![]() From Australia, in turn, gold dredging technology spread to New Guinea, at the time an Australian territory, in the 1930s. Gold dredges also operated, extensively, in Victoria and in Queensland. Gold Dredge that was in use in Eldorado, Victoria until 1954Ī New Zealand born mining entrepreneur, Charles Lancelot Garland, bought the technology to New South Wales, Australia, launching the first dredge there, in March 1899, resulting in a major revival of the alluvial gold mining industry. It became the prototype for many similar dredges, and led to a boom in gold dredging in the South Island in Otago rivers like the Shotover River, Clutha River and the Molyneaux River, and in West Coast rivers like the Grey River (where the last gold dredge worked until 2004). ![]() This dredge was able work river banks and flats, as well as the bottoms of streams. The first really successful bucket dredge for gold mining was that of Choie Sew Hoy, also known as Charles Sew Hoy, in 1889. Much of the New Zealand dredge technology was developed locally. Gold dredges were used in New Zealand from the 1860s, although the earlier dredges were of primitive design and not very successful. Many of these large dredges still exist today in state-sponsored heritage areas ( Sumpter Valley Gold Dredge), or tourist attractions ( Dredge No. The last giant gold dredge in California was the Natomas Number 6 dredge operating in Folsom, California that ceased operations on as cost of operation began exceeding the value of the gold recovered. Massive floating dredges scooped up millions of tons of river gravels, as steam and electrical power became available in the early 1900s. The challenge of retrieving the gold took a professional mining approach to make it pay: giant machines and giant companies. History Gold Dredge operating in Nome, Alaska in 1993īy the mid to late 1850s the easily accessible placer gold in California was gone, but much gold remained. Hence the efficiency of gold dredges differs greatly depending on its specifications. Even though the concept is simple in principle, dredges can be engineered in different ways allowing to catch different sizes of gold specimen. They allow profitable mining at relatively low operational costs. Gold dredges are an important tool of gold miners around the world. Professional gold miner using an advanced dredge system. The gold dredge is the same concept but on a much larger scale. Gold then settles to the bottom of the pan, or into the bottom of the riffles of the sluice box. Each method involves washing sand, gravel and dirt in water. The original methods to perform placer mining involved gold panning, sluice boxes, and rockers. The concept is that the gold in sand or soil will settle to the bottom because gold is heavy/dense, and dirt, sand and rock will wash away, leaving the gold behind. The basic concept of retrieving gold via placer mining has not changed since antiquity. The rocks deposited behind the dredge (by the stacker) are called "tailing piles." The holes in the screen were intended to screen out rocks (e.g., 3/4 inch holes in the screen sent anything larger than 3/4 inch to the stacker). The material that is washed or sorted away is called tailings. The cylinder has many holes in it to allow undersized material (including gold) to fall into a sluice box. On large gold dredges, the buckets dump the material into a steel rotating cylinder (a specific type of trommel called "the screen") that is sloped downward toward a rubber belt (the stacker) that carries away oversize material (rocks) and dumps the rocks behind the dredge. The material is then sorted/sifted using water. Small suction machines are currently marketed as "gold dredges" to individuals seeking gold: just offshore from the beach of Nome, Alaska, for instance.Ī large gold dredge uses a mechanical method to excavate material (sand, gravel, dirt, etc.) using steel "buckets" on a circular, continuous "bucketline" at the front end of the dredge. The original gold dredges were large, multi-story machines built in the first half of the 1900s. Gold Dredge, Klondike River, Canada, 1915 The Yankee Fork dredge near Bonanza City, Idaho, which operated into the 1950s.Ī gold dredge is a placer mining machine that extracts gold from sand, gravel, and dirt using water and mechanical methods. For the historic landmark in the United States, see Gold Dredge.
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