Geology of Mauritania ore. A Neoproterozoic carbonate unit, part of a synformal nappe overturned in the Paleozoic, now forms a major copper deposit 250 kilometers northeast of Nouakchott in the Mauritanides Belt. The one kilometer, 250 meter wide deposit spans the West and East Moghrein Guelb hills. Forty meters below the deposit is a secondary deposit of cuprite, azurite, malachite and tenorite, with an additional 2.25% copper, some gold and sulfide mineralization including cubanite, chalcopyrite, pyrrohitite and aresnopyrite. In the 2000s, mining at the site had mostly ceased except for gold mining in the tailings pile. Gypsum is extracted from the N'Drahamcha quarry,
Metal detector in the chest of American President James Garfield in 1881; the metal detector worked correctly but the attempt was unsuccessful because the metal coil spring bed Garfield was lying on confused the detector. The modern development of the metal detector began in the 1920s. Gerhard Fischer had developed a system of radio direction-finding, which was to be used for accurate navigation. The system worked extremely well, but Fischer noticed there were anomalies in areas where the terrain contained ore-bearing rocks. He reasoned that if a radio beam could be distorted by metal, then it should be possible to design a