Gold Extraction at Victoria Mill

Ohinemuri Regional History Journal 30, September 1986

By Oliver Pipe

Foreword:

Oliver Pipe was born at Waihi in 1912. He did his schooling at the Convent School and left at the age of 14 in the middle of the Depression years. Jobs were very thin on the ground and he went to work on farms in the Te Aroha / Matamata areas.

The following is a talk he gave to the Waihi Historical Society on the methods of mining ore or gold-bearing rock in Waihi and the treatment or extraction of gold and silver from this ore at the Victoria Mill or Waikino Battery as it was commonly known.

* * *

Mining started in Waihi in 1882 and the Martha Mine had been operating for thirty years when I was born.

I eventually got a job at Waikino Battery and apart for a couple of years at the "New Dubbo" Battery at Karangahake, I worked at Waikino for many years. As a point of interest, the Dubbo Battery was shifted to the Emperor Gold Mine in Fiji. It was quite common for small Batteries to be shifted around when a mine became uneconomic. I can quote the case of the small Battery that used to be beside the river at Owharoa. It had been the "Rising Sun". It was shifted to Okupu on the Great Barrier and from there to "Muirs Reefs" at Te Puke. It then came to the original site and was known in our day as the "Golden Dawn".

While working at Waikino I worked in every department so I had a very good understanding of all the processes in gold extraction.

When I transferred to the Mine, it had been in operation for close on sixty years. We, as kids, knew very little about the Mine except for the fact that the Mine whistle blew at 7.30 and 8.00 and then again at 12.00 and 12.30. There was not much noise, as the explosives used were hundreds of feet underground. Our fathers were miners and worked three shifts day, afternoon and night. Some men found it hard to sleep on the night shift and were very hard to live with.

As one can only report the past as you individually saw it, my observations may be altogether different to yours.

For the past twenty years of the Mine's life, the ore was treated in two Batteries in Waihi. The Union in the East end of Waihi [the Waihi Battery at the foot of Union Hill – E]; the Silverton in the South end. Both of these plants were obsolete when the Victoria Battery was built at Waikino [no, Victoria Battery started in 1898, the Silverton, renamed the Union closed in 1911, the Waihi battery closed shortly after the 1912 strike – E]. Although the Refinery was used until the Mine closed.

The extraction rate was about 50%. For instance, all the ore broken out underground was sampled and assayed before it was wound to the surface. By that method the Company could tell how much per ton the ore was worth. Say for instance, the ore was worth £10 (Ten Pounds) per ton and the extraction rate was 50%, they would then only get £5 (Five Pounds) per ton. The other 50% was tipped into gullys or, as later on, flushed into the Firth of Thames.

The building of Victoria Battery at Waikino was brought about by several things...

1. Was the discovery of greater deposits of payable ore as the workings went deeper. At around six or seven hundred feet, the Reef System was about 150 feet wide and all payable, and existing plant was too small to treat it.

2. The non-available supply of wood to fire the Boilers as all the timber on the Bulltown Hills had been used.

3. The availability of sufficient water from Waihi, Waitekauri and Waitawheta to gravitate by water races. There were quite sizeable wooden dams to divert water into these races. This water was used to drive pelton or water wheels to create power to drive machinery.

4. The biggest advantage of siteing the Mill at Waikino was the fact that the Company had been successful in getting Government approval to use the Ohinemuri river as a sludge channel [no, because of the water power available – E]. Over a period of fifty years every ton of ore mined had a minute quantity of gold and silver removed and the rest of it went to the Firth of Thames.

Through the years there was a misguided belief that the river was poisoned with cyanide, but that was not the case. It was only discoloured with minute particles of crushed ore. Cyanide was too dear to let it escape in any quantity into the river.

The first cyanide treatment plant, which was a Scottish invention, was installed in the Crown at Karangahake as a pilot plant. It was a great success and it was around that time that the Martha Company decided to change to cyanide also [no, several years later, in 1893-4 – E].

The cyanide method entailed crushing the ore to the consistency of talcum powder in water. This slurry was pumped into the big tanks that some of you folk will remember stood just over the bridge at Waikino. The cyanide came in drums of 200 lbs. and looked like salt. It had to be chopped out of these drums, broken up into chunks and loaded into 4 gallon Kerosene tins.

Victoria Battery, Waikino.

So many tins were added to each tank each day, and samples taken to see if the extraction process had started. It usually took about seven days for the gold and silver to change from solid to liquid. It then had to be changed back into a solid form. This was done by filtering the solution over zinc shavings packed into inclined wooden boxes. In this process the zinc was cannibalised and the residue that was left looked like black mud. This was then brought up to the Refinery in Waihi and was processed by heat and acids and poured into moulds and looked like blocks of lead.

The Assayer, who was a very important man, would drill a small hole in each bar and the small shaving he extracted would then be finally treated to separate the gold from the silver. (Incidentally, Waihi was more a silver mine than gold.) The scales used to weight the final results were so fine that they were in a glass case and were worked by knobs on the outside.

The Banks would pay out full value on the Assayer's final say-so.