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Information on possible gold reserves in Guinea (from 40 to 135.5 tons) varies dramatically: the best-known reserves are said to make up 60.3 tons with 4.9 grams/ton gold recovery, while supposed reserves probably amount to 135.5 tons. Guinea's three main gold-bearing regions are: Siguiri, Dinguiraye, and Niandan-Banye.
Siguiri region is known for its primary and placer deposits. Gold-bearing quartz veins belong to the cases of spar system. They may be as much as 50 meters long. Average gold recovery varies between 2.0 and 4.5 grams/ton, sometimes reaching 30-40 grams/ton level. Placers of gold are related to river and bench alluvium of Tinkisso river and its tributaries. It belongs mostly to bedrock pebble beds whose thickness is usually 0.8 to 1.0 meters. Gold runs around 1 to 3 grams/m3 in the placers. Quartz veins are gold's source here. The biggest placers are: Koba-Duban (17 tons), Koran (76.5 tons) and Sitigeya (6 tons). The active prospecting and development works that took place recently are responsible for the placers' present depletion. The numbers given above reflect the 1970s situation; unfortunately, there is no more up-to-date statistics on Siguiri region.
In the vicinity of Dinguiraye, well-explored are alluvial placers Euro-Iran, Siguirini-Ko and Bodioko. These placers occur around the upper parts of the rivers situated near gold-bearing veins, and the gold is angular, shotty, anisometric. Reserves in a number of deposits reach hundreds of kilograms, sometimes - several tons.
Gold mineralization near Niandan-Banye range is connected with Lower Proterozoic granitoid rocks and is represented by quartz veins of considerable stretch - Jean, Discover, Gobele, and others. The veins are stretched in the submeridional direction in accordance with the stretch of the effusive-sedimentary country rocks of Birrim series. Gold distribution in the veins is very irregular, varying with each sample from traces to 30-40 grams/ton. The samples that are richest in gold can be found in the oxidation zone up to 40 meters thick. Also well-known are placers along the riverbeds of Niandan's and Niger's tributaries. The placers are 100 to 150 meters wide, with gold recovery from 0.8 to 3 grams/m3, sometimes - 12 to 15 grams/m3.
Today in the eastern provinces of Guinea several international joint companies conduct gold works: they surely realize that gold is an immensely promising branch of the country's extractive industry. In February 1981 a very rich Siguiri-Mandiana region, 20 thousand sq. km. of area, was allotted to a Swiss-Canadian joint company SHEVANING-MINING Co Ltd. In 1984 the company finished its prospecting works in the Didi sector, thus getting ready for the development of a gold deposit whose reserves are assessed at 45 thousand tons. The plan provides for 2 tons a year extraction. In December 1985 the company was supposed to have started prospecting in the gold-bearing placers of Mandiana province (near Guinean-Mali border). The reserves are expected to be abundant: prospectors discovered numerous nuggets in local alluvium. In 1982 FAMA PRECIOUS MIN joint company received Mamou-Farana region, 900 sq. km. of area. Main development works took place in the Fitaba and Kaba-Mongo sectors, famous for gold occurrences. The company's productivity was expected to make up 10 tons of gold a year. There is information that yet another joint company SEMOA (Guinea and China) did prospecting in this region, at the Bakari-Kanke deposit (near border with Sierra-Leone). In 1982, a 10 by 10 kilometer field near Dinguiraye was allocated to AP&V INDUSTRIES (Guinea, USA). The extraction started with Banora ("Old Vein") manifestation; gold content - 13.6 grams/ton. A joint Guinean-Belgian PRECOMA company soon began its prospecting in the nearby Kolinko sector. In 1985 another similar enterprise (this time joint Guinean and French with an Arabian financier company) was prospecting and preparing Jean vein in the gold-bearing Kouroussa province. The past experience prompts that average gold recovery in the vein is 14 grams/ton. It was decided to begin the extraction in a year's time.
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