alluvial mining diamond barge

basic principles of alluvial diamond exploration - sciencedirect

There is no single, universally applicable method of target selection for alluvial diamond deposits. Climatic and geomorphic history, stratigraphy, structure and tectonic history are important factors that require study and need to be understood for each alluvial diamond province prior to target selection. What is appropriate in one part of the world may be entirely inappropriate in another, but there are some basic principles which must be followed in planning and executing any alluvial diamond exploration program.

The general principles that govern any search for alluvial diamonds, the processes involved in alluvial diamond deposition and the methods and technology used in exploring for and evaluating such deposits are also discussed. The principles are illustrated, where possible, by reference to a case history of exploration for alluvial diamonds in the south-western Transvaal, South Africa.

Before starting field exploration, it is important to have a comprehensive knowledge of (i) the regional geology of the drainage basin under revue; (ii) the constituent lithologies of the gravel being prospected for; (iii) the geomorphic and climatic factors which have affected the exploration area; (iv) the type of deposit to be sought; and (v) any post-depositional processes which may have affected the alluvial deposits being considered for exploration. This overall information is necessary to construct a concise, yet comprehensive regional model upon which to base any alluvial diamond exploration program. Remote sensing methods are useful, but there is no substitute for an observant, well-trained field geologist expert in mapping and air-photo interpretation. Sampling of drainages for indicator minerals has limited application in alluvial exploration. A brief review of the evaluation methods recommended for an alluvial deposit is included.

marine diamond mining in the benguela current large marine ecosystem: the case of namibia - sciencedirect

The first diamonds from the sea floor were recovered in shallow waters off the Namibian coast some 110 years ago. However, it took 50 more years, before some systematic sea floor diamond mining with purpose-built barges occurred in Namibian waters in the early 1960s. This was followed by a period of detailed exploration and mining tool development, which saw Namibia emerge as the leading nation in marine diamond mining in the late 1980s. Today, a fleet of seven modern mining and exploration vessels is involved in the recovery of more than three quarters of Namibia's diamond production. As the process involves modification of the sea bed, careful monitoring and impact mitigation is carried out according to international best standards.

imilingo and the the future of alluvial diamond mining

Its latest technological innovation, the iDredgeXRT which combines dredging with sensor-based sorting will be instrumental in changing the alluvial mining game in Africa and will help unlock its diamond wealth, MD Jaco Prinsloo tells Chantelle Kotze.

No stranger to diamonds or minerals processing, Prinsloo, a mechanical engineer by profession, has gained extensive knowledge in diamond processing while working as lead engineer for DRA Global on several large diamond mining projects.

These projects included the incorporation of an X-Ray transmission (XRT) circuit into the processing plant at Lucara Diamond Corp.s Karowe diamond mine in Botswana and the design of an XRT diamond sorting machine and recovery area for Stornoways Renard diamond mine in Quebec, Canada.

Understanding the breakthrough that XRT sorting brings to the diamond mining industry, and as a result of the surge in the application of sensor based sorting, Prinsloo joined Imilingo in 2015 as general manager.

In 2017 he acquired a 50% shareholding in the company and was appointed MD. He joined Imilingo with a clear goal in mind to develop new technologies, not only to improve the efficiency of mining operations, but also to help solve complex problems in the mining sector.

With a concept in hand, the Imilingo team spent time in the Democratic Republic of Congo (DRC) and Angola understanding how the companys dredging and sorting technology could be implemented to improve the conventional mining method using barges equipped with centrifugal pumps and suction hoses guided by underwater divers to transfer the recovered material to surface, which is then sorted by hand.

While in the DRC, Imilingo was enlisted by privately-owned Swedish company Africa Resources AB to provide a solution for the profitable recovery of greater volumes of alluvial diamonds from its 674 concession along the Tshikapa River in the south eastern part of the country.

Following a site visit in late 2016 to assess the needs and requirements of Africa Resources AB, Imilingo set out to design a fit-for-purpose vessel at its head offices and manufacturing facility in Centurion, South Africa.

The iDredge consists of a 60 kW Dragflow submersible pump and high depth pressure compensators housed within a pontoon structure. The electrically-driven pump, supplied by Tsurumi Pumps Africa, is designed to accommodate 200 m3/h of gravel, and can operate at depths of up to 50 m pumping particle sizes of between 0 and 60 mm through a 150 NB pipe.

The pump issuspended from a rotatable crane structure, which also functions as the lifting equipment for maintenance tasks, while an on-board control panel enables the operator to determine the position and movement of the iDredge.

While the diamond-bearing gravel is currently being hand sorted at the Africa Resources AB site, Prinsloo explains that the iDredge can be complemented with Imilingos modular sorting plant the iPlant for a complete onsite mining and sorting solution. The iDredge has been in operation in the DRC since May 2018.

By consulting with Angolanowned MONTHE REAL LDA a business incorporated by three Angolan entrepreneurs with oil & gas and logistics experience and having the first mining venture to be funded by Banco de Comercio e Industria through the Angola Investe programme, Imilingo has taken its iDredge technology to new heights by incorporating XRT sorting on board a larger, more refined version of the iDredge to form a single step mining and sorting solution.

The companys iDredgeXRT, a world first in alluvial diamond mining, consists of a larger 20 x 20 m dredging unit, a 200 m3/h submersible pump with excavators, a clamshell, a sizing screen fitted with two TOMRA XRT sorting machines and two diesel-electric generators to power the system.

The dredge also includes 3Dsonar scanner technology for viewing the pumping operations and a GPS to track the locations where mining has been done. The iDredgeXRT works by pumping diamond-bearing gravel from depths of up to 80 m onto a sizing screen which then sizes the material into three different size fractions (3-9 mm, 9-20 mm and 20-50 mm).

The tailings material from the sorters report to two sumps located beneath the dredge where the material is collected for deposition. The level of water and gravel in these pumps also act as a level control for the dredging unit, explains Prinsloo.

The fact that only one processing step is required when using the iDredgeXRT makes this solution a huge win in terms of process efficiency, says Prinsloo, explaining that there is no need to further process a sorters concentrate before final hand sorting.

Moreover, diamond recovery by means of XRT sorting replaces the conventional concentration and recovery stages such as dense media separation (DMS) for the size fractions above 3 mm in a diamond recovery process.

We are excited about the prospects of this latest innovation in drastically changing the way alluvial mining is executed. Any opportunity to actively contribute to the sustainable transformation of the mining industry is a massive driving force for us, concludes Prinsloo.

alluvial and placer mineral deposits | geology for investors

Technically a placer deposit is the general term for a mineral deposit formed by the concentration of moving particles by gravity. Alluvial is the name for placer deposits formed by water action in a stream or river. For most people, its all about alluvial deposits, or to be blunt, the allure of gold, with the odd precious and semi-precious gem thrown into the mix.

You can still become an amateur gold or gem miner. Youre not going to wake up one morning, pack up the truck and decide to start an open-pit or underground mine. Clearly, such things involve serious resources and skills, well beyond a single persons resources. Alluvial mining is a little different; you can work a gold claim with cheap gear, and you can learn the skills involved in a few hours.

For a mineral to be concentrated in a placer deposits, it needs to be both relatively heavy and resistant enough to withstand the pounding of water. The placer itself must also be old enough (millions of years) to have sorted and concentrated the heavy and resilient minerals. Commodities commonly mined in placer deposits include:

The pattern with many placer mining areas is the original deposits were quickly found and exploited. Surface placer deposits are easy to mine, only requiring scooping up the gravel and then concentrating the valuable minerals.

The ease of discovery meant that as metal-hungry Western Civilisation spread out across the world, there was a wave of gold rushes. New settlers literally tripped over gold in colonial rivers, which led to gold rushes in practically every continent they came to.

Placer deposits are also the ultimate path finder deposits if a valuable commodity is available on the surface in a placer deposit, where did it come from? Gold, particularly, has often not moved far, so a minor alluvial gold deposit can result in a major underground gold mine as in Australias Kalgoorlieor Bendigo gold rushes. In other places, most of the gold was in the alluvial deposits as in the Klondike/Alaska Gold Rush and the California gold rushes of the 19th century.

Gold rushes in Alaska, California and the Yukon and many others started with alluvial discoveries. The gold rushes often had lasting effects, even when the gold ran out, or became a more normal percentage of the economy, some percentage of the people stayed on. What had changed though was the population and the infrastructure. California was an outpost until gold put it on the map, and connected it by road to the eastern states, replacing a long sea voyage via Panama or South America. To a lesser extent the same thing happened in Alaska and the Yukon. Large placer deposits are still mined in Alaska, and smaller commercial operations produce across the western US; an echo of the gold rush still lives on.

Tin was mined as far back as the third millennium BC as a key component of bronze weapons. Historic mining in England in the counties of Devon and Cornwall started with alluvial tin deposits, which was later followed by underground mining.

Myanmars ruby fields, diamonds from southern Africa Semi-precious stones in Australia. Like gold, amateur fossickers, in Western countries, often seek gemstones. In less developed countries, local villagers mine to supplement their income.

Gold panning is the simplest technique to extract gold from gravel. Washing the gravel allows the heavier gold particles to separate at the bottom of the pan. The design of pans hasnt changed for hundreds of years, but new lighter weight materials do make them easier to use. Panning requires a lot of water and is not a scalable technology. Panning is often used to locate gold, but after a claim is established, even amateur prospectors will generally use a different method. Geologists may use panning as part of an exploration program.

A rocker or cradle box is capable of moving much larger volumes than a pan. The technology was developed by Chinese miners who followed the gold rushes to Australia and North America. Rockers are still used in areas where water is scarce, and for small-scale production.

Larger scale version of a rocker, in which water is forced down a series of steps, the base of which is sometimes lined with fabric to catch the gold. This method is more efficient than panning or a cradle box, but uses a lot of water.

In many gold areas, water is a scarce resource, so dry washing was developed where gravel has air forced over it to winnow out the lighter material and leave gold concentrated in the residue. Companies mining placer deposits Kinross, Fort Knox gold placer mine, Alaska. PT Padmanaba Putra Mandiriiron sand, Java, Indonesia New Zealand Steel iron sand, Waikato, New Zealand De Beers diamond bearing beach placers, Namibia