Although mineral production in Tunisia was not diverse, it was an important source of revenue. Of $5.8 billion in total exports in 2000, $542 million came from cement, phosphate-based fertilizers, phosphate rock, salt, zinc, and other minerals. Mining and solid mineral processing accounted for 1% of GDP. Petroleum and mining, particularly of phosphates and iron ore, were Tunisia's top two industries in 2002, phosphates and chemicals comprised the country's third top export commodity, and hydrocarbons ranked fifth. Phosphate rock production (12.9 million tons in 2000; 90% from open-pit mining) was entirely controlled by the government-owned Compagnie des Phophates de Gafsa (CPG), founded in 1896. CPG was the largest company in Tunisia, both in terms of employees and capital investment, directly employing 9,000 people and indirectly employing over 200,000. The Kef Eschfair Mine accounted for 29.5% of total ore volume; the Kef Eddour Mine, 19.6%; and the Jallabia Mine, 18.2%. The underground M'rata Mine was closed in 2000. Known reserves of crude phosphate, in the south, amounted to 100 million tons (5% of world reserves). High-grade iron ore was found in the north, while lead and zinc, mined intermittently since Roman times, were widely dispersed. International interest in developing Tunisia's lead-zinc deposits continued to grow. High-quality marine salt was exploited along the coast. In 2000, mineral production included washed phosphate rock (gross weight), 8.34 million tons; iron ore (metal content), 98,000 tons, down from 119,000 in 1999; zinc, 41,247 tons; lead, 6,602 tons; cement (hydraulic and white), 5.4 million tons; marine salt, 481,000 tons; and gypsum, 100,000 tons. Barite, clays, fertilizers (triple-superphosphate, phosphoric acid, diammonium-phosphate, and ammonium nitrate), gravel, lime, sand, and stone were also produced. No fluorspar was mined in 2000, and uranium was discovered in 1965.