Ohinemuri Regional History Journal 13, May 1970

MINING - HOW IT WAS DONE Ohinemuri Regional History Journal 13, May 1970

By Les Morgan.

My attention was recently drawn to the fact that, although Waihi owed its beginning to the gold mining era, there is nothing in any of our Journals describing the method used to obtain the gold bearing ore for treatment, and it was suggested that an article describing the method, briefly, may be of interest. Also it may serve to remind the younger generation how their forebears won the wealth from mother earth.

The discovery of gold bearing quartz was made on the surface and the reef or lode containing it went downwards. It was therefore necessary to sink shafts into the reef, and it was then found that the reef, and also others discovered later, were not vertical, but were on an angle or underlay. As the shafts were vertical it was necessary at intervals to make levels and drive tunnels to find if the reef still was in existence. At each level a large hole was mined out round the shaft. This was called a chamber. The distance between levels was between 100 and 150 feet. The approximate position of the reef was plotted and a drive or tunnel put in from the chamber until the reef was struck.

When the reef was struck a further drive was put along the lower or foot wall. The drives were about 5 feet wide and 7 feet high. Samples of the reef were taken at frequent intervals and sent to the assaying office for testing. If the reef was not very wide one wall of the drive was extended out to the top or hanging wall. These walls were usually very clearly defined and the appearance could be likened to a deep ravine filled with metal of a different composition.

The machine used in driving was known as a water liner. In the very early days holes to hold the explosive to blast out the rock were drilled with hand steel, but later the machines driven by compressed air were used. The first ones were known as dry borers, and as the drill penetrated the rock clouds of dust were created and this was injurious to the operator, as it settled on the lungs. The water liner was then invented. With this machine a stream of water was forced through the drill steel and it washed out the borings so there was no dust. The method of operating this machine was;- an iron bar with an adjustable foot about 7 feet long was placed in the centre of the drive a short distance from the face and fixed firmly in place by screwing out the adjustable foot. An arm was then placed on the bar and on the arm there was a saucer shaped receptacle to which the machine was fixed. This arm could be moved up and down the bar and to either side according to where the operator wished to drill a hole. As the drill cut into the stone, pressure was kept on it by means of a feeding screw at the rear of the machine cradle. Each run of the screw was about 2 feet, and then a longer drill was used until the full depth of the hole, usually 6 feet, was obtained.

When it was decided to take out part of a reef to go for treatment the length of the portion was decided on and a party of miners assigned to that job. The first job was usually the making of a travelling way between the two levels, as the quartz was taken from one level to the one above it and for the full width of the reef. The travelling way was usually put up on the footwall and could be likened to driving or tunnelling on end. Starting from the bottom level the operation was called rising and if work was done from the top level downwards it was sinking a winze. This travelling way besides giving access, later on also served as a ventilator.

The machine used in rising was a popper drill. This machine had a telescopic base and when the compressed air which operated it was turned on the base extended, and forced the drill up against the roof where it was intended to bore holes. These machines were also dry borers in the early days, but later had the water liners, and also had rotary chucks which automatically turned the drill. One of these machines is an exhibit in the Museum.

If the travelling way was to be made as a winge [winze – E] the machine was a jackhammer. This was a smaller machine and the operator had to put his weight on to it as it was boring. Later machines had a water liner, and a valve to blow out the borings from the hole, and there was many an operator showered through touching the valve accidentally.

Taking out of the quartz was called "stoping". The first operation was to widen the drive to the full width of the reef so as to expose both the foot and hanging walls. In the very wide reefs it was necessary to have two or three drives. The drive was then heightened to about 10 feet. Sets of timber were then placed in the drive. Those were from 9 in. to 14 in. square pieces about 7 feet long. A piece, called a joggle, about 2 in. square was cut from one corner of these pieces which were known as legs. One leg was placed against the footwall and another about 8 feet from it, towards the other side of the drive. Another pair of legs were placed about 5 feet further along the drive, and similar pairs at 5 feet intervals for the length to be stoped. A cap, consisting of a piece of timber of the same thickness, but with a joggle at each end, was then placed on each pair of legs. The inside measurement between the legs at the top was about 5 feet. Slabs of wood were then nailed between each set of timber, making a sort of covered in tunnel. In between each alternate set of timber a slide, called a pass, was made, so that when the quartz was mined trucks could be filled from it.

Everything was now in readiness for the actual stoping to commence. The miners got on top of the timber, and using a popper machine commenced to drill holes in the roof above them. The first holes were in the vicinity of the travelling way, as it was necessary to have a weak place to blast to. When sufficient holes were bored gelignite was used to blast out the quartz, which when blasted fell on the timber. At the end where the travelling way was, timber called cribbing was used to keep this open. Cribbing was about 6 feet long and had joggles cut in each end, and when placed in position interlocked and left a passageway inside it. The miners used this to take their water and air hoses to the stope, and to travel up and down themselves.

When one length of the roof of the stope had been blasted off the miners then went up the travelling way on to the top of the broken quartz and proceeded to bore and blast off another length, and so on until the level above was reached.

As the broken quartz was often too close to the roof for the miners to work, it was necessary to take some of the quartz out. This was done by taking it in trucks, from the passes in the timber and out to the shaft, where it was sent to the surface on its way for treatment. This was known as the shrinkage stope method of mining and. was the most common in the Waihi mines, as the solid condition of the surrounding country rock was such that there was little fear of cave ins. Where the ground was not so solid however, mullock stoping was used. This consisted of cleaning out all the quartz after each firing of the roof and filling the space with valueless metal and rubbish, mostly sent down special mullock shafts from the surface.

Most of the work underground was done on a. contract basis, the miners being paid on a footage basis for driving, and a tonnage basis for trucking and stoping. The company's surveyor would come to each stope each four weeks, and from measurements calculate the number of tons of broken quartz in the stope, and payment was based on this.

Miners on contract work were required to purchase their supplies - gelignite, fuses, candles, shovels etc. from the company, and there was also a charge for tool sharpening. These charges were deducted from the payment due each month. Tonnage and footage prices varied according to the nature of the quartz or rock in which the work was being carried out.

In order to distinguish which job quartz came from, each job was allotted a token, a large iron washer with a mark similar to an earmark. One of these was put on each truck of quartz and the daily totals of trucks were displayed so that a check was able to be kept.

Each miner, before going underground, had to pick up a numbered disc from the tally office at the shaft head, and return it when he came up at the end of his shift. In this way it was certain that no man had been left in the mine.

In conclusion a few words as to the method used in blasting out the solid face of a drive may be timely. The method of boring the holes was the same, but the number required varied with the texture of the rock. The machine used was the water liner, and as stated previously it was operated from an arm, on a bar, in the centre of the drive. The usual depth of the holes was 5 feet. The first to be bored were the lifters, or the holes for the floor. For these the arm was lowered right down the bar and the machine swung underneath it. Three lifters were usually required - centre and each wall. The arm was then raised about knee height, the machine brought on top, and knee holes on each wall bored. In hard ground hip holes, a little above the knee holes were necessary, and then above them there were the shoulder holes and again, in hard ground, one in the centre for the top. In order to make an opening for the gelignite to blast to, for it was recognised that gelignite struck to the weakest point, a cut was bored, with the object of blasting out the centre of the face. This was done by boring four holes on an angle so that they would meet when they reached a. depth of 5 feet, and the gelignite would be in a concentrated place when loaded. The cut was fired first, and when the opening made by it was cleared the other holes, with the exception of the lifters, were loaded and fired. After they were cleared up the lifters were fired and the drive fully advanced another 5 feet.

It is rather difficult to convey in words the exact picture of how so much wealth was won from the ground under Waihi, but I trust that in this article I have been able to place on record how the pioneers of our historic town toiled in the days that are rapidly becoming but a memory.

OUR CONTRIBUTOR MR. LES MORGAN, past President of Waihi Society is still on the sick list but never fails to help us in our search for articles. We are most grateful to him !