The oil sector was the cornerstone of the Nigerian economy— Nigeria was Africa's largest oil producer, and petroleum and petroleum products accounting for 95% of exports in 2002. Crude oil, coal, tin, and columbite production were Nigeria's top four industries, and other leading industries included cement and other construction materials, chemicals, fertilizer, ceramics, and steel.
Nigeria produced 300 tons (gross weight) of cassiterite tin concentrate in 2000, up from 150 in 1997. A smelter at Jos produced refined tin for export. In 2000, production of columbium and tantalum concentrates totaled 80 tons, up from 60 in 1997. Because of surging demand for tantalite in 2000 by the manufacturers of consumer electronics, the price rose from $14 per kg to $165. Nigeria had plentiful supplies of limestone, and production totaled 2 million tons in 2000, supplying cement plants. In addition, Nigeria produced amethyst, aquamarine, barite, bitumen, clays, diamond, emerald, feldspar, garnet, gold, granite, kaolin, lead, marble, phosphate rock, sand and gravel, sapphire, shale, soda ash, stone, talc, topaz, tourmaline, tungsten, zinc, and zircon. Gypsum output declined from 383,250 tons in 1996 to 30,000 in 2000. Nitrogen production was halted in 1999, and no iron ore was produced in 1998–2000, even though extensive iron deposits included reserves of 2,500 million tons with an average content of 37%.
To attract local and foreign investment in the development of the nonfuel minerals sector and to broaden the country's industrial base, the Mining and Minerals Decree No. 34, enacted in 1999, provided for three-year tax holidays, exemption from customs duties for mining equipment, convertibility of foreign currency, and free transferability of funds. It also reaffirmed that all mineral rights were held by the federal government, although the national legislature was debating reallocation of mineral rights to the states. However, the country's reputation for civil strife, corruption, environmental degradation, fraud, poor infrastructure, and political uncertainty continued to temper international investors' interest in most projects. The adoption of Islamic Shari'ah law in many of the northern states added uncertainty to internal mineral projects in northern Nigeria. Mineral resource companies also had to cope with expectations that the companies should provide extensive physical and social infrastructure.