Iron ore mining and processing accounted for more than 50% of Mauritania's export earnings in 1999. Iron ore output (metal content) was 7.5 million tons in 2000—from open pits at the Guelb El Rhein, the Kedia d'Idjill, and the 'Haoudat mine, in the Tiris region, northern Mauritania. Declining reserves and technical difficulties have hindered production at the Guelb El Rhein. The Iron Mines Co. of Mauritania (MIFERMA), formed in 1951 and nationalized in 1974, began production at three mines in 1963, and, since then, iron has been a primary source of foreign exchange earnings. Port facilities and a rail link to the mine were constructed during the peak mining period, 1960–1974.
Gypsum output, from some of the greatest reserves in the world, was 100,000 tons in 2000; technical problems brought production to a halt in 1993, but it was resumed in 1996. In 2000, Mauritania also produced cement, clays, gypsum, petroleum refinery products, salt, sand and gravel, and stone. Mauritania was rich in copper; in the 1980s, the mine at Akjoujt was estimated to contain 100 million tons of ore averaging2.25% copper, with trace amounts of gold. In 1996, gold recovery from tailings at the mine was discontinued, because the stockpile was depleted. The nearby Guelb Moghrein Project, which contained resources of 23.7 million tons (144 grams per ton of cobalt, 1.88% copper, and 1.41 grams per ton of gold), continued to be delayed, because of low gold and copper prices, and problems at the pilot plant. Phosphate deposits, and reserves of platinum, palladium, and nickel, have been identified, and prospecting continued for petroleum, tungsten, and uranium. Mineral exploration efforts were focused on diamond (on the Archean Reguibat craton), gold (in the Inchiri region), oil (offshore), and continued evaluation of copper-gold, kaolin, and peat deposits.