The classic image of the felt-hatted old-timer panning merrily beside a stream is only part of the story of gold extraction, but it’s a true enough depiction of the first couple of years of the Otago gold rush. Initially all a miner needed was a pick and shovel, a pan, and preferably a special wooden box known as a “rocker” for washing the alluvial gravel. As the easily accessible gravel beds were worked out, all manner of ingenious schemes were devised to gain access to fresh pay dirt. The most common technique was to divert the river, and some far-fetched schemes were hatched, especially on the Shotover River: steel sheets were driven into the riverbeds with some success, landslides induced to temporarily dam the flow, and a tunnel was bored through a bluff.
When pickings got thinner miners turned to sluicing guns that blasted the auriferous gravel free, ready for processing either by traditional hand-panning or its mechanical equivalent, where “riffle plates” caught the fine gravel and carpet-like matting trapped the fine flakes of gold. Eventually the scale of these operations put individual miners out of business and many pressed on to fresh fields.
To get at otherwise inaccessible gravel stock, larger companies began building gold dredges, great clanking behemoths anchored to the riverbanks but floating free on the river. Buckets scooped out the river bottom, then the dredge processed the gravel and spat the “tailings” out of the back to pile up along the riversides.
Otago’s alluvial gold starts its life underground embedded in quartz reefs, and when economic returns waned, miners sought the mother lode. Reef quartz mining required a considerable investment in machinery and whole towns sprang up to tunnel, hack out the ore and haul it on sledges to the stamper batteries. Here, a series of water-driven (and later steam-powered) hammers would pulverize the rock, which was then passed over copper plates smeared with mercury, and onto gold-catching blankets, before the remains were washed into the berdan – a special kind of cast-iron bowl. Gold was then separated from the mercury, a process subsequently made more efficient by using cyanide.
Although returns are far from spectacular, small-time panners still extract “colour” from the streams all over the province. There’s very little appliance of science: instinct counts for much and fancy mining theories not at all. Bigger capital-intensive companies occasionally gauge the area’s potential, and as one mining engineer pithily put it, “there’s still a shitload of gold out there”.