copper ore processing in Palabora Mining South Africa

Copper ore processing in Palabora Mining South Africa decided to extend the underground mining of copper. Below the surface mining blocks with a daily production of 30,000 tons is an acceptable way of economically maximize the recovery of the deposit. This will facilitate the copper ore processing in Palabora Mining South Africa were at least able to walk for 20 years. When mining the copper deposits below the surface, it is planned to increase further the efficiency of mining process of copper using modern equipment automation and tele-controlled machine. The aim is to extend the daily operations, increase productivity, integrating data acquisition and diagnostic features and increase the level of automation. On the one hand, the system is designed to provide comprehensive information on the operations throughout the mine to management. At the same time, the operating personnel in the control panel needs direct control and monitoring of underground mining activities.

Underground Copper Ore Stream in  Palabora Mining South Africa

       Copper ore from the underground block-cave mine – less than 300mm in size – is conveyed to two stockpiles, each feeding two separate, autogenous wet-grinding circuits. These in turn, each comprise a 9.75 meter-diameter tumbling mill rotated by 2 x 3.5 MW drives. Large rocks impact, scrub and attrition against each other, reducing their size, which results in the liberation of the copper sulphides.






      Mill products are sized by vibrating screens to produce coarse feed to the pebble crushers. Fine particles of 0.3mm removed from the circuit as the main product of milling up to 30,000Tpd (tonnes per day?) Product rough cyclone underflow is recycled. Cyclone overflow from both circuits is then pumped 1.5 kilometres to the secondary milling plant (SMP) where the ore is further ground to less than 0.15mm, using steel balls in up to five parallel 1.2 MW milling circuits. Secondary milling has been applied since 2003 by reconfiguring the existing equipment. This is to improve the liberation and recovery of copper in underground ore grade higher.

      Chemicals are added to allow the copper sulfide particles to separate from the fine ore particles through the process of ‘froth flotation’. A xanthate collector metered into the slurry and adsorbs to the particles to the copper sulfide to increase their hydrophobicity. Frother also added to produce a stable foam. The flow is then divided between the parallel rows of flotation cells. Each row contains several agitator to maintain the suspension and for the air to disperse the slurry. As the air bubbles rise to the surface of the cell, the copper mineral particles attach hydrophobic privileged to bubble and form a stable foam, which continues to overflow into launders. The process is then repeated two more times to recover almost 90% of the copper feed to only 2% of the weight of feed to produce 32% of copper sulphide concentrates. The latter is then pumped to the dewatering plant. 

Conventional Process Leaching Of Copper in  Palabora Mining South Africa
Transition to underground mining has allowed 50,000 tpd of destroying conventional milling and flotation capacity. Copper and magnetite recovered on behalf of Foskor (neighboring mining company) by a 20,000 tpd ore processing toll marginal of stock from open pit operations. These Conventional process leaching of copper are also applied to underground ore available in more than autogenous grinding capacity.

      A main rotating crusher is used to reduce the dump material from 200mm to 1500mm down in size before relaying to one of the two stocks. Feeders and conveyors transport the ore to a two-stage dry crushing plant where two secondary crushers reduce the size to below 50mm. Additionally, 5 tertiary crushers further reduce the ore to below 20mm, operating in closed circuit with vibrating screens. Crushing plant product is then conveyed 1.4 kilometres to fill any one of six fine ore bins, each one feeding six rod mill flotation sections, all operating in parallel. Certain sections are used for wet grinding marginal ore to below 0.3mm, followed by a copper flotation process similar to that used for the underground ore. Concentrate is pumped to a dewatering plant, while magnetite removed from the tailings thickening and pumping before the final product for Foskor for flotation of phosphate
       A third secondary crusher-feed stockpile is reserved for ‘minus 200mm’ underground ore that can be diverted by means of a moveable chute and transfer conveyor. Underground ore is batched through the secondary crushing plant and directed to the fine ore bins. Each section is able to grind 6,000 Tpd of ore finer than 0.2mm before froth flotation.

 Dewatering, Magnetite Production And Tailings Disposal In  Palabora Mining South Africa
Concentrated sludge is pumped to a thickener using a vacuum filter disc and rotary dryers coal successively removing water to reach 8% residual moisture. Dryer product weighed by the belt scale and sample before submission to the receiving warehouse smelter. Flotation tailings from the second circuit and conventional Autogenous pumped into magnetic separation plant, where a rotating magnetic drum magnetite extract 16% by weight of the slurry. Nine three-drum magnets are used for the three stages of upgrades to produce up to 5,000 TPD of 98% pure magnetite concentrate. The concentrate separated into two size by rising currents of water (elutriasi). On average, 600 TPD fine magnetite directed to classifier overflow, thickened, filtered and stockpiled prior to the delivery of domestic heavy media consumers who are used to upgrade coal. The majority of magnetite to be transported to underflow classifier and then pumped either to drying of the desert to the fence and export, or dam large magnetite deposit, depending on the sales commitment. Export magnetite is used for the production of iron and steel.
      After removing magnetite, ore tailings underground flows to three parallel 90 meter diameter tailings thickener to recover and reuse water, while the combined underflows pumped to various points around the perimeter of a large tailings dams. The dam wall is maintained at a higher level with coarse solids beach. Fines flowing into the central pool, where the clear water contained by the siphon and stored in a dam the water back for reuse in the process.

Palabora Mining Companies In South Africa

Palabora Mining Company in South Africa

      Palabora Mining Company was founded in South Africa in August 1956. The company is owned and managed by Rio Tinto. 57.7% owned by Rio Tinto and Anglo American has a 16.8% stake. On September 5, 2012, the two companies announced their intention to sell their respective interests in Palabora. On December 11, 2012, Rio Tinto announced that it reached an agreement with a consortium binding sales that are committed to the sustainable management continuously from Palabora. The consortium is comprised of South Africa and China entity led by the Industrial Development Corporation (IDC) of South Africa Limited and China’s Hebei Iron & Steel Group. The sale agreement was concluded in July 2013, and the company name changed from Palabora to Palabora Copper Mining Company (Pty) Limited.
       Located 360km north east of Pretoria, close to Kruger National Park, Palabora is South Africa’s leading copper producer and also a major source of vermiculite and baddeleyite (zirconium oxide). The majority shareholder in Palabora Mining Co. is Rio Tinto plc (57.7%) and Anglo-American. Palabora Copper (Pty) Limited and beneficiates extract copper and other by-products in Ba-Phalaborwa area of Limpopo Province. Palabora just fine copper producer South Africa and supply the local market with 85% of copper needs.
       Copper operations consist of underground mines, a concentrator, a copper smelter with anode casting facilities and associated acid plant, an electrolytic refinery tank house, rod casting plant, magnetite separation plant and plant by-product recovery. Vermiculite operation comprises open pit mining operations and recovery plants. Open-pit mining began in Palabora in 1964 and ended in 2002 when the economy reaches a depth hole final. The development of an underground mine to work ore remaining under the bottom of the pit began in the last years of open pit mine production, at a cost of about $ 465m, with the prospect of life of over 20 years in the underground operation. Integrated copper production complex has a metal-refining capacity of 135,000t / y, despite the change to underground mining means that some of this capacity is now redundant. Operation employs about 1,800 people.
      Palabora containing magnetite, vermiculite, apatite, zirconium, titanium and uranium and copper. Deposit is hosted in a complex consisting of alkali particularly frozen pyroxenite with events pegmatites, foskorite and carbonatite. Three separate mineralized zones have been identified in outcrop 20km² complex surfaces, from the north is rich in phosphates and the center (Loolekop) zone forms the basis for this Palabora copper production. Copper ores are hosted in carbonatite pipe where the value is usually concentric with the highest value (1.0% copper) at its core. High grade mineralization extends down the center of the projected end of the pit open floor. Underground mine has been developed on the proven reserves 225Mt at 0.7% copper, plus the possibility of additional reserves of 16Mt grading 0.49% copper. At the end of 2005, proven and probable reserves of 112Mt levels reached 0.56% copper, representing a significant reduction of the tonnage and grade quoted previous year. Rio Tinto recorded a US $ 161m asset write-down in the 2005 accounts to reflect this.

operation Underground mine in Palabora       Throughout the 35-year life, Palabora often at the forefront of technological development of surface mining. The main feature is the use of trolley-assist systems for haul trucks out of the pit, to save diesel, and it was one of the early users both in pit crushing and computerized despatching trucks. Open pit fleet consists of about 20 Euclid and Unit Rig trucks, with the four P & H 2100XPA and 2,800 shovel. Cargo truck monitored using Pit control systems on-board overload the shovel, associated with Modular Mining Systems’ despatching and monitoring program. Fuller-Traylor rotating in-pit crusher, with a nominal capacity of 5,000t / h, feeding the main conveyor that carried a 1.8-width crushed ore drift up on the pit wall to the rough surface of the ore stock.

open pit mines in Palabora       Underground mine is block caving operation, the first such system to be used in metal mining in South Africa. With the introduction of underground operations, ore output had fallen from the 82,000t / d achieved in the previous open pit to 30,000t / d. However, the transition to underground production has proved problematic, especially in relation to the handling of large ore in drawpoints, and I have struggled to meet production targets. Average output during the end of 2003 was about 20,000t / d, and additional secondary breaking system is being built to help alleviate the bottleneck drawpoint.
       Shaft sinkers contracted to install the service shaft and axle production in the main-1,280m, while RUC Mining Contractors have carried out underground development. This includes driving around 36km of tunnels plus the underground crusher station, ore handling infrastructure and weaken level to block the first cave, located 500 m below the base of the final hole. Destroying the station was equipped with four ThyssenKrupp 900T / h double-toggle jaw crusher feed conveyor which connects to the shaft 1.32km production.
       Palabora employs one of the most complex recovery circuit installed in each copper mine, producing eight metals, minerals and chemical products in about 20 different varieties and grades. The complex includes a concentrator, a copper smelter and refinery, is now capable of producing 135,000t / y of copper plus by-product. Phosphate-rich tailings sent to Foskor, while Palabora sells its own copper, precious metals, nickel, zirconium, magnetite and vermiculite in domestic and world markets.

Copper Smelting Process At Palabora Mine South Africa

Underground ore stream 

      As a first step copper smelting process At Palabora Mine South Africa, dried copper concentrate is blended with fine quartz flux and process materials, which are recycled from upstream. This copper smelting process is then poured into a continuous basis, with coal reverberatory furnaces, as well as operate up to 1400 ° C. The resulting melt will separate into two layers on the hearth furnace The denser molten matte layer captures the copper-iron sulphides below the unwanted uppe r slag layer, which is skimmed off periodically via skim bays and launders into large pots destined for rail transportation to the slag stockpile..
      Then process of copper matte with a copper content of 42% is tapped periodically through launders open into a large ladle, which will be directly transferred by rail and overhead crane into one of the three furnaces oblique converter. This copper smelting process are operated batch-wise, by blowing hot air through the matte to oxidise the sulphur and the iron, and then adding silica flux to form an iron-rich slag before returning it to the reverberatory furnace. After all the iron content from copper smelting process has been lost and, air is blown further without residual flux so that oxidize sulfur, and ultimately produce blister copper which is 98% pure. The converting process is exothermic and the excess heat is used to melt internal recycle materials and copper scrap from the refinery..























      Blister copper is then transferred to one of three anode furnaces, where the last traces of sulphur are removed by blowing air through the molten metal. This is followed by an injection of hydrocarbon fuel to reduce oxygen to very low levels. 99.5% copper is cast into copper anodes by means of a single rotating anode casting wheel. Anodes are hoisted into water quench tanks and racks for sorting and cooling; and then transferred by rail to the copper refinery. A ‘melting’ or ‘holding’ furnace is used to supplement copper production process by smelting process anode scrap that has returned from the refining process.














      Off-gas from the reverberatory furnace passes through two waste heat boilers and a balloon flue before it reaches a final process of cleaning by electrostatic dust precipitation. The flue dust is returned to the furnace and the low concentration off-gas can be discharged directly into the atmosphere via a 152 meter high concrete stack. It can also be treated in the wet gas scrubbing plant, if the precipitator is off-line. In this instance, once scrubbed, the off-gas is released to the atmosphere via a 70 meter high clean gas stack. Steam generated by the waste heat boilers is used to pre-heat primary combustion air for the coal pulverisers and to direct secondary air to the furnace. Excess steam is used to drive a 9.6 MW turbo-generator. Higher strength off-gas from each of the converters is passed through separate electrostatic precipitators for gas cleaning. The gas is then treated in a single contact sulphuric acid plant to produce 98% sulphuric acid for sale to the domestic market.

Mining Methods And Gold Processing Musselwhite Mines


      Mining methods and gold processing musselwhite mines initially operated both open-pit and underground mines, open-pit production having been designed to ensure mill feed at a rate of 3,300t/d for about five years following mill commissioning. Most of the mine’s ore is now sourced from underground. And gold processing from musselwhite mines processing includes crushing, grinding, leaching by cyanidation, carbon in pulp recovery and electrowinning, to achieve an overall recovery of approximately 96%.
      The stratigraphy in the Musselwhite mine vicinity is dominated by mafic volcanics, chemical sediments and felsic volcanics. External into the supracrustal sequences are a series of undifferentiated gneisses and granitoids. All mineral lithologies within the immediate mine area have been metamorphosed at mid to upper amphibolite facies. Mineralization is predominantly hosted within meta-chemical sediments (banded iron formations) and in particular within garnet-magnetite-grunerite facies meta-banded iron formations (locally termed the Northern Iron Formation). The location of mineralization is controlled by the intersection of shear zones and folded meta-banded iron formations. These geological controls result in mineralized shoots, which plunge at approximately 15 degrees to grid north, have a down dip extent of up to 150 metres, down plunge continuation in excess of 1.5 kilometres, and across-lithology width of up to 10 metres. Mineralized zones are characterized by abundant pyrrhotite, quartz flooding and, rarely, visible gold.

Mining Methods In  Musselwhite Mines
     
      Mining methods in Musselwhite mines is Longhole, Underhand and Overhand Cut and Fill. The Musselwhite mine which is located in Weagamow – North Caribou Greenstone Belt of the Sachigo Subprovince, part of the Archean Superior Province. In 1997 Phase first , underground production gold mine from the T Antiform (T-A) deposit, built up to a design rate of 2,700 t/d, and supplemented by ore, at a rate of 1,000 t/d, from the PQ zone. The T-A was increased to 3,300 t/d by expanding operations the fleet of 40-tonne haul trucks. The first phase of project development of the underground mine section of the T Antiform deposit involved developing a decline from surface to access some 5Mt of ore mineral reserves above the 275m level. Other infrastructure included a ventilation raise to surface. 
      Mining Methods during phase two, the reserves mineral ore were accessed via a production shaft, achieving a mining rate of 3,500t/d. A new ventilation shaft was sunk and the existing ventilation shaft converted into a mining production shaft. Mining methods underground is from transverse longhole stopes where the mining width is greater than 12m, the ore being blasted using ring drilling. Cemented rockfill is used in primary stoping blocks and uncemented rockfill in secondary stopes. Longitudinal stopes use conventional longhole benching and are backfilled with waste rock and crushed material from open-pit stripping. Mineral ore is extracted via a blast hole process and moved via a series of scoop-trams and underground dump trucks to one of 2 rockbreakers, either on the surface or at a 400 meter level. The ore then travels once through a jaw crusher and through a series of conveyor belts and countinously along a cone crusher rock sizing circuit. When the ore reaches a specific size it is transported to the mill building. Ore handling underground is undertaken by remote-controlled LHDs, with 40t-capacity trucks used to haul the mineral ore to surface.
      Musselwhite ore is crushed underground in a Nordberg jaw crusher, then hoisted to another Nordberg jaw crusher on surface. Final mineral ore reduction to --9 mm is accomplished in a Simplicity cone crusher. The mineral ore is further reduced to 80% --106 microns in a grinding circuit consisting of a Nordberg rod and a Nordberg ball mill. The seven existing 40-mm Technequip hydrocyclones are soon to be replaced with four 510-mm Weir Cavex cyclones.
   
Gold processing Musselwhite Mines
     
      Gold processing Musselwhite mines uses a gold cyanidation and CIP (carbon in pulp) extraction process. The mill Musselwhite gold mines is designed to treat 3300t/d and employs conventional gravity separation, cyanide leach and carbon-in-pulp (CIP) processes to recover the gold from the ore. Gold processing first is primary mineral crushing, is carried out on surface using a jaw crusher, the output being fed directly to a secondary crushing plant. Gravity concentration using a Knelson concentrator and shaking tables recovers coarse free gold from the ore, with the remainder being leached for 32 hours in agitated tanks. The slurry is then thickened, exposed to a cyanide treatment to extract it from the ore and into the solution, absorbed from the solution with activated carbon.
      Gold in solution is recovered by absorption onto activated carbon in a CIP circuit. Loaded carbon is eluted using the conventional pressurized Zadra technique. The CIP tailing flows by gravity to a two-stage CCD washing circuit to recover cyanide. The washed tailing is pumped to a reaction vessel for cyanide destruction. The Inco/S02 air process with two stages of washing is used in order to provide an effluent containing less than 5ppm cyanide for discharge to the tailings pond. The gravity circuit includes two Knelson concentrators. The recovered free gold is placed in a ConSep Acadia reactor, also provided by Knelson. This is a patented, high-efficiency batch leaching system and EW reactor. Between 26% and 30% of the gold is recovered in the gravity/Acacia circuit.
     
      Ninety-three per cent of the remaining gold is recovered by conventional CIP means, bringing the total gold recovery rate to 95.5%. The mill houses four stirred-tank reactors in which the slurry is leached, and six CIP tanks. Loaded carbon passes through an elution column using a caustic-cyanide solution to strip the gold. The pregnant solution passes into three EW banks, where the gold is plated onto cathodes. Gold is washed from the cathodes, dried, smelted and poured into doré bars containing 85-93% Au.
      Tails from the CIP circuit are washed with reclaim water in a two-stage counter-current decantation circuit. Cyanide is destroyed using the Inco SO2 process. The final slurry is impounded behind a tailings dam. The current plans are to increase the existing tailings disposal capacity using a dry stacking method and backfill system to help accommodate the mine life that could extend up to the year 2026.Twice a year the excess water is drained off the tailings pond where it flows naturally through a series of polishing ponds and a freshwater marsh. By the time the runoff reaches the natural watershed system the cyanide content is drastically reduced and poses no environmental or safety hazard.
      Since achieving its first commercial production in April of 1997, Musselwhite mine has produced over three million ounces of gold. The 2010 discovery of the Lynx zone—a zone of higher-grade ore above the cornerstone PQ Deeps underground operation—has created the potential to significantly enhance economics and extend productive mine life. Exploration continues to test other high-potential lateral targets and extension of existing gold structures. During 2014 the operation produced 278,300 ounces of gold and is forecast to produce between 250,000 and 270,000 ounces in 2015.

Mining Operations And Mining Methods Porcupine

Mining Operations And Mining Methods Porcupine
       Mining operations Porcupine is located in Timmins, Ontario, one of the world’s great gold producing camps. Located within the city limits of Timmins, Ontario, the Porcupine complex includes approximately 38,000 hectares of mining claims. Paved-road access is readily available, as the principal properties. The Porcupine mines consist of ultramafic and mafic volcanic rocks of the Keewatin subgroup overlain by sedimentary rocks of the Timiskaming group. The lands lie adjacent and to the north of the regionally significant Porcupine Destor Fault. Gold mineralization is found in a number of different structural settings and consists of continuous quartz carbonate veins, quartz tourmaline veins, quartz stockworks and gold associated with disseminated sulphides.
      Porcupine mining consists of the Hoyle Pond and Dome underground mines, the Hollinger open pit mine, several large tonnage stockpiles, and a central milling facility. Progress is steadily advancing on a deep underground shaft (winze) that will provide increased access to zones such as the TVZ and VAZ in the underground Hoyle Pond mine operation and significantly extend the mine’s productive life.

Methods of gold mining operations Hoyle Pond
      Methods of gold mining operations Porcupine, exploration drilling at underground. The Hoyle has demonstrated improving gold grades and the extension of several gold structures at depth. This success is spurring new investments in mine development to position the revitalized Porcupine mine complex for long-term success.
      The Hoyle Pond underground mine is accessed by decline and by a shaft. The current winze configuration has the potential for expansion to access below 2,000 metres. Mining methods employed are conventional cut and fill, shrinkage, panel mining and longhole methods in wider zones.
      Gold is recovered using a combination of gravity concentration and cyanidation techniques. The circuit consists of primary, secondary and tertiary crushing, rod/ball mill grinding, gravity concentration, cyanide leaching, carbon-in-pulp gold recovery, stripping, electro winning and refining.

Methods of gold mining operations Hollinger       The Hollinger open pit is located in the City of Timmins adjacent to residents and businesses. The pit will reclaim 250 acres of currently unusable and unsafe land for future safe public use. All permits have been received following a period of public consultation and the installation of a monitoring system ensuring the pit can meet the Best Management Plan, signed with the City of Timmins, and the Ministry of Environment’s noise, air and vibration guideline limits. Site stripping and mining activities currently take place during the day until the Environmental Control Berm is constructed around the pit periphery. The berm is designed to reduce noise levels and once complete, fulltime 24 hour operations will commence.
      In 2015, Porcupine marked its 105 th year of continuous mine and mill operations and has produced more than 67 million ounces of gold since production began.  In 2014 gold production totaled 300,000 ounces. Production during 2015 is expected to be between 300,000 and 320,000 ounces.

Mining Operations Red Lake

mining operations red lake
              

       Red Lake is located within one of the world’s most prolific gold camps, located approximately 230 kilometres northwest of Dryden, Ontario. Goldcorp’s active mining operations covers approximately 2,335 hectares and is accessible by Highway 105, which heads north from the Trans-Canada Highway. Daily commercial air services connect the numerous local communities to both Thunder Bay and Winnipeg. Red Lake, Canada. Located in one of the world’s most prolific gold districts, Red Lake is one of Goldcorp’s top producers, yielding 414,400 ounces in 2014. The High Grade Zone is the backbone of mining operations red lake , with an average grade of more than two ounces of gold per tonne. Recent investments in infrastructure and development have positioned this renowned mine for many more years of long-term sustainable production.
      Operations gold mining Red Lake and gold mining process are situated in the eastern part of the Red Lake Greenstone Belt in the Birch-Uchi Lake Subprovince of the Superior Province, within the core of the Canadian Shield. The Balmer Assemblage, which hosts the Red Lake Gold Mines, is part of the oldest sequence in the belt, consisting of a highly deformed Mesoarchean tholeiitic volcano-sedimentary complex, which locally plunges steeply to the southwest. This folded volcanic package is in contact with the main regional unconformity up against the Neoarchean sedimentary dominated Bruce Channel Assemblage.

operations underground mining at Red Lake     All operations underground mining at Red Lake is carried out by using three mining methods to maximum ore extraction: Overhand Cut and Fill (OCF), Underhand Cut and Fill (UFC), and Long Hole (LH). The high-grade zone mining operations red lake, which primarily consists of a narrow vein system, is mined at the rate of 450 tonnes per day with an average grade of over 45 grams per tonne (1.3 ounces per tonne). The high-grade mineralization and complex geometry of the ore body require specialized operations expertise.
Red lake gold ore
       Mineral ore types include silica replaced carbonate veins with free milling gold, siliceous replacement-type mineralization (rich with arsenopyrite) marginal to veins, broad disseminated sulphide mineralization along major shears, and some minor sulphidized chemical sediment-hosted ore.
gold leaching red lake      Innovative mining techniques and mining operations red lake have improved efficiency, such as a wet shotcrete system, the use of larger trucks, use of electric man carriers and a portable diamond drill mounted on a jumbo carrier. Mining operations red lake is supported by two mill processing facilities, providing a total milling capacity of 3,100 tonnes per day, including crushing, processing and pastefill plants. The processing plant’s operations consist of grinding, gravity concentrating, leaching, carbon-in-pulp (CIP), carbon elution and reactivation, electrowinning, bullion smelting/refining and cyanide destruction, flotation and concentrate handling—all of which are required to recover the gold in Red Lake’s ore types.
       The Cochenour/Bruce Channel deposit is key to plans for future consolidation. The work on enlarging and upgrading the existing Cochenour shaft is nearly complete. The development of a 6.0-kilometre haulage drift that will connect the existing Red Lake underground infrastructure with Cochenour is ~90% complete. The haulage drift will enable the efficient hauling of Cochenour/Bruce Channel ore to the Campbell mine for processing at the existing mill. The drift also opens up exploration of over six kilometers of untested ground in one of the world’s richest gold districts.
      Exploration in 2015 will continue to focus on the high-grade HG Young discovery. Rehabilitation of the 14-Level access in the Campbell Complex is completed underground drilling has commenced and will continue throughout 2015. Exploration drilling will also continue to focus on expansion of the R zone, NXT zone and the High Grade Zone (HGZ) up-plunge and at depth.

Gold Mining Industry In Ghana

     Ghana has a long history of mining, especially for gold. Gold from West Africa was traded to Europe at least as early as the tenth century. Most of this gold came by Sahara caravan, the original sources being the kingdoms of Ghana, Mali, and Songhai. In the early colonial time, it is thought that annually more than a quarter of a million ounces of gold reached Europe from African sources. Based mainly on native workings, numerous gold deposits, both bedrock and placer, were rediscovered during the latter part of the nineteenth century throughout Senegal, Guinea, Sierra Leone, Ghana, Nigeria, and the other nations of the Gold Coast.
The Precambrian auriferous Tarkwa conglomerates of Ghana were developed in a modern way during the period 1876-1882 by Pierre Bonnat, the father of modern gold mining in the Gold Coast. In 1895, Ashanti Goldfields Corporation began work in the Obuasi district of Ghana, developing the Ashanti and other mines, which have produced the largest proportion of gold since 1900 in the countries of the Gold Coast. All of these deposits are of Precambrian age.
At the Obuasi mine, over the years, 25 million ounces of gold were mined. At Bogoso, since mining operations commenced in 1873, more than nine million ounces of gold were produced, largely from extensive underground operations.
GOLD AND PRECIOUS METALS INFORMATION:
Gold is one of the most precious metals in the world. It is present in the rivers, seas, and the earth’s crust and trace amounts are present in plants and animals. It is, however, difficult and expensive to extract. In modern mining operations approximately 3 tons of ore are needed to extract one ounce of gold. The many desirable qualities found in gold, along with its scarcity, have made it the most popular metal for use in jewellery today.
PROPERTIES OF GOLD
Gold in its pure state:
  • Has a melting point of 1945 degrees Fahrenheit (1063 degrees Celsius). When alloyed (chemically combined) with other base metals the melting temperature of the resulting alloy is changed. 18K yellow gold has a melting point of 1675 degrees Fahrenheit and 14K yellow gold has a melting point of about 1550 degrees Fahrenheit.
  • Has a specific gravity of 19.33. It is relatively heavy compared to most metals, such as silver (SG 10.7) or iron (SG 7.8). A notable exception is platinum (SG 21.4).
  • Is more malleable than any other metal and can be hammered into foil so thin that it is almost transparent.
  • Has a unique ductility property allowing it to be drawn into wire so fine it can barely be seen.
  • Is deep yellow in color. Its great reflectivity properties help keep its brightness and color from fading with time.
  • Will not rust, tarnish or corrode. Gold jewellery recovered from ancient Egyptian tombs is in the same state as when placed there over 4000 years ago.
  • Is softer than most other metals. On the Mohs scale of hardness (which is a measure of a gemstone or mineral’s resistance to scratching), gold has a hardness value of 2 to 2.5. Diamond has a value of 10. Pure gold may easily be scratched. Fortunately, gold becomes harder when alloyed with other base metals.
  • Is relatively scarce and therefore expensive. It is estimated that only 125,000 tons of gold have been mined the world over since the beginning of time.
  • Is able to bond with other base metals. This property gives rise to the many different colors available in modern gold alloys.
FINENESS (KARAT VALUE)
Since ancient times the purity of gold has been defined by the term karat, which is 1/24 part of pure gold by weight. Pure gold is equivalent to 24K. Gold purity may also be described by its fineness, which is the amount of pure gold in parts per 1000. For example, a gold ring containing 583 fine gold has 583 parts (58.3%) gold and 417 parts (41.7%) of other base metals.
Karat Value Definitions:
  • Karat System: A system of measurement based on 24 karats being “fine” or “pure” gold. 1 karat equals 1/24th fine gold by weight. This is the system used in the United States.
  • Plumb Gold: Karat weights are usually determined with a small, fractional variance allowed. Karat gold which has no variance and is exactly the precise fractional karat weight is called “plumb” gold.
  • European System: A system of measurement based on a fraction of 1,000; or the number of grams of gold in 1 kilogram of alloy.
The following table lists the relationship between different international gold markings.
GOLD KARAT INFORMATION CHART
Karat Gold Parts Gold Percentage Gold Normal European Stamping
9 kt 9 in 24 37.50% 375
10 kt 10 in 24 41.67% 416
12 kt 12 in 24 50% 500
14 kt 14 in 24 58.33% 583 or 585
18 kt 18 in 24 75% 750
22 kt 22 in 24 91.67% 917
24 kt 24 in 24 99.99% 999 or .99999
WEIGHING PRECIOUS METALS:
The weight of a piece of gold jewellery is a factor that helps to determine its value. It is important because it is an indication of the amount of fine gold in an item of jewellery. Grams (g) and pennyweights (dwt) are the units of weight most commonly used in weighing gold. Gold and silver are almost always weighted in the troy system of weights where one pound troy equals twelve troy ounces and twenty pennyweights equals’ one troy ounce. The Avoirdupois weight system, where one pound equals 16 ounces, is used in the United States for most everything except precious metals. The following table summarizes useful weight conversions.
WEIGHT CONVERSION TABLE
1 gram (g) = 0.643 dwt = 0.0032 oz t = 0.035 oz av
1 pennyweight (dwt) = 1.555 g = 0.05 oz t = 0.055 oz av
1 troy ounce (oz t) = 31.103 g = 20 dwt = 1.097 oz av
1 ounce avoirdupois (oz av) = 28.3495 g = 18.229 dwt = 0.911 oz t

The New Minerals and Mining Act 703, 2006
The purpose of the Act is to revise the existing Minerals and Mining Law, 1986 (PNDC Law 153) to reflect in our laws, new thinking and developments in the mining industry and to consolidate it with the enactment on small scale gold Mining. The PNDC Law 153, when it was enacted in 1986, was hailed as one of the best enactments on the subject in Africa and made Ghana an attractive destination for mining investment.
However, after nearly two decades of operation of the Law, it has been realized that development in the mining industry requires a revision of the Law to reflect international best practices in the industry, as well as to re-position Ghana as a major mining investment destination in Africa. The provision by Law, of an internationally competitive framework that ensures a stable and equitable tax regime and also takes cognizance of environmental protection as well as community interests is necessary in order to provide the basis for the development and sustainability of mining in the country.
Welcome to the Web Portal of the Mining Authorities of Ghana.
The Ministry of Lands, Forestry and Mines (Mines Section) and its Agencies offer to provide a transparent information source and equal opportunities for all investors and the general public.
History of Ghana
Medieval Ghana (4th – 13th Century): The Republic of Ghana is named after the medieval Ghana Empire of West Africa. The actual name of the Empire was Wagadugu. Ghana was the title of the kings who ruled the kingdom. It was controlled by Sundiata in 1240 AD, and absorbed into the larger Mali Empire. (Mali Empire reached its peak of success under Mansa Musa around 1307.)
Geographically, the old Ghana is 500 miles north of the present Ghana, and occupied the area between Rivers Senegal and Niger. Some inhabitants of present Ghana had ancestors linked with the medieval Ghana. This can be traced down to the Mande and Voltaic peoeple of Northern Ghana–Mamprussi, Dagomba and the Gonja. Anecdotal evidence connected the Akans to this great Empire. The evidence lies in names like Danso shared by the Akans of present Ghana and Mandikas of Senegal/Gambia who have strong links with the Empire. There is also the matrilineal connection.
Gold Coast & European Exploration: Before March 1957 Ghana was called the Gold Coast. The Portuguese who came to Ghana in the 15th Century found so much gold between the rivers Ankobra and the Volta that they named the place Mina – meaning Mine. The Gold Coast was later adopted to by the English colonisers. Similarily, the French, equally impressed by the trinkets worn by the coastal people, named The Ivory Coast, Cote d’Ivoire. In 1482, the Portuguese built a castle in Elmina. Their aim was to trade in gold, ivory and slaves. In 1481 King John II of Portugal sent Diego d’Azambuja to build this castle.
In 1598 the Dutch joined them, and built forts at Komenda and Kormantsil. In 1637 they captured the castle from the Portuguese and that of Axim in 1642 (Fort St Anthony). Other European traders joined in by the mid 18th century. These were the English, Danes and Swedes. The coastline were dotted by forts built by the Dutch, British and the Dane merchants. By the latter part of 19th century the Dutch and the British were the only traders left. And when the Dutch withdrew in 1874, Britain made the Gold Coast a crown colony.
By 1901 the Ashanti and the North were made a protectorate
Britain and the Gold Coast. The first Britons arrived in the early 19th century as traders in Ghana. But with their close relationship with the coastal people especially the Fantes, the Ashantis became their enemies.
Economic and Social Development (Before 1957)
1874–Gold Mine in Wassa and Asante. Between 1946-1950 gold export rose from 6 million pounds to 9 million pounds.
Political Movements and Nationalism in Ghana (1945 – 1957)
The educated Ghanaians had always been in the fore-front of constructive movements. Names that come into mind are –Dr Aggrey, George Ferguson, John Mensah Sarbah. Others like king Ghartey IV of Winneba, Otumfuo Osei Agyeman Prempeh I raised the political consciousness of their subjects. However, movements towards political freedom started soon after WWII.This happened because suddenly people realised the colonisation was a form of oppression, similar to the oppression they have just fought against. The war veterans had become radical. The myth surrounding the whiteman has been broken. The rulers were considered economic cheats, their arogance had become very offensive. They had the ruling class attitude, and some of the young District Commissioner (DC) treated the old chiefs as if they were their subjects. Local pay was bad. No good rural health or education policy. Up to 1950 the Govt Secondary schools in the country were 2, the rest were built by the missionaries.
There was also the rejection of African culture to some extent. Some external forces also contributed to this feeling. African- Americans such as Marcus Garvey and WE Du Bois raised strong Pan-African conscience.
In 1945 a conference was held in Manchester to promote Pan African ideas. This was attended by Nkrumah of Ghana, Azikwe of Nigeria and Wallace Johnson of Sierra Leone. The India and Pakistani independence catalysed this desire. Sir Alan Burns constitution of 1946 provided new legislative council that was made of the Governor as the President, 6 government officials, 6 nominated members and 18 elected members.
The executive council was not responsible to the legislative council. They were only in advisory capacity, and the governor did not have to take notice. These forces made Dr J.B. Danquah to form the United Gold Coast Conversion (UGCC) in 1947. Nkrumah was invited to be the General Secretary to this party. Other officers were George Grant (Paa Grant), Akuffo Addo, William Ofori Atta, Obetsebi Lamptey, Ako Agyei, and J Tsiboe. Their aim was Independence for Ghana. They rejected the Burns constitution.

Gold Mining Industry

      The gold mining industry is an important economic contributor by numerous countries around the world. Gold has been mined on every continent with the exception of Antarctica, but the top producing countries are China, the United States and Australia. Other countries with high production include China, Russia, Peru and Canada. New mining efforts are taking place in places such as Ghana, Chile, Africa, Latin America and Asia
Gold Mining Industry       The gold mining industry has a long and rich history that dates back to the first millennium.Mining gold can be dangerous, costly and time consuming. It is estimated that more than 4.97 billion ounces has been extracted since the beginning of civilization. The first known mine was in the Kolar Gold Fields as early as the 2nd and 3rd century. Gold was mined in this area by the royalty of South India in the 11the century, by the Vijayanagar Empire from 1336 to 1560 and by the British. Today, there are hundreds of gold mines located throughout the world and thousands of people who earn a living working in the mines. The largest are most productive mines are Barrick Gold, Goldcorp, AngloGold Ashanti and Newmont Mining Corporation.
Gold Mining Equipment
      The gold mining industry uses a variety of techniques to extract and produce gold. The size and complexity of the mining operation will determine which method is used to extract the gold. The first technique is called panning, which is a manual technique. Gold hunters submerge pans that are filled with gravel or sand into water and shake it, which separates the gold from the other material because it settles to the bottom. Another technique is to use a metal detector, which detects deposits of gold below the surface. The next technique is sluicing, which uses box with channels set in the bottom that allow the gold to settle. This is a method commonly used in small mines and streams. Dredging is a technique that uses small machines that float on water. Finally, mining techniques include hard rock mining, byproduct mining and gold ore processing.
      Today, the gold mining industry plays an important role in the global economy because this precious metal is used in a number of quickly developing technologies. This includes gold coated electrical connectors used in computers and home appliances, weather satellites with gold plated shields, laser technology that uses gold coatings. It is also important in modern medicine, which uses gold in different procedures that include the treatment of cancer, viruses, bacterial diseases and even allergies.

Mineral Processing in Mines

      
      Minerals mining is a huge natural wealth, where mineral resources are optimally utilized if the will is essential for the continuity of economic growth. In the belly of this earth to save countless millions metal content and non-metallic materials that can be utilized as industrial equipment needs of society at large. Environmental components that have the potential to support the development of a mining exploration to create jobs. Where mining exploration activities require the expertise of trained and skilled professional and technical personnel who may be widely available in local communities. In addition to the manpower requirements of mineral properties and mine development activities often require additional materials and specialized technical services. It is also often provided by the company’s geological and mining engineering, who seek office in the local community to participate in exploration and mine development contract.
      Gold prospectors have won a lot of wealth and there is a finding that smaller-scale artisanal mining and managed by local residents. Natural resources are very abundant must be utilized efficiently and should refer also to the security environment. Because of environmental aspects will have a major impact on mining. But it also depends on how where we manage these resources.
     In the field of extractive metallurgy, mineral engineering, mineral processing, also known as mineral dressing or ore dressing, is the process of separating commercially valuable minerals from their ores. Mineral processing, treating crude ores and mineral products in order to separate the valuable minerals from the waste rock, or gangue. It is the first process that most ores undergo after mining in order to provide a more concentrated material for the procedures of extractive metallurgy. The primary operations are comminution and concentration, but there are other important operations in a modern mineral processing plant, including sampling , analysis and dewatering

SAMPLING AND ANALYSIS


       Routine sampling and analysis of the raw material being processed are undertaken in order to acquire information necessary for the economic appraisal of ores and concentrates. In addition, modern plants have fully automatic control systems that conduct in-stream analysis of the material as it is being processed and make adjustments at any stage in order to produce the richest possible concentrate at the lowest possible operating cost.
 
SAMPLING
Sampling is the removal from a given lot of material a portion that is representative of the whole yet of convenient size for analysis. It is done either by hand or by machine. Hand sampling is usually expensive, slow, and inaccurate, so that it is generally applied only where the material is not suitable for machine sampling (slimy ore, for example) or where machinery is either not available or too expensive to install. Many different sampling devices are available, including shovels, pipe samplers, and automatic machine samplers. For these sampling machines to provide an accurate representation of the whole lot, the quantity of a single sample, the total number of samples, and the kind of samples taken are of decisive importance. A number of mathematical sampling models have been devised in order to arrive at the appropriate criteria for sampling

ANALYSIS
      After one or more samples are taken from an amount of ore passing through a material stream such as a conveyor belt, the samples are reduced to quantities suitable for further analysis. Analytical methods include chemical, mineralogical, and particle size.

Chemical analysis
Even before the 16th century, comprehensive schemes of assaying (measuring the value of) ores were known, using procedures that do not differ materially from those employed in modern times. Although conventional methods of chemical analysis are used today to detect and estimate quantities of elements in ores and minerals, they are slow and not sufficiently accurate, particularly at low concentrations, to be entirely suitable for process control. As a consequence, to achieve greater efficiency, sophisticated analytical instrumentation is being used to an increasing extent.
In emission spectroscopy, an electric discharge is established between a pair of electrodes, one of which is made of the material being analyzed. The electric discharge vaporizes a portion of the sample and excites the elements in the sample to emit characteristic spectra. Detection and measurement of the wavelengths and intensities of the emission spectra reveal the identities and concentrations of the elements in the sample.
 
Mineralogical analysis
A successful separation of a valuable mineral from its ore can be determined by heavy-liquid testing, in which a single-sized fraction of a ground ore is suspended in a liquid of high specific gravity. Particles of less density than the liquid remain afloat, while denser particles sink. Several different fractions of particles with the same density (and, hence, similar composition) can be produced, and the valuable mineral components can then be determined by chemical analysis or by microscopic analysis of polished sections.
Size analysis
Coarsely ground minerals can be classified according to size by running them through special sieves or screens, for which various national and international standards have been accepted. One old standard (now obsolete) was the Tyler Series, in which wire screens were identified by mesh size, as measured in wires or openings per inch. Modern standards now classify sieves according to the size of the aperture, as measured in millimetres or micrometres (10-6 metre).
 
Mineral processing can involve four general types of unit operation: 

COMMINUTION


      In all of these processes, the most important considerations are the economics of the processes and this is dictated by the grade and recovery of the final product. To do this, the mineralogy of the ore needs to be considered as this dictates the amount of liberation required and the processes that can occur. The smaller the particles processes, the greater the theoretical grade and recovery of the final product, but this however is difficult to do with fine particles as they prevent certain concentration processes from occurring.
     In order to separate the valuable components of an ore from the waste rock, the minerals must be liberated from their interlocked state physically by comminution. As a rule, comminution begins by crushing the ore to below a certain size and finishes by grinding it into powder, the ultimate fineness of which depends on the fineness of dissemination of the desired mineral. Whereas crushing is done mostly under dry conditions, grinding mills can be operated both dry and wet, with wet grinding being predominant.

CONCENTRATION


      Concentration involves the separation of valuable minerals from the other raw materials received from the grinding mill. In large-scale operations this is accomplished by taking advantage of the different properties of the minerals to be separated. These properties can be colour (optical sorting), density (gravity separation), magnetic or electric (magnetic and electrostatic separation), and physicochemical (flotation separation). There are a number of ways to increase the concentration of the wanted minerals: in any particular case the method chosen will depend on the relative physical and surface chemical properties of the mineral and the gangue. Concentration is defined as the number of moles of a solute in a volume of the solution. In case of mineral processing concentration means the increase of the percentage of the valuable mineral in the concentrate.
GRAVITY CONCENTRATION


      Gravity separation is the separation of two or more minerals of different specific gravity by their relative movement in response to the force of gravity and one or more other forces (such as centrifugal forces, magnetic forces, buoyant forces), one of which is resistance to motion (drag force) by a viscous medium such as heavy media, water or, less commonly, air. Gravity separation is one of the oldest technique in mineral processing but has seen a decline in its use since the introduction of methods like flotation, classification, magnetic separation and leaching. Gravity separation dates back to at least 3000 BC when Egyptians used the technique for separation of gold.
It is necessary to determine the suitability of a gravity concentration process before it is employed for concentration of an ore. The concentration criterion is commonly used for this purpose, designated CC in the following equation (where SG represents specific gravity):
CC = \frac {SG(heavy\ mineral) - SG(fluid)}{SG(light\ mineral) - SG(fluid)}
  • for CC > 2.5, suitable for separation of particles above 75 micron in size
  • for 1.75 < CC < 2.5, suitable for separation of particles above 150 micron in size
  • for 1.50 < CC < 1.75, suitable for separation of particles above 1.7 mm in size
  • for 1.25 < CC < 1.50, suitable for separation of particles above 6.35 mm in size
  • for CC < 1.25, not suitable for any size
      Gravity methods use the difference in the density of minerals as the concentrating agent. In heavy-media separation (also called sink-and-float separation), the medium used is a suspension in water of a finely ground heavy mineral (such as magnetite or arsenopyrite) or technical product (such as ferrosilicon). Such a suspension can simulate a fluid with a higher density than water. When ground ores are fed into the suspension, the gangue particles, having a lower density, tend to float and are removed as tailings, whereas the particles of valuable minerals, having higher density, sink and are also removed. The magnetite or ferrosilicon can be removed from the tailings by magnetic separation and recycled.
      In the process called jigging, a water stream is pulsed, or moved by pistons upward and downward, through the material bed. Under the influence of this oscillating motion, the bed is separated into layers of different densities, the heaviest concentrate forming the lowest layer and the lightest product the highest. Important to this process is a thorough classification of the feed, since particles less than one millimetre in size cannot be separated by jigging.
      Finer-grained particles (from 1 millimetre to 50 micrometres) can be effectively separated in a flowing stream of water on horizontal or inclined planes. Most systems employ additional forces—for example, centrifugal force on spirals or impact forces on shaking tables. Spirals consist of a vertical spiral channel with an oval cross section. As the pulp flows from the top to the bottom of the channel, heavier particles concentrate on the inner side of the stream, where they can be removed through special openings. Owing to their low energy costs and simplicity of operation, the use of spirals has increased rapidly. They are especially effective at concentrating heavy mineral sands and gold ores.
Gravity concentration on inclined planes is carried out on shaking tables, which can be smoothed or grooved and which are vibrated back and forth at right angles to the flow of water. As the pulp flows down the incline, the ground material is stratified into heavy and light layers in the water; in addition, under the influence of the vibration, the particles are separated in the impact direction. Shaking tables are often used for concentrating finely grained ores of tin, tungsten, niobium, and tantalum.

FROTH FLOTATION


       Froth flotation is an important concentration process. This process can be used to separate any two different particles and operated by the surface chemistry of the particles. In flotation, bubbles are introduced into a pulp and the bubbles rise through the pulp. In the process, hydrophobic particles become bound to the surface of the bubbles. The driving force for this attachment is the change in the surface free energy when the attachment occurs. These bubbles rise through the slurry and are collected from the surface. To enable these particles to attach, careful consideration of the chemistry of the pulp needs to be made. These considerations include the pH, Eh and the presence of flotation reagents. The pH is important as it changes the charge of the particles surface and the Eh affects the chemisorption of collectors on the surface of the particles.
     Flotation is the most widely used method for the concentration of fine-grained minerals. It takes advantage of the different physicochemical surface properties of minerals—in particular, their wettability, which can be a natural property or one artificially changed by chemical reagents. By altering the hydrophobic (water-repelling) or hydrophilic (water-attracting) conditions of their surfaces, mineral particles suspended in water can be induced to adhere to air bubbles passing through a flotation cell or to remain in the pulp. The air bubbles pass to the upper surface of the pulp and form a froth, which, together with the attached hydrophobic minerals, can be removed. The tailings, containing the hydrophilic minerals, can be removed from the bottom of the cell.
      The addition of flotation reagents also affects the operation of these processes. The most important chemical that is added is the collector, This chemical binds to the surface of the particles as it is a surfactant. The main considerations in this chemical is the nature of the head group and the size of the hydrocarbon chain. The hydrocarbon tail needs to be short to maximize the selectivity of the desired mineral and the headgroup dictates which minerals it attaches to. The frothers are another important chemical addition to the pulp at it enables stable bubbles to be formed. This is important as if the bubble coalesce, minerals fall off their surface. The bubbles however should not be too stable as this prevents easy transportation and dewatering of the concentrate formed. The mechanism of these frothers is not completely known and further research into their mechanisms is being performed.
       Depressants and activators are used to selectively separate one mineral from another. Depressants inhibit the flotation of one mineral or minerals while activators enable the flotation of others. Examples of these include CN−, used to depress all sulfides but galena and this depressant is believed to operate by changing the solubility of chemisorbed and physisorbed collectors on sulfides. This theory originates from Russia. An example of an activator is Cu2+ ions, used for the flotation of sphalerite. There are a number of cells able to be used for the flotation of minerals. these include flotation columns and mechanical flotation cells. The flotation columns are used for finer minerals and they typically have a higher grade and lower recovery of minerals than mechanical flotation cells. The cells in use at the moment can exceed 300 m3. This is done as they are cheaper per unit volume than smaller cells, but they are not able to be controlled as easily as smaller cells.
       Flotation makes possible the processing of complex intergrown ores containing copper, lead, zinc, and pyrite into separate concentrates and tailings—an impossible task with gravity, magnetic, or electric separation methods. In the past, these metals were recoverable only with expensive metallurgical processes.

MAGNETIC SEPARATION
      Magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using a magnetic force. This separation technique can be useful in mining iron as it is attracted to a magnet. In this machine the raw ore, after calcination was fed onto a moving belt which passed underneath two pairs of electromagnets under which further belts ran at right angles to the feed belt. The first pair of electromagnets was weakly magnetised and served to draw off any iron ore present. The second pair were strongly magnetised and attracted the wolframite, which is weakly magnetic. These machines were capable of treating 10 tons of ore a day.This process of separating magnetic substances from the non-magnetic substances in a mixture with the help of a magnet is called magnetic separation.
      Magnetic separation is based on the differing degrees of attraction exerted on various minerals by magnetic fields. Success requires that the feed particles fall within a special size spectrum (0.1 to 1 millimetre). With good results, strongly magnetic minerals such as magnetite, franklinite, and pyrrhotite can be removed from gangue minerals by low-intensity magnetic separators. High-intensity devices can separate oxide iron ores such as limonite and siderite as well as iron-bearing manganese, titanium, and tungsten ores and iron-bearing silicates.
      This process operates by moving particles in a magnetic field. The force experienced in the magnetic field is given by the equation f=m/k.H.dh/dx. with k=magnetic susceptibility, H-magnetic field strength, and dh/dx being the magnetic field gradient. As seen in this equation, the separation can be driven in two ways, either through a gradient in a magnetic field or the strength of a magnetic field. The different driving forces are used in the different concentrators. These can be either with water or without. Like the spirals, washwater aids in the separation of the particles while increases the entrainment of the gangue in the concentrate.

ELECTROSTATIC SEPARATION
      The electrostatic method separates particles of different electrical charges and, when possible, of different sizes. When particles of different polarity are brought into an electrical field, they follow different motion trajectories and can be caught separately. Electrostatic separation is used in all plants that process heavy mineral sands bearing zircon, rutile, and monazite. In addition, the cleaning of special iron ore and cassiterite concentrates as well as the separation of cassiterite-scheelite ores are conducted by electrostatic methods.
       There are two main types of electrostatic separators. These work in similar ways, but the forces applied to the particles are different and these forces are gravity and electrostatic attraction. The two types are electrodynamic separators (or high tension rollers) or electrostatic separators. In high tension rollers, particles are charged by a corona discharge. This charges the particles that subsequently travel on a drum. The conducting particles lose their charge to the drum and are removed from the drum with centripetal acceleration. Electrostatic plate separators work by passing a stream of particles past a charged anode. The conductors lose electrons to the plate and are pulled away from the other particles due to the induced attraction to the anode. These separators are used for particles between 75 and 250 micron and for efficient separation to occur, the particles need to be dry, have a close size distribution and uniform in shape. Of these considerations, one of the most important is the water content of the particles. This is important as a layer of moisture on the particles will render the non-conductors as conductors as the layer of the water is conductive.
      Electrostatic plate separators are usually used for streams that have small conductors and coarse non-conductors. The high tension rollers are usually used for streams that have coarse conductors and fine non-conductors. These separators are commonly used for separating mineral sands, an example of one of these mineral processing plants is the CRL processing plant at Pinkenba in Brisbane Queensland. In this plant, zircon, rutile and ilmenite are separated from the silica gangue. In this plant, the separation is performed in a number of stages with roughers, cleaners, scavengers and recleaners.

DEWATERING


      Dewatering is an important process in mineral processing. The purpose of dewatering is to remove water absorbed by the particles which increases the pulp density. This is done for a number of reasons, specifically, to enable ore handling and concentrates to be transported easily, allow further processing to occur and to dispose of the gangue. The water extracted from the ore by dewatering is recirculated for plant operations after being sent to a water treatment plant. The main processes that are used in dewatering include dewatering screens such as Sepro-Sizetec Screens, sedimentation, filtering, and thermal drying. These processes increase in difficulty and cost as the particle size decreases.
     Dewatering screens operate by passing particles over a screen. The particles pass over the screen while the water passes through the apertures in the screen. This process is only viable for coarse ores that have a close size distribution as the apertures can allow small particles to pass through
Sedimentation operates by passing water into a large thickener or clarifier. In these devices, the particles settle out of the slurry under the effects of gravity or centripetal forces. These are limited by the surface chemistry of the particles and the size of the particles. To aid in the sedimentation process, flocculants and coagulants are added to reduce the repulsive forces between the particles. This repulsive force is due to the double layer formed on the surface of the particles. The flocculants work by binding multiple particles together while the coagulants work by reducing the thickness of the charged layer on the outside of the particle.
       Thermal drying is usually used for fine particles and to remove low water content in the particles. Some common processes include rotary dryers, fluidised beds, spray driers, hearth dryers and rotary tray dryers. This process is usually expensive to operate due to the fuel requirement of the dryers.

READ MORE >>>Gold Precipitation Methods

Exploration AngloGold Ashanti Gold Mines In World


      Gold mining companies AngloGold began in South Africa in May of 1998, when the gold and uranium mining interests of Anglo American Corporation of South Africa were consolidated. AngloGold Limited was formed in June 1998 through the consolidation of the gold interests of Anglo American Corporation of South Africa Limited (AAC) and its associated companies, namely East Rand Gold and Uranium Company Limited; Eastvaal Gold Holdings Limited; Southvaal Holdings Limited; Free State Consolidated Gold Mines Limited; Elandsrand Gold Mining Company Limited; H.J. Joel Gold Mining Company Limited and Western Deep Levels Limited into a single, focused, independent, gold company. Vaal Reefs Exploration and Mining Company Limited (Vaal Reefs), the vehicle for the consolidation, changed its name to AngloGold Limited and increased its authorised share capital, effective 30 March 1998. AngloGold acquired minority shareholders interest in Driefontein Consolidated Limited (17%); Anmercosa Mining (West Africa) Limited (100%); Western Ultra Deep Levels Limited (89%); Eastern Gold Holdings Limited (52%); Erongo Mining and Exploration Company Limited (70%)
      In August 1998, AngloGold became the first South African company to list on the NYSE. AngloGold Ashanti Limited is a global gold mining company by the merger of AngloGold and the Ashanti Goldfields Corporation in 2004 AngloGold Ashanti Limited constitute mining for a gold exploration, development and production company with operations in South Africa, Ghana, Guinea, Mali, Namibia and Tanzania. The AngloGold constitute largest gold mines in the world. They are listed on the Johannesburg Stock Exchange (JSE:AGA), the New York Stock Exchange (NYSE:AU), the London Stock Exchange (LSE:AGD), the Ghana Stock Exchange (GhSE:AGA) and the Australian Securities Exchange (ASX:AGG).
      AngloGold Ashanti headquartered in Johannesburg, South Africa and South African gold producer with has 20 operations in 10 countries on four continents, as well as several exploration programmes in both the established and new gold producing regions of the world. Its Latin American assets include the Cerro Vanguardia mine in Argentina, a joint venture with local firm Fomicruz located in Santa Cruz province, while in Brazil it has the mines Córrego do Sítio Mineração, in Minas Gerais state, and Serra Grande, in Goiás state. The company is also exploring the Graben project, where it has an agreement with Graben Mineração to explore its tenement in the Juruena belt. Finally, its Colombian properties include La Colosa, Gramalote and Nuevo Chaquiro, a copper-gold porphyry-style deposit within its Quebradona project, a JV with Vancouver-based B2Gold. AngloGold Ashanti employed 61,242 people, including contractors, in 2011 (2010: 62,046) and produced 4.33Moz of gold (2010: 4.52Moz), generating $6.6bn in gold income, excluding joint ventures (2010: $5.3bn). Capital expenditure in 2011 amounted to $1.5bn (2010: $1.0bn). As at 31 December 2011, AngloGold Ashanti had an attributable Ore Reserve of 75.6Moz (2010: 71.2Moz) and an attributable Mineral Resource of 230.9Moz (2010: 220.0Moz).
      Anglo American started reducing its stake in AngloGold Ashanti in April 2006 via equity placement. Thereafter, Anglo American continued to implement small sales of its remaining interest in AngloGold Ashanti via the market and in March 2009, sold its remaining interest.AngloGold Ashanti remains an independent gold producer, with no dominant investor and a diverse spread of shareholders which count among the world’s largest financial institutions AngloGold Ashanti endeavours to maximise the returns delivered to shareholders through the economic cycle, by producing gold safely, responsibly and efficiently.

Exploration AngloGold Ashanti
Exploration at AngloGold Ashanti has 2 key high level objectives to form important price and create significant value for the company:

1. Greenfields Exploration
      Greenfields Exploration aims to make large, high-value gold discoveries leading directly to new mines. AngloGold Ashanti’s Greenfields Exploration team has been recognized as the industry’s most successful discoverer in the last fifteen years.* It has a proven track record that includes the world-class discoveries of La Colosa, Gramalote and Tropicana.These discoveries are attributed to our committed and professional team of explorationists working on a portfolio of highly prospective and strategic ground holdings. Greenfields Exploration provides a pipeline of high-quality and rigorously prioritised exploration projects, which in turn lead towards discovery of new deposits and mines.

2. Brownfields Exploration
      Brownfields Exploration focuses on delivering value through incremental additions to reserves in existing mines as well as new discoveries in defined areas around existing operations. AngloGold Ashanti continues to actively drive the creation of value by growing its major asset, namely its Mineral Resource and Ore Reserve. This is based on a well-defined and effective brownfields exploration programme about existing operations, innovation in geological modelling and mine planning, and continual optimisation of its asset portfolio.
AngloGold Ashanti Mining Operations 

 

READ MORE >>> AngloGold Ashanti Operations Gold Mines In World

Exploration AngloGold Ashanti gold mines in Region American

       Anglo American, one of the world’s largest mining companies, had its origins in the gold and diamond mines of South Africa, and after the Second World War it expanded and diversified to the point that it controlled large portions of that country’s economy. It later sold off its non-mining businesses, moved its headquarters to London, and spun off its gold mining operations into the company now called AngloGold Ashanti. Anglo American remains a major player in platinum, copper, coal and diamonds (through its affiliate De Beers).
      For decades, Anglo American was known as the company that got rich from exploiting oppressed black miners within the apartheid economy of South Africa. It has worked hard to change that image, though it still has tense relations with mineworkers (especially over safety issues) in its South African operations. The company has also been at the center of controversy over environmental or human rights issues in countries such as Ghana, the Democratic Republic of the Congo and Peru.
     The Americas Region is an important growth area for AngloGold Ashanti, with operations in Argentina, in Brazil, and in the United States.The operations of Anglo American and those of its spinoff AngloGold have been associated with environment problems in numerous countries.

This is operations AngloGold Ashanti gold mines in world in Region American :

1. United States

Cripple Creek Victor mine


      AngloGold Ashanti holds a 100% interest in the Cripple Creek & Victor (CC&V) Gold Mining Company’s Cresson mine, located in the state of Colorado. A surface mining operation provides oxidised ore to a crusher and valley leach facility, one of the largest in the world. Higher-grade ore with more sulphidic properties will be processed in a carbon-in-pulp (CIP) mill to achieve better recoveries. A two-phase mine-life-extension (MLE) project is well underway and is expected to increase production significantly from 2015.
      The Cripple Creek & Victor Gold Mine, formerly and historically the Cresson Mine, is an active gold mine located near the town of Victor, in the Cripple Creek mining district in the US state of Colorado. It is the largest current producer of gold in Colorado, and produced 211,000 troy ounces of gold in 2014. It was fully owned and operated by AngloGold Ashanti through its subsidiary, the Cripple Creek & Victor Gold Mining Company (CC&V). In June 2015, AngloGold agreed to sell the mine to Newmont Mining   Corporation. The purchase by Newmont was completed in August 2015.
      The mine is an open pit operation. The gold is recovered from the ore by heap leaching. CC&V’s heap leach pad is one of the biggest in the world. The mine has a visitor center with displays about modern mining procedures, historical photos, ore and core samples, and mineral uses. Visitors can tour the mine with advance reservation through the Victor Lowell Thomas Museum in Victor, Colorado.

2. Argentina

Cerro Vanguardia Mine


      The Cerro Vanguardia Mine is a gold and silver mine located 150 km north west of Puerto San Julián, in the Santa Cruz province of Argentina., in which AngloGold Ashanti has a 92.5% stake, and is the company’s sole operation in Argentina. Fomicruz, a state company operating in the province of Santa Cruz, owns the remaining 7.5%. Located to the northwest of Puerto San Julián in the province of Santa Cruz, Cerro Vanguardia operates multiple small open pits with high stripping ratios and multiple narrow-vein underground mines. The metallurgical plant has a daily capacity of 3,000t and includes a cyanide recovery facility.
      AngloGold acquired the 46.25% Anglo group interest in 1998–99 and the equal Perez Companc holding in 2002, then merged with Ashanti Goldfields to form AngloGold Ashanti in April 2004. Fomicruz has a 7.5% carried interest.Construction work started in 1997 and the first gold was shipped in 1998, close to schedule and budget. The overall investment from exploration to start-up was estimated at US$270m. The plant throughput rate has since risen from 1,800t/d to 2,700t/d. The operation employed 487 directly with a further 459 people working for contractors in 2005. Capital expenditure for the year was US$15m.
      Cerro Vanguardia is mining the 17 structures by means of separate open pits, with three to five of these working at any one time in order to achieve an optimal blend for processing. Average stripping ratio over the 15-year mine life should be 15:1. Mining is conventional drill-and-blast, with a load-haul fleet of medium-sized equipment including Caterpillar 988 wheel loaders.

3. Brazil

Córrego do Sítio Mineração (AGA Mineração )


AngloGold Ashanti Córrego do Sítio Mineração (AGA Mineração ), which is wholly owned, comprises two operational complexes located in the state of Minas Gerais, close to the city of Belo Horizonte:
  • The Cuiabá complex includes the Cuiabá and Lamego mines and the Cuiabá and Queiroz plant complexes. Cuiabá has been in operation for 29 years while Lamego is a more recently developed underground mine. Ore from the Cuiabá and Lamego mines is processed at the Cuiabá gold plant. The concentrate produced is transported 15km by aerial ropeway to the Queiroz plant for processing and refining. Total annual capacity of the complete Cuiabá circuit is 1.7Mt. The Queiroz hydrometallurgical plant also produces around 200,000t of sulphuric acid as a by-product, which is sold commercially on local Brazilian markets. The Cuiabá complex is changing its mining method from cut-andfill to sub-level stoping so as to increase the contribution of narrow-vein ore bodies to production (from 15% to 40%) and to improve rock engineering controls.
  • The Córrego do Sítio complex comprises one surface (oxide) and two underground (sulphide) mines, as well as a heap leach pad and sulphide plant.
Serra Grande Gold Mine


      The Serra Grande Gold Mine is a gold mine located is located in central Brazil in the state of Goiás, about 5km from the city of Crixás. It is jointly owned by AngloGold Ashanti and Kinross Gold Corporation, who are equal partners. The mine is operated by AngloGold Ashanti but revenue is spread evenly between the two companies.. It comprises three mechanised underground mines: Mina III (the ore body IV), Mina Nova (the Pequizão ore body) and Palmeiras – and an open pit in the outcrop of the Mina III ore body. One dedicated metallurgical plant treats all ore mined. Annual plant capacity is 1.3Mt. The mine has enhanced the group’s production, Ore Reserve and Mineral Resource profiles through the 100% ownership, making a positive contribution toward AngloGold Ashanti’s near-term gold production profile in Brazil.

3. Colombia

La Colosa and Gramalote 

 
      Two advanced major exploration projects, La Colosa and Gramalote, are currently underway in Colombia. Extensive exploration activities are also being conducted in the region, across a reduced mineral tenement portfolio, by either AngloGold Ashanti teams or together with joint venture partners. A significant portion of the year was devoted to a third noteworthy Quebradona project area, releasing the maiden resource for Nuevo Chaquiro deposit. Refer to the section Planning for the future for further details.