{"id":20,"date":"2018-02-12T14:47:11","date_gmt":"2018-02-12T14:47:11","guid":{"rendered":"http:\/\/grspiegelmining.com\/?page_id=20"},"modified":"2023-04-26T10:23:48","modified_gmt":"2023-04-26T10:23:48","slug":"about","status":"publish","type":"page","link":"https:\/\/psglghana.com\/?page_id=20","title":{"rendered":"About"},"content":{"rendered":"\t\t
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About Us<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
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Ownership<\/em><\/strong><\/p>

Prestea Sankofa Gold Limited was incorporated in 1994 with a United Kingdom based Company name Samax Limited owning 50.4 percent, Ghana National Petroleum Corporation (GNPC) owning 39.6 percent and the Government of Ghana with the remaining 10.0percent.\u00a0 Samax Limited, which traded on the Canadian stock exchange, was taken over by Ashanti Goldfields Company (AGC) in September 1998.\u00a0 AGC had little interest in the Prestea project because it did not fit into her corporate portfolio released the 50.4 percent share it owned to GNPC, with the Government of Ghana approval in November 2000.\u00a0<\/p>

The Company is now essentially a Ghanaian gold mining company extracting gold mainly from old tailings and waste ore dumped as a result of 100 years mining activity in the Prestea Gold belt.<\/p>

Location and Accessibility<\/em><\/strong><\/p>

The Prestea Sankofa Gold Limited (PSGL) operation is located at Prestea, within the Wassa West District in the Western Region of Ghana,\u00a0 a second class tarred road 148 kilometres from Takoradi and about 135 kilometres from Kumasi through Obuasi accesses the town, it is also about 56km by road and 29km by rail north west of Tarkwa the district capital.<\/p>

Climate<\/em><\/strong><\/p>

The climate within the Prestea area is tropical with high temperature and humidity.\u00a0 The main seasons are dry (November to February) and rainy (March to October) seasons.\u00a0 The peak rainy months fall between June and July the peak dry months are January and February.<\/p>

The mean annual rainfall peaks at 1500 mm as the area lies within the high rainfall belt of Ghana.\u00a0 The mean annual temperature is 27.5o<\/sup>C with a variation of +<\/u>3o<\/sup>C.\u00a0 Annual relative humidity ranges from 65% in December and January to 81% in June and July.<\/p>

The South-western equatorial climatic seasons are influenced by the moist, southwest monsoon winds from the South Atlantic Ocean and the dry dust-laden north east trade winds (Harmattan) which blow over the Sahara desert from the northern sub tropical high pressure zone.\u00a0 The wind direction is predominantly in the SW\/NE quadrant with winds rarely originating from the easterly direction.<\/p>

Mining<\/em><\/strong><\/p>

Mining is on contract, and based on a mining plan. Currently most equipment (such as excavator and trucks) are hired and used for mining under the control of the Exploration & Mining Manager. The material excavated is hauled to the Run-of-Mine (ROM) Stockpile at the Processing plant.<\/p>

Ore<\/em><\/strong> Processing<\/em><\/strong><\/p>

The ore mined is treated at the Processing Plant, which is made up of the Feed Preparation, Milling, Leaching and Adsorption, Elution and Electro-winning, and Smelting sections.\u00a0 A picture of the Prestea Sankofa Gold Limited Cyanide Leach Plant is shown on Plate 1.<\/p>

The process consists of feeding oxide \/ rocks onto a grizzly feeder by front-end-loader, to feed through a jaw and cone crushers and \/ or Tailings onto the tipping bin. This is followed by ball milling to 80% passing 75 microns (\u00b5m). The constituents are interlinked by conveyor belting.\u00a0 The pH of the resultant slurry of fine solids is adjusted to 10+ by the addition of lime before addition of cyanide to leach the contained gold. The gold thus is absorbed onto activated carbon by the Carbon-In-Leach process (CIL).<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Plate 1: Prestea Sankofa Gold Limited Cyanide Leach Plant<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The activated carbon is removed from the CIL circuit when laden with gold, and this gold is then stripped from the carbon in an Elution plant by hydrometallurgical means with dilute solutions of cyanide and caustic soda, after pre-treatment of the carbon with dilute hydrochloric acid. The gold is electrowon from the carbon elution liquor onto steel wool cathodes, which are then calcined and the gold subsequently smelted to bullion.\u00a0 The diluted acid and a bleed from the elution are the only effluents from this section which are discharged to the CIL circuit, where the high pH neutralises the acid and the residual cyanide is re-utilised in the leach process.<\/p>

The tailings from the CIL process, containing residual cyanide levels of 50 \u2013 80 parts per million (ppm) are pumped to the tailings impoundment. By filtering, solids are retained and the water recovered is returned to the plant, thus closing the water circuit and precluding the need to discharge effluent streams to the environment. Residual cyanide contained in the tailings dam breaks down relatively quickly to no hazardous products.<\/p>

The only emissions to air are dust in the feed (stockpile area) and crushing area and negligible fumes from the calcining and smelting furnaces that operate \u00b13 hours on a weekly basis.<\/p>

Dust suppression is provided at all points of generation in the plant.<\/p>

All wet processing areas in the plant are provided with concrete bunded spillage areas to allow recovery of spillage.<\/p>

The average monthly reagents usages are as follows:<\/p>

Sodium Cyanide\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 1.2\u00a0 kg \/ t\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 30,000\u00a0\u00a0 kg \/ month<\/p>

Lime\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 1.5\u00a0 kg \/ t\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 37,500\u00a0\u00a0 kg \/ month<\/p>

Caustic Soda\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 3,000\u00a0\u00a0 kg \/ month<\/p>

Hydrochloric Acid\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 2,400\u00a0\u00a0 kg \/ month\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/p>

Process Residue Disposal (Tailings Dam)<\/em><\/strong><\/p>

The tailings dam is located in the Subri valley (1km from the processing plant), with the dam embankment on the western side of the Subri stream, as shown on Plate 2.\u00a0 The dam is that of an upstream design.\u00a0 Tailings are spigotted (by means of 5cm diameter pipes) from the crest of the embankments, with discharging points relocated around the perimeter of the dam on two weekly bases.\u00a0 This results in a decant pond forming away from the walls, leaving beaches of solids, which consequently provide delay time to allow high free cyanide decay levels, as well as strengthening the geotechnical stability of the dam.\u00a0 The dam is constructed from chemically stable quartz clay earth that was locally available.<\/p>

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Plate 2:\tPrestea Sankofa Gold Limited Tailings Storage Facility (Dam)<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The design is in accordance with sound structural and hydraulic engineering principles. It was designed to achieve the following:<\/p>