|
Goldmining - Stamper Battery ruins in Broken Hills - February 1999
We spent the following morning in Thames soaking up more goldmining history. Firstly we went to the Thames Goldmine and Stamper Battery, which has a working Stamper Battery, separating table, Berdan and Mercury Distillation separator. You also a brief tour underground following the first trial adits (tunnel to non miners) which identified some Quartz reefs containing Gold. A very well spent $6 and a must to visit in the Coromandel - Gold was a major influence in the area and plays a unique part of NZ history. Thames was the first area where gold was exploited in the Coromandel and had some exceptional rich Bonanzas, one where the Bullion (Gold and Silver) was over 50% of the Quartz reef and one blast reputedly produced 2 tons of quartz which contained 25,000 oz. of Bullion. Mostly it was only a few ounces per ton and as time went on the workings were taken as deep as 1000 ft and massive steam pump engines had to be installed. The guided tour and the comprehensive photo museum put into place a lot of what we had seen at Broken Hills in the way of abandoned batteries, adits and tramways.
We also visited the Mining Museum and School of Mines. The School is no longer open every day out of season so we will have to return to see the most interesting part. The complex is owned by the NZ Historic Places Trust and it is worth noting that they have reciprocal arrangements with the UK National Trust so one can get in free. We now have a list of their properties and will follow up further. We bought a fascinating book "Coromandel Gold - A guide to the Historic Goldfields of the Coromandel Peninsula which has a lot of background and maps of all the major Goldfields and associated information producing a practical guide for visitors to experience something of the 'magic' of the old mining areas from the surviving features - long abandoned tunnels and shafts, crumbling foundations of Stamper batteries, rusting pieces of machinery and disused tramways and water races. We had seen many of these Stamper batteries in Broken Hills even on our short walks.
There is far too much to cover here about gold mining but I will attempt to give a brief flavour in a few lines. The Bullion (Gold and Silver) is mostly concentrated in "reefs" of Quartz which were followed underground and largely mined by hand during the important initial years. The Quartz was then broken up to cm size pieces in jaw crushers then Stamper Batteries were used to pond the quartz to a fine sand releasing particles of Gold. The Stampers crushed the ore by lifting and dropping huge iron stamps onto the ore. The stamps were raised and dropped using cams driven by water wheels, Pelton water turbines or steam engines. Once reduced to a fine powder the initial separation was on vibrating water covered tables or amalgamating tables covered with a thin layer of mercury on the surface which trapped and amalgamated the gold.
A lot was missed and the heavy 'tailings' were then further treated in Berdans - inclined, revolving cast-iron basins containing a heavy iron block. The slow revolving action ground the sludge even finer enabling even tiny particles of Gold to be freed and recovered by amalgamation with mercury which was in the bottom of the Berdan. When the Mercury got thick the amalgam was separated by squeezing the paste through a chamois leather and distilling off the mercury from the Gold and Silver which was melted and cast into bars. These techniques only extracted about 50% of the Bullion and were latter augmented by a Cyanide treatment which increase the extraction to about 90%. The whole process from hand mining underground to use of mercury and cyanide was not the most healthy way of life!
|
