The mineral industry was poised to become a significant segment of Chad's economy as the Doba Basin petroleum project got under way, with exportation of crude oil scheduled to begin in 2004. The production of construction materials was a leading industry in 2002. In 2001, in addition to clay and salt, mineral output included gold produced from a mine at Ganboké and placer deposits in the Mayo Dala Départment (formerly the Mayo Kebbi Préfecture); gravel, sand, and silt from the Chari and Logone rivers; limestone from the Louga quarry; natron (soda ash, the natural form of sodium carbonate) from Lake Chad; and crushed rock from Dandi. The country's undeveloped mineral resources included bauxite, columbium (niobium)-tantalum, diatomite, graphite, kaolin, quartz, soapstone, tin, thorium, tungsten, and uranium. There were also occurrences reported of chromite, copper, diamond, iron, lead, nickel, titanium, and zinc. The government actively encouraged foreign investment in the development of domestic hydrocarbons, but Chad's landlocked geography and lack of infrastructure and water remained impediments to development.