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Koffiefontein Mine is a diamond mine situated in the Free State province, about 80 km from Kimberley, South Africa. It is one of the many Kimberley mines of which Kimberley mine, de Beers mine, Dutoitspan, Bultfontein and Wesselton are its more famous neighbours. The mine was opened in 1870 and consisted of 1200 claims and worked at a large scale in the beginning of the century. However several sources quote it to have a poor yield: 4 to 5 carat (800 to 1000 mg) in 100 loads〔(Diamond yield and quality of Koffiefontein Diamond mine ) by Gardner F. Williams "History of Diamond Mines in South Africa" former De Beers general manager〕 and according to Streeter the mines were not profitable at all by the end of the 19th century.〔(Comments on profitability of Diamond mining in Koffiefontein by Edwin Streeter: Precious Stones and gems (1898) )〕 Streeter also noted that in particular the diamonds of the Koffiefontein and Jagersfontein were of the "first water"; meaning of very good clarity. There was little on the surface to mark the position of these deposits, some deposits were slightly raised above the surface, some showed a small depression, and it was only after mining started that the extent of the deposits became clear.〔(Goodchild: Precious Stones, on diamond occurrence in Koffiefontein )〕 The mine has been closed several times in its history and never became a large production site. The total production of the mine was 7.3 million carats (1460 kg), and the largest gem weighed 139 carats (27.8 g). The mine was most recently reopened in 1987 however De Beers announced its final closure in January 2006.〔(De Beers on Koffiefontein )〕 In November Petra announced it was in advanced talks with De Beers to take over the mine.〔(Petra talks about takeover mine )〕 == Footnotes == 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Koffiefontein mine」の詳細全文を読む スポンサード リンク
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