EXCEPTIONAL GOLD DREDGING
IN NEW ZEALAND
New Zealand is located in the southwest Pacific Ocean and is made up of two main islands, North and South, as well as the much smaller Stewart Island to the south and a number of minor islands. It's a prosperous country with a population of 4 million. The climate is temperate with moderate to abundant rainfall.
Gold was first discovered in New Zealand during the early 1840s, but it was only when prospectors located rich alluvial deposits of easily won gold in the South Island in 1861 that the country experienced its first true gold rush. In the early years of the rush, mining almost entirely consisted of simple hand sluicing in the gravels of rivers and streams. Later, with the arrival of great numbers of experienced miners from the then declining goldfields of California and Australia, mining methods rapidly progressed, and by the turn of the century bucket dredging was being carried out in the South Island on a scale greater than in any country.
In the North Island, rich quartz reefs were discovered in the late 1800s, which greatly boosted the country's already considerable production of alluvial gold from the South Island. Then, following the First World War, gold production declined with only a few hard rock mines remaining in production and a small number of the largest bucket dredges continuing.
Gold mining activity remained at a low level until there was a renewed interest in prospecting and mining due to the rise in the price of gold in 1979. New technology was introduced and during the 1980s most alluvial gold was produced by the use of hydraulic excavators, which fed skid mounted or floating rotary screens. These plants, which were conceived of, and perfected, in New Zealand, were highly successful and are now in use throughout the world.
A trommel plant in New Zealand.
During the 1980s there was an increase in the number of independent miners who utilized suction dredges for the in-stream mining of rivers and streams. At that time, the dredges in use were mostly home built and of poor design, and little was then known of any dredging techniques. And apart from a few substantial gold finds that owe more to luck rather than any expertise, gold production by these independent miners during the 1980s was not great.
A small 5-inch prospecting dredge (Keene triple-sluice dredge).
Suction dredging underwent evolutionary change during the 1980s and 1990s, and presently suction dredging in New Zealand is no longer carried out in the haphazard manner it was during its early years. Experience has been a good teacher, and New Zealand's dredgers are now just as knowledgeable as dredgers in any other country. Furthermore, the dredges presently in use are as efficient as those used anywhere, and most dredgers now routinely employ sophisticated, modern dredging techniques to maximize gold production.
An 8-inch production dredge in New Zealand.
The gold dredging season in New Zealand commences each year in October and ends shortly after the first cold southerly of the year dumps snow on the high country -- usually in April when the water temperature quickly falls to 40 degrees F, or less! During the dredging season the water temperature will vary from a low of about 45 degrees F up to a maximum of 65 degrees F. And this is when New Zealand's recreational dredgers, along with a much lesser number of professionals, disappear into many of the auriferous rivers and streams of the South Island to dredge for gold. Only a small number of hardy professionals do any dredging out of the season.
Alluvial gold is widely distributed in the South Island provinces of Otago, Westland and Southland, and also in much of the northern part of the South Island (Tasman and Nelson-Marlborough districts). In the province of Canterbury, gold is non-existent except for a small area of reef gold that has never been a viable economic proposition. The North Island has little alluvial gold and is therefore of no interest to dredgers.
The nature of the South Island's auriferous rivers and streams varies considerably -- from waterways that are so boulder-choked they are impossible to dredge, to rivers as easy to dredge as can be. Rivers such as the Kawarau in Otago run fast and extremely deep in many sections, which makes it a river to be dredged only by teams of experienced professionals using dredges built specifically for severe conditions. At the other extreme is Otago's Arrow River, which anyone could dredge, as the water runs clear and slow over a shallow overburden.
The Arrow river at Macetown.
The Arrow River has always been New Zealand's most popular waterway for recreational dredging. And even though it's been dredged continuously since the 1960s (though never on a commercial scale), it still amazingly produces good gold each season. The largest nugget to come from the Arrow River in modern times was a well worn piece of just over 8 ounces that was hand-sniped from a shallow section during the summer season of 2005/06, previously to this nugget being found the largest nugget found in modern times was a piece just over 4 ounces in weight taken out in the mid 1990s with a 6-inch dredge, from a shallow section a few miles upstream from the Arrows junction with the Kawarau River. And in the early 1990s a good number of 1/4 ounce nuggets, along with a few 1-ouncers and a great deal of fine gold was dredged from a short section of riverbed not far downstream from the town of Arrowtown.
New Zealands Arrow river downstream from Macetown.
The most famous of all auriferous New Zealand Rivers is without doubt Otagos Shotover River. Once called "The richest river in the world", it's now of little interest to gold seekers, except for those who are interested in learning about its fascinating history. Virtually all small-scale mining stopped in the Shotover during the early 1980s when a mining company bought up every claim on the river. Two large, excavator-fed floating trommel plants then went to work, 24 hours a day, 7 days a week, to each produce over 100 ounces of gold a week -- with one plant having a best week of 1,206 ounces produced after striking virgin ground in November 1986. These plants ceased working in 1992 after mining the river from bank to bank and down to bedrock over most of its length. There are however a few tributaries of the Shotover River that remain of interest to gold seekers. Some tributaries such as the lower reaches of Stony Creek, the upper reaches of Moonlight Creek, and the upper reaches of Skippers Creek, were thoroughly mined by mining companies in the 1980s, and little riverbed gold remains. Other tributaries, such as the lower Moonlight Creek and the lower Floodburn, are currently under claim for commercial scale suction dredging, and dredging rights are exclusive to the claim owner.
L & M Minings Number 2 dredge on the Shotover river.
An area of greater interest to today's gold seekers is the South Island's West Coast. Practically all waterways on The Coast from Karamea in the north, down to Ross in the south and west of the Alpine Fault, are auriferous. The Coasts main goldfield is found within a narrow strip of country a few miles wide called the "Golden Line", that runs from Reefton to Ross over a distance of 10 miles. Vast quantities of gold have come from the "Golden Line", with the gold being found in leads along its entire length.
In the late 1800s the West Coast was a bonanza field, comparable to the 1849 rush in California and the Klondike rush. Most Coast gold is alluvial, in all forms from speaks to reasonably sized nuggets. The auriferous gravels came originally from the Southern Alps where glaciers eroded alluvium, known as moraine. Over thousands of years these moraines eroded and the gold concentrated and re-deposited into terraces. The present day watercourses have cut into these terraces to redeposit and further concentrate the gold.
The largest suction dredging claim in New Zealand is located on The Coast's Buller River, and because of regular massive flooding this claim is the most difficult to dredge in the entire country. Overnight rain in this river's massive catchments can easily raise the downstream river level 20 feet or more, and any dredges not made secure will be swept away to be destroyed. Since suction dredging was first attempted in the Buller River over 20 years ago, the great majority of dredgers have been defeated by this mighty river. Ironically, a claim owner of recent years is the most successful of all the dredgers who preceded him. His success in making a good living for himself was largely attributed to his professionalism, combined with the not insignificant fact that he was lucky enough to take over the claim at the start of a period of extremely dry years.
The Buller river in its middle reaches.
To dredge on a commercial scale in New Zealand, using production dredges, requires a substantial capital expenditure in the purchase and importing of equipment; in the time taken to locate a potentially suitable waterway and to prospect it; in gaining legal title to permit dredging on a suitable scale; and in getting the dredges on to the granted claim. Once established, and dredging commences, running costs are made up of petrol, equipment repairs and personal expenses. The professional dredgers of New Zealand establish legally registered claims by first applying to the Crown Minerals Division of The Ministry of Economic Development for either an Exploration or Mining Permit, and then applying to the appropriate Regional Government Authority for Resource Consents as required by the Resource Management Act (1991). And to better provide for the recreational dredgers, the authorities have been investigating the means of introducing an entirely new category of Mining Permit.
An 8-inch production dredge in Southland Province, New Zealand.
In New Zealand the weather conditions are a major influence on the success, or otherwise, of the dredging season. Water is abundant in the South Island, with free-flowing rivers everywhere. And since a short dry period in the early 1980s, wet conditions have been consistent up until 1998-99, which were two of the driest years ever.
Gaining physical access to the auriferous waterways of the South Island varies from simply driving right up to a river, to utilizing helicopters to access remote high country streams. Helicopters are common throughout New Zealand and are frequently hired by prospectors to lift dredges or to eyeball a waterway. They are also helpful in providing an emergency lift of a dredge from a flooding river.
A helicopter lift of an 8-inch production dredge from New Zealands Arrow river.
The working conditions when dredging in New Zealand can differ from any other country. In New Zealand particular consideration needs to be given to providing protection against the low water temperatures, and precautions must be taken daily in preparation against any overnight flooding. It's also very important in New Zealand -- more so than in any other country -- to custom design a dredge to suit the operating conditions existing in the river to be dredged!
There is payable gold in numerous New Zealand rivers and streams, and dredging for this scattered wealth can be greatly rewarding as a hobby. And for those few rare individuals with the fitness, skills and determination to make a good living for themselves, it's an exceptional lifestyle as well as a livelihood.
Pacific Rim Dredging Services http://www.nzgold.co.nz
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This article was first published in the Sept 2000 issue of the International California Mining Journal, and this updated version is reproduced with permission of the publisher.