A number of other mineral deposits are known, but none had been commercially exploited by the mid-1980s. Bauxite is found in the soudanian zone, and gold-bearing quartz is reported in Biltine Prefecture. Uranium is reported in the Aozou Strip, as are tin and tungsten in other parts of the Tibesti Mountains, but exploration reports in 1971 for these three minerals did not indicate large or rich deposits. As of 1987, conflicts in the region prevented further exploration.