown, Woodstock, Talisman, and later the Dubbo.
The Crown Company opened a reef that crossed the Waitawheta River at the end of the tram track that now carries the Paeroa water supply pipe-line.
The Woodstock Company drove in just above the concrete abutment in the same stream on the right branch of the tram track just past the short tunnel.
The Talisman Company drove a level into a gully about a half way up the mountain at the back of the peculiar hump commonly referred to as the plum pudding. (Origin of name ? - possibly from its shape, or maybe perhaps, like a Christmas pudding it was full of rich pickings).
CROWN. The reef here was unusual in that it lay at around a 40 degree angle. The shaft was sunk on the reef, so that it was described as an inclined shaft. The ore was hauled up with most of its weight on wheels rather than on the winding rope of the conventional vertical shaft. In the higher workings the ore was broken out and dropped from level to level by "passes" to the river level, from whence it went by horse-tram to the Battery, near the present Railway Bridge. Here it was hauled up another incline to the breakers at the top floor and thence by gravitation through the various processes until it finally reached the smelting room. This Battery was the first in N.Z. to use the Cyanide process of gold recovery [the first Crown Battery, at the site of Railey's Battery, was the first – E].
WOODSTOCK. This shaft was vertical and is situated in a large chamber just inside the hill above the concrete abuttment previously mentioned. In this chamber was the engine (steam) which hauled up the workers and the ore from deep down, and also drove the huge pump that kept the mine dry. Folk of to-day night well ask "Where were the boilers that supplied the steam?" They were sited outside on the concrete foundations now seen, and together with them was a large corrugated iron "change-house" where the men would wash and hang their clothes to dry in readiness for their next shift. The ore from here came down the same tram-track to the Battery which was situated on the bank of the Ohinemuri River.
Unfortunately, this Company had a short working life, as its Battery was burned to the ground a very few years later. The Talisman Company took over the Mine and worked it in conjunction with their own.
At this stage it may be of interest to mention some of the reef systems in the vicinity - Rhoderic Dhu, Ivanhoe, Peverill of the Peak, Kenilworth, - all names associated with Sir W. Scott's writings.
TALISMAN. Here again the shaft was inside the hill, and the ore came up from far below river level. From almost the top of the hill it was dropped to No.8 or Aerial Tram Level. This was the main feeding point to the Battery, and was an inexpensive method of transportation, as the full bucket going down pulled the empty one back up for refilling.
The value of the ore was very consistent, with the richest values being found at the highest and lowest points. Indeed, it was in the top area that in later years the Dubbo Coy., carried out operations on a smaller scale.
Since there were many thousands of feet of drives or tunnels travelling in different directions underground, some method of air movement had to be arranged in order to get rid of fouled air, particularly from blasting. In many cases air was driven in through a large pipeline by fans from outside. As well, connections were made between each level - "winzes", and most of these had a rough ladder so that a man could go from level to level without having to go right out to the mouth.
Other connections called "passes" were used solely for the passing of ore down to a lower level, so that the trucks from one drive could handle the ore from several working "faces" up above. Ore from deep down was handled in a similar way, and the "cage" would draw off from each level and haul to the main aerial or tramway level.
METHOD OF BREAKING OUT THE REEF
Hand Drilling: This was a tedious job. Perhaps two men would be working together on a "face", one to hold and turn the drill and the other to strike. Each had to have great faith in his mate, for a six or eight pound hammer coming in on a four foot swing to hit the size of a penny in candle light meant that both men had to be steady and sure. Mates on these jobs often worked together for years. They got to know intimately not only themselves, but also the nature of the country and the danger sounds of the ring of the stone above or around them.
When the holes were drilled, a meticulous system was planned. The depth and spacing was worked out, for each shot had to fire in its correct order. The men retired to a safe distance, and each man counted the shots. In the event of doubt as regards a misfire, no one approached that "face" for a good period in case of a delayed fuse-burn or some similar reason. Sometimes the fumes might take an hour or so to disperse, depending on ventilation. Normally it was the practice to fire a round of holes about an hour before "end of shift" or knock off time. This gave the opportunity to locate and defuse or detonate any misfire before the next shift of men came on. Considering the hundreds of shots fired in a mine each day, very rarely was there a fatal accident that could be blamed on the carelessness of a previous shift. Each man knew that not only his own life but also those of a number of men depended upon his own carefulness.
Machine Drilling: The Popper Drill was a machine driven by compressed air. It was much larger but very similar to the modern drill often seen on road works or in the demolition of concrete buildings. These drills could penetrate to depths of ten feet or more. The drill itself was hollow and the fine hole enabled water to force the dusty drillings up and out of the hole in the form of mud. In the earlier years the dust was continually blown out by air pressure, and this was the main cause of what in those days was called "miners complaint" [medical term – phthisis – pulmonary consumption resulting from accumulated dust in the lungs – E]. The compulsory use of water in these drills was written into the Mining Laws after the turn of the century, and is a law most strictly enforced in quarries and all internal or confined spaces to this day.
The Compressor Plant of the Talisman mine was situated just over the present pipe bridge and on the left. There are still to be seen the massive concrete foundations and huge bolts that held down the compressors. Later the Dubbo Coy, built its Battery over a portion of this site.
The air from these compressors was piped to a "balancing" tank at the mouth of No.8 level and thence piped into the mine to the working faces.
Adjoining the compressor building was the smelting room, and often on an afternoon a small boy of between five and six years old used to tramp from above the town and across the bridge with a billy of hot soup in one hand and a hot dinner in the other to deliver his father's hot meal. Many a recollection I have of the great coke furnaces with the flames billowing up as the lids were removed, the great white-hot pots of bullion being hoisted and poured, and the men in action protected by long wet sacking gloves, manipulating the great tongs.
POWER FOR MACHINERY
Of course we must realise that we are dealing with the period prior to the use of Hydro-Electric Power.
Both the Talisman and Woodstock used steam, and water-turbines for power. Steam mostly to run the compressors and the shaft winding gear, and the turbines to run the mill machinery. The Talisman drew its water from a low dam just below the narrow canyon in the Waitawheta gorge, and the Woodstock from a similar dam just upstream from the railway bridge on the Waikino side of the Karangahake gorge.
These dams were built of timber, and were not more than twelve feet in height - if that, and the water flowed through pipes 30 to 36 inches in diameter. In those days the total cost of both dams and pipelines would be about £500. The Talisman was most fortunate in that its dam was only about 600 yards upstream.
The Crown Battery machinery was driven by both steam and by Pelton wheel. Its water supply came from a long way up the Waitawheta stream and followed down the tram track in a nine or ten inch pipe. Coming as it did from a great height, it developed its greatest pressure at its lowest point - the Battery.
With a Turbine, pressure is not necessary, but volume is, and this volume must remain constant. For instance if the pipeline were to be only partly filled with water a surge will develop, and immediately the turbine will begin to run erratically and lose power.
With a Pelton wheel, height of intake is the essential necessity.
This Company operated in comparatively recent years and worked in an area far up the mountain, and the ore came from a very early Claim of the same name. It was very good stone, carried good values, and was reasonably easy to crush. A very long Aerial [cableway – E] brought the stone down to a spur on the Hill Road, from whence it was lorried down to the Mill. The Aerial itself, gave quite a bit of trouble, mainly on account of its length.
The Mill, for so it must now be called, having no battery of stampers, was of a newer type. The broken ore passed through a tube-mill type of pulveriser, which certainly reduced the sands to a much finer degree than stampers were capable of doing. However they lacked an economic Power. Had they copied the Talisman's idea and installed a turbine, instead of purchasing from outside, they could have carried on for many years. Other Companies who made the same mistake come readily to mind – the Golden Dawn (Owharoa), Ohinemuri Gold& Silver Mines (Maratoto). Water is the cheapest power, and is usually readily available in most if not all mining districts.
TREATMENT OF ORE
So far we have dealt only with the "mining" of the ore. The heaviest of man's labour - the drilling, the heaving of the broken reef into trucks, and the pushing of these along many feet to a "Pass" or to the shaft for haulage to the surface, is over.
There now remains the action of recovering the precious metal from the material. The scene changes from man-power to mechanical power.
From now on economy is the keynote, and movement by gravitation is the answer, for the stone eventually adds to the sands of the sea, and the gold finally ends up deep in the vaults of a Bank.
Since we are dealing with past history of a definite area we must describe the treatment as it was at the turn of the century.
This was always as near to a good supply of water as possible. Second consideration was proximity to the Mine, and thirdly at a point where the ore could be most economically handled. In every respect the Karangahake area was ideal in having all three.
TYPICAL BATTERY LAY-OUT:
The side of a hill gave the best position, as with a reasonably small amount of excavation, a sufficiently firm foundation could be prepared for each floor level.
Top Floor. Breaker floor. The number of floors was a minimum of five. On the top floor the ore as received from the mine was passed through "stone-breakers" into a large hopper or holding bin.
Second Floor. Stamper Floor. From this floor the stamps could be stopped or "hung up" either individually or in batches of five or ten. One man could comfortably handle 20 head of stamps, as his main work entailed oiling bearings, keeping a check on the ore passing to the mechanical feeders, and watching for any mechanical faults. The stamps were raised by cams on a shaft and dropped at intervals, the usual order of "fall" being 1 4 2 5 3. The centre stamp of each section of five activated the mechanical feeder by a system of levers, so that the ore passed into the stamper-box fairly evenly.
Third Floor. Amalgamation Floor. Here we are on the final crushing floor where we see the stamper-box and the copper plates. Water is of course flowing into the box with the ore. As the centre stamp falls it splashes the ore outwards, and in their turn the others splash it back so that the ore is constantly under pounding and movement.
In front of the box is a screen through which the pulp is running, and this fine sand and water flows over gently sloping copper "plates" which are coated with mercury. The loose gold is caught by the mercury and is now termed "amalgam". At the lower end of the plates are two recesses which will catch any amalgam that slips off the plates. The sand and water pass on into a trough or "launder" which delivers into the "vats".
Fourth Floor. Cyanide Treatment. Here are the great vats, usually about sixteen feet in diameter and around four feet in depth. On the bottom a false floor of wooden slats is laid, and this is covered with heavy canvas. As the vat is being filled with the sand and water, cyanide (potassium) is added in a pre-determined strength. The sands in the vat are continually kept in motion by agitation, .either by paddles driven mechanically, or by the bubbling action of compressed air. This motion allows the cyanide solution to act efficiently, and also allows a better percolation of the solution through the false canvas floor. Assay samples are taken at periods in order to test for efficiency.
Fifth Floor. Precipitation Floor. We have now come to perhaps the most interesting part of the treatment of gold-bearing ore.
With the exception of what we might have seen on the copper-plates, all our gold is now in solution, and we have to get it back into a metallic state. From the bottom section of the vats the solution is drawn off and passed through "extractor" boxes. These boxes are long, and are divided into a number of narrow and wide compartments. The larger compartments are filled with zinc shavings (compare kitchen pot-mitt). The cyanide solution is led into the top end, passes up through the shaving in the next compartment, over and down and up through each zinc box until the lower end of the box is reached. This filtering action causes a black muddy substance to be gathered upon the zinc shavings, and a certain amount will fall to the bottom of the box. The shavings are taken out and washed, and that muddy precipitate which we now call "slimes" is dried in a large roasting pan. Fluxes are added and the material is put into pots and smelted in a big furnace.
When molten and poured, the gold and silver, which we now refer to as "bullion", sinks to the bottom of the mould. The fluxes form the "slag" - the familiar green, black, and brownish glass to be found at times around batteries. The pouring demands care, for a careless pour will result in globules of bullion being held within the slab [slag - E]. Such slags should be re-treated, - generally through a berdan.
The bullion in its bar form is ready for delivery to Bank or Refinery, and its gold and silver content is ascertained by Assay.
Query; What has happened to the cyanide solution that finally emerged from the extractors boxes? It is not lost, or passed on into the river as was once commonly thought. It is returned to a holding vat, tested for strength, renewed, and re-used through the agitators and extractor boxes again and again.