After graduating from the University in 1990, my first job experience started at Legadembi gold mine, which is the biggest gold mine in the horn of Africa. I feel this is my home place where I passed the most time of my youngest age. I tried to serve the company and get good job experience doing all my best efforts. On this regard I believe that I got what is supposed to get.
Looking back that time I feel proud of it because at did electronics memory of the mining area, about the community basic infrastructure, about the city of Shakiso, the Guji ethnic group and employment residence area. It was done just driven by personal love to the sector of video editing and production of electronics catalogue.
Hence, the following videos posts are summary of the CD about the gold mining process plant that I have experienced during year 1990 up to year 2003. It was designed to make an electronics catalogue prepared as the company profile that may be upgraded to the company general database management system.
Note on this post except on picture, all are video that can be played by clicking on the arrow located at the lower left side of the media.
A little story about gold in ethiopia
Ethiopian mining and more specifically the gold mining history starts on Adola, which start back to the period of the Italian invasion (1930th). Adola is vast area known as the source of placer gold in eastern Africa. Some of the small town that belong into Adola area are our production site (Shakisso residential town, Legadembi production site), Kibremengist, Megado., Kanticha, ...etc.
As per the retired peoples in Adola Hospital, (see the following viedo), the first mention of gold production in the area dates back to 1936. During the early forties, placer hand mining was active with an annual production over 1000 kg. Since that period, placer gold exploration and production are going on with some mechanization activities. Govern owned exploitation of new placer gold area and primary gold started in 1971 and in 1979 the constitution of the Adola gold exploration project managed by Soviet specialist allowed a detailed geological mapping minerals exploration. .As results of this well-organized activity, various primary-gold occurrences were discovered. Among these, our Legadembi is the best
Gold production 
Geological studies show that a numbers of mineral resources are available in Ethiopia, among these construction materials like cement, kaolin, limestone, marble, artisan mining of precious metals, gemstone, salt, potash, tantalum and gold are few of minerals known practically as exploited mineral resource in Ethiopia.
Among these the case of gold has bold importance because of being the only industrial scale gold mining company in horn of Africa .
Gold ore is a rock or mineral which can be mined (extracted) at profitable cost. Therefore, an ore body is concentration of gold near the earth’s surface, which can be profitably mined. This activities require extensive mine planning and systematical geological ore control. Basically the gold can be produced by two general methods
1) Artisan miners: the hand work where few mechanization processes are involved. This is done when the ore is located on the surface and not mainly on rock form. Among these the elementary one is known as gold panning.The following video show a gold panning i.e. the process of techniques employed in the removal of gold from the ground, washing & gravitation process to separate the gold and the trench worked out on this process in southern part of Ethiopia.
2) Industrial Processing: This involve extraction of the gold from any gound level and using the physical and chemical transformation tecnology. The following example show a gold extraction process diagram
Physical transformation involve extraction from mining gound area by drilling and explosion, size reduction by crushing and milling. Finally the gold will be concentrated by magnetic sepration or/& gravitation
Gold extraction at Mine area
After evaluation of rock contents of the mine production area as ore and waste, the mine production start by drilling and continued by blasting. For this, a heavy drilling and blasting works is done. For example, the systematical and hard work of mine production section permit to supply 500 000 tones per day to processing plant
Loading and hauling process consist on loading the blasted ore onto transport media (in Legadembi) Dump track and transportation of: -
1) Waste, which is a blasted rock without gold content (not economical for production) will be transported to area prepared for this accumulations. this is done to free access to future ore supply
2) Gold ore to crusher plant stock pile then after this will continue the remaining process plant.
On typical day, this production section can load and transport 25000 tones to crushing plant by using excavators and dump-tracks.
Crushing process plant
The first step in the processing of mine ore is the braking down of large rocks up to manageable sizes. At the end of this crushing process the ore size is kept to approximately 18 mm particle size, which is enough to feed Rod mill. Size reduction permit to increase the surface area of the ore for chemical attack take place.
The crushing plant basic operation involves compression or impact of the ore against rigid surface. Then separations of smaller size by the use of screen mesh at different crushing stages. Now our crushing plant have tow crushing process circuits that helped to increase the production reliability by stocking more crushed ore.
Grinding (milling) plant
Grinding (milling) plant consist on the same principle as of crushing plant i.e. it involve impact of the ore against rigid surface (rod or ball) in a wet surround i.e. rotating cylinder called mill. If the grinding media is rod the mill is called Rod Mill while if ball the mill is called Ball Mill.
The out put of mills is fed to screen mesh and cyclones which permit to resize the ore pulp on different pulp particle sizes. By the process of grinding the ore size is kept to a pulp particle size. From this unit, the ore pulp will be pumped to thickening plant
b. Chemical transformation: Once the ore is mined and reduced to apropiate size the chemical reaction process will start. These may included process like cyianadation (leaching), Carbon in pulp (CIP), elution process, electrolysis by mercury and amalgam (mercury removal), calcinations and smelting to get bar of Gold of high concentartion (karat). As example the following are given.
Leaching plant
The gold loaded pulp coming from grinding plant is dissolved in dilute solution of sodium cyanide, which is strong poison chemical that need special disposal into the environment. This process is performed on numbers big tanks arranged on two rows, e.g. size of 30s 4m diameter and 30s meter height. After the required retention time and sufficient dissolution of gold mineral the process will follow to the CIP tanks
The gold loaded carbon is firstly soaked in solution of NAOH (sodium hydroxide) and NACN (sodium cyanide) to wash it then treated on high temperature to remove gold cyanide from the carbon (known as Elution process). At the end of this process we get pure solution of gold as electrolyte which will continue the electrowinning process
g unit by gravity and reserved on big six tanks. In this unit gold is recovered from this sodium cyanide solution by adsorption on to activated carbon. Since an activated carbon has more surface area than the gold particle located in the solution of sodium cyanide it is used for extraction of the gold from the solution.
The gold loaded carbon is firstly soaked in solution of NAOH (sodium hydroxide) and NACN (sodium cyanide) to wash it then treated on high temperature to remove gold cyanide from the carbon (known as Elution process). At the end of this process we get pure solution of gold as electrolyte which will continue the electro-winning process.
The electrolyte solution pumped from Elution process will be treated here in this electrowinning process. Electrowinning process is the electrolysis process which is the separation of gold by applying electric currant. As result of electrowinning process we obtain the gold onto steel wool, which contains irons (i.e. steel & wool) these impurity are mostly removed by the process of calcinations. The calcined gold slime is melted in a pot with a flux of silica & borax. The slag is poured first then the molten gold goes into mould to get final bar of gold plus Silver, which is a called Dore. the smelted Dore product is sent to a refinery of Europe for final refining to 24 carat gold bullion bars and sold to a major bank which is the sole client of our gold production, which make our company a major exporter of gold hence one of the major foreign currency generator for the country.
Tailing process
The residue product outgoing from the CIP plant is discharged to a dam know as tailing dam but since it has sodium cyanide and many others toxic (poison) chemicals it is detoxified at the plant known as detoxification plant then finally the detoxified water is discharged to the ambient or can be returned to process as process row water
Shakisso city, the city of Ethiopian gold mining workers
Shakisso as a town has been formed upon the step of development of placer gold in Adola region. The town has been the commercial and relaxation city for placer gold hand miners. Now, it has a hospital and it is the major transport terminal to go to others part of the gold area gold source and other part of the country. the town on 2002/3 has got secondary school, purified water for drinking, private kindergarten, computer training center, clinics ... etc. the town administration is working on the town master plan, pure water supply, polyclinic and supporting to private economy of the town.
Around the town (in all Adola in general) lives the Oromo nationality or more specifically the ethnic group known as Guji. Like most of the Ethiopian ethnics group a Guji family lives as farmers and farmer related activates.
To get more vision about the Guji ethnic watch the left side video by moving the mouse pointer over the left side video
With the origin of Legadembi, the population, the town infrastructure and the importance of the town has been increased a lot. the town has got 24 electricity, even so purified water is not yet sufficient for all the town citizen any body can get for drinking from key point and Legadembi employee residence area
In Shakisso town, the MIDROC employees residential houses and the camp services are located at area known as Kaletch employee residential camp, which is situated at the exit from Shakisso to production area, i.e. to Legerdembi. Taking into consideration the nature of mining activities, MIDROC has made all the effort to facilitate reasonable leisure and relaxations to employees. It has cable TV, broadcasting center for the communities and health care clinic. In addition to this the company is trying to improve the town infrastructures and the employee residential area camp and canteen services. More detail watch the video shown at different area of this page.
References
http://www.mapsofworld.com/ethiopia/ethiopia-mineral-map.html
http://www.mbendi.com/indy/ming/af/et/p0005.htm#5
Pending reference
