Gold dredge

A gold digger (English gold dredge ) is a Dredging ( dredging ) with integrated processing plant, used for washing gold from placer deposits, that is, from alluvial surface ( fluvial sediments, boulders, gravel, sand, mud ) in bed or shore area of ​​a gold-bearing body of water.

Had their heyday in the early 20th century, such excavator in continuation of the gold rush era of the 19th century, when the tedious manual work of thousands of gold miners has been increasingly supported, with the industrialization of high-performance machines. With declining income and prices, the large excavator mid-20th century largely disappeared from the former gold regions of the West, in other countries in the world but they are still used today in various sizes.

Similar soap excavators besides gold also for the recovery of other metals (or ores ), minerals and gemstones (especially diamonds ) are used, which occur in some placer deposits in bauwürdiger concentration. The metals, in particular tin (usually as cassiterite ) to name but also titanium (commonly used as ilmenite or rutile), zirconium, tungsten, platinum, and various others.

• 2.1 -preserved historical specimens

Technology

Detail Bucket Brigade

Detail settler boom

Design and operation

For its application a floating dredger is mounted on a pontoon. As the excavator barely moved forward in his work, he has no streamlined hull shape, but rather a rectangular, oriented to the function floor plan. In general, the excavator receives a weather protective cover so that it looks more like a floating factory building than a ship. The excavator has also drawn not have its own drive for locomotion, but is. The machines in the interior took place in the first gold diggers by steam engine, and later by an electric motor or internal combustion engine. In rare cases, when used in a stream with sufficient flow, was the engine driving on the side of the excavator -mounted water wheel, similar to a ship mill.

For continuous promotion of aluvialen material of the gold digger has on the front over the actual excavator. This is in the classical style around a bucket chain excavators. More recently, smaller suction dredger (often with cutting head ) is used instead of bucket chain excavators often.

The excavator raises the material directly to a processing plant, consisting of a perforated drum for presorting and one or more wash troughs or other separator for the separation of gold.

After separation of the gold the washed material ( tailings, tailings disposal ) is ejected at the rear of the excavator with a settler with a long boom again. The coarse debris from the drum is issued usually separated from the fines, but a mixing favored a quick restoration.

Operational environment

Thawing of the permafrost in the run-up to the excavator by means of steam

Typical " crocodiles ", left by a gold digger

The gold in placer deposits originates from primary deposits, which are found mainly in tectonically and hydrothermally very active zones of the earth. The weathering products of such deposits are washed out in the mountains and transported downhill by streams and rivers through water where the heavy gold deposited in quiet zones of the waters in soaps as a secondary deposit, and concentrated. Such secondary deposits found in sand and gravel banks, terraces and meander loops in gold bearing rivers, rarely also on beaches of lakes or even oceans (the latter eg, in Nome, Alaska).

To obtain the soap, the excavator is working either directly in natural waters (as far as the water depth and the reach of the excavator allowed) or a specially built for the excavator quarry alongside the actual body of water. In extreme cases, the excavated hole is not much bigger than the excavator itself; the material, which taketh away the front of the excavator, he throws behind him, and so "eats" the excavator through the underground - the excavated hole migrates with the excavator. By swinging back and forth and the slow forward movement of the excavator arise behind the excavator typical ridge-like mounds in the field ( " banana ", " crocodile "), in which the track of the excavator is often many decades later, identifiable if no reclamation is carried out.

In use regions with permafrost (Alaska / USA, Yukon / Canada, Siberia / Russia, ... ), it was often necessary to thaw the frozen ground in advance of the excavator only by steam lances before the excavators could promote the material ( see picture).

Because of the remote locations and their large dimensions and weights of gold diggers are usually assembled in a mechanical factory, transported in modules as heavy transport to the site and assembled ready there.

Performance

Currently the largest gold dredge in operation in the world, the Kanieri in New Zealand, achieved with cantilevers have a length of 170 meters and can dig up to 30 feet deep. Without the boom excavator dimensions of 80 x 36 x 30 meters has. The total weight is 3500 tons. A single bucket holds 560 liters of material, the conveying capacity of the excavator is up to 850 cubic meters per hour.

The Western world was once the largest gold diggers, initially operated by the Austral Malay Tin Ltd. on the Clutha River in New Zealand from 1938, was with a length of 176 meters as large as that Kanieri, but still significantly heavier. He had two spreaders. 1952, the excavator for the recovery of tin was transferred to Malaysia. Nearby, at Batu Gajah in Perak state, is now a similarly large Zinnbagger (size 75 mx 35 m, weight 4500 tons ) to visit from the same era as a museum object.

Largest ever gold digger in the world was in 1969 by the Russian heavy machine factory Irkutsk ( Иркутский завод тяжёлого машиностроения ) manufactured for use in the gold field Marakan near Bodaibo. The excavator of the type 600D had a working weight of almost 11,000 tons and a size of 236 mx 50 m ( without extension ). His bucket preconceived per 600 liters and he could dig 50 feet deep.

Under favorable conditions, a single excavator, a yield of up to 800 troy ounces obtain (25 kg) of gold per day, which corresponds to the typical earnings of more than ten thousand miners with traditional pans. A modern large excavators in Mongolia, on the Tuul River, promotes more than 1 ton of gold per year.

History

Gold diggers were developed in New Zealand as part of the Otago gold rush. First attempts, derived from dredgers, as they were used for dredging of fairways, channels or harbor in the shipping industry, there were already from 1863. The first powerful gold digger Dunedin worked from 1881 to 1901 on the Clutha River. Due to the great success of the technology quickly spread, first in the New Zealand gold region on the west coast and from the 1890s also in all other gold regions of the world. At the peak of the distribution ( in 1920 ) were the world hundreds of great gold diggers in action, only about 200 in New Zealand, about 120 in the United States ( including 60 in California, 42 in Alaska, others in Colorado, Montana, ...), but in Canada ( about 25 in the Yukon territory ), Australia, Russia (eg Ural region, at Kachkanar, Siberia, ... ), in Papua New Guinea ( Bulolo, Morobe Province ) and in various other countries of South America, Asia and Africa.

Also in Germany was made in the context of self-sufficiency efforts of the Nazi regime from 1939 to 1943 to try to win with the excavator Rheingold gold from the Rhine. The success, however, was moderate: In the four years of its operation, the excavator promoted only around 300 grams of gold. Supposedly about 30 grams thereof were used to make a Nibelungenring for Hermann Goering. The ring - if it ever existed - has been lost. The former place of work of the excavator near Rastatt is now known as the Gold channel.

In some countries of the world, in South America (Peru, Brazil, Guyana, Colombia, ... ), Asia (Russia, China, Mongolia, Papua New Guinea, ... ) and Africa (Sierra Leone, ... ) until today are traditional gold diggers of various sizes in use.

Preserved historical specimens

Often were gold diggers, when the operation was uneconomic, simply on their last location - usually in a remote valley far away from the nearest settlement - left and left to decay. The majority of the excavator is rotted with time and possibly get a ruin. To many of these ruins is horror stories are told about ghosts of gold diggers who are said to haunt there.

A few excavators were preserved due to favorable climatic or local conditions and are preserved to this day in some good condition, often protected as an industrial monument and / or to visit as a tourist attraction.

Here is the list - not exhaustive - some well-known gold digger:

• Fairbanks Creek Dredge (No. 2)
• Chatanika Dredge (No. 3)
• Dome Creek Dredge (No. 5)
• Goldstream Dredge (No. 8)
• Cripple Creek Dredge (No. 10)

• No. 2: Fairbanks Creek ( 65 ° 2 ' 35 " N, 147 ° 5' 36 " W65.042975 - 147.093394 )
• No. 3: near Chatanika (65 ° 6 ' 51 " N, 147 ° 30' 23" W65.114038 - 147.506486 )
• No. 5: in the Upper Creek Dome north of Fox ( 65 ° 1 ' 47 " N, 147 ° 34 ' 35" W65.029599 - 147.576288 )
• No. 8: in Goldstream Creek southwest of Fox ( 64 ° 56 ' 14 " N, 147 ° 39' 27" W64.937148 - 147.657548 )
• No. 10: Cripple Creek in the south of ester (64 ° 50 ' 19 " N, 147 ° 59' 8" W64.83863 - 147.985582 )

• No. 17
• No. 21

• No. 17:
• No. 21: 39 ° 10 ' 34 "N, 121 ° 27' 31" W39.176218 - 121.458578

• No. 17: 1917-1967, reopening in 2008
• No. 21: 1916-1988, 2003 sunk.